Commodity and engineering polymers

The difference between these polymers is arbitrary because the properties of commodity polymers can be enhanced by additives. Perhaps the main criterion is price, from which follows usage and therefore production capacity. The prices (1985) of commodity polymers are in the range 500- 700/tonne rising to 1500- 2500/tonne for engineering polymers 7000/tonne for PTFE) and culminating at 150000/tonne for high-temperature and performance fibre reinforced composites (the latter compounds are purchased only on the kg scale ) 

The main engineering polymers are polyamides (nylon 6,6 and 6), polycarbonates (bisphenol A-derived), polyphenylene oxides (PS-modified), acetals, polyesters (PETP and poly butylene terephthalate) and polyfluorocar-bons (mainly PTFE). Together with the synthetic elastomers and rubber-modified thermosets they make up the bulk of added-value products. 

A unique situation exists in the polymer industry whereby a substantial proportion of the effort of the large manufacturing polymer producers involves working in conjunction with the users. This technical service is necessary because of the various applications of the polymers, i.e. they are effect chemicals. Thus, a fabricator will co-operate with the manufacturer as to the optimum method (and, in some cases, which polymer to use) for producing the finished article. Space does not permit discussion of the various techniques used, but they include injection and blow moulding, extrusion and the production of films, vacuum forming, etc. 

A potentially large application area for polymers which is now being 

In this chapter, it is proposed to illustrate the practical aspects of polymers, both in the manufacture and applications. The properties of polymers and how they can be estimated and modified is also an important aspect and will be discussed initially Obviously specialized books should be consulted if more information is required from either the industrialist or the academic s viewpoint, and the bibliography at the end of the chapter suggests some starting points. 

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New developments are hydroxylamines and lactones (for processing stability), which operate at an earlier stage during stabilisation. Lactone (benzofuranone) chemistry has been identified as commercially viable, and marks a revolutionary advance in comparison to hindered phenols and phosphites [18]. New lactone chemistry (Figure 10.1) provides enhanced additive compatibility, reduced taste and odour (organoleptics), resistance to irradiation-induced oxidation, and inhibition of gas fade discoloration. The commercial introduction of fundamentally new types of stabilisers for commodity and engineering polymers is not expected in the near future. 

Commodity and engineering polymers. On the basis of end use and economic considerations, polymers can be divided into two major classes commodity plastics and engineering polymers. Commodity plastics are characterized by high volume and low cost. They are used frequently in the form of disposable items such as packaging film, but also find application in durable goods. Commodity plastics comprise principally of four major thermoplastic polymers polystyrene, polyethylene, polypropylene, and poly(vinyl chloride). 

Carbon-chain commodity and engineering polymers (PH) suffer dining all phases of their lifetime in the earth atmosphere from oxidative degradation, either thermal or phototriggered. Mechanism of oxidation was studied in detail [1,2]. The oversimplified free radieal oxidation scheme involves initiation (1), propagation (2 and 3) and termination steps (4) followed by reactions of primary intermediates and produets. 

Low thermal stability aromatic polymers with high SEA (ABS, EP, PS) produce 50% more smoke per unit mass when brominated flame retardants are added to inhibit combustion. These materials, listed at the bottom of Table 15, produce 5-20 times more smoke per unit mass than the commodity and engineering polymers in the top half of the table. Silicones are anomalous with respect to... 

Smith, R. Georlette, P Finberg, I. Reznick, G. Development of environmental friendly multifunctional flame retardants for commodity and engineering plastics. Polymer Degradation and Stability, 1996, 54(2-3), 167-173. 

The modern tendency is to develop polymer blends that will preserve the desired performance characteristics upon reprocessing. Pew examples of commodity and engineering resin blends are given below. More detailed discussion can be found in [Utracki, 1989a 1998]. 

More bio-based polymers are in the chemical industry s pipeline for all performance specifications from commodities and engineering up to high-performance polymers. Biotechnology restarted the innovation cycle which stopped for petrochemical polymers 15 years ago (Figure 12.4). 

It has been generally accepted that new polymers are not always necessary to meet the need for new materials. Blending of existing commodity or engineering polymers often can be implemented more rapidly and can be a less expensive alternative than the development of new polymers (Koning et al. 1998). 

Thermoplastic polymers have links of intermolecular interactions or van der Waals forces in the form of linear or branched structures. They can melt easily when they are heated, are soluble in certain solvents, and have good resistance to creep. Two main groups of thermoplastic polymers are commodity polymers [eg, polyethylene (PE), polypropylene (PP), and polystyrene (PS)] and engineering polymers [polyoxymethy-lene (POM), polyamides (PA), and polycarbonate (PC)] [1]. 

Engineering polymers are characterised by high ratings for mechanical, thermal, electrical and chemical properties. Their properties are reproducible and predictable and also retained over a wide range of environmental conditions. Distinct from the high volume/low volume commodity plastics, engineering polymers are in a special category [36]. 

J. P. Hogan, D. D. Norwood, and C. A. Ayres, Applied Polymer Symposium Vol. 36 Commodity and Engineering Plastics, Wiley-Interscience, New York, 1982. 

In addition to those PEs listed in the tables, there are others designed to meet different requirements, such as cross-linked PE (XLPE), which by chemical or irradiation treatment becomes essentially a TS with outstanding heat resistance and strength. There is an extra high-gloss HOPE (Fortiflex, by the Soltex Polymer Corp.), another that retains its toughness at very low temperatures and performs at levels between the commodity and engineering resins (Zemid, by Du Pont), and various others. 

Endex is a high efficiency mini-pelletized concentrate, in a thermoplastic resin carrier. It is designed for use in both commodity and engineering thermoplastics, and may be dried with the polymer if necessary. It produces a very fine, closed cell structure, and smooth surfaces. It combines its endothermic properties, quality and efficiency, with versatility and cost effectiveness. 

Polyolefin blends with crystalhne engineering polymers (e.g., polyamides, aromatic polyesters) offer specific cost/performance advantages over the individual components. As these blends are positioned between the commodity polyolefin polymers and engineering polymers, they wiU be discussed in this section. These blends are highly immiscible and also mechanicaUy incompatible as binary blends, thus the majority of the pubhshed investigations involve compati-... 

Acrylic ESTER POLYMERS Acrylonitrile POLYMERS Cellulose esters). Engineering plastics (qv) such as acetal resins (qv), polyamides (qv), polycarbonate (qv), polyesters (qv), and poly(phenylene sulfide), and advanced materials such as Hquid crystal polymers, polysulfone, and polyetheretherketone are used in high performance appHcations they are processed at higher temperatures than their commodity counterparts (see Polymers containing sulfur). 

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