Study on inpact strength and effect of accelerated weather testing on some properties of polyoxymethylene / silica nanocomposites#

Abstract

The impact strength, some properties and morphology of nanocomposites based on polyoxymethylene (POM) and nano-silica (NS) with different content before and after accelerated weather testing are discussed in this paper. The impact strength of all POM/NS nanocomposite samples is larger than that of POM but decreased when the content of NS is more than 0.5 wt.%. The greatest value is 70.43 J/m at 5 wt.% of NS content (POM/0.5NS). The FTIR spectra of POM and POM/NS nanocomposites show the appearance of characteristic peaks of POM and NS in the nanocomposites. Carbonyl index (CI) for POM and POM/NS nanocomposites are changed after testing responding to the increase of C=O group content. The change of CI of POM before and after testing is 0.34, while that of all POM/NS nanocomposites is only around 0.15. The results of the tensile properties of POM/NS nanocomposites indicate that samples are decomposed by ultraviolet (UV) radiation and photo-oxidation degradation of POM. The tensile properties of POM/NS nanocomposites are larger than those of POM, and they are increased when rising NS content (from 0 to 1.5 wt.%). The retention of tensile strength and elongation at break of all POM/NS nanocomposites are reduced significantly while their Young modulus is less decreased after accelerated weather testing. The dielectric constant and dielectric loss tangent of the nanocomposites after testing are increased with rising NS content (from 0 to 2 wt.%). Contrary, volume resistivity of POM/NS nanocomposites after testing is reduced from 5.9 × 10+11 to 6.4 × 10+10 with rising NS content (from 0 to 2 wt.%). SEM images of the nanocomposites display the appearance of cracks on the surface of samples after testing. The number of the crack is decreased and the size of crack becomes smaller and fewer deeps when increasing NS content to 2 wt.%.