The morphology and properties of melt-mixed polyoxymethylene/monosilanolisobutyl-POSS composites

In this study, the morphology and thermo-mechanical behavior of composites formed by a polyoxymethylene (POM) matrix and monosilanolisobutyl polyhedral oligomeric silsesquioxane (msib-POSS) filler have been studied. The msib-POSS molecules were added to the POM by direct melt blending at loadings between 0 and 10 wt.%. Hydrogen bonding interactions were detected between POM and msib-POSS Si-OH groups, increasing their mutual compatibility and leading to nanometer-size dispersion of some msib-POSS molecules. These interactions do not prevent POSS aggregation during blending, but lead to micron-scale msib-POSS domains. The thermal decomposition temperature of the composites remained practically constant under inert and oxidative conditions. The low temperature thermal transition (γ) and glass transition temperature (T_g) of POM were found to move to higher temperatures only when 2.5 wt.% of msib-POSS was added, indicating that POSS is physically linked to the POM chains, restricting their motion under those conditions. Low content (2.5 wt.%) of msib-POSS results in antiplastization, whereas higher levels of POSS lead to a decrease in the storage modulus of the polymer. The relationships among these effects and the morphological characteristics of the systems will be discussed herein.