Nylon plastic amorphous

Polymers Elastomers (rubbers) Soft plastics (e.g. low density PE) Isotropic hard plastics ( Amorphous [ Semi-crystalline Conventional fibres (nylon, PETP) "Extended chain" fibres (Extended zig-zag chains (Extended helical chains ( Glassy. Cross-linked (Tg < 275 K lTg> 325 K 0.001 0.2 2.5- 3 2.5- 5 1-3 3 5-15 250fl ca 50fl... 

Fatigue data for amorphous nylon plastics are shown in Figs. 8.66-8.69. 

Nylon 6,6 and nylon 6 accounted for most of the 4 million ton nylon fibers as well as the 2.7 million ton nylon plastics used in 2011. Some of the large-volume fiber products include carpets, apparel, and tire cord. Smaller markets include strings for guitars, tennis racquets, and fishing lines. Molded and extruded nylons are used in automotive, electronics, and electrical parts. Other applications of amorphous nylons include coatings and adhesives. 

In order for a plasticizer to enter a polymer stmcture the polymer should be highly amorphous. Crystalline nylon retains only a small quantity of plasticizer if it retains its crystallinity. Once it has penetrated the polymer the plasticizer fills free volume and provides polymer chain lubrication, increa sing rotation and movement. 

The properties of elastomeric materials are also greatly iafluenced by the presence of strong interchain, ie, iatermolecular, forces which can result ia the formation of crystalline domains. Thus the elastomeric properties are those of an amorphous material having weak interchain iateractions and hence no crystallisation. At the other extreme of polymer properties are fiber-forming polymers, such as nylon, which when properly oriented lead to the formation of permanent, crystalline fibers. In between these two extremes is a whole range of polymers, from purely amorphous elastomers to partially crystalline plastics, such as polyethylene, polypropylene, polycarbonates, etc. 

An important subdivision within the thermoplastic group of materials is related to whether they have a crystalline (ordered) or an amorphous (random) structure. In practice, of course, it is not possible for a moulded plastic to have a completely crystalline structure due to the complex physical nature of the molecular chains (see Appendix A). Some plastics, such as polyethylene and nylon, can achieve a high degree of crystallinity but they are probably more accurately described as partially crystalline or semi-crystalline. Other plastics such as acrylic and polystyrene are always amorphous. The presence of crystallinity in those plastics capable of crystallising is very dependent on their thermal history and hence on the processing conditions used to produce the moulded article. In turn, the mechanical properties of the moulding are very sensitive to whether or not the plastic possesses crystallinity. 

As regards the general behaviour of polymers, it is widely recognised that crystalline plastics offer better environmental resistance than amorphous plastics. This is as a direct result of the different structural morphology of these two classes of material (see Appendix A). Therefore engineering plastics which are also crystalline e.g. Nylon 66 are at an immediate advantage because they can offer an attractive combination of load-bearing capability and an inherent chemical resistance. In this respect the arrival of crystalline plastics such as PEEK and polyphenylene sulfide (PPS) has set new standards in environmental resistance, albeit at a price. At room temperature there is no known solvent for PPS, and PEEK is only attacked by 98% sulphuric acid. 

Typical crystalline plastics are polyethylene, polypropylene, nylon, acetals, and thermoplastic polyesters. Typical amorphous plastics are polystyrene, acrylics, PVC, SAN, and ABS. 

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