Synergistic effect of PTFE and sodium etched PTFE on polyacetal ternary blends

Abstract

Large surface area polytetrafluoroethylene(PTFE) powder has been treated at −40° with Na-naphthalene complex in tetrahydrofuran(THF) to change the surface of the polymer. The treated PTFE (WPTFE) was added to polyoxymethylene(POM) and POM/PTFE blends. POM/PTFE blends possess very good wear resistance but the mechanical properties are poor. For POM/WPTFE blends, rather different results were obtained; WPTFE acted as a reinforcement filler. In POM/(WPTFE + PTFE) blends, WPTFE functions as a reinforcement filler and also as a dispersion agent for PTFE in POM. Therefore, the mechanical properties of POM/WPTFE and POM/(WPTFE + PTFE) blends were better than those of POM and POM/PTFE blends respectively. When the weight ratio of WPTFE/PTFE in POM/(WPTFE + PTFE) blends was 3/97, the wear resistance was better than for POM or POM/WPTFE blends. This effect resulted because PTFE could be better dispersed by the aid of WPTFE in the blends; the processability of ternary blends of POM/(WPTFE + PTFE) was better than those of POM/PTFE and POM/WPTFE blends. Consequently, the addition of a small amount of WPTFE(WPTFE/PTFE < 9/91) into POM/PTFE blends produces materials with high strength, good wear resistance and good processability.