recycling of polyolifins 05-09-2013.docx

7/27/2019 recycling of polyolifins 05-09-2013.docx

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INTRODUCTION

Reasons and significance of this article

In the past few decades, improvement in people living conditions led to an increase polymer

consumption (mainly plastic) and its production in the last 10 years have become equal to the

production during entire 20th century [1]. Under the same scenario global plastic production will

increase three times by 2050 [2]. Our future generations are at risk and in order to guarantee their

livings we have to put limits on profligate production by avoiding waste production and recycling the

post-consumer items [3, 4]. Owing to such environmental pressures, polymer recycling is the prime

fcus in tdays industry. Innvatins in plymer waste reductin technlgies under the umbrella f

environmental standpoint are a difficult task, because of intricacies in reuse of polymers. However, the

challenge can be overcome via establishment of optimal processes. Attention from the importance of

plymer recycling cant be withdrawn as majrity f these materials are nn -degradable, have

comparative short life cycles, distinctly visible in the waste streams ( >30% of domestic waste) and are

under the great deal of public criticism . Different technological advancement has taken place in the

recent years for accounting plastic waste recycling and new approaches are also under investigation [5].

Biodegradable & Non-Biodegradable polymers

Biodegradable polymers first introduced in early 1980s. Biodegradable polymers have varying sources

ranging from natural polymers available in large abundance to synthetic polymers produced from non-

renewable sources.

There are different processes responsible for biodegradation like chemical deterioration by living

organisms or enzymatic action. Mechanism of polymer degradation has been reviewed [6]. Overall, the

process occurs in two steps:


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1. High molecular mass polymer is broken down into lower molecular mass species with the helpof biotic reactions (oxidation, hydrolysis or photo degradation) or abiotic reactions (degradation

of microorganisms).

2. Bio assimilation and mineralization of the polymer fragments by microorganisms.

Biodegradability of the polymer depends on different factors like origin of the polymer, its chemical

nature and environmental conditions. Mechanical properties of biodegradable polymers is affected by

their chemical composition [7, 8], processing & storage characteristics [9, 10] and application conditions

[11]. Biodegradable polymers have gained attention in the past few decades due to their potential

applications in the field of health and environment. However, numerous biopolymers are of market

importance while others are dependent on their price level which is noncompetitive yet and need some

promising development. Different methods like grafting and copolymerization have been developed to

improve the physic-chemical properties of biodegradable polymers, which not only improve the rate of

biodegradation but also enhance the mechanical properties of the desired product. Blending is another

process which enhances morphology and physical properties of the final product. In addition, some

advanced technologies including nanobiocomposites, natural fiber reinforcement, use of nanoclay and

active packaging technology have also been applied [12].

Non-biodegradable materials are man-made materials which do not decompose or breakdown into

simpler ones. Unfortunately these materials are not recycled at an efficient rate and causes

environmental pollution. Recycling not only saves natural resources but also lower down the impact of

the waste ending up in landfill throughout the world [13].

Biotechnological/ renewable production of non-biodegradable materials have also been reported e.g.

prductin f lng chain alkanes by using prkarytic and eukaryotic organisms [14] and aromatic

compounds from carbohydrates by using bacteria [15]. Moreover, persistant polymers can be


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specifically produced from low molecular weight compounds e.g. ethanol and acrylamide. Ethanol

obtained from carbohydrate fermentation is converted into polyethylene [16] while acrylamide is

converted into polyacrylamide [17].

What are polyolefins?

Polyolefins a commodity polymers and are formed by polymerization of olefins and. They are widely

spread in the whole range of polymers and play a vital rle in building up natins ecnmy due t their

massive consumption volumes in industry[18]. They show resistance to biodegradation, hydrolysis and

peroxidation due to the presence of stabilizers and antioxidants[19, 20]. However, adding pro-oxidants

additives to them turns hydrophobic surface into hydrophilic one. Thus, a friendly environment for

microorganisms is formed resulting in bio-assimilation to low molar mass oxidation products[21-25].

In European countries one third of total plastic production is polyolefins[26]. Recent economic growth in

China also sparked the demand of polyolefins. In fact, the largest market of polyolefin ns in 21st century

is china and pace is increasing even faster [27].

Polyolefins are essentially divided in to two classes: thermoplastics (TP) and thermosets (TS).

Thermplastics, sften upn heating (reversible prcess) while thermsets dnt (irreversible prcess).

Polyolefins have unlimited applications like bags, film, insulation, piping (LDPE), gas pipes (HDPE), toys,

industrial wrappings, automotives and electrical components (PP) etc. Nearly 80% of the total waste

comprises of thermoplastics and thermosets. Among thermoplastics polyolefins, low density

polyethylene (LDPE) 17%, high density polyethylene (HDPE) 11% and polypropylene (PP) 16% are

present whereas, thermosets are mainly epoxy resins and polyurethane[28].

Polyolefins contain photoinitiators and stabilizers which make them resistant to biodegradation,

hydrolysis and oxidation[29]. Pro oxidant additives like Mn+2/Mn+3 can make them oxo-degradable and

a free radical chain reaction results in the degradation of polyolifins by producing hydro peroxides which


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are then thermolysed or pyrolysed to yield low molecular mass products with hydrophilic properties

favorable to microorganisms.

Why selected Non-biodegradable

Polyolifins waste has got increased environmental concerns during the past decade. Despite significant

advancement in recycling processes, major polyolifins generated waste is still disposed to landfill which

is of high cost and poor biodegradability [30]. In 2002 in Europe 61% of the plastic waste generated is

disposed to landfill while 39 % is recovered by using different techniques. From 2002 to 2009 energy

recovery has got the higher percentage of 22% by consuming 4.7 million tons, while mechanical and

chemical recycling as got 15% (3.13 million tons) and 2% (0.35 million tons) [31]. From 2009 about 60

million ton of plastic is produced but only 6% is recycled i.e. just 2% of 100 billion Euros of turnover [32].

Similarly in Greece, a low amount of 2.2 % was recovered and recycled [33].

Reprocessing of polyolefins especially PE and PP by traditional processes such as intrusion or continuous

extrusion has got certain limitations like comingled plastic wastes, low product price & quality and

limited market for such recycled products [34]. The Impurities like adhesives, metals, pigments and

other incompatible components like polyesters and polyamides causes a low interfacial adhesion

resulting in poor physic-chemical properties [35].

This indicates that recycled polymers have low value due to poor quality and there is a need for high

grade polymers. Technologies to address post-consumer polyolefins should be cost effective and

accurate enough to meet the purity demands. Thus, potential market for such technologies is large to

valorize a substantial fraction of the materials.

Recent trends in polyolefin waste generation


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Polyolefins are widely spread in the whole range of polymers and are in constant development to meet

the changing demands. Recent studies has shown that avg. weight of individual packaging items is

decreasing e.g. drinks bottles and PE sheets have been dropped in weight up to 15 % [36]. LDPE is most

recovered polyolefin because of its abundant usage in packaging. On the other hand other polyolefins

especially PP volumes are projected to increase due to increasing demands in packaging, automotive

and EEE sectors. Volumes of more technical polymer waste (ABS, PA, PU) are not expected to grow

substantially. The total Polyolefin waste scenario in Europe, 2005 and 2015 are described below for each

waste stream [37].

Fig : Estimated volumes of the most common polyolefin waste in Europe, 2005 and 2015

The production of petroleum/natural gas derivative ethylene exceeded the demand limit of 115 Mt and

reached 126.7 Mt during the start of 2009 as a result of vast production in the Middle East. Thus 56%

increase in Middle East raised the total production to 19 Mt and is predicted to rise to 145 Mt by 2010.

On the other hand, consumption is expected to stay relatively smooth at around the current rate [38].

prior to 2008 growth in global demand figures for ethylene remained at an average annual rate of 4-

0

5000

10000

15000

LDPE

HDPE PPPolyo

lefinsfrom

waste,

th.

tonnes

Most common Polyolefins

Polyolefin waste scenario in Europe, 2005 and 2015

2005

2015


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4.5% and fell by approximately 3% (about 4 Mt) in 2008. In China in 2008 production of polyethylene

thermoplastic resins (LDPE, LLDPE and HDPE) consumes approximately 60% of ethylene. In the first half

of 2009, PE imports to China were as were nearly equal to the imports for the whole of 2008. The import

level of HDPE has seen an increase by 90% in 2009 compared to 2008 [39]. PP is a versatile and low cost

Polyolefin and has a growth rate above an average of 7-8% in 2007. However, PP consumption fell to

45.5 Mt in 2008. Despite the fact that PP has beneficial properties, it is losing its competitive price

position to other polymers, owing to the increase in feedstock prices [40].

Impact on socio economic life

A depletion of non-renewable natural resources would be very dangerous for the future existence of

human civilization. Protection of the natural environment, a decrease of CO2 emissions and mitigation

of climate change is feasible only by reducing consumption of natural resources. Therefore, a search for

options to increase energy efficiency, an increase in the use of renewable energy sources and reuse of

different types of waste seems to be the obvious direction of scientific activity

M. Stelmachwski , K. Swioski. THERMAL AND THERMO-CATALYTIC CONVERSION OF WASTE

POLYOLEFINS TO FUEL-LIKE MIXTURE OF HYDROCARBONS Chem. Process Eng., 2012, 33 (1), 185-198

Feedstock recycling of waste raw materials (biomass, waste plastics, waste tires) is the best way to reuse

primary energy and raw materials. Figure 1 shows a relationship between energy production from fossil

fuels and their recovery from waste and technological similarities between these processes. This

indicates also the need to develop and improve technologies of waste conversion into raw materials

and/or energy.


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Thermodynamic analysis based on exergy approach indicates that the best technologies to utilise waste

plastics and used tires are gasification and thermal degradation (cracking and pyrolysis) (Fratzscher and

Stephan, 2001; Stelmachowski, 2010a). These technologies ensure the highest rate of recovery of

primary energy.

Fratzscher W., Stephan K., 2001. Waste exergy utilisation An appeal for an entropy based strategy. Int.

J. Therm. Sci., 40, 311-315. DOI: 10.1016/S1290-0729(01)01222-4.

Stelmachowski M., 2010a. Thermodynamic analysis and modeling of the process of thermal and catalytic

convertion of waste polymers into liquid fuels and electricity. Polish Academy of Sciences Branch in

Ldz, the Envirnment Cmmittee (Plska Akademia Nauk Oddziaw dzi, Kmisja Ochrny

rdwiska), d, 2010. ISBN 978-83-86492-60-2 (in Polish).

Waste plastics contribute to many environmental and social problems due to the loss of natural

resources, environmental pollution, depletion of landfill space and demands of an environmentally

oriented society. The advantages of plastics (such as lightness, sturdiness, chemical resistance, and low

cost) that make them suitable for an enormous number of practical uses simultaneously are their

disadvantages due to their impact on the environment. Chemical resistance and sturdiness result in long

time of natural decomposition, low price brings out low profitability of recycling and low weight

contributes to the fact that scrap plastics take up a large volume. The consumption of plastics per capita

differs very much in the world even in developed countries. In Europe, the consumption of plastics was

about 24-150 kg/person in 2003-2005, while 10 years earlier the average consumption in the EU had

been about 20-60 kg/person (Aguado et al., 2008; Spokas, 2008; Stelmachowski, 2010a).

Aguado J., Serrano D. P., Escola M. J., 2008. Fuels from waste plastics by thermal and catalytic processes:

A review. Ind. Eng. Chem. Res., 47, 7982-7992. DOI: 10.1021/ie800393w.

Spokas K., 2008. Plastics still young, but having a mature impact. Waste Management, 26, 473-474,

DOI:10.1016/j.wasman.2007.11.003.


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Stelmachowski M., 2010a. Thermodynamic analysis and modeling of the process of thermal and catalytic

convertion of waste polymers into liquid fuels and electricity. Polish Academy of Sciences Branch in

Ldz, the Envirnment Cmmittee (Plska Akademia Nauk Oddziaw dzi, Kmisja Ochrny

rdwiska), d, 2010. ISBN 978-83-86492-60-2 (in Polish).

The amount of waste polymers increases by 6.6 to 12% each year, depending on the country. Waste

plastics represent only 7 to 9% of total waste in terms of mass but about 30% in terms of volume. About

70% of waste are polyolefin, including polyethylene (PE), polypropylene (PP) and polystyrene (PS). The

majority of these waste are disposed in landfills or incinerated (2025%), with no attempt to recycle

using of chemical recycling or thermal degradation processes (Scheirs and Kaminsky, 2006; Williams and

Slaney, 2007).

Scheirs J., Kaminsky W., (Eds.) 2006. Feedstock recycling and pyrolysis of waste plastics: Converting

waste plastics into diesel and other fuels. Wiley Series in Polymer Sciences. John Wiley & Sons, Ltd,

Chichester.

Williams P.T., Slaney E., 2007. Analysis of products from the pyrolysis and liquefaction of single plastics

and waste plastic mixtures. Resour. Conserv. Recycl.,51, 754-769. DOI:10.1016/j.resconrec.2006.12.002.

In the near future, a disposal of organic waste and plastics in landfills will be almost impossible due to

the law, high costs and growing ecological social awareness. However, there are also some technological

and economic constraints that limit full and efficient recycling of waste plastics into useful products.

General recycling procedure

Recycling is a complex method of environment protection, which aim is the limitation of the raw

materials consumption and decrease of waste quantity. It should be a multiple system of the same

materials using in the next material and usable goods. In the literature, there appears many definitions


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of recycling. Recycling is reprocessing of old materials into new products, with the aims of preventing

the waste of potentially useful materials. Another meaning of recycling is taking a product or material at

the end of its useful life and turning it into a usable raw material to make another product. In

accordance with Act on Waste recycling shall mean recovery which involves re-processing of substances

or materials included in waste in the manufacturing process in order to obtain substances or material of

original or other designated usage, including also limited recycling, excluding energy recovery [1].

In practice, recycling is often the necessity and it always becomes the only reasonable strategy of the

working if consider waste formation in the End of Life phase EoL [2]. Every product has to be designed,

prduced, sld, cnsumed r explited and every prduct, after time, desnt satisfy the needs because

of the physical or moral consumption [2, 3]. It becomes waste. The EoL analysis leads to resources

sustainment model. Product recovery as an elongation of product life cycle can concern the whole

products, theirs components and materials and raw materials, generally recovered value. The basic

possibilities of recovery: reuse, remanufacturing, reclaim, recycling (Fig. 1)

The most beneficial and durable way of waste problem solution is avoidance of waste formation. The

healthy for the environment life style, goods consumption and waste treatment promotes 3R principle.


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The first principle (Reduce) reminds about possibility of waste quantity reduction by limitationof unnecessary products consumption.

The second one (Reuse) takes into consideration a possibility of products reuse which aregenerally recognize as disposable. It decreases environment pollutions scale which are formed

during technological process or waste accumulation.

The third principle (Recycle) speaks that not all waste can be avoidance like not all kinds ofproducts can be repeatedly usage.

The recycling stages consist of initial and secondary processes.

To the first one include:

sorting and separation washing;size reduction pressing briquetting and granulation.

The secondary processes consist of [4, 5]:

composting of solid waste (biological processing); combustion and pyrolysis (thermal processing); biogas generation (biochemical processing); electrochemical metals recovery (electrochemical processing).

Waste processing technologies containing the secondary processes make possible waste utilization on

the basis of methods:

Chemical recycling; resources recycling; thermal recycling; material recycling


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biological recycling.

[1]Act on Waste of 27 April 2001.[2]A. Hamrol, P. Wiegandt, Enlarged life cycle of product, Cleaner Production in Poland 6 (2000) 12-15 (in Polish).

[3]M. Dudek-Burlikowska, D. Szewieczek, Quality estimation methods used in product life cycle, Journal of Achievements inMaterials and Manufacturing Engineering 24/2 (2007) 203-206.[4]B. Bieda, The role of thermal treatment in an integrated waste management, Proceedings of International ConferenceWaste Recycling, Cracw, 2005, 104-113.[5]P. Vindis, B. Mursec, C. Rozman, M. Janzekovic, F. Cus, Biogas production with the use of mini digester, Journal ofAchievements in Materials and Manufacturing Engineering 28/1 (2008) 99-102.

Magnetic density separation

The standard route of processing ore or waste to high grade materials is to first liberate the various

materials that are present in the feed by crushing, milling, cutting or shredding. Then, the resulting flow

of particles is classified with screening, into narrow size fractions to improve the final separation.

Density separation is used on a large scale in the beneficiation of ore and waste. Methods that use solely

the density differences of materials are successful because the separation is, in principle, not influenced

by size or shape of the materials, resulting in high grade products.

Unfortunately, conventional methods have limitations in the density that can be reached.

E.J. Bakker*, A.J. Berkhout, L. Hartmann and P.C. Rem. Turning Magnetic DensitySeparation into Green Business Using the

Cyclic Innovation Model. The Open Waste Management Journal, 2010, 3, 99-116

The MDS setup, which has been built up, consists of injection zone, laminator, separation zone and

product collection zone (Fig. 2). The separation is a complex mix of fluid dynamics, particle-particle

interactions and magnetic separation forces. Particles of polymers are easily packed so that poor

separation behaviour will be shown. For this reason, the mixture of wetted particles is mixed with the

process fluid in a turbulent flow, which disperses the various materials over the cross-section of the

channel. However, entering the magnetic separation zone, the fluid must become as laminar as possible

in order to let the magnetic forces create the separation without turbulence. Hence, the flow of the


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process liquid and the movement of the particles are essential for simulation, especially in the

separation zone.

A model of the separation zone has been done (Fig. 3). By continuously comparing the simulation and

experiments, the design of the MDS setup will be optimized. And the simulation must give multiple

answers in order to have sufficient flexibility for the elaboration of the final design.

Fig. (2). Medium Density Separation (MDS) setup.

One of the major opportunities is the recycling of polyolefin waste. Polyolefin fractions are often end

fractions resulting from the recycling of cars, waste from electric and electronic equipment (WEEE) and

packaging waste. Sinkfloat with water as the medium is the most commonly used process that creates

mixtures of PP and PE as a float fraction. Typically, the PP:PE ratio ranges from 70:30 for car scrap to

25:75 for packaging waste. Such mixtures can be disposed in a safe way or used for energy recovery. A

third option, reusing the mixture for consumer products, can only be possible after mechanical

recycling. When reusing it as a high quality product the grade of PP and PE should be better than 97%.

Which of the three options is preferred should be determined by a Life Cycle Analysis. When opted for

mechanical recycling, MDS is one of the promising techniques [11].

E. J. Bakker, P. C. Rem and N. Fraunhlcz, Nvel methd t separate polyolefins from sredder residue

based on inverse magnetic density separatin, Prceedings f the 6th IdentiPlast biennial conference

on the recycling and recovery of plastics, 2007.

In order to produce high-purity granulate from complex streams of post-consumer waste, of a quality

comparable to materials presently produced from post-industrial waste, a separation technology is

needed that is sensitive to very small differences in the physical properties of the materials.


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At the same time, in order to be economically and ecologically sound, the process should recover most

of the polyolefins into useful products and minimize process residues.

Current available separation technology is mainly based on a accurate identification of the primary

plastic contained in a particular item, followed by some type of manual or automated sorting are

essential [1]. In the case of plastic bottle sorting, automated selection procedures, commonly based on

optical-sensing-techniques (OST) can be applied.

They are not so successful because of the different bottles size and shape characteristics. Furthermore

the presence of labels, surface contamination, presence of paint and coating, represent an other

obstacle in the utilisation of OST. Another wide applied sorting strategy is based on density. Also this

approach is not particularly helpful, especially to perform a very strict separation. Most plastics, in fact,

are very close in density (HDPE = 0.941 g/cm3, MDPE = 0.9260.940 g/cm3, LDPE = 0.9150.925

g/cm3, LLDPE = 0.910.94 g/cm3, PP = 0.96 g/cm3). In the case of rigid plastic rigid waste, resulting

from electronic parts, a heavy medium separation is usually applied [2]. This can be done by adding a

modifier to water or by using tetrabromoethane (TBE). However, this is a costly process and can lead to

contamination of the recovered plastic [2, 3]. Hydrocyclones can represent a good tool to strength

density separation efficiency.

Hydrocyclones, which use centrifugal force, enhance material wettability. Some of the factors affecting

liquid separation of a given plastics material are: i) degree of wettability, ii) variation in density, related

to polymeric structure, fillers materials utilised, typologies of pigments, etc., iii) morphological and

morphometrical characteristics of plastic particles as they result from comminutionclassification

processes, iv) degree of liberation of one polymer in respect of another one or to other non-plastics

materials. The presence of air bubbles attached to plastic particles produce different negative effects of

specific plastic recovery, that is: i) a reduced wetting of the surface and ii) a floating of the particles due

to the fact that the system airplastic flake float in a solution less dense than that of bulk material [4].


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Triboelectric separation, which can distinguish between two resins by simply rubbing them against each

other, is another sorting strategy currently applied to separate plastics. A triboelectric based separation

device sorts materials on the basis of a surface charge transfer phenomenon. When materials are

rubbed against each other, one material becomes positively charged, and the other becomes negatively

charged or remains neutral. Particles are mixed and contact one another in a rotating drum to allow

charging. Materials with a particle size of approximately 24 mm were the highest in both purity and

recovery in the

triboelectric process [5]. Plastic solid waste can also be sorted by a speed accelerator technique,

developed by Result Technology AG (Switzerland). This technique uses a highspeed accelerator to

delaminate shredded waste, and the delaminated material is separated by air classification, sieves, and

electrostatics [2]. Using X-ray fluorescent (XRF) spectroscopy, different types of flame-retardants (FRs)

can be identified. On this basis, MBA Polymers, Inc. has developed a technology that can separate pure

resin with FRs [6, 7].

W2Plastics is applying the emerging technology called Magnetic Density Separation (MDS) [8] to

separate the various types of Polyolefins: polypropylene (PP), low density polyethylene (LDPE) and high

density polyethylene (HDPE), from each other and from contaminant materials such as wood, rubbers

and minor amounts of metals and foams. MDS technology is potentially very cheap because it separates

a complex mixture into many different materials in a single process step, using one and the same liquid.

The entire separation is performed as the mixture flows through a channel and segregates in a few

seconds into as many different layers as there are products. The water-based

W2Plastics is applying the emerging technology called Magnetic Density Separation (MDS) [8] to

separate the various types of Polyolefins: polypropylene (PP), low density polyethylene (LDPE) and high

density polyethylene (HDPE), from each other and from contaminant materials such as wood, rubbers

and minor amounts of metals and foams. MDS technology is potentially very cheap because it separates


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a complex mixture into many different materials in a single process step, using one and the same liquid.

The entire separation is performed as the mixture flows through a channel and segregates in a few

seconds into as many different layers as there are products. The water-basedprocess liquid is recovered

mechanically to the point that only about 5 kg of liquid remains per ton of de-watered product. Since

each kg of process liquid contains as little as 6 grams of iron oxide (the active material for the

separation), most applications of the polyolefin products do not require that such a minor amount of

liquid need to be washed from the plastics. Therefore very low costs are associated with the recycling

and quality control of the liquid, usually one of the expensive steps in advanced sink-float separations.

MDS is also potentially very sensitive to small differences in material density, provided that the

turbulence in the liquid can be accurately controlled. Preliminary results obtained with a small MDS

laboratory setup have shown that PP could be separated cleanly from PE.

[1] S. M. Al-Salem, P. Lettieri and J. Baeyens, Recycling and recovery routes of plastics solid waste(PSW): A review, WasteManag., vol. 29, pp. 2625-2643, December 2009.

*2+ H. Kang and J. M. Schenung, Electronic waste recycling: a review of U.S. infrastructure andtechnlgy ptins, Resour.Conserv. Recycl., vol. 45, no. 4, pp. 368-400, March 2005.

*3+ H. M.Veit, C. Pereira and A. M. Bernardes, Using mechanical processing in recycling printed wiringboard.J. Minerals MetalsMater. Soc., vol. 54, no. 6, pp. 45-47, January 2002.

*4+ American Plastics Cuncil (APC), Development of hydrocyclones for use in plastic recycling.Technical paper, 1999.

*5+ C. Xia, A. Laurence and M. B. Biddle, Electrostatic separation and recovery of mixed plastics. In:Society of Plastics Engineers (SPE) Annual Recycling Conference (ARC), Dearborn, Michigan (US), 1999.

*6+ S. Tlken, Cmputers, plastics dnt mix well. In: Waste news; June 1st. Available at:

http://www.wasterecyclingnews.com/arcshow, 1998.

*7+ American Plastics Cuncil (APC), An industry full of potential: ten facts to know about plastics fromcnsumer electrnics. Technical paper, 2003.

[8] E.J. Bakker, P.C. Rem, N. Fraunhlcz, Upgrading mixed polyolefin waste with magnetic densityseparatin, WasteManagement, vol. 29, no. 5, pp. 1712-1717, June 2009.
http://www.wasterecyclingnews.com/arcshttp://www.wasterecyclingnews.com/arcshttp://www.wasterecyclingnews.com/arcs


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Triboelectric separation

Whenever two materials of different nature are subjected to either a simple contact or a friction test,

electrical charges are generated and exchanged between them. This phenomenon has been known as

the triboelectricity [1-4]. Triboelectricity is attributed to the electron transfer from one body to another

[5-8]. However, in some specific cases (especially invlving plymers), its shwn that the tribelectric

chargecreated on the surfaces of particles may be the result of a ions transfer [9] or mass transfer [10].

In some systems, the three mechanisms of charge transfer can occur simultaneously [7]. The

electrostatic separation methods such as coronadischarge and electrostatic induction can separate

mixtures of metals/insulators, whereas the triboelectrostatic method is specific for separating

variousmixtures of insulator/insulator particles [11-13]. Industrial applications of triboelectrostatic

separation are numerous. The most important are thetreatment of ash from coal power plants [14-17]

andseparation of granular plastic mixtures in the recycling [18-19].

In triboelectrostatic separation, the charged particles separate through an electric field by the particle

particle and particlesurface charging mechanisms. The charging method and charge density (nC/g) of

the plastics have beenreported by various researches. Many studies have been performed to analyze

performance of triboelectric separators forsorting different types of insulating particles. There are

currently several methods of triboelectric charging using rotating tubes [20-22], fluidized beds [23-28], a

vibrating feeder[29-30], tribo-cyclones [31-32], fans [33-34], static charger, a honeycomb and a spiral

tube charger.

[1] W. R. Harper, Contact and Frictional Electrification, London: Oxford University Press, 1967.

[2] J. Lowell, "Contact electrification of metals," J. Phys. D: Appl. Phys, vol. 8, p. 53-63, 1975.

[3] L. B. Loeb, Static Electrification, Springer, Berlin, 1958.

[4] D. K. Davies, "Charge generation on dielectric surfaces," J. Phys. D: Appl. Phys., vol. 2 , p 1533-1537,

1969.

[5] E. G. Kelly, and D. J .Spottiswood, "The theory of electrostatic separation: a review," part II. Particle

Charging. Miner Eng, vol. 2, p. 193-205, 1989.


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[6] C. Pounder, "The Quest for a Charging Mechanism to the End of the 19th Century," J.

Electrostatics,vol. 3, p. 389-394, 1977.

[7] G. S. P. Castle, "Contact Charging Between Insulators," J. Electrostatics, vol. 40-41, p. 13-20. (1997)

[8] S. Mazuda, M. Toragushi, T. Takahashi, and K. Haga, "Electrostatic beneficiation of coal, using a

cyclone-tribocharger," IEEE Trans.Ind. Appl., vol. 19, p. 789-793, 1983.

[9] A. M. Gaudin, "The Principles of Electrical Processing with Particular Application to Electrostatic

Separation" Miner. Sci. Engng., 3, 46-57. (1971)

[10] W. R. Salanek, A. Paton, and D. T. Clark, "Doublemass transfer during polymer-polymer contacts,"

J. Appl. Phys., vol. 47, p. 144-147. 1976.

[11] E. G. Kelly, and D. J. Spottiswood, "The theory of electrostatic separations: a review," part I.

Fundamentals, Miner Eng, vol. 2 p. 3346, 1989.

[12] A. Tilmatine, S. Bendimerad, M. Younes, and L. Dascalescu, "Experimental analysis an doptimisation of a free-fall triboelectric separator of granular plastic particles," International Journal of

Sustainable Engineering, Vol. 2, No. 3, p.p. 184191, Sep. 2009.

[13] A. Tilmatine,S. Bendimered, F. Boukhoulda, K. Medles, and L. Dascalescu, "Electrostatic separators

of particles.Application to plastic/metal, metal/metal and plastic/plastic mixtures," Waste management,

Elsevier, 29, p.p. 228232, 2009.

[14] P. Carbini, M. Carta, R. Ciccu, C. Del Fa, M. Ghiani, and G. Rossi, "Beneficiation methods for coal

desulphurization," 64th Proc. CIC Coal Symp, 1982.

[15] D. Gidaspow, D.T. Wasan, S. Saxena, Y.T. Shih, R.Gupta and A. Mukherjee, "Electrostatic

Desulfurization of Coal in Fluidized Beds and Conveyers," AIChE Symposium(Series no.255), 83, 74-85.

(1987).

[16] D. H. Finseth, T. Newby and R. Elstrodt, "Dry Electrostatic Separation of Fine Coal," 5th Int. Conf.

Proc. and Util. of High Sulfur Coals. Amsterdam: Elsevier Science Publishers. (1993).

[17] I. I. Inculet, R.M. Quigley, M. A. Bergougnou, J. D. Brown, and D. K. Faurschou,. "Electrostatic

beneficiation of hat creek coal in the fluidized state," Canadian Inst. Mining and Metallurgy Bulletin, vol.

73, p. 51-61. (1980)

[18] V. Gente, F.L. Marca, F. Lucci and P. Massacci, "Electrical separation of plastics coming from special

waste," Waste Manag23, 951958, 2003.

[19] R. D. Pascoe and B. O. Connell, "Development of a method for separation of PVC and PET using

flame treatment and flotation," Miner Eng, vol. 16, p. 12051212, 2003.


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[20] I.I. Inculet, G.S.P. Castle and J.D. Brown, "Electrostatic separation of plastics for recycling," Part Sci

Technol, p.p. 1691100, 1998.

[21] Y. Wu, G.S.P. Castle and I.I. Inculet, "Particle size analysis in the study of induction charging of

granular materials," J Electrost63, p.p. 189202, 2005.

[22] A. Tilmatine, K. Medles, M. Younes, A. Bendaoud andL. Dascalescu, "Roll-type versus free-fall

electrostatic separation of tribocharged plastic particles," IEEE/IAS Industry. ApplicationSociety. Volume

46, Issue: 4, pp: 1564 1569. 2010.

[23] M .Bilici, L. Dascalescu, C. Dragan, O. Fati, A. Iuga and A. Samuila, "Tribocharging and electrostatic

separation of mixed granular solids in fluidized bed devices," IEEE Trans. DEI, vol. 18, p. 1476-1483,

2011.

[24] L. Calin, A. Mihalcioiu, A. Iuga and L. Dascalescu, "Fluidized bed device for plastic granules

triboelectrification," Part. Sci .& Technol., vol. 25, p. 205-211, 2007.

[25] L .Calin L. Caliap, V. Neamtu , R. Morar, A. Iuga, A. Samuila, and L. Dascalescu, , "Tribocharging of

granular plastic mixtures in view of electrostatic separation," IEEE Trans. Ind. Appl., vol. 44, p. 1045-

1051, 2008.

[26] C. Dragan,O. Fati, M. Radu, L. Calin, A. Samuila, and L. Dascalescu, "Tribocharging of mixed granular

plastics in a fluidized bed device," IEEE Trans. Ind. Appl., vol. 47, p. 1922 1928, 2011,

[27] F.S. Ali, I.I. Inculet and A. Tedoldi, "Charging ofpolymer powder inside a metallic fluidized bed," J

Electrost45, p.p. 199211, 1999.

[28] A. Iuga, and al., "Tribocharging of plastics granulates in a fluidized bed device," J Electrost63, p.p.

937942, 2005.

[29] R. McCown, and F.B. Gross," Medium velocity impacttriboelectrification experiments with JSC

Mars-1 regolith stimulant, " J Electrostat64, p.p. 187193, 2006.

[30] Y. Higashiyama, Y. Ujiie, and K. Asano, "Triboelectrification of plastic particles on a vibrating feeder

laminated with a plastic film," J Electrostat42, p.p. 6368, 1997.

[31] M.J. Pearse, and T.J. Hickey, "The separation of mixed plastics using a dry triboelectric technique,"

Resour Conserv Recy3, p.p. 179190, 1978.

[32] D.K. Yanar and B.A. Kwetkus, "Electrostatic separation of polymer powders," J Electrostat35, p.p.

257266, 1995.

[33] M. Miloudi, K. Medles, A. Tilmatine, M. Brahami andL .Dascalescu. "Optimisation of belt-type

electrostatic separationof granular plastic mixtures tribocharged in a propeller-type device," Journal of

Physics: Conference Series Volume 301 Number 1, 2011. 14 Apr2011 Electrostatics 2011 - 13th

International Conferenceon Electrostatics in Bangor, UK at Bangor University.


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[34] M. Miloudi, K. Medles, A. Tilmatine, M. Brahami and L. Dascalescu. "Modeling and Optimization of

a Propeller-type Tribocharger for Granular Materials," J. Electrostat.,vol. 69, p.p. 631-637, 2011.

application of triboelectric separation of plastics is relatively new. One of the earliest publications on

this subject dates back to the early 1990s and originates from Canadian researchers that developed a

triboelectric fluidizing bed (Fig. 13) for separation of different binary plastic mixtures results showed an

effective triboelectric separation of acrylic, nylon PE or PVC, achiev-ing a purity of 95% or more Later,

triboelectric charging of plastics by vibrating chute was also reported [53,54]. Moreover, Matsushita et

al.[56] triboelectrically sorted mixed plastics by means of a rotating drum (Fig. 15), which was comprised

of a cylinder with rotary blades, whose form was adapted to enhance mutual friction between plastic

pieces. He reported that a mixture of two kinds of plastics was success-fully separated and the purity of

products was not less than 90%

[52] I.I. Inculet and G.S.P. Castle, Tribo-electrification of commercial plastic in air. Inst. Phys. Conf., Ser.

N. 118: Sectin 4, paper presented at Electrstatics 91 (1991), pp. 217222.

[53] T. Fujita, Y. Kamiya, N. Shimizu and T. Tanaka, Basic study of polymer particles separation using

vibrating feeder and electrostatic high voltage generator. Proceedings of the Third International

Symposium on East Asian Resources Recycling Technology(1995), pp. 155164.

[54] M. Saeki, T. Inoue, M. Tukahara and H. Maehata, Vibro-electrostatic separation of plastics mixtures,

Transactions of the Japan Society of Mechanical Engineers, 68(2002), 1420. (In Japanese with English

abstract.)

[56] Y. Matsushita, N. Mori and T. Sometani, Electrostatic separation of plastics by friction mixer with

rotary drum blades,Electrical Engineering in Japan, 127(1999), 3340.

Electrostatic separation appears as possible method on their separation. At this method electric field

that is created between positive and negative electrode separates particles on the basisof charge size

and polarity. By electrostatic separation of HDPE/PP mixture with particle size 11 mm was made

possible from negative charged product to separate HDPE withrecovery 96.10% and from positive

charged product to separate PP with recovery 97.52%.


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Martin SISOL Frantika MICHALKOV Ivana KOZKOV Miroslava KOLESROV Triboelectric

separation of PE and PP from municipal wastes ACTA FACULTATIS ECOLOGIAE, 16: Suppl. 1, 5-10 Zvolen

(Slovakia), 2007

a three-component plastic mixture is purified by using the triboelectrostatic separation system, which

employed a tribo-cyclone and a high voltage supply. Products of ABS, PS and PP with a grade of 92.1%,

84.9% and 90.0% respectively have been achieved with recoveries above 73.0%

Gjergj Dodbiba, Atsushi Shibayama, Toshio Miyazaki and Toyohisa Fujita. Triboelectrostatic Separation

of ABS, PS and PP Plastic Mixture. Materials Transactions, Vol. 44, No. 1 (2003) pp. 161 to 166

Rodbibaet al.[60] employed an air cyclone as a charging device to produce a higher frictional speed. He

developed a triboelectric cyclone separa-tor (Fig. 16), which has been successfully tested in the

laboratory for separating plastics. Considering his experimental results, the recovery of each collected

product was higher than 75% while the purity was higher than 95%.

G. Dodbiba, A. Shibayama, T. Miyazaki and T. Fujita, Electrostatic separation of the shredded plastic

mixtures using a tribo-cyclone,Magnetic and Electrical Separation, 11(2001), 6392

Reactive blending

Blends of high-density polyethylene (HDPE) and polypropylene (PP) were prepared in different twin-

screw extruders. Two additives, a peroxide initiator and a polymerizable monomer, were added to the

polymeric feed components. A large influence on the physical properties, such as toughness and impact

strength,. and on the morphology was observed. Reactive extrusion substantially improves mechanical

properties: a three-fold increase of elongation at break and doubling of the impact strength. Variation of

extruder settings also had a large influence on the product; the final properties were improved when

the shear rate was raised, but sufficient residence time is necessary in reactive compatibilization.

R. HEl3EM.A. J. VANTOL, andL. P. B. M. JANSSEN. In-Situ Reactive Blending of Polyethylene andPolypropylene in Co-Rotating and Counter-Rotating Extruders. POLYMER ENGINEERING AND SCIENCE,

SEPTEMBER 1999, Vol. 39, NO. 9

An attractive alternative is chemical modification of a blend by reactive extrusion (5) which can be a

relatively cheap approach for improvement of the properties of a polymer blend (6). In a recent paper,


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Hu (7) performed both grafting of PP with glycidyl methacrylate and blending with PI3T in a one-step

extrusion process. The mechanical properties of the resulting blends were superior compared to the

uncompatibilized blend. Fellahi et al. (8) have improved the stress at break and the impact strength of

mixed plastics simply by processing it in the presence of a dialkyl peroxide. These improvements are

most likely due to the formation of copolymers acting as compatibilizer by recombination of

macroradicals. In addition, a reduction of the rheological mismatch for a blend containing low viscosity

PE and high viscosity PP can enhance dispersive mixing. This is caused by the preferred reaction of these

polymers with peroxide. The PE phase has a tendency for crosslinking (9). whereas PP with a peroxide

mainly results in chain scission. Randall et al. (10) describe the preparation of impact modified PP blends

by treating a reactor blend of PP and LLDPE with a peroxide. Various fragments will be present and

recombine to form block or graft materials. This method increases the Gardner impact strength by 30%.

Teh et al. (11) have concluded that one of the main problems in the modification of PE/PP blends with

peroxide is the difficulty in controlling the degradation of the PP. These unwanted side reactions, such

as chain scission and disproportionation, can be suppressed by addition of an unsaturated monomer

(12). One function of these low molecular weight compounds is to promote the formation of copolymers

(random, block or graft) resulting in improved compatibility. The monomer can stabilize the polyolefin

macro radical sites (13) formed by the peroxide radicals, and create interchain block or graft copolymers

by recombination. Another function of the monomer could be that of a vector fluid (14). This fluid is

preferentially immiscible with both phases and carries the reactive ingredients to the interface. If the

vector fluid is a polymerizable monomer, both polymers could obtain the Same grafts, resulting in

stronger interactions at the interface (15).

5. M. Xanthos, Reactive Extrusion, Principles and Practice, Hanser Publishers, Munich (1992)

6. W. Wiedemann and H. Wohlfart-Laymann. Kunstst0ffe German plastics, 82, 10 (1992)

7.


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The HyperSpectral Imaging (HSI) Technology

HyperSpectral Imaging [11] is a fast emerging technology that can be also profitably utilized for the

analysis of particulate solid systems in terms of composition and spatial distribution. The technology can

be used on-line and is cheap and powerful. HSI was originally developed for remote sensing applications

[12] but has found application in such diverse fields as astronomy [13, 14], agriculture [15- 17],

pharmaceuticals [18-20] and medicine [21-24]. In this last years several operative procedures and logics

based on such a technology have been developed both at research and application level also in the

recycling sector [25] for different waste materials [26, 27].

Hyperspectral cameras are able to deliver a wide spectrum of information on particulate solids streams.

Investigated spectral responses are usually those belonging to VIS (400-700 nm) and VIS-NIR (400-1000

nm and 1000- 1700 nm) wavelengths ranges; they are usually correlated to particle composition.

Together with spectral response other parameters are collected, as particle morphological and

morphometrical attributes distribution, spatial and temporal fluctuations of the particle stream, etc.

The development beyond the state-of-the-art will be to interpret the possibilities of HSI in determining

the quality of feed and product streams in the recycling of post-consumer waste and translate the

collected information into the parameters that are requested by the recycling operation, both in terms

of control strategies set up and products quality assessment at the different stages of the processing. As

an alternative to hyperspectral imaging, and to make operative comparisons, Dual Energy X-ray sensors

are investigated as a means to detect chlorinated or bromated plastics as well as metallic impurities in

the feed and separation products.

[12] A. F. H. Goetz, G. Vane, T. E. Solomn and B. N. Rck, Imaging spectrmetry fr earth remte sensing,Science, vol. 228, pp.1147-1153, September 1985.

*13+ E. Hege, D. OCnnell, W. Jhnsn, S. Basty and E. Dereniak, Hyperspectral imaging fr astrnmy and spacesurveillance,Proceedings of the SPIE, 5159, 2003, pp. 380-391.


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*14+ K. S. Wd, A. M. Gulian, G. G. Fritz and D. Van Vechten, A QVD detectr fr fcal plane hyperspectralimaging. Astrnmy.Bull. Am. Astronom. Soc., vol. 34, pp. 12-41, January 2002.

[15] S. Monteiro, Y. Minekawa, Y. Ksugi, T. Akazawa and K. Oda, Predictin f sweetness and amin acid cntentin sybean crps frm hyperspectral imagery, ISPRS J. Photogramm. Remote Sens., vol. 62, no. 1, pp. 2-12,

January 2007.

*16+ V. Smail, A. Fritz and D. Wetzel, Chemical imaging of intact seeds with NIR focal plane array assists plantbreeding, Vib.Spectrosc., vol. 42, no. 2, pp. 215-221, February 2006.

*17+ Y. Un, S. Prasher, R. Lacrix, P. Gel, Y. Karimi and A. Viau, Artificial neural netwrks t predict crn yieldfrom CompactAirbrne Spectrgraphic Imager data. Comput. Electron. Agric., vol. 47, no. 2, pp. 149-161, January 2005.

*18+ R. C. Lyn, D. S. Lester, E. N. Lewis, E. Lee, L. X. Yu and E. H. Jeffersn, Near-infrared spectral imaging forquality assurance f pharmaceutical prducts: analysis f tablets t assess pwder blend hmgeneity,AAPSPharm. Sci. Technol., vol. 3, no. 3, pp. 1-7, January 2002.

*19+ O. Rdinva, L. Humller, A. Pmerantsev, P. Geladi, J. Burger, V. Drfeyev, NIR spectrmetry forcunterfeit drug detectin: a feasibility study,Anal. Chim. Acta, vol. 549, no. 1-2, pp. 151-158, January 2005.

*20+ Y. Rgg, A. Edmnd, P. Chalus and M. Ulmschneider, Infrared hyperspectral imaging fr qualitative analysisof pharmaceutical slid frms,Anal. Chim. Acta, vol. 535, no. 1-2, pp. 79-87, January 2005.

*21+ D. Ferris, R. Lawhead, E. Dickman, N. Hltzapple, J. Miller and S. Grgan, Multimdal hyperspectral imagingfr the nn invasive diagnsis f cervical neplasia,J. Lower Genital Tract Dis., vol. 5, no. 2, pp. 65-72, January2001.

*22+ D. Kellicut, J. Weiswasser, S. Arra, J. Freeman, R. Lew and C. Shuman, Emerging technlgy: hyperspectral

imaging,Perspectives Vascular Surg. Endovasc. Ther., vol. 16, no. 1, pp. 53-57, January 2004.

*23+ G. Zheng, Y. Chen, X. Intes, B. Chance and J. D. Glicksn, Cntrast-enhanced near-infrared (NIR) opticalimaging forsubsurface cancer detectin,J. Porphyrins Phthalocyanines, vol. 8, no. 9, pp. 1106-1117, December 2004.

[24] A. A. Gwen, C. P. ODnnel, P. J. Cullen, G. Dwney and J. M. Frias, Hyperspectral imaging an mergingprcess analytical tl fr fd quality and safety cntrl, Trends Food Sci. Technol., vol. 18, pp. 590-598, April2007.

[25] S. Serranti and G. Bonifazi, Slid waste materials characterizatin and recgnitin by hyperspectral imagingbased lgics, The 2ndInt. Symposium MBT 2007: Mechanical Biological Treatment andAutomatic Sorting ofMunicipal Solid Waste, pp. 326-336, 2007.

[26] G. Bonifazi and S. Serranti, Imaging spectrscpy based strategies fr ceramic glass cntaminants remval inglass recycling, Int. J.Waste Manage., vol. 26, pp. 627-639, June 2006.

*27+ G. Bnifazi and S. Serranti Hyperspectral Imaging Based Techniques in Fluff Srting. The 21stInternationalConference onSolid Waste Technology and Management: ICSWM 2006, pp. 740- 747. March 26-29, Philadelphia, PA, USA.


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*28+ S. A. Sanaee and M. Bakker, Ultrasund fr mnitring and quality inspectin in MDS plastics recycling,ISWA-APESB, Lisbon, Portugal, 2009

HSI is a cost-effective emerging technology for the online assessment of particulate product streams.

The aim of the project is to develop this technology into a monitoring tool for detecting foreign

materials, such as rubber or wood in the input waste as well as in the polyolefin products. For the most

ambitious applications, the sensors must be able to recognize materials other than Polyolefins at levels

of 1% and less.

HSI is based on the utilization of an integrated hardware and software architecture able to digitally

capture and handle spectra, as an image sequence, as they results along a predefined alignment on a

surface sample properly energized.

According to the different wavelength of the source and the different spectral sensitivity of the device,

different physicalchemical superficial characteristics of the sample can be investigated and analyzed.

The hyperspectral imaging acquisition system adopted in this study is based on the utilization of a

device: the ImSpectorTM V10E, belonging to the ImSpector series spectrometers, developed by

SpecIm Oy, the system shown in (Fig. 5). The ImSpectorTM V10E operates in the spectral range

between 400 nm and 1000 nm with a resolution of 2.8 nm.

The acquired images are 780x580 pixel size, corresponding to 6.5x14.2 mm. The spectrograph is

constituted by optics based on volume type holographic transmission grating. The grating is used in

patented prism-grating-prism construction (PGP element) characterized by high diffraction efficiency,

good spectral linearity and it is nearly free of geometrical aberrations due to the on-axis operation

principle. A collimated light beam is dispersed at the PGP so that the central wavelength passes

symmetrically through the grating and prisms and the short and longer wavelengths are dispersed up

and down compared to central wavelength. This results in a minimum deviation from the ideal on-axis

condition and minimizes geometrical aberrations both in spatial and spectral axis. The result of

acquisition is a digital image where each column represents the discrete spectrum values of the


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corresponding element of the sensitive linear array. Such an archi tecture allws, with a simple

arrangement of the detectin device (scan line perpendicular to the moving direction of the objects)

to realize a full and continuous control. Line lighting, as energizing source with uniform spatial

distribution, was thus used.

Fig. (5). Hyperspectral Imaging (HSI) based acquisition device to collect secondary plastic particles flow streams spectra

Chlorosulfonation

Ultrasound process

A precise and on-line assessment of the composition of process streams is of the utmost importance for

both the recycling and compounder industry in the transition to the recycling of post-consumer wastes.

The former needs it to monitor the separation process. The latter demands it for the most accurate (and

fast) composition assessment to calibrate the extruders (equipments) and t fulfill custmers

requirements as well. Therefore fast on-line assessment is a key point to increase the value of secondary

Plylefins. The state-of-the-art analysis of PP or PE concentrates in terms of the concentration of the

other Polyolefin as well as non-polyolefin contaminants is by means of hand-sorting and thermal DSC

analysis of samples in the laboratory.

Other methods are CRYSTAF, Infra-red spectroscopy [9] and TREF [10]. Neither of these methods is

suitable and accurate for the required on-line quality assessment and so sensor technology must be


26/48

developed that is able to quantify the concentration of contaminants and particle size distribution in

each of the products. Ultrasound has proved to be a useful tool in the quality assessment of materials

and 4-D imaging of interfaces between solids and liquids. The technology is extremely advanced in

geology, navigation and in medical fields.

Applications also concern with leak detection, tightness testing, and predictive maintenance, etc.

Ultrasound imaging technology has developed very fast into a tool with a high resolution (about 1 mm

pixel width) and a short capture time (less than 0.1 second per frame). The special feature of the

technology is that the image clearly shows internal interfaces between solids and liquids with a slightly

different speed of sound. Therefore, the technique has the potential to measure both the spatial

distribution of solids as well as their shape and material/interface properties. Ultrasound imaging

technology uses the pulse-echo technique as in navigation (SONAR) and other applications. The

ultrasound arrays transmit ultrasonic sound pulses (also known as sound waves), into the part of

interest inside the imaged volume, which can range from industrial parts to organs of human bodies. As

soon as the sound waves hit the boundary between materials with different phases they are reflected

back to the probe/receiver. These ultrasonic echoes and the time intervals for them to be reflected are

recorded. From the time f each echs return and the known speed of sound, the distances of the

different interfaces from the probe/receiver are determined. Then data are processed by inversion

algorithms and the distances as well as the intensities of these echoes are displayed, resulting in a two,

three or four dimensional image (movie). Best results are obtained in applications where the various

materials have a comparable speed of sound, to facilitate a balance of transmission and reflection along

with the generation of echoes.

The development beyond the state-of-the-art in ultrasound technology in this project is to design an

array and solve the inverse problem of sound travelling through the suspension to create 4D images of

the suspension of particles in the MDS channel for the present application. The aim is to interpret the


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echo into the spatial distribution and brightness of particles. These data can be related to the apparent

density, internal speed of sound and surface texture of the particles and therefore to the quality of the

feed and the separation.

[10] N. Samoth, S. Tantayanon, V. Tangpasuthadol and K. Phalakornkul, Plyethylene Fractionation by

Modified Temperature Rising Elutin Fractinatin Technique. Proceeding of the 8th Polymers for Advanced

Technologies InternationalSymposium. Budapest, Hungary, 2005.

*11+ G. Bnifazi and S. Serranti, Hyperspectral Imaging Based Techniques in Particles and Particulate S lidsSystems Characterizatin. The 5th International Conference for Conveying and Handling of Particulate Solids:CHoPS-05, Sorrento, Italy, 2006.

Despite the potential accuracy of MDS, some contamination of the products is unavoidable due to the

natural overlapping of density ranges of the different materials. The extent to which this problem occurs

depends on the composition of the actual feed material and so it cannot be solved in the design stage.

For this reason, a precise and on-line assessment of the composition of process streams will be

developed on the basis of ultrasound to allow making the best possible product from a given feedstock.

The ultrasound imaging technology needed is beyond the state-of-the-art and aims to interpret the echo

from particles suspended in the magnetic fluid into the spatial distribution and brightness of materials,

such that differences between the various polyolefins and contaminants can be recognized and through

the differences of their spatial distribution can be translated into product qualities. The same ultrasound

technology is also crucial to detect obstructions of the flow or sub-optimal splitter settings.

To date the possibility to adapt off-the-shelf medical imaging technology was investigated with an eye

towards the real-time requirements for industrial MDS monitoring. It is shown that a medical system can

be adapted for monitoring the flowing plastics for particle speeds up to 30 cm/s. The imaging quality can

be quite good under optimum viewing angle conditions, and may then also allow for quantitative

through-put analysis (Fig. 4). Moreover the potential of ultrasound for materials characterization from


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inside the magnetic fluid was investigated through research on wave generation and propagation in

wave attenuating media through experiments and 3D acoustic modelling.

Using a calibrated measurement setup it has been shown that different polyolefin groups are

acoustically distinctive, which is the primary condition for ultrasound quality inspection.

Fig. (4). Example of the potentialities offered by the application of medical ultrasound imaging technology applied to plasticsparticles identification inside a fluid.

Partial oxidation

Thermal treatment

Mechanical treatment

Mechanical milling

Mechanical milling is the process whereby solid powders are generated, reduced in size and mixed

together to produce alloys at the molecular level. Application of this technique has lagged far behind

initial efforts by Shaw and Pan[1], followed by studies by Klementina and Torkelson[2], Smith et al.[35]

and Cavalieri et al.[6]. Various methods have been used by these researchers to pulverize the mixed


29/48

polymer. Ball milling was the most commonly used pulverizing technique, although Klementina used a

twin-screw extruder at cryogenic temperatures. Good improvements in the physical properties of the

resultant polymer have been reported in all the above-mentioned processes.

[1] J.K. Shaw, J. Pan, Microstructural Science 19 (1992) 659.

[2] K. Klementina, J.M. Torkelson, Solid-state shear pulverization of plastics: a green recycling process,

Polymer-Plastic Technology Engineering 38 (3) (1999) 445457.

[3] A.P. Smith, H. Ade, K.C. Koch, S.D. Smith, R.J. Spontak, Addition of block copolymer to polymer blends

produced by cryogenic mechanical alloying, Macromolecules 33 (2000) 11631172.

[4] A.P. Smith, H. Ade, K.C. Koch, S.D. Smith, R.J. Spontak, Solid-state blending of polymers by cryogenic

mechanical alloying, Material Research Society Symposium 629 (2000) 691696.

[5] A.P. Smith, H. Ade, C.C. Koch, R.J. Spontak, Cryogenic mechanical alloying as an alternative strategyfor the recycling of tires, Polymer 42 (9) (2000) 44534457.

[6] F. Cavalieri, F. Padella, S. Bourbonneux, C. Romanelli, Mechano-chemical recycling of mixed plastic

waste, retrieved fromhttp://modest.unipa.it/conferences/2000/html/symp9/P9Th01.pdf, 2000.

Cryogenic ball milling

Cryogenic ball milling is a mechanical alloying process where the high energy impact conditions in a ball

mill pulverizes the mixed plastics into a powder. Smith et al.[3 5]used SPEX 8000 mixer/mills

manufactured by SPEX Certiprep Sample Preparation Incorporated for the mech-anical alloying. This is a

high energy shaker mill capable of mixing up to 10 ml of material per batch. Milling was performed to

incorporate two rubbery polymers, polyiso-prene (PI) and polyethylene-alt-propylene (PEP) into a

commodity thermoplastic, polymethyl methacrylate (PMMA), which are known to be immiscible, and

found that blend was formed with acceptable mechanical proper-ties[3,8]. It took nearly 10 h to

pulverize the mixed polymer to a size of 2mm. The process was carried out at cryogenic temperatures by

means of liquid nitrogen[3,5]. Impact tests on PI/MI/PMMA 22/6/72 blends were reported to show an

improvement in the impact strength.

[7] A.P. Smith, Solid-State Blending and Compatibilization of Polymers by Cryogenic Mechanical Alloying,

PhD Thesis, North Carolina State University, 1999.
http://modest.unipa.it/conferences/2000/html/symp9/http://modest.unipa.it/conferences/2000/html/symp9/http://modest.unipa.it/conferences/2000/html/symp9/http://modest.unipa.it/conferences/2000/html/symp9/


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[8] A.P. Smith, J.S. Richard, H. Ade, S.D. Smith, C.C. Koch, High-energy cryogenic blending and

compatibilizing of immiscible polymers, Advanced Materials 11 (15) (1999) 12771281

Carbon dioxide assisted ball milling

Cavalieri performed mechanical alloying to reprocess mixed polymer waste of unspecified composition

by means of a high-energy ball milling process in a liquid carbon dioxide medium. The process was found

effective to pulverize polymer particles or shredded polymer films, in a very short-milling time,

promoting a substantial size reduction and mechano-chemical modification on the material, resulting in

good mechanical properties of the blend. The process claims to compatibilize polymeric mixtures,

regardless of the chemical composition[9]. This was reported effective to co-pulverize polymer particles

in a very short-milling time (10 min compared to 10 h in the previous case), while compatibilizing the

immiscible polymers involved in the mixed polymer waste [10]. Punch strength was reported to improve

with milling.

In the case of CO2assisted ball milling, CO2is claimed to act as catalyst, which enhances the mechano-

chemical effects promoted by the milling action. The energy transfer from the milling device to milled

powder occurs during the hit between balls and the vial wall. The CO2trapped between the ball and the

vial wall absorbs the energy of the hit and produces micro-explosive evaporation of liquid CO2that

disrupts the solid material[9]. Hence, the material is pulverized much quicker compared to the one using

liquid nitrogen.

[9] F. Cavalieri, F. Padella, High-energy mechanical alloying of thermoplastic polymers in carbon dioxide,

Polymer 43 (4) (2002) 11551161.

[10] F. Cavalieri, F. Padella, Development of composite materials by mechano-chemical treatment of

post-consumer polymer waste, Waste Management 22 (13) (2002) 913916

Cryogenic extrusion

Cryogenic extrusion refers to the mechanical alloying process using an extruder at cryogenic

temperatures. Solid-state shear pulverization (S 3 P) ([1113]) and the solid-state shear extrusion (S 3

E)[4,15]are similar cryogenic extrusion processes used to recycle single or commingled post- or pre-


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consumer polymeric waste. The S 3 P-made powders are reported to be melt-processable by all

conventional plastic fabrication techniques and possess a higher tensile strength and modulus compared

to the melt-extruded polymer. S 3 P has been used to recycle a wide range of post- and pre-consumer

plastics (HDPE, LDPE, PP, PS, PVC, PET), and their blends, into value added materials.

[11] K. Klementina, S. Carr, Solid-state Shear Pulverization: A New Polymer Processing and Powder

Technology, Technomic Publishing Company, Lancaster, PA, 2001.

[12] K. Klementina, E. Riddick, Recycling of post-consumer agricultural film via solid-state shear

pulverization, Global Plastics Environment Conference (GPEC 2002) of the Society of Plastics Engineers,

February 1314, Detroit, Michigan, 2002.

[13] K. Klementina, E. Stephen, A new environmentally friendly recycling technology: solid-state shear

pulverization (S3P), retrieved fromhttp://dtwws1.vub.ac.be/chis2/ISFR%202002%20CD/paper/A47.doc,

2002.

[14] F. Shutov, G. Ivanov, H. Arastoopour, Solid-state shear extrusion pulverization, US Patents

5,397,065, 1995.

[15] H. Arastoopour, Single-screw extruder for solid-state shear extrusion pulverization and method, US

Patents, 5,397,065, 1998

Solid state shear pulverization

Solid-state shear pulverization (SSSPTM/ is a novel, environmentally benign, and continuous processing

technique that applies high shear and compressive forces to polymeric materials, resulting infragmentation and fusion steps in the solid state.1 One key advantage of SSSP over conventional melt-

processing techniquese.g., twin screw-extrusion (TSE)is that SSSP overcomes physical hindrances

such as thermodynamic barrier and viscosity mismatch to synthesize materials with desired structures

(morphologies). Thus far, SSSP has been suc-cessfully employed for mechanochemical modification of

polymers, 25 compatibilization of polymer blends, 3, 4, 68 exfoliation and dispersion of fillers in

polymer nanocomposites,912 solid-state compound-ing of colored powders, 13 and recycling of

commodity plastics. 6, 1416 Despite its proven success in producing novel polymeric mat-erials with

enhanced properties, little has been published about the detailed mechanism of the process

1. K. Khait and S. H. Carr, Solid-State Shear Pulverization: A New Polymer Process-ing and Powder

Technology, Technomic Publ. Co., Lancaster, 2001.

2. C. Pierre, A. Flores, K. Wakabayashi, and J. M. Torkelson, Solid-state shear pulver-ization: an

alternative to nucleating agents for some semi-crystalline polymers, SPE ANTEC 66, p. 2082, 2008.
http://dtwws1.vub.ac.be/chis2/http://dtwws1.vub.ac.be/chis2/http://dtwws1.vub.ac.be/chis2/http://dtwws1.vub.ac.be/chis2/


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3. A. H. Lebovitz, K. Khait, and J. M. Torkelson, Sub-micron dispersed-phase particle size in polymer

blends: overcoming the Taylor limit via solid-state shear pulverization, Polymer 44 (1), pp. 199206,

2003.

4. Y. Tao, J. Kim, and J. M. Torkelson, Achievement of quasi-nano structured polymer blends by solid-

state shear pulverization and compatibilization by gradient copolymer addition, Polymer 47 (19), pp.67736781, 2006. doi:10.1016/j.polymer.2006.07.041

5. M. Diop and J. M. Torkelson, Ester functionalization and structural modification of polypropylene via

solid-state shear pulverization, SPE ANTEC, 2012. accepted

6. K. Khait and J. M. Torkelson, Solid-state shear pulverization of plastics: a green recycling process,

Polym.-Plast. Technol. Eng. 38 (3), pp. 445457, 1999. doi:10.1080/03602559909351592

7. M. Ganglani, J. M. Torkelson, S. H. Carr, and K. Khait, Trace levels of mechanochem-ical effects in

pulverized polyolefins, J. Appl. Polym. Sci. 80 (4), pp. 671679, 2001.

8. K. Wakabayashi, Y. Tao, A. H. Lebovitz, and J. M. Torkelson, Solid state shear pulver-ization as a real-

world process for polymer blends and nanocomposites, SPE ANTEC 65, p. 1528, 2007.

9. K. Wakabayashi, C. Pierre, D. A. Dikin, R. S. Ruoff, T. Ramanathan, L. C. Brinson, and J. M. Torkelson,

Polymer-graphite nanocomposites: effective dispersion and ma-jor property enhancement via solid-

state shear pulverization, Macromolecules 41 (6), pp. 19051908, 2008. doi:10.1021/ma071687b

10. J. Masuda and J. M. Torkelson, Dispersion and major property enhancements in polymer/multiwall

carbon nanotube nanocomposites via solid-state shear pulver-ization followed by melt mixing,

Macromolecules 41 (16), pp. 59745977, 2008. doi:10.1021/ma801321j

11. K. Wakabayashi, P. J. Brunner, J. Masuda, S. A. Hewlett, and J. M. Torkelson, Polypropylene-graphite

nanocomposites made by solid-state shear pulverization: effects of significantly exfoliated, unmodified

graphite content on physical, mechanical, and electrical properties, Polymer 51 (23), pp. 55255531,

2010. doi:10.1016/j.polymer.2010.09.007

12. J. Masuda and J. M. Torkelson, Polym. Eng. Sci, to be submitted.

13. P. Brunner and J. M. Torkelson, Overcoming technological issues associated with color additives in

polymers via solid-state shear pulverization, SPE ANTEC, in press.

14. K. Khait and S. H. Carr, Value-added materials made from recycled plastics, SPE ANTEC 55, p. 3086,1997.

15. K. Khait and S. H. Carr, Mixed polyolefin powders recycled via solid-state shear pul-verization

process, SPE ANTEC 56, p. 2533, 1998.

16. K. Khait and S. H. Carr, Toughened recycled polypropylene: blends produced via the solid-state shear

pulverization process, SPE ANTEC 56, p. 2939, 1998.


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Surface Plasmon Resonance

Polymer wise processing

Concluding remarks

Future prospects


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12. Tighzert, I.V.a.L., Review Biodegradable Polymers. Materials, 2009. 2: p. 307-344.13. Slabosz, T. Waste and Sustainability - Biodegradable and Non-Biodegradable Materials. 2009.14. Metzger P, L.C.B.b.,A rich source for hydrocarbons and related ether lipids. Appl Microbiol

Biotechnol, 2005. 66: p. 486-496.

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18. Galli P, V.G., Technology: Driving force behind innovation and growth of polyolefins. Prog PolymSci, 2001. 26(8).

19. Scott, G., Green polymers. Polym. Degrad. Stab, 2000. 68(1): p. 1-7.20. Wiles, G.S.a.D.M., Programmed-Life Plastics from Polyolefins: A New Look at Sustainability.

Biomacromolecules, 2001. 2(3).

21. Scott, G.,Atmospheric Oxidation and Antioxidants, Elsevier, Editor 1993: New York. p. Chapters3, 5, 8, and 9.22. Omichi, H., Degradation and Stabilisation of Polyolefins, N.S. Allen, Editor 1983, Applied Science

Publishers: London. p. Chapter 4.23. Scott, G., Biodegradable Plastics and Polymers, Y. Doi, Fukuda, K., Editor 1994, Elsevier Science

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25. Scott, G., Polymers and the EnVironment, 1999, Royal Society of Chemistry: Cambridge. p.Chapter 5.

26. Sanaee., M.C.M.B.a.S.A., Capabilities of Ultrasound for Monitoring and Quantitative Analysis ofPolyolefin Waste Particles in Magnetic Density Separation (MDS). The Open Waste ManagementJournal, 2010. 3.

27. Development and Forecast of China Polyolefin Industry, in CPIC2013, CNCIC Consulting:Singapore. p. 10.

28. ACHILIAS, D.S., ANTONAKOU, ., ROUPAKIAS, C., MEGALOKONOMOS, P., LAPPAS, A. ,RECYCLING TECHNIQUES OF POLYOLEFINS FROM PLASTIC WASTES. GLOBAL NEST JOURNAL,2008. 10(1).

29. Jakubowicz, I., Evaluation of degradability of biodegradable polyethylene (PE). Polym. Deg. Stab,2003. 80: p. 39-43.

30. Cornell, D.D., Plastics, Rubber, and Paper Recycling-A Pragmatic Approach. American ChemicalSociety, Washington,, 1995.

31. ; Available from: http://www.plasticseurope.org.32. (EEA), E.E.A., Earnings, jobs and innovation: the role of recycling in a green economy, in Plastics-

the Fact2011, EEA: Copenhagen.

33. .34. Van Ness, K.E.N., J.T. ; Ehrig, R.J., In Plastics Recycling, Products and Processes, R.J. Ehrig, Editor

1992, Hanser Publ: Munich. p. 187 pp.35. Pracella, M., Chionna, D., Ishak, R and Galeski, A, Recycling of PET and Polyolefin Based

Packaging Materials by Reactive Blending. POLYMER-PLASTICS TECHNOLOGY ANDENGINEERING, 2004. 43(6): p. 1711-1722.

36. Agency, E.E., Generation and recycling of packaging waste (CSI 017), 2010, EEA.37. Commission, E.,Assessment of the Environmental Advantages and Disadvantages of polymer

recovery processes, 2007, JRC IPTS (Joint Research Centre, Institute for ProspectiveTechnological Studies).

38. Plastemart.com, Overcapacity expected in ethylene uptil 2013, 2010.

39. Plastemart.com, PE, PP grow in 2009 in China, but supply to outpace demand growth in 2010,2010.40. Environment), E.C.D., Plastic waste in the environment - Final Report, 2011: Paris, France.

1. KMPG. The future of the chemical industry. 2010.2. Wurpel G., V.d.A.J., Pors J., Ten Wolde., Plastics do not belong in the ocean. Towards a roadmap

for a clean North Sea. IMSA Amsterdam, 2011.3. Yoshida H, S.K., Aizawa H. R, strategies for the establishment of an international sound material-

cycle society. Journal of Material Cycles and Waste Management, 2007. 9(2).4. Larsen AW, M.H., Mller J, Christensen TH. , Waste collection systems for recyclables: an

environmental and economic assessment for the municipality of Aarhus (Denmark). WasteManagement 2010. 30(5).



7. Cho, J.W.W., K.S.; Chun B.C.; Park, J.S, Ultraviolet selective and mechanical properties ofpolyethylene mulching films. Eur. Polym. J, 2001. 37: p. 1227-1232.


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8. Willett, J.L., Mechanical properties of LDPE/granular starch composites. J. Appl. Polym. Sci, 1994.54: p. 1685-1695.

9. Lawton, J.T., Effect of starch type on the properties of starch containing films. Carbohydr. Polym,1996. 29: p. 203-208.

10. Jaserg, B.S., C.; Nelsen, T.; Doane, W, Mixing polyethylene-poly(ethylene-co-acrylic acid)copolymer starch formulations for blown films. J. Polym. Mat., 1992. 9: p. 153-162.

11. Briassoulis, D., Mechanical behaviour of biodegradable agricultural films under real fieldconditions. Polym. Deg. Stab, 2006. 91: p. 1256-1272.

12. Tighzert, I.V.a.L., Review Biodegradable Polymers. Materials, 2009. 2: p. 307-344.13. Slabosz, T. Waste and Sustainability - Biodegradable and Non-Biodegradable Materials. 2009.14. Metzger P, L.C.B.b.,A rich source for hydrocarbons and related ether lipids. Appl Microbiol

Biotechnol, 2005. 66: p. 486-496.15. Frost JW, D.K., Biocatalytic syntheses of aromatics from D-Glucose - renewable microbial sources

of aromatic compounds. Annu Rev Microbiol, 1995. 49: p. 557-579.16. Scheeline HW, I.R., Ethylene to ethanol, in InProcess Economics Program Reports and

Reviews1980, SRI Consulting: Houston.17. Yamada H, K.M., Nitrile hydratase and its application to industrial production of acrylamide.

Biosci Bitechnol Biochem, 1996. 60: p. 1391-1400.18. Galli P, V.G., Technology: Driving force behind innovation and growth of polyolefins. Prog Polym

Sci, 2001. 26(8).19. Scott, G., Green polymers. Polym. Degrad. Stab, 2000. 68(1): p. 1-7.20. Wiles, G.S.a.D.M., Programmed-Life Plastics from Polyolefins: A New Look at Sustainability.

Biomacromolecules, 2001. 2(3).21. Scott, G.,Atmospheric Oxidation and Antioxidants, Elsevier, Editor 1993: New York. p. Chapters

3, 5, 8, and 9.22. Omichi, H., Degradation and Stabilisation of Polyolefins, N.S. Allen, Editor 1983, Applied Science


BV: Amsterdam. p. 79-91.24. Wiles, D.M., Tung, J. F., Cermak, B. E., Gho, J. G., Hare, C. W. J. . in Biodegradable Plastics. 2000.Frankfurt: European Plastics News.

25. Scott, G., Polymers and the EnVironment, 1999, Royal Society of Chemistry: Cambridge. p.Chapter 5.

26. Sanaee., M.C.M.B.a.S.A., Capabilities of Ultrasound for Monitoring and Quantitative Analysis ofPolyolefin Waste Particles in Magnetic Density Separation (MDS). The Open Waste ManagementJournal, 2010. 3.

27. Development and Forecast of China Polyolefin Industry, in CPIC2013, CNCIC Consulting:Singapore. p. 10.

28. ACHILIAS, D.S., ANTONAKOU, ., ROUPAKIAS, C., MEGALOKONOMOS, P., LAPPAS, A. ,RECYCLING TECHNIQUES OF POLYOLEFINS FROM PLASTIC WASTES. GLOBAL NEST JOURNAL,

2008. 10(1).29. Jakubowicz, I., Evaluation of degradability of biodegradable polyethylene (PE). Polym. Deg. Stab,

2003. 80: p. 39-43.30. Cornell, D.D., Plastics, Rubber, and Paper Recycling-A Pragmatic Approach. American Chemical

Society, Washington,, 1995.31. ; Available from: http://www.plasticseurope.org.32. (EEA), E.E.A., Earnings, jobs and innovation: the role of recycling in a green economy, in Plastics-

the Fact2011, EEA: Copenhagen.


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33. .34. Van Ness, K.E.N., J.T. ; Ehrig, R.J., In Plastics Recycling, Products and Processes, R.J. Ehrig, Editor

1992, Hanser Publ: Munich. p. 187 pp.35. Pracella, M., Chionna, D., Ishak, R and Galeski, A, Recycling of PET and Polyolefin Based

Packaging Materials by Reactive Blending. POLYMER-PLASTICS TECHNOLOGY ANDENGINEERING, 2004. 43(6): p. 1711-1722.

36. Agency, E.E., Generation and recycling of packaging waste (CSI 017), 2010, EEA.37. Commission, E.,Assessment of the Environmental Advantages and Disadvantages of polymer

recovery processes, 2007, JRC IPTS (Joint Research Centre, Institute for ProspectiveTechnological Studies).

38. Plastemart.com, Overcapacity expected in ethylene uptil 2013, 2010.39. Plastemart.com, PE, PP grow in 2009 in China, but supply to outpace demand growth in 2010,

2010.

1. KMPG. The future of the chemical industry. 2010.

2. Wurpel G., V.d.A.J., Pors J., Ten Wolde., Plastics do not belong in the ocean. Towards a roadmapfor a clean North Sea. IMSA Amsterdam, 2011.3. Yoshida H, S.K., Aizawa H. R, strategies for the establishment of an international sound material-

cycle society. Journal of Material Cycles and Waste Management, 2007. 9(2).4. Larsen AW, M.H., Mller J, Christensen TH. , Waste collection systems for recyclables: an

environmental and economic assessment for the municipality of Aarhus (Denmark). WasteManagement 2010. 30(5).



7. Cho, J.W.W., K.S.; Chun B.C.; Park, J.S, Ultraviolet selective and mechanical properties of

polyethylene mulching films. Eur. Polym. J, 2001. 37: p. 1227-1232.8. Willett, J.L., Mechanical properties of LDPE/granular starch composites. J. Appl. Polym. Sci, 1994.

54: p. 1685-1695.9. Lawton, J.T., Effect of starch type on the properties of starch containing films. Carbohydr. Polym,

1996. 29: p. 203-208.10. Jaserg, B.S., C.; Nelsen, T.; Doane, W, Mixing polyethylene-poly(ethylene-co-acrylic acid)

copolymer starch formulations for blown films. J. Polym. Mat., 1992. 9: p. 153-162.11. Briassoulis, D., Mechanical behaviour of biodegradable agricultural films under real field

conditions. Polym. Deg. Stab, 2006. 91: p. 1256-1272.12. Tighzert, I.V.a.L., Review Biodegradable Polymers. Materials, 2009. 2: p. 307-344.13. Slabosz, T. Waste and Sustainability - Biodegradable and Non-Biodegradable Materials. 2009.

14. Metzger P, L.C.B.b.,A rich source for hydrocarbons and related ether lipids. Appl MicrobiolBiotechnol, 2005. 66: p. 486-496.

15. Frost JW, D.K., Biocatalytic syntheses of aromatics from D-Glucose - renewable microbial sourcesof aromatic compounds. Annu Rev Microbiol, 1995. 49: p. 557-579.

16. Scheeline HW, I.R., Ethylene to ethanol, in InProcess Economics Program Reports andReviews1980, SRI Consulting: Houston.

17. Yamada H, K.M., Nitrile hydratase and its application to industrial production of acrylamide.Biosci Bitechnol Biochem, 1996. 60: p. 1391-1400.


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18. Galli P, V.G., Technology: Driving force behind innovation and growth of polyolefins. Prog PolymSci, 2001. 26(8).

19. Scott, G., Green polymers. Polym. Degrad. Stab, 2000. 68(1): p. 1-7.20. Wiles, G.S.a.D.M., Programmed-Life Plastics from Polyolefins: A New Look at Sustainability.

Biomacromolecules, 2001. 2(3).21. Scott, G.,Atmospheric Oxidation and Antioxidants, Elsevier, Editor 1993: New York. p. Chapters

3, 5, 8, and 9.22. Omichi, H., Degradation and Stabilisation of Polyolefins, N.S. Allen, Editor 1983, Applied Science


BV: Amsterdam. p. 79-91.24. Wiles, D.M., Tung, J. F., Cermak, B. E., Gho, J. G., Hare, C. W. J. . in Biodegradable Plastics. 2000.

Frankfurt: European Plastics News.25. Scott, G., Polymers and the EnVironment, 1999, Royal Society of Chemistry: Cambridge. p.

Chapter 5.26. Sanaee., M.C.M.B.a.S.A., Capabilities of Ultrasound for Monitoring and Quantitative Analysis of

Polyolefin Waste Particles in Magnetic Density Separation (MDS). The Open Waste Management

Journal, 2010. 3.27. Development and Forecast of China Polyolefin Industry, in CPIC2013, CNCIC Consulting:

Singapore. p. 10.28. ACHILIAS, D.S., ANTONAKOU, ., ROUPAKIAS, C., MEGALOKONOMOS, P., LAPPAS, A. ,

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