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The development of polyurethane

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Abstract

Polyurethane is one of the six promising synthetic materials in the world. Due to its excellent product performanceand wide application field, it is a crucial industry of development in the world. This paper introduces the progressof polyurethane industry in recent years which includes polyurethane raw materials, classification and applicationprospects. The research methods and principles of waterborne polyurethane were mainly studied. At the same time, thedevelopment of new polyurethane materials was held forward.
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Materials Science: Materials Review2017
Original Research Article
The development of polyurethane
Yanping Ye,Qingxuan Zhu
Department of Chemical Engineering, Beihai University of Technology, Guangxi, China
ABSTRACT
Polyurethane is one of the six promising synthetic materials in the world. Due to its excellent product performance
and wide application field, it is a crucial industry of development in the world. This paper introduces the progress
of polyurethane industry in recent years which includes polyurethane raw materials, classification and application
prospects. The research methods and principles of waterborne polyurethane were mainly studied. At the same time, the
development of new polyurethane materials was held forward.
KEYWORDS: Polyurethane; Application; Waterborne polyurethane synthesis; Development
Citation: -Yanping Ye, et al. The development of polyurethane.(2017); 1(1): 1–8.
*Correspondence to: Qingxuan Zhu, Department of Chemical Engineering, Beihai University of Technology, Guangxi,
China. zhuqingxuan@qq.com
1. Overview
1.1. History of World Polyurethane
Polyurethane (PU) is made from polyisocyanate (OCN-R-NCO) and polyhydroxy compound (HO-R-OH) and there
are a plurality of -NHCOO-repeating macromolecular compounds in the main chain. Polyurethane is known as the
'fi fth largest plastic'. In modern industry it is more routinely used as a polymer organic materials. Due to its relatively
superior performance, it is widely applicable in daily life. For instances, its application in building construction
metallurgy, automobile construction, light industry, textile industry, building construction, medical equipment, energy,
defense equipment and ships are evident.
Professor Otto Baye r is the founde r of polyur ethane. Professor Otto Bayer had successfully synt hesized
polyurethanes in Germany in 1937. Without his discovery, the current industrial development would not be such rapid.
PU has almost 80 years of history. After the end of World War II, Britain and the United States obtained the method
of production of polyurethane from Germany and had applied the technology to the industrial production. However
the use of PU was of limited function initially. As time passed, the technology had flourished. The United States
begun active research about polyurethane after its introduction. In the early 1950s, they were the pioneer in combining
polyurethane, ethylene oxide, copolymer ether and toluene diisocyanate into polyurethane soft foam plastic. It was a
major invention and was a crucial milestone for PU development in the world. The original German companies utilized
high cost synthetic raw materials which was not suitable for a wide range of applications. However after this invention,
the cost for PU production had greatly reduced which created an important foundation in PU's industrialization and
its development. Within 1950 to 1960, the United States, Germany and British team had made a great contribution to
the development of PU. They developed castor oil and polyether polyol synthetic PU adhesive, with polyester polyol
and NDI composition of the liquid PU cast rubber (CPU), polyester rigid PU foam technology and PU exible ber
(Lycra) Lycra. After the mid-1960s, PU industry developed more rapidly and was widely used in various industries. By
the mid-1980s, the world's polyurethane consumption had reached four million t/a. By the 1990s, the consumption of
PU had doubled. With the passage of time, the world's consumption of polyurethane is multiplying and PU industry is
developing more rapidly.
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1.2. History of the development of polyurethane in China
From the late fi fties of the last century to the late seventies, China's PU industry has entered the germinating period
[1]. China's rst PU industry was launched in the 20th century which was 50years from now. In 1958, the synthesis
of isocyanates (TDI) in Dalian and in 1968 the creation of production machine which had a production capacity of
500T per year production. These two achievements has laid a vital foundation in China's polyurethane industry in
order to create a favorable development conditions. In the early 60s, China had independently developed a polyether
PU soft foam. At the same time, China had also introduced three polyurethane foam production lines and they were
installed in the three relatively large plastic factory. In the early 1970s, China had successfully synthesized the mixture
of PU elastomer (MPU) and PU coating and had developed the PU adhesive for industrial production. In 1974, China
developed a PU waterproof material and grouting material. In 1976, the technique of PU runway glue was discussed and
researched. In 1978, it was applied to all kinds of sports places in the country. Before the 1970s, although PU industry
was nearly starting to develop, the amount of production was still insuffi cient to provide industrial development due to
the lack of equipment and smaller modality. The initial era of China's PU industry was from 50s to late 70s.
20th century 80s is the period whereby domestic PU industry started to reach a stable state of development.
Advanced PU synthetic machine was introduced in Jiangsu and Guangzhou from abroad as the domestic economic
policy was remodel. Meanwhile, PU synthetic leather technology was introduced in Shandong from and later a 10,000
t/a MDI production device is also introduced and was officially utilized. At the same time, Gansu Silver Chemical
Industry Company introduced TDI manufacturing technology and equipment and the use of this technology in 1990
built 20,000 t/a production scale. From the late 80s to the late 90s, a number of advanced PU production machines
was introduced in the domestic industrial from some of the most developed countries. This initiative for China's
PU industrial development had laid a huge foundation. In the mid-eighties of last century, the line of professional
organizations set up a PU industry collaboration group. The eff orts of all parties fi nally won the national approval and
the 'China PU Industry Association' was established in a decade later. Since then, China's PU industry has undergone a
qualitative improvement as evident by annual increment of PU resin production. Until 2000, a variety of PU products
had reached an unprecedented peak.
After 2000, China's PU industry has entered a period of rapid development and had gradually became one of the
fastest growing domestic chemical production among the industry. From 2000 to 2005, the domestic PU production and
consumption of the annual growth rate are maintained at a relatively high position as evident by increment of almost
2.5 times of production and consumption than before. According to this development, in the future China will become
the world's largest PU production and consumption among the developed countries. Shanghai Gaoqiao Petrochemical,
Tianjin Petrochemical three plants, Jiangsu Chemical Industry and other units have made a lot of contributions for the
PU industry had laid an important foundation.
1.3. Chemical properties of polyurethane
Since the molecular chain has a carbamate group, the polyurethane has a strong polarity and is insoluble in a non-
polar solvent. Its molecular material has excellent toughness, anti-aging properties. In the synthesis of PU products,
the use of different raw materials and composition, the resulting products will have different properties, including
elastomers, thermoplastic resin and thermosetting resin.
Th e re ar e ma n y mon omers for polym e rizin g PU produ c ts. F o r exa mple, tol u ene d i isocy a nate (TDI) ,
diphenylmethane and the like simple polyols. Preparation of polyester-based polyurethane required terminal hydroxyl-
containing polyester oligomers. Preparation of polyether polyurethane requires terminal hydroxyl-containing polyether
oligomers. Since the nature of the polymer material is diff erent, the polymerization method also varies. The resulting
products are also diff erent which include thermoplastic elastomers, cast elastomers, elastic bers, rigid foams, exible
foams, paint and adhesives.
The advantages is extensive. PU elastomers are commonly used in conveyor belts, hoses, auto parts, soles and
medical artifi cial organs. On the other hand, soft foam are used in home cars, insulation, noise and packaging. PU paint
can be eff ective for the protection of wood and metal integrity.
1.4. Polyurethane varieties
Polyurethane Adhesive is also known as Ulida gum. Polyurethane adhesives contain NCO-groups and NHCOO-
groups in the molecular structure, and the polyurethane adhesives can be divided into polyisocyanates and polyurethanes
because of their ranking in the molecular chain and the structure of the molecular chains. Since the polyisocyanate
contains a carbamate group (-NH-COO-) and isocyano (-NCO), the polyurethane adhesive has a high activity and
polarity. Foam, glass, rubber, plastic, wood and other substances containing active hydrogen have a good sticky nature.
Polyurethane adhesives are used in a wide range of applications, and can be used in other aspects of automotive, wood,
footwear, packaging, construction, book binding and railway construction.
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Polyurethane coating, can be divided into two-component and one-component polyurethane coating. It is a more
common coating. The two-component polyurethane coating is typically composed of a low molecular weight urethane
polymer (commonly referred to as a curing agent component) and a hydroxyl-containing resin (commonly referred to as
a main component). This kind of coating performance is excellent and has a great developing potential. PU coatings are
usually used for repair, leak-proof aspects. However the shortcomings are obvious. Its construction process is complex
which demands a high construction environment. One-component performance on the other hand is not as good as two-
component, this is why the range of applications is not wide enough for both components.
PU foam is the product of isocyanates and hydroxyl compounds from the polymerization reaction. Polymerization of
PU foam has distinct textures. Sometimes they are hard and sometimes they are relatively soft. Hence, it can be easily
distinguished based on their hardness. It has good elasticity, softness, chemical stability, adiabatic function and is a good
cushioning material. It usually acts as a cushioning material for some of the more expensive upscale items to avoid
damage to the items.
Polyurethane leather is soft, natural color, strong. It has an excellent wear resistance, aging resistance, cold
breathable and low cost advantage. Thus it is the best alternative to natural leather. It is mostly used among the ordinary
citizens.
Polyurethanes are the main components of polyurethane rubber and polyurethane prepolymer. PU Polyurethane
Sealant has many good properties such as good elasticity. PU polyurethane sealant can be used for a long time. However,
the polyurethane sealant also has some shortcomings. It could not withstand heat for a long time, slower curing rate and
has poor water resistance. PU polyurethane sealant is commonly used in the construction and transportation.
Polyurethane fi ber is known as polyurethane elastic ber but is named as spandex in China. Spandex is very fl exible
and elastic and is widely used in the textile industry. Due to its outstanding elasticity, the general clothing is not 100%
of the use of spandex to maintain appropriate fl exibility. This is done by involving the usage of diff erent proportions of
spandex.
Polyurethane paint has strong adhesion, water and abrasion resistance and is widely used in the surface of advanced
wood furniture and metal. Its main drawbacks are formation of bubble on the surface when come in contact with
water and turns yellow when time goes. 'Polyester paint' sold in the market nowadays is in fact the polyurethane paint.
They are the master paint, while the other is a curing agent. They should be used in accordance with a certain ratio of
deployment and it is achievable after mixing. It is suitable for the use of family.
2. Polyurethane raw materials
Toluene diisocyanate (TDI), diphenyl methane diisocyanate (MDI), acrylic (AA) and other organic matter should
not be referred as polyurethane products. They can only be said that they contain raw materials of polyurethane.
Polyurethane raw materials also include: isocyanate, polyester polyol, polyether polyol (PPG, POP, PTMEG), solvent
(DMF, TOL, MEK), chain extender (BDO) and various additives.
2.1. Isocyanates
The ester compounds of isocyanic acid are collectively referred to as isocyanates. (R-N = C = O ~ N-). Isocyanates
can be classified according to the amount of the NCO group. For instance, Isocyanates (O = C = N-R-N = 1) and
polyisocyanates. Toluene diisocyanate (TDI) is the largest yield and the most commonly used material in the daily life
among them.
TDI applications are mainly paint, glue and soft foam. Among them, soft foam is the largest area of consumption
TDI, its consumption accounted for 70% of total consumption, while the coatings industry accounted for 15 percent.
Soft polyurethane foam (referred to as polyurethane soft foam) are applied in the furniture mats, vehicle seat mats and
a variety of soft cushion layer. In addition, TDI can also be used to produce other polyurethane products such as rigid
polyurethane foam, polyurethane coatings and polyurethane elastomer intermediates.
MDI can be further divided into pure MDI, polymer MDI, liquefi ed MDI and modifi ed MDI [2]. TDI and MDI are
the raw materials for the production of polyurethane as they are substitutes for each other. Pure MDI is mainly used for
the production of slurry and polyurea spray. Polymer MDI mainly produces polyurethane foam which is mainly used for
refrigerators, water heaters and other facilities of the insulation [3].
Polyphenylene polyisocyanate (PAPI), English full name polyaryl polymethylene isocyanate is a well-known crude
MDI. It is a mixture of MDI and polyisocyanates with more than two functional groups. Self-polymerization occurs
automatically at elevated temperatures. It can be used to create polyurethane adhesives or directly into the rubber
adhesive to improve the adhesion properties.
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In addition to the above mentioned PU synthetic raw materials, other raw materials are HDI, XDI and NDI. Xylylene
diisocyanate (XDI) and naphthalene 1,5 - diisocyanate (NDI) have relatively limited role and hence smaller production
in domestic industries. On the contrary, l, 6-diisocyanate (HDI) has a good resistance for yellowing so HDI will replace
TDI's in the coatings industry. It has now become increasingly common for HDI to be used as high-grade car paint.
2.2. Polyols
A product derived from condensation of an organic dibasic acid with a polyol - a polyester polyol.
1,4-butanediol is referred to as BDO. It is a very useful polymer raw materials in the daily life of industrial
development and is used in diff erent elds. Because BDO can be used to synthesize PU resin. In the PU industry, it
plays a very important role to produce pulp and spandex. Currently there are four ways to produce BDO technology in
the world. The four methods are Reppe method, butadiene method, butane anhydride method and propylene alcohol
method.
In addition to BDO, there are several products that are similar. It is the main production of polyester polyol raw
materials (ethylene glycol and propylene glycol.). Although they are the production of polyester polyol raw materials,
but as compared to BDO, the role and application of these raw materials in the PU industry is still relatively small.
Polyacrylic polyols (collectively referred to as PPG), derived from the condensation of propylene oxide, are one of
the most crucial raw materials for polyurethane synthesis. However, due to the use of diff erent types of starting agent,
the type of polyether polyols produced are also diff erent. The production of polyurethane plastic is the best application
of polyether. In addition, it can also be used as a surfactant, the manufacture of industrial defoamers, high effi ciency,low
foam detergent, lubricant, heat exchange fl uid and quenching Agent, drafting agent components and special solvents.
Polytetramethylene ether glycol, referred to as PTMEG, the main purpose is the production of spandex, polyurethane
elastomer, synthetic leather, and other substances.
2.3. Chain extender
Chain extenders are essential reagents for PU production. Other polyurethane raw materials fully react with each
other, the polyurethane ready to condense into the product, this time should be added to the amount of chain extender
resin molding. A relatively small molecule of alcohol or ether containing two or more hydroxyl groups.
The principle of the use of chain extenders in the production is to allow the isocyanate-terminated prepolymer to
react with some active hydrogen-containing compounds, which extends the chain diff usion of the molecules and cure
the resin into the desired shape.
2.4. Catalysts
(1) Polyurethane catalyst A-1 catalyst is mainly used in the production of soft polyether polyurethane foam and
packaging with a rigid foam. It can be brought to reduce the foam density, because he has a strong catalytic eff ect with
water. The A-1 catalyst controls the gas production to account for 80% of the reaction, controlling the eff ectiveness
of the gel reaction of 20%. This type of catalyst has a high activity and is used in a small amount. With appropriate
timing and the correct adjustment on the amount of catalyst, the gel time can be controlled precisely. The use of a tin-
tin catalyst with this catalyst can improve the fault tolerance in the production of foam and prevent the quality problems
in the production due to some artifi cial or non-human, careless or computational errors. The quality of the soft foam is
guaranteed. The A-1 catalyst is quite popular in the industrial manufacture of various polyurethane foams, especially for
high resilience, semi-rigid and low density foams.
(2) Polyurethane Catalyst A-33 This highly active catalyst promotes the reaction of the polyurethane feedstock,
crosslinking the foam, and imparts good mechanical properties to the exible polyurethane foam. The best outcome
could be expected while using A-33 together with NIAX catalyst A-1.
3. Polyurethane synthesis process
3.1. Polyurethane synthesis method
PU synthesis method has a one-step synthesis process and two-step synthesis process. Although the two methods are
diff erent, the chemical principle behind both methods is similar.
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3.1.1 One step synthesis process
The one-step synthesis process is a step in which the reaction of the isocyanate and the polyol and the reaction of
the produced prepolymer with the chain extender are completed at the same time by mixing the various polyurethane
synthetic materials in a one-time reaction.
3.1.2 Two-step synthesis process
The two-step process involves reacting the polyol with the polyisocyanate fi rst, and then producing a prepolymer of
suffi cient molecular weight. A suffi cient amount of chain extender is then added to the resulting prepolymer to form the
prepolymer into a high molecular weight compound.
Polyols and polyisocyanates produced by the reaction of the prepolymer is a very soft material, its own strength is
very low, it must be added chain extender to form a polymer polymer has just the value of the use. The prepolymer can
also be sold, but some need to add some other chemicals, so that the shelf life of the prepolymer can be extended.
Although the synthesis of polyurethane can be divided into two methods, but the principle is similar. The only
diff erence is the order of sequence. However most of the experts suggested that two-step method is generally better than
the one-step system as the product quality is better.
3.2. Waterborne Polyurethane
Waterborne polyurethane is a new polymer material with water as the dispersion medium and PU resin as the base
material. It retains the advantages of traditional polyurethane, but also has some traditions do not have new advantages
such as non-toxic, energy conservation and so on. Because of its advantages, water-based polyurethane became the
center of attention.
3.2.1 Preparation of aqueous polyurethane
Due to polyurethane strong hydrophobicity and isocyanate can react quickly with water, the traditional synthetic
technician cannot produce the desired waterborne polyurethane. In this regard, both local and abroad expertise carried
out various researches to create such properties. Finally, they divide the waterborne polyurethane into two categories
which include external emulsifi cation and self-emulsifi cation.
3.2.1.1 External emulsifi cation method
The outer emulsifi cation method [4] refers to the preparation of the corresponding prepolymer in various organic
solvents in an organic solvent, which has a strong hydrophobicity and is diffi cult to dissolve in water. This necessitate
the addition of appropriate high-performance emulsifi er and through the external force to form a polyurethane emulsion.
The lower the viscosity of the prepolymer, the easier it is to emulsify it. The addition of emulsifi ers is sodium alkyl
sulfate polyoxyethylene ether and other substances.
3.2.1.2 Self-emulsifi cation method
Self-emulsifying method [5] is the introduction of hydrophilic groups in the molecular skeleton of polyurethane. PU
molecules have a certain hydrophilicity. PU molecules dispersed into the water to get waterborne polyurethane and then
through the hydrophilic group emulsifi ed PU molecules made of waterborne polyurethane emulsion. Until now, self-
emulsifi cation can continue to be broken down into several ways. The way is as stated below.
3.2.1.3 Prepolymer dispersion method
The prepolymer with -NCO end group was synthesized and a small amount of N-methylpyrrolidone was added to
the prepolymer to adjust the viscosity of the prepolymer. Next, it is placed in a water with diamine. With high-speed
mixing, the prepolymer dispersed into the water while expanding the water-based polyurethane.
3.2.2 Water-based polyurethane synthesis principle
Anionic water-based polyurethane is the most important water-based polyurethane products, the following is
the synthesis of aromatic water-based polyurethane chemical reaction, said the synthesis of aromatic water-based
polyurethane principle:
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After neutralization, the addition of water and water played the role of emulsifi cation and chain extender, and the
terminal-NCO group of the macromolecule changed to -NH2, and the -NH2 was further reacted with NCO. The
molecular weight of the aqueous polyurethane is further improved by -NH-CO-NH-.
4. Practical applications of polyurethane
Polyurethane is known as the fth largest plastic, it is a modern industrial emerging polymer organic materials. It
has a relatively superior performance, so in all areas of national life are more commonly used. It covers a wide range
of applications, including building construction metallurgy, automobile construction, light industry, textile industry,
building construction, medical equipment, energy, defense equipment, and ships.
4.1. Application of PU Material in Daily Life
Polyurethanes play an important role in life. We can see its application virtually anywhere including at home and on
the streets. Even what we are wearing are made from it but we do not realize what is made of polyurethane. Our home
furniture, sofa, mattress, refrigerator, water heater insulation layer, seat armrest are made of polyurethane. We see the
wire insulation paint, cable sheath, oor paint, shoes, outsole, shoes, adhesives, sports track, plastic stadium (soccer,
basketball and badminton) and plastic fl ooring are made of polyurethane. Also, its application also includes things we do
not usually see in daily life which embraces aircraft car interior parts seats, door panels, dashboard, bumper and fender.
4.2. The specifi c application of various PU materials
4.2.1 PU soft foam Flexible PU
PU soft foam in mat materials has sound-absorbing properties whereas fabric composite materials has a considerable
application areas. Polyurethane soft foam texture is relatively soft, feel comfortable, so often with the same to
manufacture mats, sofas. The aperture of the PU has a good sound-absorbing eff ect, it can be used to install in the indoor
noise and is a good sound insulation material. As for fabric composite material, due to it has good fl exibility, it is usually
used to make cotton.
4.2.2 PU Rigid PU
PU foam has excellent insulation properties, so most of the refrigeration equipment (refrigerators, cold storage and
refrigerated trucks) and industrial equipment insulation are applied to the PU foam. In addition to thermal insulation in
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this area of application, it can also be applied to transportation such as car roof, imitation wood, grouting material and
ower industry.
4.2.3 Semi-rigid PU
Absorbent foams are often used in the production of automobile bumper, because the energy-absorbing foam has a
good shock absorption capacity and cushioning ability, which has these two excellent performance can improve the life
of the bumper.
The Integral Skin Foam is used to make car steering wheel, handrails and car interior trims. Since the crust foam
products are usually RIM processing technology.
Polyurethane microporous elastomers are the most widely used for the footwear industry.
4.2.4 Polyurethane elastomer
PU elastomers are classifi ed into three categories: cast PU elastomer (CPU), thermoplastic PU elastomer (TPU) and
kneaded PU elastomer (MPU) [6]. CPU production is much higher than the other two and the scope of application is far
greater than the other two drugs. These three elastomers have a vital role in the mining, metallurgy, machinery industry,
automobile industry, light industry and construction industry. It plays an excellent performance in these aspects.
4.2.5 Polyurethane slurry
PU slurry is divided into wet PU slurry and dry PU slurry. Artifi cial leather can be synthesized with the PU slurry,
the use of PU slurry synthetic leather looks naturally comfortable and soft as compared to the natural leather. And most
importantly, it has anti-aging properties and the cost of producing artifi cial leather is low, so in the future it will be the
best alternative to natural leather material. Where there is leather applied to the eld, it can replace some of the high
price of natural leather.
4.2.6 Spandex
Spandex has a very high resilience (sponge high resilience is now the best of all elastic fi bers), good tensile strength,
tear strength, resistance to ultraviolet radiation, chemical resistance, does not damage the material after repeated
washing and the affi nity of the dye is good.
Because spandex has so many advantages, so it is now widely put into the production of textile materials. In the
traditional textiles, addition of a small amount of spandex can greatly improve its traditional fabric quality. It is also
more comfortable, beautiful and stylish.
5. Development and Development of Polyurethane and Its Raw Materials
5.1. The future of polyurethane
At present, the world's annual demand for polyurethane is 7 million T, and now the annual growth rate of 7 percent
faster growth. Advancement in industrial development have contributed to the advancement of the polyurethane industry
and the increased demand for polyurethanes has led to a gradual increase in the demand for synthetic polyurethane
feedstock. PU is one of the world's most promising synthetic materials. PU industry and national economic life are
closely related, in all areas have played an important role. So PU industry and its raw materials will usher in a chance to
play.
5.1.1 Market analysis
PU products and more types, each with a diff erent nature and superior performance, so the scope of application and
the area involved is quite wide [7]. So far, the world's annual consumption of polyurethane is considerably huge, of
which the United States accounted for one-third of the weight, Europe is slightly less than the United States, the Asia-
Pacifi c region is similar to Europe. Currently the global demand for polyurethane on average has reached the annual
growth rate of seven percent while the growth rate of some developing regions are even higher [8]. In the near future,
the Asian region's PU industry will be developed with Europe, the United States is not comparable. In the Asia-Pacifi c
region, China and Japan's PU products production and demand is the largest [9].
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5.1.2 Raw material market demand
TDI and MDI are the main raw materials for synthetic PU. With a variety of TDI, MDI raw materials for the
preparation of a variety of PU materials widely used in the production of auto parts, coatings, adhesives and so on.
The world's MDI and TDI are almost in the hands of several well-known companies. MDI appears later than TDI and
is slightly higher in price than TDI. However, toxicity of MDI is minor and mold better than TDI, so the future TDI is
likely to be replaced by MDI. As the demand for PU continues to increase, the market with MDI and TDI increases.
Some domestic and foreign businessmen want to expand their share in this market, so they make investment in China's
productivity to expand their industry accounted with a larger market share [10].
5.1.3 China PU industry status and progress
In the near future, China will become the global PU consumer products center [11]. China is now accounted for 30
percent of the total consumption of PU products, and is currently one of the fastest area in MDI and TDI production
in the world. As China's PU industry is developing more rapidly, it catches up with the pace of Europe and the United
States. Multinational companies had spotted this point and they focus investment on PU production in China, hence
shifting the global PU development center from Europe and the United States and other countries to China.
In recent years, well-known foreign companies continue to increase investment in China's PU production industry.
Relevant research and development centers were established in China together with introduction of some of the
international advanced technology. This fully demonstrates the shift of development of the world's PU from Europe and
the United States to China. China will become the world's top PU industry to and acts as a fundamental driving force [12].
6. Conclusions
Polyurethane products is inseparable from our daily life. It is virtually everywhere and is readily available.
Polyurethane synthesis and synthesis of raw materials are diverse. Diff erent types of synthetic materials will produce
polyurethane products with diff erent natures. According to their diff erent characteristics, they play diff erent roles in
eld. Polyurethane is the most promising polymer organic materials and in the future its development will promote the
rapid development of world industry.
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... The oligomers with hydroxyl end functional groups which have two or higher functionality are used to make biodegradable polyurethanes [9]. However, biobased polyols, such as vegetable oils and their derivatives, are being used to make PUs, which are made up of triglyceride molecules of different reactive groups such as carbon-carbon double bonds, ester and hydroxyl groups, and are made by transesterification or epoxidation of oils followed by a ring-opening reaction with glycerol, alcohol, or ethanol [11]. ...
... Chain extenders are diols or diamines with a low molecular weight in PU production to lead the reaction between isocyanate-terminated prepolymer and active hydrogen-containing compounds to enhance the block length of the hard segment and resin curing into the desired shape [11]. ...
Article
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This review highlights a critical concern in the manufacturing of polyurethane, which traditionally relies on substantial quantities of petroleum-derived materials. With the increasing awareness of environmental sustainability and the need for materials that minimize harm to the environment, researchers have been exploring bio-based raw materials as alternatives for synthesizing polyurethane. The focus on bio-based raw materials aligns with the growing demand for sustainable practices across various industries. This review delves into the potential applications of bio-based polyurethane in diverse industries, emphasizing the need for more environmentally friendly alternatives. Furthermore, the article examines recent advancements in the field of biodegradable polyurethane, reflecting a broader trend toward materials that break down naturally over time. This aspect is crucial in addressing concerns related to plastic pollution and waste management. Given the diverse range of vegetable oils and other biodegradable compounds available, the review places particular emphasis on the utilization of biodegradable materials for polyurethane. This approach not only provides a sustainable alternative to petroleum-derived materials but also capitalizes on the abundance and versatility of vegetable oils and other raw materials. The paper's concise overview of raw materials used in the production of biodegradable polyurethane and their applications provides valuable insights for researchers, industries, and policymakers. As the demand for sustainable materials continues to rise, the exploration and development of bio-based and biodegradable polyurethanes represent a promising avenue for addressing environmental concerns and creating more eco-friendly products.
... Thermoplastic polyurethane (TPU) enhances PVDF with its elasticity and hydrophilicity, 12,34,56,57 making it suitable for applications requiring high mechanical properties, including blood clotting, 58 purification, 59 and biosensing. 60 TPU's hydrophilic carboxyl groups and excellent mechanical qualities offer benefits like elastic strain recovery and wear resistance. 3,[61][62][63][64][65] This paper investigates converting acoustic energy into electrical energy using polymeric nanofibers. ...
... In 1937, one of the most special polymer types with versatile properties was discovered [3]. This special type of polymer is polyurethane (PU), which was developed by Otto Bayer to compete with nylon [4,5]. Bayer's invention ranks among the most important breakthroughs in polymer science. ...
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A general mechanism for catalytic urethane formation in the presence of acid catalysts, dimethyl hydrogen phosphate (DMHP), methanesulfonic acid (MSA), and trifluoromethanesulfonic acid (TFMSA), has been studied using theoretical methods. The reaction of phenyl isocyanate (PhNCO) and butan-1-ol (BuOH) has been selected to describe the energetic and structural features of the catalyst-free urethane formation. The catalytic activities of DMHP, MSA, and TFMSA have been compared by adding them to the PhNCO–BuOH model system. The thermodynamic properties of the reactions were computed by using the G3MP2BHandHLYP composite method. It was revealed that in the presence of trifluoromethanesulfonic acid, the activation energy was the lowest within the studied set of catalysts. The achieved results indicate that acids can be successfully employed in urethane synthesis and the mechanism was described.
... Synthetic and bio-based polyurethane (PU) are two categories of polyurethane that can be differentiated. Synthetic polyurethane is traditionally produced by the reaction of polymeric diols or amines with multifunctional isocyanates to form urethane or urea linkage [1]. It is also possible that other pertinent catalysts and additives are incorporated into the production of PU. ...
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In this study, fluoroacrylate palm oil polyurethane (FPOPU) was synthesized with different synthesis methods. FPOPU was synthesized stepwise starting with the synthesis of acrylated epoxidized palm oil (AEPO) by a reaction of acrylic acid (AA) and triethylamine (TEA) as the catalyst. Then, palm oil polyurethane (POPU) was formed by the reaction of AEPO with isophorone diisocyanate (IPDI) and hydroxyethyl acrylate (HEA) as an end cap agent. POPU was further added with 1,6 hexanediol diacrylate (HDDA), trimethyloltripropane triacrylate (TMPTA), and heptafluorodecyl methyl-metacrylate (HDFDMA) monomers to form FPOPU. FPOPU synthesis methods were studied by manipulating the sequence of chemicals added, temperature, and mixing time of POPU. The FPOPU mixture was finally cast onto a silicone mold with 1 mm thickness and cured under UV radiation at 120 seconds. Based on the analysis, pre-mixed IPDI with HEA at 60°C for 15 min followed by the addition of AEPO at 60°C and further mixed for 3 hours (Method 2) shows the complete formation of the urethane chain. It is proven by the existence of NH peak at 3500 cm⁻¹ and the disappearance of NCO peak at the range of 2200-2500 cm⁻¹ indicating the NCO functional group has completely reacted with OH group in AEPO. The addition of fluorination also can be proved by the existence of CF stretching at 1012 cm⁻¹. This study provides information regarding comparison between the synthesis method of FPOPU.
... TPU materials have unique properties due to incorporation of soft and hard segments in their chains. Soft segments, mainly composed of long polyols, provide elasticity, while hard segments, comprising rigid diisocyanates and chain extenders, enhance the mechanical stability, ensuring strength and durability [7][8][9]. A urethane group is formed upon completion of the reaction between the hydroxyl and isocyanate groups. ...
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Currently, the preparation and application of bio-based thermoplastic polyurethane (TPU) are hot research topics in the field of polyurethane. In the present work, a series of polylactic acid (PLA)-based TPUs were synthesized using bio-based PLA and 4,4’-methylene diphenyl diisocyanate (MDI). The effects of three chain extenders, including 1,3-propanediol (PDO, PD), 1,4-butanediol (BDO, BD), and 1,6-hexanediol (HDO, HD), on the characteristics and properties of PLA-based TPUs were investigated. The successful synthesis of PLA-based TPUs was confirmed by the absence of isocyanate groups and the presence of characteristic peaks corresponding to urethane and other functional groups. The analyses revealed the potential for greater crystallization in the PLA-BD and PLA-HD series. Among the examined groups, the PLA-HD variant with a 55% hard segment content displayed the highest molecular weight and fracture stress, and an appropriate elongation value, indicating its suitability for specific applications. The study also investigated the stress relaxation rates and residual forces and found them to be within clinically acceptable ranges. These findings demonstrate the potential of these synthesized TPUs for orthodontic applications, with the ability to tailor mechanical properties by adjusting hard segment contents and modifying chain extenders.
... Polyurethane (PU) is one of the most versatile polymeric materials with a wide range of industrial applications such as thermal rigid insulation foam, exible foam, coatings, adhesives, elastomers, etc. [1][2][3][4] Its application depends on its properties, which are highly inuenced by the type of polyol and isocyanate used in its production. 1,5,6 Conventional PUs are derived from non-renewable fossil fuels. ...
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Coconut oil (CO) has become one of the most important renewable raw materials for polyol synthesis due to its abundance and low price. However, the saturated chemical structure of CO limits its capability for functionalization. In this study, a novel reaction mechanism via the sequential glycerolysis and amidation of CO triglycerides produced an amine-based polyol (p-CDEA). The synthesized biopolyol has a relatively higher hydroxyl value of 361 mg KOH per g relative to previously reported CO-based polyols with values ranging from 270-333 mg KOH per g. This primary hydroxyl-rich p-CDEA was used directly as a sole B-side polyol component in a polyurethane-forming reaction, without further purification. Results showed that a high-performance poly(urethane-urea) (PUA) hybrid foam was successfully produced. It has a compressive strength of 226 kPa and thermal conductivity of 23.2 mW (m-1 K-1), classified as type 1 for a rigid structural sandwich panel core and type 2 for rigid thermal insulation foam applications according to ASTM standards. Fourier-transform infrared (FTIR) spectroscopy was performed to characterize the chemical features of the polyols and foams. Scanning electron microscopy (SEM) analysis was also performed to evaluate the morphological structures of the synthesized foams. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were conducted to investigate the foam's thermal characteristics. Thus far, this work is the first to report a novel and effective reaction mechanism for the synthesis of a highly functional CO-derived polyol and the first CO-based polyol with no petroleum-based replacement that may serve as raw material for rigid PUA foam production. PUA hybrid foams are potential insulation and structural materials. This study further provided a compelling case for enhanced sustainability of p-CDEA PUA hybrid foam against petroleum-based polyurethane.
Chapter
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Polyurethanes (PUs) are types of multilateral polymers that are widely used for various industrial purposes. Nevertheless, the structure of these polymers suffers from weak points of high flammability, poor thermal stability, and evolution of toxic gases and smoke. This results from their porous and cellular morphology, in addition to the presence of aliphatic segments restricting further applications. Therefore, the flammability of polymers is considered a breakthrough research topic. Particularly, halogen-based fire retardants are known to possess an effective behavior against fire growth; however, they are limited because of their apparent toxicity. For such reasons, a new generation of flame retardants must be more developed. In this chapter,an overview of the performed research on fire-retardant materials for PU polymer is given, along with their corresponding retardation mechanisms against flames. This chapter will also provide an introduction for enriching the flame retardancy of new nanomaterials for PU polymers.
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A theoretical study of urethane formation through the reaction of phenyl isocyanate and butan-1-ol was carried out, without and in the presence of morpholine, and 4-methylmorpholine catalysts. The reaction with and without catalysts was studied at BHandHLYP/6-31G(d) and G3MP2BHandHLYP levels of theories. The reaction mechanism in the presence of catalysts differs significantly from the catalyst-free case and includes seven steps. The catalyst-free system was investigated along with the catalytic process, the geometries were optimized, and the corresponding thermodynamic properties were calculated. Calculated reactant complexes were compared with crystal structures of morpholine, and 4-methylmorpholine complexed with diols found in the literature. The structures were strikingly similar and thus, the validity of the proposed and studied general organocatalytic reaction mechanism was partially verified. Meanwhile, an irregularity in the energy profile occurred due to the zwitterionic nature of an intermediate. To handle the irregularity, a correction was implemented which handles the appearance of a zwitterionic structure and the corresponding energetic properties. The results showed that morpholine is less effective catalyst compared to 4-methylmorpholine, which can be associated with the difference in their PA (1523.95 and 963.07 kJ/mol, respectively). The current results prove the important role of amine catalysts in urethane synthesis which can be applied in polyurethane catalyst design and development.
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This paper is concerned with chemistry of polyurethane used for preparation of aqueous dispersions used in adhesive applications. The discussion is presented under headings - chemistry, emulsifier-shear force method; acetone process; prepolymer-ionomer-mix method; melt dispersion condensation method; application areas; comparison to solvent adhesives. A general remarks about technology and economics of polyurethane dispersions are concluded with a remark that they have a future with their own reputation and marketplace alongside the other adhesive systems. They are, however, presently carrying the high expense of development.
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