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POLYMERS TO POLLUTION: AN EXAMINATION OF POLYURETHANE FOAM
AND SOLUTIONS FOR ITS DEVASTATING EFFECTS ON THE ENVIRONMENT
by
Erin Straw
BS, University of Pittsburgh, 2014
Submitted to the Graduate Faculty of
Environmental and Occupational Health
Graduate School of Public Health in partial fulfillment
of the requirements for the degree of
Master of Public Health
University of Pittsburgh
2017
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UNIVERSITY OF PITTSBURGH
GRADUATE SCHOOL OF PUBLIC HEALTH
This essay is submitted
by
Erin Straw
on
April 28, 2017
and approved by
Essay Advisor:Jim (James) Peterson, PhD ____________________________________Department of Environmental and
Occupational HealthGraduate School of Public HealthUniversity of Pittsburgh
Essay Reader:George C. Bandik, PhD ____________________________________Department of ChemistryDietrich School of Arts and SciencesUniversity of Pittsburgh
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Copyright © by Erin Straw
2017
ABSTRACT
Contrary to what many still believe, global warming is a serious issue that demands answers
now. One effective, and rather simple, method to combat climate change is to recycle.
Recycling reduces greenhouse gas emissions as well as the total amount of waste disposed.
Unfortunately, the amount of waste being thrown away is increasing, but recycling is not. Due
to new political circumstances, one being that the new head of Environmental Protection Agency
is a climate change denialist, environmental responsibilities will shift to local governments and
communities. An area of recycling innovation revolves around polyurethane foam, a low
density, high volume material that makes its way into landfills and oceans around the world.
This essay takes a comprehensive look at public health significance of polyurethane foam, its
effects on the environment and promising mitigations.
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James Peterson, PhD
[POLYMERS TO POLLUTION: AN EXAMINATION OF POLYURETHANE
FOAM AND SOLUTIONS FOR ITS DEVASTATING EFFECTS ON THE
ENVIRONMENT
Erin Straw, MPH
University of Pittsburgh, 2017
TABLE OF CONTENTS
1.0 INTRODUCTION.........................................................................................................1
2.0 REVIEW: BACKGROUND OF POLYURETHANE FOAM..................................3
2.1 PROPERTIES, USES AND POLYURETHANE FOAM WASTE.................3
2.2 SYNTHESIS AND PRODUCTION OF POLYURETHANE FOAM.............5
3.0 ANALYSIS: ENVIRONMENTAL SOLUTIONS TO POLYURETHANE FOAM
POLLUTION.................................................................................................................................9
3.1 DISPOSAL AND RECYCLING METHODS....................................................9
3.2 ENVIRONMENTALLY FRIENDLY POLYURETHANE FOAM FOR
IMPROVED DEGRADATION.........................................................................................16
4.0 CONCLUSION...........................................................................................................18
BIBLIOGRAPHY........................................................................................................................21
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LIST OF FIGURES
Figure 1. Polyurethane Synthesis Reaction.....................................................................................6
Figure 2. Polyether vs. Polyester Structures....................................................................................7
Figure 3. Cyclical Incorporation of Hydrogen Cyanide................................................................11
Figure 4. Glycolysis of Polyurethane Foam..................................................................................15
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1.0 INTRODUCTION
One field where simple changes can be made to improve environmental health is
recycling. Recycling waste can recover not only reusable materials, but also energy which can
then be used to provide power and electricity. Recycling materials has benefits including
reducing the amount of greenhouse gas emissions as well as the total amount of waste disposed.
Unfortunately, the amount of waste thrown away is increasing, but recycling is not keeping pace;
for instance, 254 million tons of trash was produced by Americans in 2013, but only a 34.3%
recycling rate was obtained [18]. It has been estimated that more than five trillion plastic pieces
are currently polluting the world’s oceans, the most visible being foamed materials [8].
One of the most desirable qualities of plastics and foams is their high durability, which
unfortunately, pairs with poor environmental degradation [13]. In 2000, Japan enacted the “The
Basic Law for Establishing the Recycling Based Society” which included reduction of pollution
through restrictions in the generation of waste, reuse of materials, recycling and appropriate
disposal of waste; feasible steps that can be applied to any society [9]. Since so many novel
materials are present in the world today, some of them produced in vast quantities, improvement
in overall waste reduction of any one of them would likely be beneficial to the environment and
the organisms that rely on it.
Political side note: Following the 2016 presidential election, the United States of America
was faced with new policies and regulations that many individuals have deemed as controversial.
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The newly elected, 45th president has promised to increase factories and manufacturing here in
the US, as well as the utilization of US resources including coal and natural gas [14].
Unfortunately, an increase in these practices means an increase in burning of fossil fuels,
consequent pollution and, ultimately, an increase in climate change and its results. Previously,
these factors have not been as much of a concern, as branches of government exist, like the
Environmental Protection Agency, that uphold the standards and regulations in place to protect
the environment and provide clean air and water for the people and other resident organisms.
However, the newly appointed Head of the Environmental Protection Agency is on record a
denialist of climate change [15,16]. Since the inauguration, resources like the White House
climate change web site have been removed, reducing climate change information to the public
[17]. Without the support of the federal government, protecting the environment is placed in the
hands of individuals and local governments requiring effort at new levels across the nation in
order to reduce the inevitable effects of global warming and increased pollution.
This essay is an in-depth examination of an everyday material, polyurethane foam,
especially its properties and characteristics that have led to its nuisance value for the
environmental world. A review of available literature has provided insight into several recycling
and environmentally friendly production options for polyurethane foam, that will ultimately
reduce the amount present in landfills and oceans. Targeted readers include concerned citizens
of the United States as well as anyone interested in improving the quality and health of the
environment as the future of the environment now currently resides in the hands of the people.
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2.0 REVIEW: BACKGROUND OF POLYURETHANE FOAM
2.1 PROPERTIES, USES AND POLYURETHANE FOAM WASTE
Polyurethane foam is a subset of synthetic plastics. The main properties of polyurethane
foam include the ability to be easily molded into various shapes and the capacity to return to its
original shape. Polyurethane foam comes in three types: flexible, rigid and viscoelastic (i.e.
memory) foam. These foams are typically either polyether or polyester based polyols, that are
not considered to be biodegradable compounds and are obtained from petroleum based resources
[7,23,26]. In general, polyether is softer, less scratchy and more cost effective than polyester
[23]. Due to its various formations, polyurethane foam is present in a wide array of applications
including cushions found in furniture and car seating, packaging, footwear, mattresses and
bedding, insulation for refrigerators, freezers and buildings, sports equipment, carpet padding
and many others [6,11,12,19,20]. A more novel use for polyurethane foam has been
demonstrated in the medical field where was studied as a topical hemostatic agent comparable to
collagen or gelatin to control local bleeding [2]. Polyurethane foam has incorporated itself into
the daily lives of individuals around the world and new applications are continually being
developed.
Considering the versatility of polyurethane foam, it is understandable that demand is
going to continue to increase with increased usage and application. At the global level,
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polyurethane foam utilization reached 8 million tons and was expected to reach 9.6 million tons
by 2016 [1]. In 2010, the top consumers included North America, Asia-Pacific and Europe, with
95% of the global demand [12]. Also in 2010, polyurethanes reached number six on the top
most produced chart with polyurethane foams accounting for about half [11]. Of all
polyurethane foam produced, reaching over three quarts of global production, an estimated 28%
accounts for furniture materials and 25% for construction materials [12]. There is no doubt that
polyurethane foam is of high demand of the global level and with the increase in demand and
production, there ultimately will be an increase in the amount of polyurethane foam waste
present throughout the environment.
The next question to consider is where all of this polyurethane foam ultimately ends up
after it has served its purpose and is no longer of use to the consumer. The answer, in general, is
either a landfill or the ocean. An analysis conducted by Marcus Erikson and colleagues to
estimate the amount of plastic pollution currently residing in the world’s oceans found that
92.3% of all samples collected contained plastic materials and of the visual surveys conducted,
they identified that the most frequently observed larger plastics were synthetic polymer foams.
The group discovered plastics in all ocean regions, including those with low coastal populations.
This evidence suggests that the ocean pollution is dispersing, leading some to consider synthetic
polymers as hazardous waste [8]. In 2011, approximately 675,000 tons of polyurethane foam
was discarded with as much as 15% occurring during the foam production in China alone [3].
To help put this in perspective, Wenqing Yang and colleagues identified appliance, furniture and
consumer goods as the main components of foam waste. In China, they estimated 14.66 million
refrigerators to be thrown away each which would result in an estimated 93,200 tons of wasted
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polyurethane foam each year from a single household item [3]. One can imagine the global
amount to be significantly more.
Another study, conducted by Lee Mahoney in 1974, examined the amount of
polyurethane foam present in discarded vehicles. Their analysis concluded that, on average,
approximately 23.4 lbs of polyurethane foam would be recovered from each junked vehicle by
1981 [5]. The European Diisocyanate and Polyol Producers Association estimates about 120 to
150 kg of plastic material per car. Ten to 15% (12-22.5 lbs) of the plastic material is
polyurethane foam, which is fairly consistent with Mahoney’s estimation from 1974 [21]. In
total, millions of tons of polymeric material will be thrown away each year [10]. Before one can
begin to identify potential methods and technologies to more efficiently discard this polymeric
material, specifically polyurethane foam, one must first gain an understanding of how this foam
is produced, and the chemical properties that contribute to its versatility and environmental
persistence.
2.2 SYNTHESIS AND PRODUCTION OF POLYURETHANE FOAM
By definition, a polymer is a macromolecule (i.e large molecule) made up of basic
repeating structural units otherwise known as monomers. The general synthetic reaction for
polyurethane-type polymers includes the condensation reaction between an alcohol with more
than two reactive hydroxyl groups, known as a polyol with difunctional iisocyante or a
polymeric isocyante. The reaction is conducted in the presence of a catalyst to decrease the
overall activation energy. The polyols are usually obtained from ethelyne gas, a product from
crude oil refining; a controversial field in the current feud between the environmental and
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political worlds. The diisocyantes or polymeric isocyanates are generally MDI (Methylene
diphenyl diisocyante) or TDI (Tolulene diisocyanate) [1,23,24]. Figure 1 depicts the synthesis
reaction below.
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Figure 1. Polyurethane Synthesis Reaction
Polyurethane synthesis reaction of an isocyanate and diol depicting characteristic urethane linkage in final polyurethane product. (The figure was created using Chem Draw.)
In the above reaction, the 4,4’-MDI provides the isocyanate group and the ethane-1,2-diol
is the necessary polyol. Initially, there is no distinct urethane monomer present in the reaction; it
is the reaction that occurs between the two reagents that creates the urethane linkage,
contributing to the polyurethane polymer [25]. The polymerization/depolymerization between
the polyols and isocyanate groups contribute to the overall stability of the urethane linkages
present in the resulting polyurethane foam [26].
In order to turn the polyurethane polymer into a polyurethane foam, some additional
reagents must be included in the reaction process. Depending on the type of foam desired for
production, either polyether or polyester polyols may be used for the creation of a co-polymer
[7,23]. The polyether/polyester co-polymer ultimately provides the structural chemical backbone
for the final foamed product. As mentioned in the introduction, polyether polyurethanes will
produce a softer, more flexible foam product, whereas polyester will produce a more rigid foam
[23]. These products are a result of the structural properties of the polyether and polyester
polyols, which are depicted below in Figure 2. It is important to understand the role that the
starting materials play in the qualities and characteristics of the final polyurethane foam
products.
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Figure 2. Polyether vs. Polyester Structures
Structural depiction of differences between polyethers and polyesters.The figure was created using Chem Draw.)By comparing the shape and size of the ester and ether functional groups and resulting
polyester and polyether chains, one can better understand how differences in the two functional
groups result in a difference of foam structure. Due to the smaller, more compact nature of the
polyether, the resulting foam will be made of smaller cells with more compact air flow, which
ultimately results in a more rigid foam. The larger size of the polyester chains, do not allow for
the such tight air flow and cell formation, resulting in a more flexible, less rigid foam. The
functional groups present in the reaction’s reagents will ultimately determine any linearity or
crosslinking present in the final foam product [7,23]. Furthermore, the addition of water to the
polyurethane reaction mixture results in the production of CO2 gas. As the reaction proceeds, the
mixture becomes heavier and more viscous, trapping the CO2 gas and ultimately producing the
air cells present in a polyurethane foam [25,32].
Production of polyurethane foam has been described by several scientists as a “one-shot”
method. In simple terms, this means that all of the raw materials or reagents needed (i.e. the
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polyols, isocyanates, catalysts, water, methylene chloride and any desired additives) are mixed
together in a single reaction container, poured into a mold then left to cure until the product foam
is complete [6,7]. As demonstrated with the comparison of polyester and polyether polyols, the
raw materials (i.e. the reagents of the polymerization reaction) are what determine the ultimate
properties of the polyurethane foam. Various additives to the initial reaction mixture produce
different properties of the resulting foam such as color, fungal and UV protection, varying
densities and others to the desired foams [23,24]. Additives may also include agents that
promote stabilization and cross-linking, fillers, and chain extenders [7]. Understanding how
polyurethane foam is synthesized enables analysis of how it can be broken down to reduce its
hazardous accumulation it the environment.
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3.0 ANALYSIS: ENVIRONMENTAL SOLUTIONS TO POLYURETHANE
FOAM POLLUTION
3.1 DISPOSAL AND RECYCLING METHODS
Landfill, incineration, or recycling are the three potential fates for any item or material
that has been deemed to have no more potential value to the consumer or manufacturer [3]. This
ideology holds true for polyurethane foam as well. Being a high volume, low-density, non-
biodegradable material is a hazard to the environment, so it is important to examine each of these
disposal methods to identify the most reasonable solution to reducing the high volume of
polyurethane foam pollution.
Landfill disposal of polyurethane foam is one of the most convenient methods of
disposal, but also the most ineffective. Items are placed in the trash by consumers and
manufacturers and relocated to landfills across the nation. A negative consequence of landfills is
the production of methane gas, a detrimental greenhouse gas, that results from the degradation of
organic materials present in the landfills [30]. Polyurethane foam is a low-density material that
often occupies large volumes, like those in couch cushions and car seats [3,5,11,12]. Once
polyurethane foam has entered a landfill (or elsewhere in the environment), it will continue to
persist and resist degradation due to its structural stability. Several countries, mostly in Europe,
have even banned landfill disposal of polyurethane foam as a result of these unfavorable
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environmental qualities [3]. A study by Ferdinand Broekema examined the biodegradation and
persistence of polyurethane foam in vivo and found the foam still present after three years, and
that was for a much smaller amount of foam compared to that ending up in landfills and the
environment [2].
The next option aside from landfill disposal, is incineration, or burning, of polyurethane
foam. Unlike landfill disposal, in terms of reducing the overall amount of waste volume, this
method is extremely effective. Incineration reduces the waste by almost 100% of its initial
volume and can reduce overall landfill volumes by 90% [31]. Incineration is also a convenient
method, as materials do not have to be sorted or purified prior to burning and the resulting heat
energy produced can also beneficial if utilized appropriately. As a result of overall landfill
reduction, the accompanying methane gas produced will also be reduced [29]. It has been
estimated that recovered energy from the combustion of waste will prevent millions of tons of
carbon dioxide from entering the atmosphere each year and is considered a renewable, low
emission power source [31].
Thermal energy obtainable by incineration of synthetic polymers, is equivalent to that
generated by coal. Approximately 1kg of both polyurethane foam and coal generate around
7000 kcal/kg each [3]. To obtain the same amount of energy from natural gas, 1.00 m3 of natural
gas is equivalent to 1.35 kg of coal. This indicates more natural gas would be required to recover
an equal amount of energy compared to coal and polyurethanes [28]. Upon full utilization of
energy recovering facilities across the nation, enough electricity could be generated to power
upwards of 14 million homes from the energy recovered from combustion [31]. As with any
combustion of materials, potentially adverse environmental pollutants are generated, some of
which can be toxic [3]. For instance, hydrogen cyanide (HCN) is a known product of
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polyurethane combustion and is therefore released into the atmosphere [27]. However, Malone
and colleagues demonstrated that the HCN released from polyurethane combustion is
incorporated into both nitrogen cycle and carbon cycle on a global level. A visual representation
is depicted in Figure 3 below. As a result of incorporation of HCN into these global cycles, the
amount of HCN released from polyurethane incineration would not be of sufficient quantities to
invoke environmental concern [27].
Figure 3. Cyclical Incorporation of Hydrogen Cyanide
Incorporation of hydrogen cyanide into both the global carbon and nitrogen cycles.(The figure is an adapted version of a figure published in Toxicology of Cyanides and Cyanogens: Experimental, Applied and Clinical Aspects, 2015 and was kindly provided by Jim Peterson, PhD.)
Recycling, of any material, is generally deemed the most “green” method of disposal
available. Under perfect conditions, the recycling process would be sustainable, limiting both
energy use and production of further environmental hazards with no compromises in terms of
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quality of manufactured items produced from recycled materials compared to non-recycled
materials [10]. Polyurethane recycling generally consists of two types: mechanical, also
referred to as physical, and chemical.
Mechanical recycling is the simpler method of the two as it simply involves changes to
the final shape(s) of the foam. By mechanical processes like grinding, crushing and pulverizing,
the foam cushion from old car seats can be physically transformed into fine flakes and powders
[3,10,12]. The finer flake and powder formation allows for easier use and purification. The
mechanical recycling method is a practical way for polyurethane foam manufacturers to directly
reuse any foam waste they produce [10]. Once the discarded foam has been physically
transformed into a flake or powder, the options for its reuse have greatly increased. The
polyurethane flakes or powders still have the same chemical properties as their high-volume
counterparts and can, therefore, be directly reincorporated into the production of new
polyurethane foam. Fabrizio Quadrini and colleagues found that the polyurethane flakes can be
compressed into a mold without the use of any adhesives or binding agents, which in turn results
in a product foam with a much higher density and good stability [12].
Often, adhesives are added to the flakes, which are then placed into a desired mold. With
the accompaniment of high temperature water vapor and high pressure, a new foam with as high
as 90% recycled polyurethane flakes is produced. Unfortunately, the direct use of recycled
polyurethane flakes and powders alone do not typically produce high quality product foams
[3,10]. As a solution to combat poor stability in recycled products, stabilizing agents may be
added to the flaked foam, improving the quality of the resulting foam [10]. The polyurethane
flakes and foams may also be used as a filler and added in smaller amounts, generally up to 20%,
to accompany and reduce the amount of raw materials that are used for production of new
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polyurethane foam [3,12]. Direct reuse of waste for new products thus offers economic benefits
as well as environmental ones.
One of the challenges to polymer recycling is the high strength and durability of the
polymer products, resulting in relatively poor recovery of the constituent monomers as well as
increased expenses to the recycler [7,9]. A unique characteristic of polyurethane polymers, is
that the polymerization of polyurethane is reversible, which allows for recovery of the monomer
subunits [3]. Chemical recycling is a more involved process than mechanical recycling but offers
promising results for both the polyurethane manufacturers and the environment. Chemical
recycling breaks down the polymer foam into various starting materials that can either be utilized
as fuels for purposes unrelated to polyurethane foam production or as starting materials for new
polyurethane foam synthesis. Due to the strong nature of polyurethane foam, degradation is not
observed until the reaction reaches a temperature greater than 200C. Subsequently, the urethane
functional groups begin to breakdown around 230C followed by degradation of the ether
linkages around 320C, indicating the two general steps of polyurethane degradation [7]. Once
the reaction reaches a temperature greater than 200C, different chemical recycling process will
yield different products. Processes of chemical recycling for polyurethane foam include
alcoholysis, hydrolysis and glycolysis. [3,5,9,10,11, 12].
Alcoholysis involves the reaction of the polyurethane foam with an alcohol and catalyst
at a temperature around 170C, which results in what is basically a low weight polyurethane
liquid. After distillation of the liquid, the main recycled products obtained from alcoholysis are
polyols and amines. These products are of good quality can then be reincorporated as starting
material for new polyurethane foam [3].
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Instead of reacting the polyurethane foam with an alcohol, another option is to react it
with high temperature water for hydrolysis, eliminating the use of additional organic chemicals.
Hydrolysis is very efficient in terms of volume reduction. A study by Lee Mahoney found that
hydrolysis reduced the volume of the initial starting foam product by a factor of 30 at 200C [5].
Like alcoholysis, a liquid is produced containing the primary products, polyols and amines, that
can be distilled and reused for the same purposes [3,5,10]. Following distillation, amine recovery
has been demonstrated to reach as high as 80% [5].
Hydrolysis often falls under a general category of recycling known as feedstock
recycling. Feedstock recycling means that the chains that make up polyurethane foam are
broken down into their monomers, like polyols and amines, and used as a stock solution for other
products [9,10]. However due to the nature of water, the reaction temperature is closer to 300 C.
Recycled product recovery only reaches up to 30% and is accompanied by high energy
consumption due to the high temperature of the reaction and secondary environmental problems
like emissions and toxins associated with hydrolysis and feedstock recycling [10].
The most well recognized chemical recycling method associated with polyurethane
materials, including foam, is glycolysis. Glycolysis is the reaction of polyurethane foam and
diols (i.e. glycol) with heat at approximately 200C yielding primarily polyols. The polyol
products of the glycolysis are primarily used as raw material for further polyurethane foam
production [10,11]. The glycolysis reaction is depicted below in Figure 4.
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Figure 4. Glycolysis of Polyurethane Foam
Glycolysis recycling reaction of polyurethane foam.(The figure was created using Chem Draw.)
The ester/ether group attached to the urethane group is exchanged with the hydroxyl
group of the diol to yield at least 61% polyols [11]. With the glycolysis process, the above
reaction is not always the reaction that takes place. Several other reactions may occur including
glycolysis of the urea groups, reaction of the urethane group with water or general degradation of
the urethane group due to the high reaction temperature [11]. An increase of subsequent
reactions leads to a decrease in polyol recovery. With the help of purification processes, the
polyol quality is not compromised. The quality of product generated with polyols comprising
20% weight was high [3]. This finding demonstrates the benefits of glycolytic recycling
including reduction in raw materials and integrity of products.
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3.2 ENVIRONMENTALLY FRIENDLY POLYURETHANE FOAM FOR
IMPROVED DEGRADATION
One final solution for reducing the accumulation of polyurethane foam in the
environment is not a recycling method, but instead a production method. By incorporating more
environmentally friendly raw materials into the production method of polyurethane foam, natural
degradation and decomposition will be more feasible should the foam make its way into landfills
or the oceans in its post-consumer life.
Several methods have been examined that ultimately increase the degradation abilities of
polyurethane foam. The most notable is to incorporate environmentally friendly polyols, bio-
polyols, into the production process. Bio-polyols utilize the natural polymer characteristics of
starch and cellulose [7]. These bio-polyols can reduce the amount of non-biodegradable
polyether and polyester polyols typically used in polyurethane foam production. Similar to the
incorporation of polyethelene oxide, addition of starting materials with hydroxyl groups can be
used as additives or fillers for polyurethane foam. Potential fillers and additives include
celluloses, starches, soy, tree bark and natural oils [7]. A study by Jan David and colleagues at
the Brno University of Technology substituted carboxyl-methyl cellulose sodium salt, acetylated
potato starch, 2-hydroxyethyl cellulose, and wheat/protein gluten for the typical polyether polyol,
with weight ranging from 1-30% and found the resulting foam products to be comparable to their
non-environmentally friendly counterparts as well as little ecotoxicity.
Another proposed method of promoting degradation is to incorporate the addition of
Polyethelene oxide as a reagent. Polyethelene oxide (also known as polyethelene glycol) is a
hydrophilic compound and therefore will allow for an increased amount of water present in the
resulting foam, increasing the potential and rate for hydrolysis and degradation [2].
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As one of the potential natural additives mentioned above, tree bark, which largely
consists of cellulose, is the focus of examination for Jason D’Souza at the University of Toronto.
D’Souza and colleagues liquefied bark at various temperatures below 200C, which as mentioned
in the recycling section is the minimum value for most polyurethane recycling, making bark
liquidation more economical and energy efficient in comparison. The liquefied bark extracts can
then be mixed with polyols for polyurethane foam production. By performing the reaction at a
lower temperature, the sugars present in the bark are better preserved contributing to foaming
behaviors consistent with polyurethane foam produced with the normal polyether or polyester
polyols. The final findings indicated that the foam produced from bark extracts obtained similar
characteristics and properties to typical polyurethane foams but in general were not as stable or
flexible [26].
The final potential solution for remediation of polyurethane foam waste involves natural
degradation processes of synthetic polyurethane materials, instead of degradation of natural
materials found in polyurethane. This is referring to the use of microbial degradation of
polyurethane foam as an environmentally friendly disposal method. The bacterial organisms
Pseudomonas putida, Alicycliphilus and fungi Pestalotiopsis microspora were found to degrade
polyurethane foam with enzymatic activity. P. putida was the most efficient and utilized
polyurethane foam as a sole carbon source [1]. Enzymatic properties that allow microorganism
like P. putida to break down polyurethane foam can be identified and carried out on a larger
scale. Utilizing microorganisms for disposal of polyurethane foam eliminates some of the
secondary environmental concerns that occurring during chemical recycling processes and
provides an economical option for a degradation process.
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4.0 CONCLUSION
This essay examined polyurethane foam at a chemical level in order to identify the
characteristics that have contributed to polyurethane foam’s negative environmental
consequences based on available literature and resources. The desirable properties of
polyurethane foam that allow it to be a strong and versatile material inadvertently allow it to be a
persistent environmental pollutant. The low-density, high volume material resists biodegradation
in the environment and requires mechanical and chemical recycling, or incineration, in order to
reduce its volume and overall waste present.
In summary, the options for disposal of polyurethane foam include landfill, incineration
or recycling. Recycling is the most desirable in terms of product recovery, but also the most
challenging of the three. Landfill disposal is good for convenience, but bad in terms of resource
waste (i.e. polyurethane foam taking up space in the landfill). Incineration is another rather
convenient disposal method that can allow for the use of energy production from the heat
produced by burning polyurethane foam but is may have some negative consequences if carried
out irresponsibly.
Each recycling method has its own pros and cons. Mechanical recycling eliminates the
need for additional chemicals and reduces the amount of raw materials needed for new foam
production, but the new foam may not uphold the qualities that consumers desire in traditional
polyurethane foam. Alcoholysis, hydrolysis and glycolysis all allow for the regeneration of
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reagents for new polyurethane foam production. If the desired recycled product is amines, then
hydrolysis the most suitable method of amine recovery and recycling. If polyols are the desired
recycled product of interest, then glycolysis is the most efficient method of the three chemical
processes examined and also requires lower energy expenditure than both alcoholysis and
hydrolysis.
Production of polyurethane foam with more eco-friendly and biodegradable starting
materials reduces the need for post-consumer recycling techniques. Should this environmentally
friendly foam make its way to a landfill or ocean, which it still probably will, the environmental
burden will be reduced due to its improved ability to degrade on its own. If it can’t degrade on
its own, the assistance of microorganisms that break down polyurethane foam may be utilized as
another environmentally friendly disposal method, however it may not be as rapid as the other
techniques mentioned.
Utilizing any one of these methods will lead to an improvement in the environmental
accumulation of polyurethane foam for the future, especially when considering the versatility
and the impending increased production at a global level. Considering the pros and cons of each
method however, a combination might be the best option for faster results. Convenience is large
factor of whether or not anything gets accomplished. Therefore, despite environmental
consequences, polyurethane foam will continue to be disposed in landfills after consumer use.
The incorporation of bio-degradable starting materials into the foam will provide the most
benefit so that under the inevitable circumstances that the foam that does not end up recycled, it
can more efficiently degrade on its own. When polyurethane foam does manage to make it to the
point of recycling, incineration should be considered as the next best option of polyurethane
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waste reduction. Large amount of energy would be able to be recovered from the non-recycled
plastic materials, as well as large reduction in landfill volume, with little hazardous emissions.
Nonetheless, with the increasing demand for polyurethane foam products and
manufacturing, novel recycling methods and improvements to existing methods should continue
to be examined. Through the use of environmentally friendly materials, energy recovery
techniques and various recycling methods, individuals and organizations can begin to counteract
the negative effects of polyurethane foam pollution.
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BIBLIOGRAPHY
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