POLYACETAL POLYTETRAFLUOROETHYLENE BLENDS .2. THE EFFECT OF CHEMICAL SURFACE-TREATMENT OF POLYTETRAFLUOROETHYLENE

The mechanical, physical, wear, dielectric, thermal and morphological properties of blends of polyacetal (POM) with surface-modified polytetrafluoroethylene (CPTFE) were examined and compared with those of POM/PTFE blends. The PTFE was added to POM to improve the wear properties; the tensile strength, Young's modulus and elongation of POM/PTFE blends decreased with increasing PTFE content but the tensile strength and the Young's modulus of POM/CPTFE blends were more than twice those of the POM/PTFE blends. The NaF salt which was adsorbed on the CPTFE acted as a coupling agent and provided very strong bonding between POM and CPTFE. The free NaF salt also seemed to form nuclei aiding POM crystallization; this effect was not found in POM/PTFE systems. For POM/PTFE, SEM showed that the size of PTFE particles was in the range 15-60-mu-m. In POM/CPTFE systems, the particle size of CPTFE was < 1-mu-m. Increasing times of chemical surface treatment of CPTFE increased the tensile strength of POM/CPTFE blends.