Engineering plastic development

Tables VII and VIII sumnarize present and future RIM engineering plastic developments. This is an emerging area for RIM processable materials part of which will be made possible by recent equipment developments such as hot RIM. Polyurethane materials which now exist in this hard segment range are plastics...

Polyamides can claim to have been the first engineering plastics as a result of their excellent combination of mechanical and thermal properties. Despite being iatroduced as long ago as the 1930s, these materials have retained their vitaUty and new appHcations, and iadeed new types of nylon continue to be developed. 

As recently as 1986 almost all addition polymers were excluded from the ranks of engineering plastics. However, progress since then has been made in the development of addition polymeric resins such as polymethylpentene and polycyclopentadiene and its copolymers (see Cyclopentadiene AND DICYCLOPENTAD IENE). 

With the expiry of the basic ICI patents on poly(ethylene terephthalate) there was considerable development in terephthalate polymers in the early 1970s. More than a dozen companies introduced poly(butylene terephthalate) as an engineering plastics material whilst a polyether-ester thermoplastic rubber was introduced by Du Pont as Hytrel. Polyfethylene terephthalate) was also the basis of the glass-filled engineering polymer (Rynite) introduced by Du Pont in the late 1970s. Towards the end of the 1970s poly(ethylene terephthalate) was used for the manufacture of biaxially oriented bottles for beer, colas and other carbonated drinks, and this application has since become of major importance. Similar processes are now used for making wide-neck Jars. 

The chemical industry represents a 455-billion-dollar-a-year business, with products ranging from cosmetics, to fuel products, to plastics, to pharmaceuticals, health care products, food additives, and many others. It is diverse and dynamic, with market sectors rapidly expanding, and in turmoil in many parts of the world. Across these varied industry sectors, basic unit operations and equipment are applied on a daily basis, and indeed although there have been major technological innovations to processes, many pieces of equipment are based upon a foundation of engineering principles developed more than 50 years ago. 

In particular, it should be noted that the past traditional equations that have been developed for other materials, principally steel, use the relationship that stress equals the modulus times strain, where the modulus is constant. Except for thermoset-reinforced plastics and certain engineering plastics, most plastics do not generally have a constant modulus of elasticity. Different approaches have been used for this non-constant situation, some are quiet accurate. The drawback is that most of these methods are quite complex, involving numerical techniques that are not attractive to the average designers. 

Plastic also refers to a material that has a physical characteristic such as plasticity and toughness. The general term commodity plastic, engineering plastic, advanced plastic, advanced reinforced plastic, or advanced plastic composite is used to indicate different performance materials. These terms and others will be reviewed latter in this chapter. Plastics are made into specialty products that have developed into major markets. An example is plastic foams that can provide flexibility to rigidity as well as other desired properties (heat and electrical insulation, toughness, filtration, etc.). 

The pace of development has increased with the commercialization of more engineering plastics and high performance plastics that were developed for load-bearing applications, functional products, and products with tailored property distributions. Polycarbonate compact discs, for example, are molded into a very simple shape, but upon characterization reveal a distribution of highly complex optical properties requiring extremely tight dimension and tolerance controls (3,223). 

A three-year joint European project, RECAM, recommends that it should be possible to colleet more than 50% of carpet waste in Western Europe. High-grade materials such as PA and PP could be recovered for the manufacture of engineering plastics compounds and more than 8 million Gigajoules of energy could be reeovered from the remainder. At the heart of the proj ect are ehemieal recycling processes developed by both DSM and Enichem. 

Engineering polymers generally comprise a high performance segment of synthetic plastic materials that exhibit premium properties. In this paper, engineering thermoplastics developed for advanced applications, and particularly for enhanced thermal stability are considered. 

As indicated in Table I, most properties of polyamide derivatives of BA, nylons 13, and 13/13, are predictable from properties of commercial engineering plastics such as nylon-11 and nylon-6/10 -- the BA based nylons are have lower moduli and most physical properties are unexceptional.[9,10] However, the BA based nylons have one exceptional property -- their very low capacity to absorb moisture. This property suggests that these materials may be less affected by water plasticization than other nylons, and it has attracted interest in developing BA-based nylons commercially. Development has been impeded by the fact that BA is not produced on a sufficient scale to make it cost-competitive, and apparently the attractive markets are not large enough to justify investment in development of BA processes, creating a chicken-or-egg" problem. 

Nylon-4,6 was developed by DSM Engineering Plastics in 1990 and sold under the trade name Stanyl giving a nylon that has a higher heat and chemical resistance for the automotive industry and in electrical applications. It has a of 295°C and can be made more crystalline than nylon-6,6. A number of other nylons, such as the aromatic nylons and aramids, are strong and can operate at high temperatures, and they have good flame-resistant properties. 

Stereolithography The trend is to develop UV-curable materials that mimic engineering plastics, such as polycarbonate or ABS (see below). 

The presence of aromatic groups in polymers greatly reduces their radiation sensitivity. Aromatic polysulfones are commercially important engineering plastics with high temperature resistance and also show good radiation resistance (16). Development of polymers with improved radiation resistance should be possible by copolymerization of other aromatic structures into the chain. 

In Engineering Plastics and Their Commercial Development Foy, G. Advances in Chemistry American Chemical Society Washington, DC, 1969. 

---