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... 

Both polymers are linear with a flexible chain backbone and are thus both thermoplastic. Both the structures shown Figure 19.4) are regular and since there is no question of tacticity arising both polymers are capable of crystallisation. In the case of both materials polymerisation conditions may lead to structures which slightly impede crystallisation with the polyethylenes this is due to a branching mechanism, whilst with the polyacetals this may be due to copolymerisation. 

Some typical properties of polyester-glass laminates are given in Table 25.1. From these figures it will be seen that laminates can have very high tensile strengths. On the other hand some laminates made by hand lay-up processes may have mechanical properties not very different from those of thermoplastics such as the polyacetals and unplasticised PVC. 

Cationic initiators can also polymerize aldehydes. For example, BF3 helps produce commercial polymers of formaldehyde. The resulting polymer, a polyacetal, is an important thermoplastic (Chapter 12) ... 

POLYACETALS SOME NYLONS POLYSULFONES THERMOPLASTIC POLYESTERS FLUOROP LAS TICS... 

Thermoplastics ABS, acetal and polyacetal, acrylic (methyl methacrylate), cellulose plastic, EVA, fluorocarbon, PTFE,... 

Kumar G., Neelakantan N.R., and Subramanian N., Mechanical behaviour of polyacetal and thermoplastic polyurethane elastomer toughened polyacetal, Polym. Plastics TechnoL Eng., 32, 33, 1993. Newmann W. et al.. Preprints, 4th Rubber Technology Conference, London, May 22-25, 1962. Farrissey W.J. and Shah T.M., Handbook of Thermoplastic Elastomers (Walker B.M. and Rader C.P., eds.). Van Nostrand Reinhold, New York, 1988. 

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

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. ... 

Among the more common thermoplastics from ring opening polymerization of interest in composite processing are polylactams, polyethers, polyacetals, and polycycloolefins. It has also been shown that polycarbonates can be produced from cyclic carbonates [22], Anionic ring opening polymerization of caprolactam to nylon 6 is uniquely suited to form a thermoplastic matrix for fiber-reinforced composites, specifically by the reaction injection pultrusion process [23-25]. The fast reaction kinetics with no by-products and the crystalline... 

Polyoxymethylene (POM) plastics are highly crystalline thermoplastics that are obtained by polymerization of formaldehyde and can also be in the form of trioxy-methylene oligomers (trioxane). The world-wide consumption in 1997 was 0.5 x 106 t for car parts and other articles processed by injection moulding. Polyacetals are primarily engineering materials being used to replace metals. 

Trogamid T can be processed without difficulty by the normal methods used for thermoplastics (5). In this respect it offers fewer problems than polyacetal or polycarbonate, for example. Some Trogamid T properties can be improved by biaxial orientation. The effects, however, are lower than with crystalline polymers. 

Fortunately, the deficiencies of both the classic thermosets and general purpose thermoplastics have been overcome by the commercialization of a series of engineering plastics including polyacetals, polyamides, polycarbonate, polyphenylene oxide, polyaryl esters, polyaryl sulfones, polyphenylene sulfide, polyether ether ketones and polylmides. Many improvements in performance and processing of these new polymers may be anticipated through copolymerization, blending and the use of reinforcements. 

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. 

Data have been published dealing with successful applications of HAS in stabilization of other polymers than PO elastomers, styrenic polymers, polyamides, polycarbonates, polyacetals, polyurethanes, linear polyesters, thermoplastic polyester elastomers, polyacrylates, epoxy resins, poly(phenylene oxide) or polysulfide [12]. In spite of their basicity, HAS may also be used for stabilization of PVC. This application includes less basic derivatives of piperidine and 1,4-dihydropyridine [12,13,145,146]. 

Includes polyacetal, polycarbonate, polyphenylene sulfide, thermoplastic polyester, polysulfone, modified polyphenylene oxide, polyimide, polyamide-imide and fluoropolymers Includes acrylics (532 MM lbs.), cellulosics (114 MM lbs.), PVC copolymers (178 MM lbs.). 

Polyfine . [Advanced Web Prods.] Thermoplastic resins economical substitute to polyacetal resin in q)plics. where friction and wear props, are required for VTR U )e reel, noiseless gear, bearing surface. 

Due to its high crystallinity, polyacetal is more rigid and stronger than other thermoplastics especially at elevated T (50-120°C). Because of its semi-crystalline character, POM requires a greater heat input for melting than amorphous resins. It has a fairly high heat of fusion (160-200 kJ/kg) but because of lower melt temperature (210°C), it requires considerably lower total heat energy than other crystalline polymers (viz., POM = 435-475, HDPE = 720, PA-66 = 756-786 kJ/kg). 

Polyoxymethylene polymers, POM, commonly known as polyacetals or Acetal resins are linear thermoplastic polymers containing predominantly the -CH -O- repeat unit in their backbone. There are two types of acetal resins available commercially (1) homopolymers made by the polymerization of formaldehyde, followed by endcapping, (2) copolymers derived from the ring opening polymerization of trioxane (a cyclic trimer of formaldehyde), and a small amount of a comonomer such as ethylene oxide. Acetal resins are... 

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