Nylon thermal-physical properties

TABLE C.3 Thermal-Physical Properties of Polycaprolactam, Nylon 6... 

TABLE Thermal-Physical Properties of Poly(hexamethylene adipamide), Nylon 6,6... 

Thermal and physical properties of plastics (typical values) Nylon 66 Glut-filled Nylon 66 Nylon S Nylon 6... 

As in the case of nylons, the flexibility of PUs is increased as the number of methylene groups is increased, and the rigidity is related to the number of stiffening groups, such as phenylene groups in the chain. As the number of methylene units increases (Table 14.6), the Tm decreases. The Tm generally increases as the flexible units are replaced by nonflexible units, such as phen-ylenes and piperazines. Thermal and physical properties of aliphatic PUs are shown in Table 14.7. 

To measure the thermal stability of polymers, one must define the thermal stress in terms of both time and temperature. An increase in either of these factors shortens the expected lifetime. In general terms, for a polymer to be considered thermally stable, it must retain its physical properties at 250°C for extended periods, or up to 1000°C for a very short time (seconds). As compared to this, some of the more common engineering thermoplastics such as ABS, polyacetal, polycarbonates, and the molding grade nylons have their upper limit of use temperatures (stable physical properties) at only 80°C—120°C. 

Temperature and Moisture Properties. Thermal treatment and moisture affinity significantly influence the physical properties of nylon fibers and fabrics. The absorption of water causes the fiber to swell, which alters its dimensions and in turn changes the size, shape, stiffness, and permeability of yams and fabrics. It also alters the frictional and static behavior of yarns in mill processing as well as the performance of fabrics during use. Water, a powerful plasticizer for... 

For the processing of polymeric materials, thermal behavior of structure and the crystallization mechanism are the important factors for the final physical properties. For nylon 46, the combination NMR and TEM was applied to investigate the crystallization mechanism [83]. 

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. 

PEBA exhibit a two-phase (crystalline and amorphous) structure and can be classified as a flexible nylon. Physical, chemical, and thermal properties can be modified by appropriate combination of different amounts of polyamide and polyether blocks [149], Hydrophilic PEBAs can be prepared which can have specific applications in medical devices. Similarly to other thermoplastic elastomers, the poiyamide-based ones find applications in automotive components, sporting goods conveyor belting, adhesives, and coatings [150]. In recent years the world consumption was approximately 6400 tons per year with about 80% in Western Europe and the rest equally split between the United States and Japan [143],... 

Physical and thermal properties for Nylon 6,6 poly (hexamethylene adipamide) Epoxies have excellent electrical and thermal resistance. They are thermosets. Addition of fillers improves hardness, impact resistance and thermal conductivity. 

Physical and thermal properties for Nylon 6,6 poly (hexamethylene adipamide) Nylons are tough and strong and can be used over a wide temperature range ( 80 to 120°C). Nylons have a low coefficient of friction. This leads to extremely good abrasion resistance, further improved by adding surface lubricants or annealing at 150-200°C. Nylons perform unreliably in wet environments because they absorb water readily. 

While the tensile properties and hydrophobicity of polyester make it a superior fibre for seat belts, the greater flexibility and recovery of nylons suggest that these are preferable physical features. However, as Table 11.7 shows, the real advantages of nylons and particularly nylon 6.6 arises from their greater specific heat capacity and latent heats of fusion which enable them to absorb over 30% more thermal energy than polyester before they start to lose their tensile properties as a consequence of heat generated during bag inflation. 

Property data for GRTP s are presented in two major breakouts. In the first breakout, the basic resins—styrene acrylonitrile (SAN), polycarbonate, polysulfone, polyacetal, polypropylene, polyphenylene oxide (PPG), nylon, modified PPG, and polyvinyl chloride—are treated as the independent variables and the physical, mechanical, electrical, thermal, chemical, and weathering characteristics are treated as the dependent variables. In the second breakout, the functional relationships are reversed, te., the properties are the independent variable and the resins are the dependent variable. ASTM test methods by which the physical values were determined are listed. The. physical data versus resins are presented in both tabular and graphic form. 

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