再生利用によるPTFE粉末粒子形態の変化がPTFE成形物の機械強度に与える影響

抄録

It is known that PTFE compacts fabricated using recycled PTFE powder which is melted once show much lower mechanical strength than those fabricated using virgin PTFE powder as-polymerized. However, the reason has not been clear still. Then, in this study, characters of virgin PTFE and recycled PTFE powders and properties of virgin PTFE and recycled PTFE compacts were investigated. The crystallinity and the melting point of the recycled PTFE powder were lower than those of the virgin PTFE powder, which are well-known differences between the recycled PTFE and the virgin PTFE powders. In addition, we first found that while the virgin PTFE powder had not only granular morphology but also fibrous morphology, the recycled PTFE powder did not have fibrous morphology. The fabricated recycled PTFE compacts had higher porosity and much lower mechanical strength than the fabricated virgin PTFE compacts. The fibrous morphology of the virgin PTFE powder was entangled with PTFE particles during compressing, which resulted in the higher packing structure, furthermore, during firing the densification and the fusion at the PTFE particle-interfaces where the entangled structure was formed proceeded much more, which resulted in the strong PTFE particle-interfaces. On the other side, because the recycled PTFE powder having no fibrous morphology could not formed the entangled structure, the densification and the fusion at the PTFE particle-interfaces did not almost proceed during firing and PTFE particle interfaces were not almost strengthened. So not only the higher porosity but also the week particle-interface where interlocking structure of fibrous morphology was not formed made the mechanical strength of recycled PTFE compacts lower.