Engineering thermoplastics polyacetals

As with other so-called engineering thermoplastics, the polyacetals are available modified with glass fibre, and may contain fire retardants, and some grades are blended with PTFE. In 1982 Hoechst introduced blends of polyacetals... 

Bottenbruch, L. (ed) Engineering Thermoplastics Polycarbonates, Polyacetals, Polyesters, Cellulose Esters. (1996) Hanser Gardner Publications, Cincinnati,... 

The most stable polyacetal polymer is polyformaldehyde (or polyoxymeth-ylene, POM) this is the only polyacetal that has reached commercial production. This resin has unique properties (e.g., selflubrication) and is very widely used in automotive applications such as engineering plastics. Acetals are widely used engineering thermoplastics with high load-bearing characteristics and low coefficients of friction. Currently, over 200 million lb of acetals are molded and extruded in the United States. 

Polyacetal polyphenylene oxide are widely used as engineering thermoplastics, and epoxy resins are used in adhesive and casting application. The main uses of poly(ethylene oxide) and poly(propylene oxide) are as macroglycols in the production of polyurethanes. Polysulfone is one of the high-temperature-resistant engineering plastics. 

To measure the thermal stability of polymers, one must define the thermal stress in terms of both time and temperature. An increase in either of these factors shortens the expected lifetime. In general terms, for a polymer to be considered thermally stable, it must retain its physical properties at 250°C for extended periods, or up to 1000°C for a very short time (seconds). As compared to this, some of the more common engineering thermoplastics such as ABS, polyacetal, polycarbonates, and the molding grade nylons have their upper limit of use temperatures (stable physical properties) at only 80°C—120°C. 

As a measure of the level of sophistication of the industry the types of polymers consumed was as shown in figure 2. Others are mainly engineering thermoplastics (ETP), such as nylon, polyacrylates, polyacetals, polycarbonates, polyesters, and polpropylene oxide etc... These ETP s are growing at rates up to 20%. The main uses for plastic products are computer and business machine parts as well as design engineered products. The consumption of styrenic plastics (polystyrene acrylonitrile butadiene styrene - ABS) is high, relative to polyolefins, because of their demand in electric/electronic end-uses. 

Polyacetals, also referred to as polyoxymethylenes (POMs) or polyfonnalde-hydes, are a semicrystalline engineering thermoplastic polymerized as a homopolymer and copolymer. The homopolymer and copolymer have somewhat different molecular structures and performance values. The difference between performance values is narrowing with new formulations (compounds). Polyacetal engineering thermoplastics were introduced to the world in 1956 with the potential of replacing metals, aluminum, brass, and cast zinc, which polyacetals continue to do. 

Polyacetals are distinguished from other engineering thermoplastics by the combined properties listed in Table 5.3. 

Thanks to their unusual miscibility polymer blends of polyphenylene oxide and polystyrene were the first commercially successful amorphous engineering thermoplastics blends, introduced back, in 1968 Pete Juliauo of GE Corporate Research Laboratories presented a comprehensive review at the last lUPAC Meeting of The Rague(l) where he showed how the evolution of science and technology of blends (2,3) based on polyphenylene oxide, blsphenol A polycarbonate, polybutylene teraphthalate, polyamides and polyacetals, created many more opportunities for the development of engineering thermoplastics with attractive combination of attributes. 

Bottenbruch L, editor. Engineering thermoplastics polycarbonates— polyacetals—polyesters— cellulose esters. NY Hanser 1996. 

The materials covered in this chapter are the crystalline members of the so-called engineering thermoplastics . They are rigid and robust, but somewhat more expensive than the commodity plastics, PE, PP, PS and PVC. Polyamides and saturated polyesters are used principally in fibres production, but plastics applications are important indeed, some materials have been developed specifically for plastics uses, notably polyamide 11, polyamide 12 and poly(butylene terephthalate). Polyacetals find application as plastics only. 

Polyacetals prepared from formaldehyde are engineering thermoplastics, which have found use in traditional metal applications. Some trade names of these polymers are Delrin acetal homopolymer (DuPont) Celcon acetal copolymer (Celanese/Hoechst) Duracon acetal copolymer (Celanese and Diacel—joint venture) Tenac acetal homopolymer by Asahi Chemical in Japan and Ultraform acetal copolymer jointly by BASF and Degussa, in Germany. The polymers have the basic structure shown below ... 

As can be deduced from plant purchases, the PRC is still at the formative stage where emphasis is on producing only the most basic petrochemicals. No plants were purchased for producing dibasic acids (phthalic and maleic anhydrides, etc.) and fluro-carbon or tetrafluoro ethylene or some of the advanced engineering plastics like ABS polyacetals, polycarbonates, polyimides or any other unsaturated polyesters. Another important area of low Chinese activity is thermoplastics for space and defense applications. ... 

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