Nylon 6, stmcture

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 materials of attention in promoting fire safety are generally organic polymers, both natural, such as wood (qv) and wool (qv), and synthetic, nylon (see Polyamides), vinyl, and mbber (qv). Less fire-prone products generally have either inherently more stable polymeric stmctures or fire-retardant additives. 

Solutions of fluorosihcones impart oil and water repeUent finishes to nylon—cotton fabrics. One series of C-1 through C-9 perfluoroalkyl substituents with varying stmctures were attached to siHcon through amide or ether linkages. The fluorosihcones having perfluorinated straight-chain... 

Some heavier gauge flexible materials, usually containing nylon, are thermoformed, ie, heated and formed into three-dimensional shapes. Such stmctures are used to provide high gas-barrier, heat-sealable containment for processed meat or cheese. 

Other reinforcements that may be used in the substrate layers of decorative laminates and throughout the stmcture of industrial laminates are woven fabrics of glass or canvas and nonwoven fabrics of various polymeric monofilaments such as polyester, nylon, or carbon fibers. Woven and nonwoven fabrics tend to be much stronger than paper and have much more uniform strength throughout the x—y plane. They greatly enhance properties of laminates such as impact and tear strength. 

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-6,6 and nylon-6 have competed successfully ia the marketplace siace their respective commercial iatroductioas ia 1939 and 1941, and ia the 1990s share, about equally, 90% of the total polyamide market. Their chemical and physical properties are almost identical, as the similarity of their chemical stmcture might suggest the amide functions are oriented ia the same directioa aloag the polymer chain for ayloa-6, but are altematiag ia directioa for ayloa-6,6. 

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). 

Macromolecular stmcture and supermolecular organization also affect dye affinity. Drawn (oriented) nylon-6 has more of a random open stmcture than nylon-6,6 (172). Nylon-6, therefore, dyes more rapidly than nylon-6,6, but is also more susceptible to color crocking, especially with disperse dyes. 

A number of high melting poiat semiaromatic nylons, iatroduced ia the 1990s, have lower moisture absorption and iacreased stiffness and strength. Apart from nylon-6 /6,T (copolymer of 6 and 6,T), the exact stmcture of these is usually proprietary and they are identified by trade names. Examples iaclude Zytel HTN (Du Pont) Amodel, referred to as polyphthalamide or PPA (Amoco) and Aden (Mitsui Petrochemical). Properties for polyphthalamide are given ia Table 2. A polyphthalamide has been defined by ASTM as "a polyamide ia which the residues of terephthaUc acid or isophthahc acid or a combination of the two comprise at least 60 molar percent of the dicarboxyhc acid portion of the repeating stmctural units ia the polymer chain" (18). 

Cord materials such as nylon, polyester, and steel wire conventionally used in tires are twisted and therefore exhibit a nonlinear stress—strain relationship. The cord is twisted to provide reduced bending stiffness and achieve high fatigue performance for cord—mbber composite stmcture. The detrimental effect of cord twist is reduced tensile strength. Analytical studies on the deformation of twisted cords and steel wire cables are available (22,56—59). The tensile modulus E of the twisted cord having diameter D and pitchp is expressed as follows (60) ... 

Another class of metal complex dyes is derived from the formazan stmcture. These dyes are appHed to wool and nylon from a neutral or weakly acidic dyebath analogous to the 2 1 premetallized OjO -dihydroxyazo complexes. The bluish-gray dye Cl Acid Black 180 [11103-91-6] (61) (Cl 13710) is a 2 1 cobalt complex of the formazan type. 

Fig. 1. Chemical stmctures of barrier polymers, (a) Vlaylidene chloride copolymers (b) hydroly2ed ethylene—vinyl acetate (EVOH) (c) acrylonitrile barrier polymers (d) nylon-6 (e) nylon-6,6 (f) amorphous nylon (Selar PA 3426), y = x - - z-, (g) nylon-MXlD6 (h) poly(ethylene terephthalate) and (i) poly(vinyl...

Some other bearing materials find extensive use for which production volume is less well defined. EiHed plastics such as nylon, acetal resin, PTEE, and phenoHcs are formed and molded into bearings in a wide variety of mechanical stmctures. Tin, lead, and bronze alloys are used for oil-film bearings in heavy industrial and power generating equipment, frequently in custom bearings manufactured directly as machine components. 

Castor is the only renewable vegetable oil resource (see Chemurgy) having a hydroxyl group stmcture and functionaHty that leads to diverse oleochemicals. In 1988, approximately 35,000 t/yr of castor oil were used to prepare raw materials for the manufacture of nylon-11. It is estimated that 40,000—45,000 t of... 

C rbocyclic Azo Dyes. These dyes are the backbone of most commercial dye ranges. Based totally on benzene and naphthalene derivatives, they provide yellow, red, blue, and green colors for all the major substrates such as polyester, cellulose, nylon, polyacrylonitrile, and leather. Typical stmctures (26—30) are shown in Figure 4. 

Nylon is similar ia its general chemical stmcture to the natural fiber wool, and therefore all the previously described processes for wool are appHcable to dyeiag nylon with acid, metallised, and other dyes. There are, however, significant differences. Nylon is synthetic, it has defined chemical stmcture depending on the manufactufing process, and it is hydrophobic (see Fibers, POLYAMIDES). 

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