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Handbook of Materials for Product Design Part 6

Tham khảo tài liệu 'handbook of materials for product design part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Plastics 4.59 TABLE 4.8 Thermal Physical and Mechanical Properties of Parylenes38 Parylene N Parylene C Typical thermal properties Melting temperature C Linear coefficient of expansion mm mm C Thermal conductivity 10 4 cal s cm2 C cm 405 6.9 3 280 3.5 Typical physical and mechanical properties Tensile strength lb in.2 6 500 10 000 Yield strength lb in.2 6 100 8 000 Elongation to break 30 200 Yield elongation 2.5 2.9 Density g cm3 Coefficient of friction 1.11 1.289 Static 0.29 0.25 Dynamic 0.29 0.25 Water absorption 24 h 0.06 0.029 in 0.01 0.019 in Index of refraction nD 23 C 1.661 1.639 Data recorded following appropriate ASTM method. TABLE 4.9 Film-Barrier Properties of Parylenes38 Polymer Gas permeability cm3-mil 100 in2 24 h-atm 23 C Moisture-vapor transmission g-mil 100 in2 24 h 37 C 90 RH N2 O2 CO2 H2 S SO2 Cl2 Parylene N 7.7 39.2 214 795 1 890 74 1.6 Parylene C 1.0 7.2 7.7 13 11 0.35 0.5 Epoxies 4 5-10 8 1.8-2.4 Silicones 50 000 300 000 4.4-7.9 Urethanes 80 200 3 000 2.4-8.7 Data recorded following appropriate ASTM method. fabrication by conventional melt-processing techniques. Typical properties are given in Ref. 40. Thermal properties. Polyaryl sulfone is characterized by a very high heat-deflection temperature 535 F at 264 lb in2 which is approximately 150 F higher than many other commercially available thermoplastics as shown in Fig. 4.35. This is a consequence of its high glass- 4.60 Chapter 4 temperatures for some engineering thermoplastics at 264 lb in2. transition temperature 550 F rather than the effect of filler reinforcement or a crystalline melting point. At 500 F it maintains a tensile strength in excess of 4000 lb in2 and a flexural modulus of 250 000 lb in2. The resistance to oxidative degradation is indicated by the ability of polyaryl sulfone to retain its tensile strength after 2000-h exposure to 500 F air-oven aging. Chemical resistance. Polyaryl sulfone has good resistance to a wide variety of chemicals including acids bases and common .