A Study Of PTFE Filament By Film Splitting And Its Properties

Due to its excellent chemical stability, low surface energy and high temperature resistance,PTFE filaments can be widely used in high temperature, corrosive environment. Along with the promotion and further implementation of energy-saving emission reducing policies, the demand to PTFE filaments will be greatly enhanced in dust removal bag filter in electric power, cement manufacturing and waste incineration plant. However, the domestic technology for high-strength PTFE filament manufacturing is still in a relatively laggard stage, therefore the development of high-strength PTFE filament is of great necessity and significance.The PTFE filament strength by emulsion spinning method and the paste extrusion method is low and the energy consumption is large, but the PTFE filament process by film splitting method is simple, non-polluting and has the potential of obtain high strength. This paper focuses on the influence of film splitting method manufacturing process to the micro-structure of PTFE filament at all stages, and this paper tries to establish the link between the processes and structure, mechanical properties, which will provide the basis for the preparation of high-strength PTFE filament. By SEM, DSC, sound velocity orientation instrument, electronic single-fiber strength instrument, high-temperature tube furnace, etc, the crystallinity, degree of orientation and mechanical properties of PTFE in various stages were measured, and the relationships between them were analyzed.Main contents and conclusions are as follows:(1) SEM, DSC, sound velocity orientation instrument, electronic single-fiber strength instrument measurement results showed the degree of crystallinity reduced significantly after heat treatment; lower end of heat treatment temperature and the smaller cooling rate was conducive to increasing the degree of crystallinity and orientation; and heat treatment greatly improved the toughness of PTFE flat filament. The best heat treatment temperature is 320℃.(2) Crystallinity and orientation of the PTFE filament first increased and then decreased with twist exerted onto the flat filament. Breaking strength of the PTFE filament showed the same trend with the crystallinity and orientation, which reached the maximum at 600 twist/m. Breaking elongation increased with twist.(3) Under small hot drawing ratios, the crystallinity, degree of orientation and breaking strength increased with the drawing ratio approximately in a linear relationship. Breaking elongation of the PTFE filament dropped with the drawing ratio in a decaying exponential manner. Breaking strength increased with hot-drawing temperature, reaching a maximum at 370℃, then it declined sharply with temperature.(4) The effective fixed elongation heat-setting treatment temperature is between PTFE glass transition temperature 127℃to melting temperature 345℃. 280℃was the best heat-setting temperature, where the crystallinity and breaking strength of the PTFE filament showed its maximum. When the heat-setting time lasted for 2minutes at 280℃, the crystallinity and mechanical properties reached a steady state. Heat-setting under fixed elongation had not obvious influence on the orientation degree of highly-oriented PTFE filament.