Nylon also properties

The polymer can be spun into an elastic yam of very fine denier. It is also claimed to exhibit good mechanical properties for molding and compares favorably with commercial polyesters and nylons. Also, polycaprolactone was reported to be used in some medical applications in biodegradable surgical sutures and postoperative support pins and splints. Similar uses are also found for two other polyesters, poly (lactic acid) and poly(glycolic acid). The two polymers form from their cyclic dimers by cationic ring-opening polymerizations with the aid of Lewis acids ... 

Nylons were one of the early polymers developed by Carothers. Today, nylons are an important thermoplastic, with consumption in the United States of about 1.2 billion lb in 1997 88 Nylons, also known as polyamides, are synthesized by condensation polymerization methods, often an ahphatic diamine and a diacid. Nylon is a crystalline polymer with high modulus, strength, and impact properties, and low coefficient of friction and resistance to abrasion. Although the materials possess a wide range of properties, they all contain the amide (-CONH-) linkage in their backbone. Their general structure is shown in Fig. 2.8. 

Combinations of PEI resins with polyamides (nylons) also produce phase-separated blends with fine particle morphology and good mechanical properties, hkely arising from phase adhesion between the two resins... 

In cases where the polyethylene alone cannot be made to resist certain chemicals, such as hydrocarbon fuels, other materials can be extruded over the outer polyethylene jacket for an additional measure of protection for exposed cable. In these cases the added materials themselves may not be ideally suited for use as a stand-alone cable jacket due to certain material properties, cost, or other considerations. However, when extruded over a base polyethylene outer jacket the overall sheath combination results in composite structure that is resistant to a wide range of operating conditions and environmental concerns. Oversheaths consisting of nylon are available from some manufacturers and can be useful in heavy industrial environments where exposure to known aggressive chemicals is likely. Nylon also has been shown to improve the sheath s resistance to boring insects. 

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

The film tube is collapsed within a V-shaped frame of rollers and is nipped at the end of the frame to trap the air within the bubble. The nip roUs also draw the film away from the die. The draw rate is controlled to balance the physical properties with the transverse properties achieved by the blow draw ratio. The tube may be wound as such or may be sHt and wound as a single-film layer onto one or more roUs. The tube may also be direcdy processed into bags. The blown film method is used principally to produce polyethylene film. It has occasionally been used for polypropylene, poly(ethylene terephthalate), vinyls, nylon, and other polymers. 

Optical properties also provide useful stmcture information about the fiber. The orientation of the molecular chains of a fiber can be estimated from differences in the refractive indexes measured with the optical microscope, using light polarized in the parallel and perpendicular directions relative to the fiber axis (46,47). The difference of the principal refractive indexes is called the birefringence, which is illustrated with typical fiber examples as foUows. Birefringence is used to monitor the orientation of nylon filament in melt spinning (48). 

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