Effect of Functionalized Nanosilica on Properties of Polyoxymethylene-Matrix Nanocomposites

Amino group and methyl group functionalized nano-silica (coded as RNS and DNS) particulates were separately used as nanofillers to prepare polyxymethylene-matrix (denoted as POM-matrix) nanocomposites by melt blending. The tensile strength, Young's modulus, and impact toughness of as-prepared POM-matrix nanocomposites were measured, and their thermal decomposition behavior and crystallization behavior were analyzed by means of thermogravimetric measurement and differential scanning calorimetry and polarized light microscope. Moreover, the morphology of as-prepared POM-matrix nanocomposites was observed with a transmission electron microscope. Results show that incorporating a proper content of RNS and DNS contributes to improve the tensile strength, Young's modulus and impact toughness of POM, and POM-DNS nanocomposites with a high content of inorganic filler have better mechanical properties than POM-RNS counterparts. Besides, POM-matrix nanocomposites have a higher crystallization onset temperature and a smaller grain size than neat POM, which is due to the heterogeneous nucleation effect of DNS and RNS. Moreover, incorporating RNS containing surface amino group helps to increase the thermal stability of POM-RNS nanocomposites and leads to an increase of initial decomposition temperature by about 27 degrees C; but the introduction of DNS has little effect on the thermal decomposition behavior of POM. The reason lies in that RNS containing surface amino group can strongly chemically interact with thermal decomposed products of POM (it can absorb formaldehyde and formic acid generated via thermal decomposition of POM) but DNS with surface methyl group cannot absorb formaldehyde and formic acid. POLYM. COMPOS., 35:127-136, 2014. (c) 2013 Society of Plastics Engineers