Nylon crystallinity

Nylon 66 Crystalline, tough, resistance to wear, high strength Gears, bearings, rollers, pulleys, fibers... 

Crystalline fructose Crystalline nylons Crystalline platelets Crystalline polymers Crystalline polypropyL Crystalline Si Crystalline silica... 

Polyetheramide. These thermoplastic elastomers are typically block copolymers of polyether rubber with nylon crystalline domains. 

Thermal microscopy Melting range Distinguishes nylon crystallinity differences... 

For additional aid in material comparisons, these resins have been grouped as follows Styrenics, Olefins, Nylons, Crystallines, Arylates, and Miscellaneous. For additional glass-reinforcement levels and other lubricants such as PTFE, MoS see specific product data sheets, ICI-LNP. 

Commercial production of PVA fiber was thus started in Japan, at as early a period as that for nylon. However, compared with various other synthetic fibers which appeared after that period, the properties of which have continuously been improved, PVA fiber is not very well suited for clothing and interior uses because of its characteristic properties. The fiber, however, is widely used in the world because of unique features such as high affinity for water due to the —OH groups present in PVA, excellent mechanical properties because of high crystallinity, and high resistance to chemicals including alkah and natural conditions. 

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. 

Nylon. The high degree of crystallinity in nylon means that plasticization can occur only at very low levels. Plasticizers are used in nylon but are usually sulfonamide based since these are generally more compatible than phthalates. DEHP is 25 phr compatible other phthalates less so. Sulfonamides are compatible up to 50 phr. 

Tensile Properties. Tensile properties of nylon-6 and nylon-6,6 yams shown in Table 1 are a function of polymer molecular weight, fiber spinning speed, quenching rate, and draw ratio. The degree of crystallinity and crystal and amorphous orientation obtained by modifying elements of the melt-spinning process have been related to the tenacity of nylon fiber (23,27). 

The crystallinity can be dismpted by substituents on the chains that interfere with the alignment process. Amorphous nylons are produced by deUberately engineering this effect, eg, nylon-NDT/INDT (also known as PA-6-3-T or PA-TMDT), which uses trimethyl-substituted hexamethylenediamine isomers combined with terephthaUc acid. 

Physically there are differences. Like all polymeric fibers nylon contains crystalline and noncrystalline areas. Only amino groups ia the noncrystalline regioas are accessible. 

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. 

Lubricity of crystalline polymers is usually higher than that of amorphous polymers. Excellent machinery parts are made from crystalline nylon-6,6 resins, eg, gears, cams, wedges, and other components not requiring lubrication. Gears made of amorphous polyimide resin, on the other hand, do not exhibit this feature. 

Fig. 1. Engineering resins cost vs annual volume (11) (HDT, °C) A, polyetheretherketone (288) B, polyamideimide (>270) C, polyarylether sulfone (170- >200) D, polyimide (190) E, amorphous nylons (124) F, poly(phenylene sulfide) (>260) G, polyarylates (170) H, crystalline nylons (90—220) I, polycarbonate (130) J, midrange poly(phenylene oxide) alloy (107—150) K, polyphthalate esters (180—260) and L, acetal resins (110—140).

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