Umer Project Final

Introduction Ch-1 Recycling of mixed plastics waste

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CHAPTER-1

INTRODUCTION It would be hard to imagine a modern society today without plastics. Plastics have found a myriad of uses in fields as diverse as household appliances, packaging, construction, medicine, electronics, and automotive and aerospace components. As can be seen from this list, plastic technology can be applied with great success in a variety of ways. So what makes plastic such a versatile material? The reason for its success in replacing traditional materials such as metals, wood and glass in such a diverse range of applications, is the ability to modify its properties to meet a vast array of designers’ needs. This, plus the ease with which plastics can be processed, makes them ideal materials for the production of a variety of components. Management of waste is one of the major problems facing modern society and is not just limited to plastics. However, a combination of legislative measures and government initiatives, the increasing cost of landfill disposal and public interest in support of recycling has meant that plastics recycling must increase. Generally, plastics are made from crude oil. Recycling of plastics therefore helps to conserve this natural resource. Any strategy for waste management is based around three guidelines. • Avoidance, i.e., reducing and, if possible, avoiding producing waste at source. No waste = no problem. • Reclamation, the recovery of materials from the waste stream for recycling. • Elimination, the disposal of non-recyclable materials, for example by landfill. The second point can be applied to the problems of plastic waste by reclaiming material that is destined for landfi ll. Hence, plastic material recovered from the waste stream is termed ‘reclaim’. A summary of the terms introduced so far is given in Table 1.1.


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A substantial part of public solid waste (MSW) streams is composed of mixed polymers. High-density polyethylene (HDPE), polypropylene (PP) and polyvinyl chloride and PET (Polyethylene terephthalate) are among the most common plastics waste, since they are the most frequently used commercial plastics in our daily lives as well as in industries [1]. A number of approaches are currently being investigated for dealing with post consumer resin. Incineration for the purpose of waste-to-energy recovery is used in a number of countries, which are feared of pollution. Another solution that is currently being developed is pyrolysis. A number of companies are now introducing low levels of plastics waste into hydrocrackers that produce Naphtha, which can then be used as part of feedstock for other applications, including polymerization. A popular solution is the reuse of plastic parts, such as PET drinking bottles in many countries. The mixed plastics waste can be recycled in the form of blends [2-5]. The processing of plastics mixtures for recycling has been attempted with some success [6-11]. But the plastics fraction obtained by sorting municipal solid wastes often contains substantial quantity of paper. The reprocessing of such material is very difficult even at paper levels as low as 10% [12], beside this, the product’s appearance is unacceptable due to the inhomogeneity of the mixture, and the mechanical properties are unsatisfactory [13].

1.1 Polymers Polymers take their name from two Greek words: poli which means many and meros which means parts. This is because they are made up of a number of repeat units, called monomers. The simplest and most commonly used monomer is ethylene. Plastics can be subdivided into three main categories: thermoplastics, thermosets and elastomers. This distinction is based on both the molecular structure and the processing routes that can be applied. It also relates to recycling routes, as each of the categories needs a different approach to utilise recovery potential. Elastomers are beyond the scope of this book and will not be dealt with here. Thermoplastics and thermosets will now be introduced. 1.1.1. Thermoplastics These materials melt and fl ow when heated and solidify as they cool. On subsequent reheating they melt and regain the ability to fl ow. This means they can be reprocessed and hence recycled by remelting them. Thermoplastics are used to make consumer items such as drinks containers, carrier bags and buckets. The most common thermoplastic materials and their applications are shown in Table 1.2.


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1.1.2. Thermosets Thermoset materials are melt processed, often in a similar manner to thermoplastics. However, once formed and cooled they cannot be reprocessed, they decompose before they can melt. Therefore, they cannot be reprocessed in the same way as thermoplastics. This is because they are chemically crosslinked by a process termed ‘curing’. The result is a highly dense molecular network making the material stiff and brittle. Thermosets are often used where their strength and durability can be utilised. Common thermosets and their applications are shown in Table 1.3


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1.2 Effects of Processing on Thermoplastics Processing in its simplest form is the act of melting, forming and then solidifying the melt. During this procedure three things need to be considered [14]. • Deformation processes, which enable the product to be formed. • Heat and heat transfer, which enable the polymer to melt, fl ow and then solidify. • Changes to structure and properties as a result of processing. We will begin with a study of deformation processes and for this, we need to consider rheology. 1.2.1. Rheology Rheology is the study of deformation and fl ow. Consider the following examples of flow:

1. Squeezing toothpaste through a tube, 2. Tipping honey from a spoon, and 3. Pouring water into a glass.

In viscous flow, a material continues to deform as long as a stress is applied. polymers combine both viscous and elastic properties and demonstrate what is called a viscoelastic response to stress. Polymers are more viscous than most liquids. Polymers are more elastic than most solids. The interaction between viscosity and elasticity frequently determines the success of any processing operation. Processing must take into account not only how the polymers flow in their molten state but also how they change as the temperature goes up and down and the polymers melt and solidify. A cheap and simple method of determining and comparing the fl ow of melts under standard conditions is a Melt Flow Indexer. This works in a similar way to squeezing toothpaste from a tube. A vertical load is applied to a piston and the polymer melt is squeezed through a die. The amount of polymer that is extruded in a fi xed time gives a measure of the flow as a melt fl ow index (MFI). A highly viscous material will have a low MFI, a low viscosity material will have a high MFI. 1.2 2. Heat A thermoplastic cannot fl ow in its solid state. To enable it to fl ow it needs to be heated above its melting point (Tm). Some melting points of common plastics are shown in Table 1.4. Just from these examples, a wide range of melting points can be clearly seen. Once a polymer is heated above the melting point the viscosity will decrease as the temperature increases. The rate of this change varies, according to the particular type of material. Eventually the polymers will reach a point where they become thermally unstable and start to degrade. Generally, this shows itself as a discolouration with the melt turning yellow or brown. This can be a problem when processing mixed plastic fractions, because of the difference in processing temperature required to melt the various fractions contained in a heterogeneous mixture.


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1.3 Reprocessing of Thermoplastic Recyclates For reclaiming used material or recyclate outside of this scenario, the situation is slightly different and greater effort may be required on the part of the reprocessor. This type of mechanical recycling is termed secondary recycling (Table 1.5).

The material from external sources may be received in a variety of forms such as bales, mouldings or large lumps. It will probably need to be reduced in size, cleaned, separated and possibly recompounded and regranulated before it can be reprocessed in production. Often little is known about the history of the material to be recycled, for example: [15]

• How many times it has been reprocessed previously? • How much thermal degradation it has already undergone? • Is it in-house or external waste? • Is it a single material or a combination of plastics (commingled)? • Is it contaminated or uncontaminated? • What it was used for previously? • Has it been damaged due to outdoor exposure, weathering, etc?


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The characteristics of plastics can change depending on the exposure to thermal, mechanical (shear), oxidative and photochemical degradation processes. The characteristics of the recyclate may be quite different from those of the original virgin plastic. Ideally, to produce high quality products, high quality materials are required. For this, consideration must be given to a number of factors. It must be determined as to whether the material is pure or commingled and whether it is contaminated, for example, with metal or wood. For ease of feeding into the processing machines be they injection moulding, extrusion or blow moulding, the size and shape of the regrind (i.e., the bulk density) must be suitable. If the material is hygroscopic (water absorbing), for example polyamide, it may require pre-drying. Finally, should the recyclate be reprocessed on its own, mixed with other virgin material or modified with additives?

1.4 Recycling Techniques Despite increasing research efforts it is not yet economical to separate the wide variety of plastics that end up in the waste stream. The ideal is streams of single, clean and homogeneous recyclates, which present little technical effort for recycling. Of course, streams of this type, mainly industrial, can and are recycled. However, mixed waste streams present more of a technical and economic challenge to recover. Mixed plastic fractions reduce the quality of the products made from them quite considerably. This is due to differences in melting and processing temperatures and the lack of compatibility [16]. However the properties of mixed plastics waste is improved by using additives. A typical recycling route for waste plastics can be split into two types of processes:

1. Physical/mechanical treatment to prepare and homogenise the waste, and

2. Melt processing. Examples of stage one processes could include storage, size reduction, washing and sorting of the waste. Stage two would include regranulation and reprocessing. An outline of the various stages of the waste cycle is shown in Figure 1.1. These will now be discussed.


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Figure 1.1 A process stream for recycled plastic material 1.4 .1 Size Reduction Size reduction is necessary, because the material particles must be a suitable size for further processing. This may involve a two-stage process, the fi rst using a shredder to produce large particles of about 25-50 mm. These materials can then be fl aked. Rotary cutters are most commonly employed for the latter, as they can be used for comminuting (breaking down the size of) virtually any plastic. 1.4.2 Washing Washing is required to remove any dirt and residues adhering to the waste plastic. It increases the purity of the plastics and in some cases improves the effi ciency of other processes such as sorting. The principles are the same as those applied to any household washing detergent. The contaminants must adhere more strongly to the cleaning medium than the plastic to allow for removal. Washing also removes labels and water soluble glue residues. Once the materials are


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away. Thermal methods use hot air to dry the plastic fl akes. washed they then need to be dried. This can be done mechanically simply using gravity and a conveyor to allow any liquid to drain away. Thermal methods use hot air to dry the plastic flakes. 1.4.3 Identification and Sorting of Plastics One way to allow easy identification of plastics is to mark the mouldings. This is mandatory in the packaging industry, so turning over a plastic bottle or container should reveal a plastics identity code such as that shown in Figure 1.2. This allows the plastics to be sorted manually.

Figure 1.2 Society of Plastics Industry (SPI) packaging codes

Manual sorting is a very labour intensive process requiring equipment. FTIR can be used to identify the mixed plastics waste. 1.4.4 Agglomeration Agglomeration is a process stage to be carried out after the material is sorted into a fairly homogeneous stream. The aim of the agglomeration is to increase the bulk density of the waste, which is necessary to ensure good feeding for some plastication units. It finds most application in waste plastics with film flake, which can have a bulk density of just 100 to 150 kg/m3. This can make both feeding and storage cumbersome. Examples of fi lm waste before and after agglomeration are shown in Figure 1.3.

Figure 1.3 Film waste before and after agglomeration


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Agglomeration can be differentiated from processing as here the aim is simply to bond the flakes together at their surfaces and therefore only the surfaces of the plastics are affected. Pressing or fusion is used for this, with the material being thermally stressed on the surface particles only for a relatively short time.

1.5 Additives for Recyclates The two biggest problems associated with plastics recycling of post consumer products are

1. The degradation of the plastics as a result of both processing and service life. 2. The difficulties associated with getting acceptable material properties when processing

mixed plastics [17]. To slow down the degradation of plastics, stabilisation additives are employed. Other additives such as fi llers or modifi ers can be incorporated to improve the properties of the recyclates. These modifi ers can also be of benefi t in mixed plastic fractions. First the issues associated with the degradation of materials will be discussed. 1.5.1 The Degradation of Plastics Due to their chemical make-up, most plastics are susceptible to damage from the influence of the environment due to the action of light, heat and weathering. This ageing process is accompanied by a drop in both the visual (commonly seen in a yellowing of white carrier bags) and mechanical properties of the plastic, and it affects both virgin and recyclate materials alike. Plastics are also susceptible to damage from the shear force that can arise during standard manufacturing processes and granulation. This action is accelerated by the high temperatures involved. The result is chemical degradation due to molecular damage in the form of chain cleavage, crosslinking or the formation of a series of double bonds. Waste plastics, therefore, will have degraded to some degree following their original usage. The level of this degradation depends on the polymer type, on thermal and shear stress history and on the initial stabilization. Additives are commonly added to plastics to inhibit or slow down these reactions. 1.5.2 Restabilization of Recyclates Most plastics processors will reprocess their waste as a matter of course. It reduces their raw material costs as well as the cost of waste disposal. Often this material is simply fed back into the system along with virgin material. This presents few problems providing attention is paid to cleanliness and the reprocessed material has not been contaminated with dirt, oil or other types of material. The amount of degradation undergone by these materials will be dependent on the processing conditions that they were subjected to and the levels of stabilisers present. If these materials are to be used for a second application, it is possible to restabilise them. For this,


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knowledge of the type and amount of stabiliser originally used is required. Some stabilisers are consumed in the process of protecting the plastic and these materials need to be kept at optimum levels to ensure continued protection. Further testing may be required to assess the stability (both processing and long-term). a) Stabilizers

I. Thermal Stabilization

A combination of heat and oxygen will cause oxidation in the polymer, resulting in degradation. The mechanism is the formation of free radicals, which are highly reactive chemical species. This reaction can be observed, as the products will tend to show a discoloration to yellow or brown. Additives called antioxidants can be used to interrupt this mechanism. The chemicals most commonly employed are hindered phenols, which act as peroxide radical decomposers. Other additives can also be employed in addition to hindered phenols. Additives called phosphites combined with hindered phenols have a synergetic effect. This combination is especially effective for polyolefins. Perhaps the most well known example of the use of additives to prevent thermal degradation is in the thermal stabilization of polyvinyl chloride. The free radicals produced in this case are chlorine, leading to the formation of hydrochloric acid. The stabilisers must stop these reactions which lead to acid corrosion of the processing equipment. II. Light Stabilization

Light, especially in the ultraviolet range can induce photooxidation causing degradation and cleavage of the polymer chains. To deter this effect, three classes of additives can be employed. These additives are usually termed UV absorbers, quenchers (scavengers) and radical traps. b) Compatibilisers The major problem with mixing plastics is the fact that they are generally immiscible with each other. However useful combinations of immiscible materials are not uncommon. Blending of existing. polymers to create new ones is a cost effective method to create new materials, since synthesizing new polymers is both expensive and difficult. A common commercial example of a blend is high impact polystyrene, which is a blend of polystyrene and polybutadiene particles. Polybutadiene is a type of rubber that gives the blend greater impact resistance than could be achieved with polystyrene alone. Polystyrene has a high modulus. The combined result is a material that is both reasonably strong and has good impact resistance.

Literature Survey Ch-2 Recycling of mixed plastics waste

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Chapter-2

LITERATURE SURVEY Since the beginning of the plastics industry it has been recognized that blending yields materials with property profiles superior to the features of the individual components. The blending of polymers provides a means of producing new materials, which combine the useful properties of all of the constituents (Utracki, 2000). The technology of blending is now advancing at a rapid pace [18]. The ability to combine existing polymers into new compositions with commercial utilities offers the advantage of reduced research and development expense compared to the development of new monomers and polymers to yield a similar property profile [19]. An additional advantage is the much lower capital expense involved with scale-up and commercialization. Another specific advantage of polymer blends versus new monomer/polymer compositions is that blends often offer property profile combinations not easily obtained with new polymeric structures [20]. Blending technology is more useful in the field of plastics recycling. It is estimated that about one third of all commercially produced polymer materials are blends of two or more polymers.

Recycling of plastics discard is one method of reducing municipal solid waste. It is difficult, however, to expand plastics recycling because of the variety of plastics wastes, the difficulty of sorting different typed plastics, the low density of post-consumer plastics wastes in comparison to other recyclables and the limited history of plastics recycling. Because of its heterogeneous nature and the amount of contaminants present, separation of post-consumer mixed plastics waste is the most difficult. The term “mixed plastics,” a mixture of plastics types or a mixture of package types which may or may not be the same plastics type or color category, has been used to describe broad scale processing of post-consumer plastic waste. It is possible to recycled mixed plastics waste with limited separation.

The two main alternatives for treating municipal and industrial polymer wastes are energy recycling, where wastes are incinerated with some energy recovery and mechanical recycling. The incineration of polymer waste meets with strong Kyoto Protocol to consider, as the UK moves towards societal opposition [21] and, there is the its domestic goal of reducing carbon dioxide emissions by 20% by 2011 [22]. Mechanical recycling (the conversion of ‘‘scrap’’ polymer into new products) is a popular recovery path for manufacturers and is carried out on single-polymer waste streams as a market for recycled products can only be found if the quality is close to that of the original. Unfortunately these products are often more expensive than virgin plastic [23, 24]. In 2002 in the UK, only 17% of 3.8 million tones of was recycled by these methods, the remainder was polymer waste land-filled or incinerated (without energy recovery) [25].


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In1978 Ghaffar A. and Scott, G studied the Morphology and mechanical properties of virgin and recycled polyethylene/polyvinyl chloride blends. They prepared blends of virgin and recycled polyethylene (PE) and poly(vinyl chloride) (PVC), with a methylmethacrylate-ethylacrylate copolymer as a processing aid in a molten state. The blends' morphologies, tensile properties, and impact properties were studied. For blends with low copolymer concentration (below 3 wt %) the mechanical test data indicated a good performance. In the case of blends with ethylene methacrylic acid ionomer, improvements in the mechanical properties were obtained also at higher additive concentrations. Of the two peroxides, better results were obtained using the dibenzoyl one. The morphological studies indicated that the blends that showed good mechanical properties were better dispersed and had improved interphase adhesion.

Recycling of waste plastics as a blend of generic types is attractive since a difficult separations problem is avoided. However, blends of incompatible polymers are frequently very brittle and cannot be considered for many applications. Additives which modify the blend to give it ductility may provide a solution to this problem. In 1972 Paul D.R., Vinson C.E. and Locke C.E suggested that addition of CPE (chlorinated PE) to such a blend generally increases the elongation at break and the energy to break very dramatically with ordinarily some loss in strength and modulus. This approach worked most effectively in blends of high polyethylene and poly (vinyl chloride) content. Three grades of CPE were studied here which revealed that the specific structure of the CPE molecule is a factor.

Guowei Ma, Zhengping Fang and Chengwei Xu inquired the co-crosslinked products and the entrapping phenomenon that may exist in a poly(vinyl chloride)/ low density polyethylene/dicumyl peroxide (PVC/LDPE/ DCP) blend were investigated. The results of selective extraction show that unextracted PVC was due to not being co-crosslinked with LDPE but being entrapped by the networks formed by the LDPE phase. SBR, as a solid-phase dispersant, can promote the perfection of networks of the LDPE phase when it is added to the PVC/LDPE blends together with DCP, which leads to more PVC unextracted and improvement of the mechanical properties of PVC/ LDPE blends.

The mechanical properties of blends of isotactic polypropylene and high-density polyethylene with a postconsumer resin (recycled dairy containers) were investigated by Blom H.P., Teh J.W., and Rudin A. (1998) over the entire composition range. Modification of these blends with an ethylene/propylene/diene copolymer or an ethylene/vinyl acetate copolymer was also investigated. Isotactic polypropylene/postconsumer resin blends have satisfactory impact and tensile properties at postconsumer resin contents of less than 50% for certain applications. At higher postconsumer resin contents, the tensile properties were adversely affected. The impact properties remained satisfactory. Addition of an ethylene/propylene/diene copolymer improved the mechanical properties of these blends to levels equal to or greater than those for neat isotactic


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polypropylene. Ethylene/vinyl acetate copolymers were also able to improve the mechanical properties, but not as efficiently as did the ethylene/propylene/diene copolymer. Blends of high-density polyethylene and a postconsumer resin had poor impact and tensile properties. Although the ethylene/propylene/diene copolymer and ethylene/vinyl acetate copolymers were able to improve these properties, the improvement was insufficient for general recycling, except at lower (≤25%) postconsumer resin contents.

A mixture of seven immiscible “virgin” plastics, namely low and high density polyethylene (LDPE and HDPE), polypropylene (PP), polyvinyl chloride (PVC), crystal and high impact polystyrene (PS and HIPS), and polyethylene terephthalate (PET), in proportions representative of those currently found in post-consumer plastics containers, was compounded in a corotating twin-screw extruder. The mechanical properties of the blend were improved through the addition of relatively high concentrations of a dialkyl peroxide which was also found to drastically affect the blend morphology. The results are interpreted in terms of improved dispersive mixing favored by the similarity in the rheological behavior of the modified blend components, improved physical properties of certain blend components upon peroxide modification, and, possibly, enhanced intefacial adhesion [26].

Klason C., Gatenholm P., Kubat J., Mathiasson A., and Abom J., in 1991 executed the work on Recycling of Mixed Plastics Using Cellulosic Reinforcement. Their research demonstrated that the effect of combining chemithermomechanical pulp (CTMP) fibers and MAH-SEBS compatibilizer (maleic acid anhydride-grafted styrene-ethylene/butylene-styrene block copolymer) with a simulated waste plastic fraction composed of LDPE and HIPS (70:30) improve the mechanical properties of blend [27]. Experimental work demonstrated that an essential improvement of the mechanical properties of waste plastics can be obtained by the presence of cellulose fibers.

Great attention has been paid to the toughening of isotactic polypropylene (PP) in recent years in order to make full use of this plastic. Yang D., Zhang B., Yang Y., Fang Z., and Sun G., studied on the compatibility of PP with ethylene-propylene-diene rubber (EPT), polybutadiene rubber (PB) or styrene-butadiene rubber (SBR) through characterization of the blends' morphology, and on. the morphology and properties of binary blends of PP with EPT (EPT/PP) and ternary blends of PP, EPT, and polyethylene (PE) (EPT/PE/PP) [28]. Addition of EPT to EPT/PP made interesting changes in morphology but no effect on properties was observed.

Experimental Setup Ch-3 Recycling of mixed plastics waste

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CHAPTER-3

Experimental Setup Before any recycling methodology is adopted, the techniques to acquire the following data have to be developed.

• The number of times the selected waste has been reprocessed previously?

• The degradation it has already undergone

• Classification of waste

• Nature of the waste i.e. Single or a combination of plastics

• Degree of contamination

• Effect due to environmental exposure

• Use history.

3.1 Objectives of research • Characterization of polymer waster

• To improve the quality of products made from recycled material and to make these properties comparable to those obtained from the virgin polymer.

• To study the thermal and rheological behavior of recycled polymer blends

• To study the morphological structure of recycled polymer blends

• To find the optimum concentration of each component of waste in recycled polymer blends that give better properties at reduced cost

• To find the optimum concentration of filler, plasticizer and stabilizer in recycled polymer blends that give better properties at reduced cost


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3.2 Methodology

Brief description of how research was conducted


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3.3 Experimental set up.

Experimental set up consists of:

• Size reduction crusher

• Plasticoder

• Universal testing machine

• Compression molding machine

• FTIR

• DSC

• Melt flow indexer

• Scanning electron microscope (SEM)

3.4 Experimentation. Three commonly used plastics such as Polyethylene (PE), Polyvinylchloride (PVC) and Polyethylene terephthalate (PET) were selected for mixing.These polymers were crushed by using size reduction crusher. The blends of PP/PVC/PET were prepared by using Brabender plasticoder. The mixing time, rotation speed and temperature for the preparation of blend was 7 min, 80 rpm and 220 OC respectively. Additives were added during processing of blends. FTIR spectroscopy technique was executed to ascertain the nature of cross linking among three polymers. DSC was performed for thermal analysis of recycled. The compression moulding technique was used for preparation of testing bars. Tensile testing was performed on TIRA test 2810 machine, according to ASTM D-638. Impact property was determined using a falling weight impact tester, according to ASTM D-4224. Rheological properties were accomplished by melt flow indexer. To observe the morphology of various blends, compression moulded samples was sputtered with gold in vacuum. These samples were examined by scanning electron microscope (SEM)


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3.5 Recipe Ingredients

• Total weight of material 40 gm

• Polymer 70% and additives 30%

• Weight of polymer 28 gm

• Weight of additives 12 gm

Additives were used to enhance the mechanical, thermal and rheological properties of recycled polymer blends, For example

Sr. No Additives Function 1 EPDM Act as a compatiblizer and enhance the flow

properties as well as impact strength of recycled blends

2 Clay

To enhance the tensile properties of blends

3 Amines

To enhance thermal properties of recycled blends

When PET is variable

Sr .No PET% & gm PVC PE EPDM Clay AMINES 1 10% =2.8 45%=12.6 45%=12.6 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 2 20%= 5.6 40%=11.2 40%=11.2 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 3 30% =8.4 35%=9.8 35%=9.8 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 4 40%=11.2 30%=8.4 30%=8.4 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 5 50%=14 25%=7 25%=7 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 6 60%= 16.8 20%= 5.6 20%=5.6 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 7 70%= 19.6 15%=4.2 15%=4.2 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm)

When PE is variable

Sr .No PE% & gm PVC PET (EPDM) Clay AMINES 1 10% =2.8 45%=12.6 45%=12.6 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 2 20%= 5.6 40%=11.2 40%=11.2 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 3 30% =8.4 35%=9.8 35%=9.8 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 4 40%=11.2 30%=8.4 30%=8.4 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 5 50%=14 25%=7 25%=7 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 6 60%= 16.8 20%= 5.6 20%=5.6 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 7 70%= 19.6 15%=4.2 15%=4.2 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm)


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When PVC is variable

Sr .No PVC% & gm

PET PE (EPDM) Clay AMINES

1 10% =2.8 45%=12.6 45%=12.6 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 2 20%= 5.6 40%=11.2 40%=11.2 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 3 30% =8.4 35%=9.8 35%=9.8 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 4 40%=11.2 30%=8.4 30%=8.4 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 5 50%=14 25%=7 25%=7 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 6 60%= 16.8 20%= 5.6 20%=5.6 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm) 7 70%= 19.6 15%=4.2 15%=4.2 60% (7.2)gm 30% (3.6)gm 10% (1.2 gm)

IR-Analysis of recycled blend Ch-4 Recycling of mixed plastics waste

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Chapter-4

IR-Analysis of recycled Blend

4.1 Infrared spectroscopy

Infrared spectroscopy (IR spectroscopy) is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic techniques, it can be used to identify and study chemicals. A common laboratory instrument that uses this technique is a Fourier transform infrared (FTIR) spectrometer.

The infrared portion of the electromagnetic spectrum is usually divided into three regions; the near-, mid- and far- infrared, named for their relation to the visible spectrum. The higher energy near-IR, approximately 14000–4000 cm−1 (0.8–2.5 μm wavelength) can excite overtone or harmonic vibrations. The mid-infrared, approximately 4000–400 cm−1 (2.5–25 μm) may be used to study the fundamental vibrations and associated rotational-vibrational structure. The far-infrared, approximately 400–10 cm−1 (25–1000 μm), lying adjacent to the microwave region, has low energy and may be used for rotational spectroscopy. The names and classifications of these subregions are conventions, and are only loosely based on the relative molecular or electromagnetic properties.

4.2 Fourier transform

The Fourier transform is a mathematical operation that decomposes a signal into its constituent frequencies. Thus the Fourier transform of a musical chord is a mathematical representation of the amplitudes of the individual notes that make it up. The original signal depends on time, and therefore is called the time domain representation of the signal, whereas the Fourier transform depends on frequency and is called the frequency domain representation of the signal. The term Fourier transform refers both to the frequency domain representation of the signal and the process that transforms the signal to its frequency domain representation.

FTIR is a measurement technique that allows one to record infrared spectra. Infrared light is guided through an interferometer and then through the sample (or vice versa). A moving mirror inside the apparatus alters the distribution of infrared light that passes through the interferometer. The signal directly recorded, called an "interferogram", represents light output as a function of mirror position. A data-processing technique called Fourier transform turns this raw data into the desired result (the sample's spectrum): Light output as a function of infrared wavelength (or equivalently, wavenumber). As described above, the sample's spectrum is always compared to a reference.


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4.3 Principle of FTIR

In a Michelson interferometer adapted for FTIR, light from the polychromatic infrared source, approximately a black-body radiator, is collimated and directed to a beam splitter. Ideally 50% of the light is reflected towards the fixed mirror and 50% is transmitted towards the moving mirror. Light is reflected from the two mirrors back to the beam splitter and (ideally) 50% of the original light passes into the sample compartment. There, the light is focused on the sample. On leaving the sample compartment the light is refocused on to the detector. The difference in optical path length between the two arms to the interferometer is known as the retardation. An interferogram is obtained by varying the retardation and recording the signal from the detector for various values of the retardation (as shown in fig 4.1)

The interference pattern is converted into an electrical signal by the detector, and after being amplified by the main amplifier, is converted into signal. The spectrum in which the horizontal axis represents the light path difference between the moving mirror and fixed mirror and vertical axis represent light intensity is called interferogram. The intensity distribution with respect to wave number can be obtained by subjecting the interferogram to Fourier transformation. Therefore, the digital signal is subjected to Fourier transformation and the resulting spectrum is displayed on the PC monitor screen (as shown in Fig 4.2)

Fig- 4.1 Optical System


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Fig-4.2 Signal flow

4.4 Common Applications

• Identification of compounds by matching spectrum of unknown compound with reference spectrum (fingerprinting)

• Identification of functional groups in unknown substances

• Identification of reaction components and kinetic studies of reactions

• Identification of molecular orientation in polymer films

• Detection of molecular impurities or additives present in amounts of 1% and in some

cases as low as 0.01%

• Identification of polymers, plastics, and resins

• Analysis of formulations such as insecticides and copolymers


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4.5 FTIR Spectra of pure components (collection from waste)

4.5 (a) FTIR spectrum of PET


23

Classification: Aromatic Polyester-Polymer IR (Group: Poly (ethylene terephthalate)

Bond Range Mode p-DISUBST 3090-3070 CH STR p-DISUBST 3070-3050 CH STR p-DISUBST 3070-3050 CH STR p-DISUBST 3025-3015 CH STR

CH2 2970-2940 ASYM_STR CH2 2900-2850 SYM_STR C=O 1730-1710 STR

p-DISUBST 1615-1590 Ring p-DISUBST 1590-1570 Ring p-DISUBST 1520-1485 Ring

CH2 1470-1440 DEF p-DISUBST 1465-1440 Ring p-DISUBST 1420-1400 Ring

CH2 1370-1330 DEF_WAG CO 1270-1240 STR

Poly (ethylene terephthalate), PET, is manufactured as a polycondensation between ethylene glycol and terephthalic acid or dimethyl terephthalate. The relative intensities of the weak-medium intensity bands, in particular, can differ significantly depending on whether the sample is amorphous or crystalline and/or oriented, and consequently the spectrum can change quite markedly according to a sample’s morphology and processing history. The first overtone of the C=O near 1725 cm-1 can be observed as weak absorption band near 3410 cm-1.

In PET, the -CH2-CH2- unit, arising from the ethylene glycol monomer, can exist in either a trans or a gauche conformation, and while the trans can be present in both the crystalline and amorphous phases, the gauche form is only found in the amorphous phase. These conformers can have distinct bands, for instance, deformation bands associated with the trans conformer occur at ca. 1466, 1335 and 847 cm-1; while, the gauche conformer has bands at ca. 1449, 1368 and 896 cm-1.


24

4.5 (b) FTIR spectrum of PE


25

Classification: Saturated Aliphatic Hydrocarbon-Polymer IR (Group: Polyethylene)

Bond Range Mode CH3 2975-2950 ASYM_STR CH2 2940-2915 ASYM_STR CH 2920-2880 STR CH3 2885-2865 SYM_STR CH2 2870-2840 SYM_STR CH2 1480-1440 DEF CH3 1465-1440 DEF CH3 1390-1370 DEF CH 1360-1320 DEF CH3 1170-1160 DEF_WAG CH3 1000-950 DEF_ROCK CH2 825-790 DEF_ROCK

Syndiotactic form, which have different infrared spectra. Isotactic PE coils up into a 31 helical structure. The spectrum shown here is for crystalline isotactic PE, which is the most common form used in industry; syndiotactic PE has no commercial interest. To the low wavenumber side of the strong CH3 deformation mode band near 1375 cm-1, the mid-infrared spectrum of crystalline isotactic PP has many weak characteristic bands, many sharp, which includes bands with maxima near 1330, 1310, 1255, 1220, 1166, 1103, 999, 975, 900, 841 and 809 cm-1. The relative intensity of bands within the infrared spectrum of crystalline, isotactic PP will be affected to small extents by both the degree of crystallinity and molecular orientation. PE is also commonly copolymerized with ethylene, which gives rise to additional absorption features in the 740 to 710 cm-1 region. A weak -C=O band observed near 1725 cm-1 is usually indicative of the presence of an additive.


26

4.5 (c) FTIR spectrum of PVC


27

Classification: Halogenated-Polymer IR (Group: Poly (vinyl chloride)

Bond Range Mode CH 2975-2950 STR CH2 2945-2925 ASYM_STR CH2 2920-2900 SYM_STR CH2 1435-1425 DEF CH 1340-1310 DEF CH 1260-1240 DEF CC 1100-1080 STR

CH2 970-950 DEF_ROCK CH2 835-825 DEF_ROCK C-Cl 700-680 STR

Poly (vinyl chloride), PVC, is relatively hard, and is often plasticized. Common plasticizers are ortho-dialkyl phthalates, for example, di-n-butyl phthalate, di-(2-ethhyl-hexyl) phthalate. The most readily identifiable mid-infrared absorption features of these phthalates in PVC are the C=O (C=O stretch) near 1725 cm-1 and the C-O bands near 1280 cm-1 and 1125 cm-1, which are accompanied by a weak sharp, doublet at 1605 and 1575 cm-1. In plasticized PVC the C=O and the C-O bands may be the most intense in the spectrum. The absorptions in the CH stretching region will also be much more intense than in unplasticized PVC.

The C-Cl (C-Cl stretch) region of poly (vinyl chloride), PVC, is complex and involves the overlap of several absorption bands arising from differing conformational and configurational forms. VC units may be present in both isotactic and syndiotactic sequences. A Cl atom may exist in either a trans conformation to a H atom or to a C atom across the common C-C bond; both conformations are possible in both isotactic and syndiotactic PVC. Atactic sequences may also be present. Syndiotactic PVC may also be crystalline, and the amorphous to crystalline ratio will also affect the relative intensities of these overlapping C-Cl bands.


28

4.6 FTIR Spectrum of recycled blend


29

When blend formation takes place at 275oC, there may be formation of different types of copolymers and complex products owing to side reactions. FTIR analysis of recycled blend shows the possibility the formation of following complex compounds,

• Poly (n-butyl acrylate) • Ethylene/Vinyl Acetate Copolymer • Vinyl chloride/Vinyl acetate Copolymer • Vinyl Chloride/Ethylene Copolymer • Poly (vinyl benzoate)

4.6 (a) Aliphatic Polyester-Polymer IR (Group: Poly (n-butyl acrylate)

Bond Range Mode CH3 2975-2950 ASYM_STR CH2 2940-2915 ASYM_STR CH 2890-2880 STR CH3 2885-2865 SYM_STR CH2 2870-2840 SYM_STR C=O 1750-1725 STR

-CH2- 1480-1440 DEF CH3 1465-1440 ASYM_DEF CH3 1390-1370 SYM_DEF C-O 1275-1240 STR

The pair of C-O stretching bands near 1270 cm-1 and 1170 cm-1 is a characteristic of most acrylate resins. The lower wavenumber band component is the most intense. The ester C=O occurs near 1725 cm-1, and its first overtone can be observed as a weak absorption band near 3450 cm-1. The weak broad band near 733 cm-1 is indicative of three contiguous CH2- units, that is (CH2)3-; this rocking mode vibration originating from the n-butyl group in the side-chain. The band pattern between 1500 cm-1 and 450 cm-1 is the mid-infrared absorption ‘fingerprint’ that essentially characterizes poly (n-butyl acrylate). Acrylate esters are frequently copolymerized.


30

4.6 (b) Copolymer-Polymer IR (Group: Ethylene/Vinyl Acetate Copolymer)

Bond Range Mode CH3 2975-2950 ASYM_STR CH2 2940-2915 ASYM_STR CH2 2940-2915 ASYM_STR CH 2890-2880 STR CH3 2885-2865 SYM_STR CH2 2870-2840 SYM_STR CH2 2870-2840 SYM_STR C=O 1750-1725 STR CH2- 1480-1440 DEF CH2 1480-1440 DEF CH3 1465-1440 ASYM_DEF CH3 1390-1370 SYM_DEF

Copoly vinyl actetate; The infrared spectrum associated with this Note is that of an ethylene/vinyl acetate (EVA) copolymer containing 18% copolymerized VA. EVA copolymers used commercially may cover a wide range of compositions from; at least, 1% to 70% copolymerized VA. The relative values (e.g. S, M, W, etc) listed in the Intensity column relate to those expected within the spectrum of the homopolymer; the relative intensities listed in the Relative Intensity column (e.g. 9, 8, 7, etc.) indicate the relative intensities expected for absorption bands within an infrared spectrum of a copolymer similar to that associated with this Note. Homopolymer spectra may be found as: polyethylene, Aliphatic Saturated Hydrocarbon 2 class; poly (vinyl acetate), Aliphatic Ester 1 class.


31

4.6 (c) Copolymer-Polymer IR (Vinyl chloride/Vinyl acetate Copolymer)

Bond Range Mode CH 2975-2950 STR CH3 2975-2950 ASYM_STR CH2 2945-2925 ASYM_STR CH2 2940-2915 ASYM_STR CH2 2920-2900 SYM_STR CH 2890-2880 STR CH3 2885-2865 SYM_STR CH2 2870-2840 SYM_STR C=O 1750-1725 STR

-CH2- 1480-1440 DEF CH3 1465-1440 ASYM_DEF CH2 1435-1425 DEF CH3 1390-1370 SYM_DEF CH 1340-1310 DEF CH 1260-1240 DEF C-O 1245-1225 STR CC 1100-1080 STR C-O 1040-1000 STR C-Cl 700-680 STR

Copoly vinyl chloride; the infrared spectrum associated with this Note is that of a vinyl chloride/vinyl acetate (VC/VA) copolymer containing 17% copolymerized VA. VC/VA copolymers may cover a wide range of compositions. The relative values (e.g. S, M, W, etc) listed in the Intensity column relate to those expected within the spectrum of the homopolymer; the relative intensities listed in the Relative Intensity column (e.g. 9, 8, 7, etc.) indicate the relative intensities expected for absorption bands within an infrared spectrum similar to that associated with this Note. Homopolymer spectra may be found as: poly (vinyl chloride), Halogenated 1 class; poly (vinyl acetate), Aliphatic Ester 1 class


32

4.6 (d) Copolymer-Polymer IR (Vinyl Chloride/Ethylene Copolymer)

Bond Range Mode CH 2975-2950 STR CH2 2945-2925 ASYM_STR CH2 2870-2840 SYM_STR CH2 1480-1440 DEF CH2 1435-1425 DEF CH 1340-1310 DEF CH 1260-1240 DEF CC 1100-1080 STR

CH2 970-950 DEF_ROCK CH2 835-825 DEF_ROCK CCl 700-680 STR

Copoly vinyl chloride; The infrared spectrum associated with this Note is that of a vinyl chloride/ethylene copolymer containing ca. 39 mol-% copolymerized ethylene. The relative values (e.g. S, M, W, etc) listed in the Intensity column relate to those expected within the spectrum of the homopolymer; the relative intensities listed in the Relative Intensity column (e.g. 9, 8, 7, etc.) indicate the relative intensities expected for absorption bands within an infrared spectrum of a copolymer similar to that associated with this Note. Homopolymer spectra may be found as: poly(vinyl chloride), Halogenated 1 class; polyethylene, Aliphatic Saturated Hydrocarbon 2 class. The very weak band near 1750 cm-1 indicates the presence of a low concentration of a carbonyl containing material, which could arise from either an additive or contamination, or indicate presence of a low concentration of a copolymerized ester.

The absorption band near 750 cm-1 may be attributed to the methylene rocking mode vibration for a sequence of -CH2-CH2-CH2-. This indicates the ethylene is largely present as isolated copolymerized units. At higher ethylene concentrations then an absorption band at ca. 720 cm-1 becomes more pronounced, arising from longer methylene sequences, such as -(CH2)5-, -(CH2)7-, etc.


33

4.6 (e) Aromatic Polyester-Polymer IR Poly (vinyl benzoate)

Bond Range Mode Ph-R 3095-3070 CH STR Ph-R 3065-3045 CH STR Ph-R 3040-3020 CH STR CH2 2940-2915 ASYM_STR CH 2890-2880 STR CH2 2870-2840 SYM_STR C=O 1740-1715 STR Ph-R 1615-1590 Ring Ph-R 1590-1575 Ring Ph-R 1510-1485 Ring CH2 1480-1440 DEF Ph-R 1465-1440 Ring CH2 1350-1300 DEF CO 1290-1250 STR

The infrared spectrum of poly (vinyl benzoate) is dominated by the two strong ester bands near 1710 cm-1 (-C=O) and 1270 cm-1 (-C-O) and the aryl ring out-of-plane deformation band near 710 cm-1.

Morphological Characterization Ch-5 Recycling of mixed plastics waste

34

Chapter-5

Morphological Characterization

The morphology of the samples was studied using Scanning Electron Microscope in order to investigate the evolution of morphology generated during processing. The samples were fractured in liquid nitrogen, in specific directions in order to probe the morphology changes that occurring during flow in different directions. The surface of the specimen was coated with gold thin film by sputter coater for good conductivity. This scanning electron microscope has a magnification range from 15x to 200,000x and a resolution of 5 nanometers.

5.1 Scanning Electron Microscope (SEM)

SEM stands for scanning electron microscope. The SEM is a microscope that uses electrons instead of light to form an image. Since their development in the early 1950's, scanning electron microscopes have developed new areas of study in the medical and physical science communities. The SEM has allowed researchers to examine a much bigger variety of specimens.

The scanning electron microscope has many advantages over traditional microscopes. The SEM has a large depth of field, which allows more of a specimen to be in focus at one time. The SEM also has much higher resolution, so closely spaced specimens can be magnified at much higher levels. Because the SEM uses electromagnets rather than lenses, the researcher has much more control in the degree of magnification. All of these advantages, as well as the actual strikingly clear images, make the scanning electron microscope one of the most useful instruments in research today.

5.2 How does a SEM work?

The SEM is an instrument that produces a largely magnified image by using electrons instead of light to form an image. A beam of electrons is produced at the top of the microscope by an electron gun. The electron beam follows a vertical path through the microscope, which is held within a vacuum. The beam travels through electromagnetic fields and lenses, which focus the beam down toward the sample. Once the beam hits the sample, electrons and X-rays are ejected from the sample


35

.

Fig 5.1: Rays rejected from the sample

Detectors collect these X-rays, backscattered electrons, and secondary electrons and convert them into a signal that is sent to a screen similar to a television screen. This produces the final image.

Fig. 5.2: Internal Layout of SEM


36

5.3 How is a sample prepared?

Because the SEM utilizes vacuum conditions and uses electrons to form an image, special preparations must be done to the sample. All water must be removed from the samples because the water would vaporize in the vacuum. All metals are conductive and require no preparation before being used. All non-metals need to be made conductive by covering the sample with a thin layer of conductive material. This is done by using a device called a "sputter coater."

The sputter coater uses an electric field and argon gas. The sample is placed in a small chamber that is at a vacuum. Argon gas and an electric field cause an electron to be removed from the argon, making the atoms positively charged. The argon ions then become attracted to a negatively charged gold foil. The argon ions knock gold atoms from the surface of the gold foil. These gold atoms fall and settle onto the surface of the sample producing a thin gold coating.

5.4 SEM Micrograph of PE/PET/PVC recycled blend

Fig. 5.3: Scanning Electron Microscopy of PP/PET/PVC recycled blend

The fracture surfaces of PP/PET/PVC blend were observed by electron microscope. As shown in fig. 5.3, the dispersed phase is easy to be pulled from the blend and leaves uneven surface, indicating low immiscibility among three polymers. Because of the high interfacial tension, the morphology of recycled blend is not stable. Coalescence readily occurs in the molten state. As


37

suggested by Macosko et al., in melt mixing of immiscible polymer blends, the disperse phase is first stretched into threads and then breaks into droplets, which can coalesce together into large droplets. The balance of these processes determines the final dispersed particle sizes.

The crosslinking and the entrapping phenomenon may exist in a poly (vinyl chloride)/ polyethylene/ Polyethylene terephthalate (PVC/PE/ PET) blend as shown in fig 5.4. The results of selective extraction show that PVC was due to not being crosslinked with PE but being entrapped by the networks formed by the PE and PET phase as shown in fig 5.5. Fig 5.6 shows that EPDM, as a solid-phase dispersant, can promote the perfection of networks of the PE phase when it is added to the PVC/PE blends together with PET, which leads to more PVC unextracted and improvement of the mechanical properties of PVC/ PE blend.

Fig. 5.4: Entrapping phenomenon


38

Fig. 5.5: Non crosslinked PVC entrapped in PE and PET

Fig. 5.6

Rheological Properties of recycled blends Ch-6 Recycling of mixed plastics waste

39

Chapter-6

Rheological Properties of recycled blends

Rabinowitsch and Begley corrections


40


41

1. Results and discussion 1.1. Melt flow rate The melt flow rate is an indication of the flow ability of a polymer melts, one would; naturally, imagine it to increase with load and increasing temperature, since the molecular layers will become more slippery with increasing heat and shear stress. The net effect is that the molten polymer will flow more readily, the experimental results obtained in thiswork, as shown in Figures 1–3, having coordinated withthis expectation. The temperature rangeused in the current work was, from 260 to290°C. The MFRs of the blends measured with L/D=5circular die at different temperatures plotted as a function of load are shown in Figs. 1 and 2.

Fig. 1. Melt flow rate (g/10min) as a function of PE compositions at different Loads

0

20

40

60

80

100

120

0 20 40 60

MFR

(g/10m

in)

PE Composition( %)20 Kg 2.1 Kg 4 Kg 7 Kg 12 Kg


42

Fig. 2Melt flow rate (g/10min) as a function of PVC compositions at different Load

Fig. 3Melt flow rate (g/10min) as a function of Temperature (oC) for PET at different Load

0

20

40

60

80

100

120

0 20 40 60

MFR

(g/10m

in)

PVC Composition( %)20 Kg 2.1 Kg 4 Kg 7 Kg 12 Kg

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60

MFR

(g/10m

in)

PET Composition( %)

20 Kg 2.1 Kg 4 Kg 7 Kg 12 Kg


43

From Figures 1-3, it is obvious that melt flow rate for all three samples increases with increasing load. This is due to the fact that as load increases, force that is being applied on the melt present in the heated barrel increases that pushes the melt rapidly through the barrel and hence the melt flow rate is increased. Melt flow rate shows similar dependence (direct relationship) upon the temperature as show in figures 1-3. 1.2. Pseudo-plasticity To confirm the prediction made by the Figures 4-6: Flow curves has been drawn for all three blends for different die sizes.Polynomial curve fitting has been applied. It is clearly observed that for all die sizes, the behavior of all three samples is shear thinning (Pseudo-plastic).

(a)

0

100

200

300

400

500

600

0 200 400 600

Pressure (K

Pa)

Strain Rate (1/s)

PE 14%

PE 28%

PE 21%

PE 7%

PE 35%

PE 42%

PE 49%

0

100

200

300

400

500

600

0 100 200 300 400

Pressure (K

Pa)

Apparent Shear Rate (1/s)

PE 14 %

PE 28 %

PE 21 %

PE 7 %

PE 35 %

PE 42 %

PE 49%


44

(b)

(c)

(d)

Figure4. Curves demonstrating Pseudo-plasticity of Blend having variable composition of PE using capillary dies of

various lengths (a) 4mm (b) 10 mm and (c) 20mm (d) 30 mm.

0

100

200

300

400

500

600

0 100 200 300

Pressure (K

Pa)

Strain Rate (1/s)

PE 14%

PE 28%

PE 21%

PE 7%

PE 35%

PE 42%

PE 49%

0

100

200

300

400

500

600

0 30 60 90 120 150

Pressure (K

Pa)

Strain Rate (1/s)

PE 14%

PE 28%

PE 21%

PE 7%

PE 35%

PE 42%

PE 49%


45

(a)

(b)

0

100

200

300

400

500

600

0 200 400 600 800

Pressure (K

Pa)

Strain Rate (1/s)

PVC 14%

PVC 28%

PVC 21%

PVC 7%

PVC 35%

PVC 42%

PVC 49%

0

100

200

300

400

500

600

0 200 400 600

Pressure (K

Pa)

Strain Rate (1/s)

PVC 14%

PVC 28%

PVC 21%

PVC 7%

PVC 35%

PVC 42%

PVC 49%


46

(c)

(d)

Figure5. Curves demonstrating Pseudo-plasticity of PVC using capillary dies of various lengths (a) 4mm (b) 10 mm (c) 20mm (d) 30 mm

0

100

200

300

400

500

600

0 100 200 300 400

Pressure (K

Pa)

Strain Rate (1/s)

PVC 14%

PVC 35%

PVC 21%

PVC 7%

PVC 35%

PVC 42%

PVC 49%

0

100

200

300

400

500

600

0 100 200 300

Pressure (K

Pa)

Strain Rate (1/s)

PVC 14%

PVC 28%

PVC 21%

PVC 7%

PVC 35%

PVC 42%

PVC 49%


47

(a)

(b)

0

100

200

300

400

500

600

0 200 400 600 800

Pressure (K

Pa)

Strain Rate (1/s)

PET 14%

PET 28%

PET 21%

PET 7%

PET 35%

PET 42%

PET 49%

0

100

200

300

400

500

600

0 200 400 600

Pressure (K

Pa)


PET 14 %

PET 28 %

PET 21 %

PET 7 %

PET 35 %

PET 42 %

PET 49%


48

(c)

Figure6. Curves demonstrating Pseudo-plasticity of PETusing capillary dies of various lengths (a) 4mm (b) 10 mm (c) 20mm (d) 30 mm

0

100

200

300

400

500

600

0 100 200 300

Pressure (K

Pa)

Strain Rate (1/s)

PET 14% PET 28% PET 21% PET 7%

PET 35% PET 42% PET 49%

0

100

200

300

400

500

600

0 30 60 90 120 150

Pressure (K

Pa)

Strain Rate (1/s)

PET 14%

PET 28%

PET 21%

PET 7%

PET 35%

PET 42%

PET 49%


49

1.3. Apparent viscosity

Figures 7-9 demonstrate apparent viscosity as a function of apparent shear rate over range of temperature for various compositions of blends. Rise in temperature causes shear rate to increase due to higher melt flow rate. As both samples exhibit pseudoplastic behavior (shear thinning), increase in shear rate causes the viscosity to decrease. At constant temperature, increase in shear rate is due to increase in applied load that pushes the melt through the capillary.

Figure 7 Apparent Viscosity (KPa-sec) as a function of apparent shear rate (1/sec) for Blends having various

compositions of PE

0

5

10

15

20

25

30

0 100 200 300 400

App

aren

t Viscosity (K

Pa‐sec)


PE 28 %

PE 14 %

PE 21 %

PE 35 %

PE 7 %

PE 42%

PE 49%


50

Figure 8 Apparent Viscosity (KPa-sec) as a function of apparent shear rate (1/sec) for Blends having various compositions of PVC

Figure 9 Apparent Viscosity (KPa-sec) as a function of apparent shear rate (1/sec) for Blends having various compositions of PET

0

2

4

6

8

10

12

14

0 200 400 600

App

aren

t Viscosity (K

Pa‐sec)


PVC 14%PVC 28%PVC 21%PVC 7%PVC 35%PVC 42%PVC 49%

0

5

10

15

20

25

30

35

0 200 400 600

App

aren

t Viscosity (K

Pa‐sec)


PET 14%PET 28%PET 21%PET 7%PET 35%PET 42%PET 49%


51

1.4. Bagley correction

The excess pressure losses due to end effects in the capillary flow of all blends were studied. The "entrance pressure" (Bagley correction) is the pressure drop associated with the flow of the polymer in the converging entry to the capillary die as well as at the exit (but mainly it is the former). These losses were determined experimentally by extrapolating experimental data of pressure drop versus length-to-radius ratios (L/D) to zero capillary length. These data were plotted on a Bagley plot (pressure drop versus capillary length for several values of apparent shear rate and consequently were extrapolated to obtain the pressure at zero L/D. By this method, one effectively subtracts out he viscous pressure drop (corresponding to fully developed flow) from the total pressure.

(a)

0

500

1000

1500

2000

2500

3000

0 10 20 30 40

Pressure(KPa)

L/R

Strain rate 01 Strain Rate 100

Strain rate 200 Strain rate 600


52

(b)

(c)

y = 0.609x + 3.589R² = 0.990

4.34.354.4

4.454.5

4.554.6

4.654.7

4.754.8

4.85

0 1 2 3

Log (She

ar stress)

Log (Shear Rate)

y = 0.609x + 3.589R² = 0.990

4.34.354.4

4.454.5

4.554.6

4.654.7

4.754.8

4.85

0 1 2 3

Log (She

ar stress)

Log (Shear Rate)


53

(d)

(e)

y = 0.576x + 3.440

4.34.354.4

4.454.5

4.554.6

4.654.7

4.754.8

4.85

0 1 2 3

Log (She

ar stress)

Log (Shear Rate)

y = 0.641x + 3.218

4.34.354.4

4.454.5

4.554.6

4.654.7

4.754.8

4.85

0 1 2 3

Log (She

ar stress)

Log (Shear Rate)


54

(f)

(g)

Figure 12 (a) Bagley correction plot (b, c, d, e, f) Determination of power law index and

consistency parameter at various compositions (PE 7%, PE 14% ,PE 21% ,PE 28% ,PE 35% ,PE 42% , PE 49% ) respectively

y = 0.703x + 2.952

4.34.354.4

4.454.5

4.554.6

4.654.7

4.754.8

4.85

0 1 2 3

Log (She

ar stress)

Log (Shear Rate)

y = 0.692x + 2.918

4.34.354.4

4.454.5

4.554.6

4.654.7

4.754.8

4.85

0 1 2 3

Log (She

ar stress)

Log (Shear Rate)


55

1.4. Viscosity Plots

To take into account the pseudoplastic nature of once recycled and twice recycled PET, correction has been made in the apparent viscosity and apparent shear rate values.

(a)

(b)

0

5

10

15

20

25

30

35

40

0 50 100 150 200

True

Viscosity (KP

a‐sec)

True Strain Rate (1/s)

PE 28% PE 14% PE 21%PE 35% PE 7% PE 42%PE 49%

0

2

4

6

8

10

12

14

0 200 400 600

App

aren

t Viscosity (K

Pa‐sec)


PVC 14%PVC 28%PVC 21%PVC 7%PVC 35%PVC 42%PVC 49%


56

(c)

Figure 10 True Viscosity (KPa-sec) as a function of True shear rate (1/sec):

(a) PE (b) PVC (c) PET

Curves of elongational viscosity for once and twice recycled PET at different temperatures are shown in Figure 14. As shear rates increases, the viscosities decrease in a non linear fashion. But it is evident from the curves that the viscosity decreases by increasing temperatures. Elongational viscosities maintained the similar temperature dependence to that ofshear viscosities i.e., decreasing by increasing the temperature.

0

5

10

15

20

25

30

35

0 200 400 600

App

aren

t Viscosity (K

Pa‐sec)


PET 14%

PET 28%

PET 21%

PET 7%

PET 35%

PET 42%

PET 49%


57

(a)

(b)

0

10

20

30

40

50

60

0 200 400 600

Elon

gation

al Viscosity(Kpa

.s)

Shear Rate(1/sec)

PE 35%

PE 28%

PE 21%

PE 14%

PE 7%

PE 42%

PE 49%

0

10

20

30

40

50

60

0 200 400 600

Elon

gation

al Viscosity(Kpa

.s)

Shear Rate(1/sec)

PVC 35%

PVC 28%

PVC 21%

PVC 14%

PVC 7%

PVC 42%

PVC 49%


58

Figure 11 Elongational viscosities vs. shear rate at different temperatures for 10mm die

(a) PE (b) PVC (c) PET 1.5. Power Law Fluid model parameters

The power law index increases with increasing temperature for all blends samples. It is very clear from the Figure 12 that power law index for blend having varying composition of polyethylene increases with increasing composition. As composition of polyethylene increases, the composition of PVC and PET is decreased in the blend, and the material approaches to the Newtonian fluids behavior due to increase in power law index values.

Figure 13 Effect of Temperature on power law index ‘n’

0

10

20

30

40

50

60

0 200 400 600

Elon

gation

al Viscosity(Kpa

.s)

Shear Rate(1/sec)

PET 35%

PET 28%

PET 21%

PEt 14%

PET 7%

PET 42%

PET 49%

0.5

0.55

0.6

0.65

0.7

0.75

0 10 20 30 40 50 60

Power Law

Inde

x 'n'

Composition %


59

Figure 15Effect Of temperature on Consistency index

It is observed in Figure 14 that with increase in temperature, consistency index shows a decreasing trend. The reason behind is the fact that as composition of polyethylene increases melt flow rate increases (less viscosity) as shown in Figures1-3. As melt flow rate increases melt behavior shifts towards Newtonian fluids. Power law index moves towards unity and consistency index (intercept of log (shear stress) vs.log (shear rate) plot) approaches zero value.Consistency index of Newtonian fluids is zero. At higher polyethylene compositions, viscosity decreases so both melts approach towards Newtonian fluids.

0.4

0.42

0.44

0.46

0.48

0.5

0.52

0.54

0.56

0 0.5 1 1.5 2

Power Law

Inde

x 'n'

Composition %

Mechanical Properties of recycled blends Ch-7 Recycling of mixed plastics waste

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Chapter-7

Mechanical Properties of recycled blends The mechanical properties measurements were done on a TIRA Testing machine 2810 E6 using dumb-bell shaped specimens at crosshead of 10mm min-1 with ASTM D-638. The samples for mechanical testing were cut from the films produced by standard dies. 7.1 Results and discussion

The results obtained from the mechanical testing are indicated in the figures below. Fig.1 indicates that tensile strength of recycled blends increases with increase of respective component in each blend. But this effect is more prominent in case of PET/PE/PVC blends and least prominent in case of PET/PV/PE recycled blends. Similar observations has been observed in case of modulus as shown in fig.2 But elongation at break decreases with increase of polymer contents in each recycled blends. This phenomena is more salient in case of PET/PVC/PE as demonstrated in fig.2

Fig-1

0

5

10

15

20

25

30

35

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Tensile

Stren

gth (M

Pa)

composition of recycled blends (%)

Tensile strength of recycled polymer blends

PE/PET/PVC

PET/PE/PVC

PET/PVC/PE

Mechanical Properties of recycled blends Ch-7 Recycling of mixed plastics waste

61

Fig-2

Fig-3

0

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60

Mod

ulus (M

Pa)

comosition of recycled blends (%)

Modulus of recycled polymer blends

PE/PET/PVC

PET/PE/PVC

PET/PVC/PE

0

5

10

15

20

25

0 10 20 30 40 50 60

elon

gation

at break (%

)

composition of recycled polymer blends (%)

Elongation at break of recycled blends

PE/PET/PVC

PET/PE/PVC

PET/PVC/PE

Conclusion & Recommendations Ch-8 Recycling of mixed plastics waste

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Chapter-8

CONCLUSION & RECOMMENDATIONS 8.1 Conclusion

As recycling of plastics becomes inevitable for sustainable development, the challenges of using these recycled materials to make useful products will increase. The challenges are significant with recycled plastics because as their properties are usually not as good as their virgin counterparts. In order to characterize the properties of a given batch of recycled plastic extensive testing of each blend needs to be done. Once the testing establishes the properties, the next step is to establish the suitability of a given blend for use in a commercial application. Suitability of recycled plastics can be established either by building a prototype similar to the targeted product and then testing it.

The results in this analysis indicate that MFI increases with increase of PET concentration in PE/PET/PVC recycled blends. But MFI decreases with increase of PVC and PE in PET/PVC/PE and PET/PE/PVC recycled blends respectively. Viscosity increases with decreasing shear rate and shear rate thinning behavior is to be observed. It is also observed that melt flow rate for all these recycled blends increases with increasing load. This is due to the fact that as load increases, force that is being applied on the melt present in the heated barrel increases that pushes the melt rapidly through the barrel and hence the melt flow rate is increased. Melt flow rate shows similar dependence (direct relationship) upon the temperature. Results demonstrate that apparent viscosity as a function of apparent shear rate over range of temperature for various compositions of blends. Rise in temperature causes shear rate to increase due to higher melt flow rate. As both samples exhibit pseudo plastic behavior (shear thinning), increase in shear rate causes the viscosity to decrease. At constant temperature, increase in shear rate is due to increase in applied load that pushes the melt through the capillary. Elongation viscosities maintained the similar temperature dependence to that of shear viscosities i.e., decreasing by increasing the temperature. The power law index increases with increasing temperature for all blends samples. It is clear from the results that power law index for blend having varying composition of polyethylene increases with increasing composition. As composition of polyethylene increases, the composition of PVC and PET is decreased in the blend, and the material approaches to the Newtonian fluids behavior due to increase in power law index values.

The mechanical properties of recycled blends are improved by adding EPDM and clay. Results indicate that enhanced tensile strength and elongation at break is achieved for all these blends.

Conclusion & Recommendations Ch-8 Recycling of mixed plastics waste

63

Micrographical studies revealed that the dispersed phase is easy to be pulled from the blend and leaves uneven surface, indicating low immiscibility among three polymers. Because of the high interfacial tension, the morphology of recycled blend is not stable. Coalescence readily occurs in the molten state.

FTIR studies divulged that when blend formation takes place at higher temperature, there will be a formation of different types of copolymers and complex products owing to side reactions.

8.2 Recommendations

Further study would strengthen the understanding of the recycling of plastics,

• Development of techniques to increase the recyclability of polymers

• Modification of recycled material (addition of additives during processing)

• Study of the effect of binary, tertiary and higher order blends on crystallization, melting, rheology, mechanical properties and morphology

• Conversion of non-upgradeable waste materials into composites and low cost fillers and insulating material

• Understand the mechanism by which stabilizers can stop the reduction of mechanical properties of polymers in polymer waste recycling process

References Recycling of mixed plastics waste

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REFERENCES

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