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Coatings Technology Handbook Episode 2 Part 8

Tham khảo tài liệu 'coatings technology handbook episode 2 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 72-4 Coatings Technology Handbook Third Edition TABLE 72.3 Effectiveness of Mold Release Agents in Acetal Release Agent Level ppm Reduction of Ejection Force N N -Ethylene bisstearamide 7500 26.0 N N -Ethylene bisoleamidea 5000 25.1 N N -Ethylene bisstearamide 5000 23.3 Stearyl stearamide 5000 21.1 Stearamide 5000 20.4 Erucamide 5000 21.8 N N -Ethylene bisstearamide 2500 15.2 N N -Ethylene bisstearamide 1000 5.3 Fluorocarbon spray-on 22.1 a Causes resin to darken during processing. TABLE 72.4 Mechanical Properties of Acetal with N N - Ethylene Bisstearamide Present N N --Ethylene Bisstearamide ppm Property 0 2500 5000 Tensile strength at yield psi 9965 9883 9818 Elongation at break 36 39 41 Izod impact ft-lb in. 1.30 1.32 1.35 72.4.1.2 Acetal The most effective mold release agents in acetal are fatty amides in general and fatty bisamides amides in particular. Ethylene bisoleamide shows 25.1 reduction of mold release force at 5000 ppm but causes a visible darkening of the resin during processing. Ethylene bisstearamide a saturated amide is nearly as good showing 23.3 reduction at a level of 5000 ppm it does not cause any color problems. Other secondary amides such as stearyl stearamide and stearyl erucamide give mold release improvement nearly as good as the bisamides see Table 72.3 . Primary amides such as erucamide oleamide and stearamide also show good mold release enhancement in acetal. None of the nonamide materials examined has the mold release effectiveness of the amides. The best ester mold release agent is cetyl palmitate which exhibited a 16.5 reduction in mold release force at a 5000 ppm treatment level. The optimum amount of ethylene bisstearamide is 5000 ppm. When used above that level there is little increase in effectiveness below that amount the maximum effectiveness is not reached. The use of fatty amides as mold release agents has negligible effect on mechanical properties see Table 72.4 . 72.4.1.3 Polybutylene Terephthalate Fatty bisamides are the