Abstract: Polyoxymethylene/reactable nanosilica composites were prepared via melt blending. The isothermal crystallization behavior of POM and its composites were studied with differential scanning calorimetry， and the effect of nanosilica was explored. The thermal decomposition was studied using thermogravimetric analysis. Avrami equation and HoffmanLaurititzen theory were used to analyze kinetics of isothermal crystallization of POM and its compositions. It showed that the reactable nanosilica (RNS) had a function of heterogeneous nucleation on the POM matrix, which enhanced the crystallization rate of POM, reduced the halftime for crystallization and the surface free energy of the developing crystals. The Avrami exponent n decreased, which indicated that RNS changed the crystallization and growth mechanism of POM. RNS improved the thermal stability and the onset temperate was improved 32 ℃ by 5 % RNS consents. The apparent activation energy of POM/RNS calculated using FOW and Friedman methods was higher than that of POM, which indicated that there must be some strong interaction between RNS and POM. RNS is both a nucleating agent and thermal stability agent of POM.

Key words: polyoxymethylene, nano-silica, isothermal crystallization, thermal decomposition