Important Plastics

Introduced in the 1950s Moderate to low pressures Metal oxide catalysis (usually) 

Stiffer, harder, higher tensile strength than LDPE 

Blow molding (containers and lids, especially food bottles, auto gas tanks, motor oil bottles), 35% injection molding (pails, refrigerator food containers, toys, mixing bowls), 22% film, 17% pipe and conduit, 14% sheet, 6% wire and cable, 1% miscellaneous, 5% 

= 170°C, higher than HDPE, can be sterilized at 140°C for hospital applications 

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Homogeneous rhodium-catalyzed hydroformylation (135,136) of propene to -butyraldehyde (qv) was commercialized in 1976. -Butyraldehyde is a key intermediate in the synthesis of 2-ethyIhexanol, an important plasticizer alcohol. Hydroformylation is carried out at <2 MPa (<290 psi) at 100°C. A large excess of triphenyl phosphine contributes to catalyst life and high selectivity for -butyraldehyde (>10 1) yielding few side products (137). Normally, product separation from the catalyst [Rh(P(C2H2)3)3(CO)H] [17185-29-4] is achieved by distillation. 

Diesters. Many of the diester derivatives are commercially important. The diesters are important plasticizers, polymer intermediates, and synthetic lubricants. The diesters of azelaic and sebacic acids are useflil as monomeric plasticizing agents these perform weU at low temperatures and are less water-soluble and less volatile than are diesters of adipic acid. Azelate diesters, eg, di- -hexyl, di(2-ethylhexyl), and dibutyl, are useflil plasticizing agents for poly(vinyl chloride), synthetic mbbers, nitroceUulose, and other derivatized ceUuloses (104). The di-hexyl azelates and dibutyl sebacate are sanctioned by the U.S. Food and Dmg Administration for use in poly(vinyl chloride) films and in other plastics with direct contact to food. The di(2-ethylhexyl) and dibenzyl sebacates are also valuable plasticizers. Monomeric plasticizers have also been prepared from other diacids, notably dodecanedioic, brassyflc, and 8-eth5lhexadecanedioic (88), but these have not enjoyed the commercialization of the sebacic and azelaic diesters. 

Until the mid-1950s the main raw material source for the European plastics industry was coal. On destructive distillation coal yields four products coal tar, coke, coal gas and ammonia. Coal tar was an important source of aromatic chemicals such as benzene, toluene, phenol, naphthalene and related products. From these materials other chemicals such as adipic acid, hexamethylenedia-mine, caprolactam and phthalic anhydride could be produced, leading to such important plastics as the phenolic resins, polystyrene and the nylons. 

It is an interesting paradox that one of the least stable of commercially available polymers should also be, in terms of tonnage consumption at least, one of the two most important plastics materials available today. Yet this is the unusual position held by poly(vinyl chloride) (PVC), a material whose commercial success has been to a large extent due to the discovery of suitable stabilisers and other additives which has enabled useful thermoplastic compounds to be produced. 

Typical Characteristics of Some Important Plastics (a) Semi-crystalline plastics... 

Short-term properties of some important plastics... 

The largest commercial process is the hydroformylation of propene, which yields n-butyraldehyde and isobutyraldehyde. n-Butyraldehyde (n-butanal) is either hydrogenated to n-butanol or transformed to 2-ethyl-hexanol via aldol condensation and subsequent hydrogenation. 2-Ethylhexanol is an important plasticizer for polyvinyl chloride. This reaction is noted in Chapter 8. 

Oxidation of n-hutane to maleic anhydride is becoming a major source for this important chemical. Maleic anhydride could also be produced by the catalytic oxidation of n-butenes (Chapter 9) and benzene (Chapter 10). The principal use of maleic anhydride is in the synthesis of unsaturated polyester resins. These resins are used to fabricate glass-fiber reinforced materials. Other uses include fumaric acid, alkyd resins, and pesticides. Maleic acid esters are important plasticizers and lubricants. Maleic anhydride could also be a precursor for 1,4-butanediol (Chapter 9). 

Acrylonitrile is mainly used to produce acrylic fibers, resins, and elastomers. Copolymers of acrylonitrile with butadiene and styrene are the ABS resins and those with styrene are the styrene-acrylonitrile resins SAN that are important plastics. The 1998 U.S. production of acrylonitrile was approximately 3.1 billion pounds. Most of the production was used for ABS resins and acrylic and modacrylic fibers. Acrylonitrile is also a precursor for acrylic acid (by hydrolysis) and for adiponitrile (by an electrodimerization). 

Polyvinyl chloride (p.v.c.) P.V.C. is one of the two most important plastics in terms of tonnage and shows many properties typical of rigid amorphous thermoplastics. More individually, it softens at about 70°C, burns only with difficulty and is thermally unstable. To reduce this instability, stabilisers are invariably compounded into the polymer. 

From this brief discussion it is clear that crosslinking in phenol-formaldehyde resins is complicated and no individual specimen of these materials can be characterised well at the molecular level. Crosslinking is irregular and variable, though it gives rise to a material having sufficiently acceptable properties that it became the first commercially important plastic material indeed, as mentioned in Chapter 1, these resins continue to retain some commercial importance in certain specialised applications. 

Apart from MPW and PVC, several feedstock recycling processes have been developed for some specific plastics. In this respect, the most important plastics are ... 

Many of the commercially important plastics such as polystyrene, polyamide, polyester, polycarbonate, polysulfone, polyphenylene oxide alloys, epoxy, and phenolics lack good impact... 

It is now a common feeling that our world cannot survive as it is without plastics [1]. Starting from 1930, when the macromolecular concept started to gain acceptance in the scientific community [2], the advances in polymer science have been so striking that plastics have invaded almost every aspect of modern human life, both as daily materials and as sophisticated substrates able to cover high-tech applications [3]. A very easy and simple way to check this assertion is to visit the The Macrogalleria web site (1st floor) [4] where an extensive exemplification of the most common and important plastic applications in different fields is provided in a really immediate and impressive way. 

It is a commercially important reaction as a step in the synthesis of nonanol, an important plasticizer alcohol. Other long chain alcohols, derived from product aldehydes by hydrogenation are used as the basis of soaps and... 

Precautionary action to reduce the exposure of humans and wildlife to the oestrogenic plastics intermediate bisphenol A looks closer following an EC technical meeting in March. Member States rejected risk assessments put forward by the UK which set aside evidence of low-dose effects on fish and laboratory animals. Bisphenol A is an important plastics intermediate used in polycarbonates and epoxy resins. Global manufacturing capacity stands at two million tonnes per year. 

Introduction The vinyl polymers are important plastics. Polyvinyl chloride is a very widely used plastic in India. 

It has been one of the three most important plastics which are currently in use. It is mainly used in cable insulation, chemical plant, leather cloth, packaging and toys. 

In Table 8.4 we see that most butadiene is polymerized either by itself or with styrene or acrylonitrile. The most important synthetic elastomer is styrene-butadiene rubber (SBR). SBR, along with polybutadiene, has its biggest market in automobile tires. Specialty elastomers are polychloroprene and nitrile rubber, and an important plastic is acrylonitrile/butadiene/styrene (ABS) terpolymer. Butadiene is made into adiponitrile, which is converted into hexamethylenediamine (HMDA), on of the monomers for nylon. 

Table 10.5 gives the uses of acetone. A very important organic chemical that just missed the top 50 list, methyl methacrylate, is made from acetone, methanol, and hydrogen cyanide. Approximately 1.2 billion lb of this compound is manufactured and then polymerized to poly(methyl methacrylate), an important plastic known for its clarity and used as a glass substitute. The synthesis is outlined as follows. 

Your own intuition and experience should give you a good idea of what a plastic is. It is more difficult to define precisely because there are so many types, they have such a wide variety of properties, and their methods of fabrication are so diverse. Not all polymers are good plastics, although many polymers serve important plastic applications. Probably the best, simplest. 

Some reactions occur very rapidly others very, very slowly. For example, in the production of polyethylene, one of our most important plastics, or in the production of gasoline from crude petroleum, we want the reaction step to be complete in less than one second, while in waste water treatment, reaction may take days and days to do the job. 

As already known, amino acids are the building units of peptides and proteins and they play an important plastic, energetic, and regulatory role in all living organisms. Almost all foods contain amino acids, either in the bound (partially hydrolyzed or intact proteins) or in the free form. High amounts of free amino acids can be found in some fermented foodstuffs as a consequence of proteolytic processes. 

Crosslinks can be controlled by the number of unsaturated sites in the polyester prepolymer. Theoretically if each molecule has only two reaction sites, then infinite, almost linear, chains could be obtained. Hence, average functionability and molecular weight distribution in the prepolymer are extremely important. Plasticizers can be used to advantage in adjusting the average properties of the binder as obtained in the solid propellant formulation. 

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