Thermomechanical properties of polyhedral oligomeric silsequioxane- poly(methyl methacrylate) nanocomposites

摘要

Poly(methyl methacrylate)s (PMMA) containing polyhedral oligomeric silsesquioxane (POSS) nanoparticles (d [approx.] 1.5 nm) were subjected to heological, mechanical, and morphological tests to determine the effects that POSS has on the melt-state and solid-state properties of this commercially important amorphous polymer. The effect of POSS on the rheological properties varied depending on the type of POSS cage and whether the POSS was covalently tethered to the PMMA backbone. A highly miscible acrylic-POSS species plasticizes PMMA, decreasing the glass transition temperature by approximately 10⁰C at a loading of 10 vol%. An essentially immiscible POSS species (cyclohexyl-POSS) does not alter the ... of PMMA but is able to decrease slightly the zero shear-rate viscosity at low loadings. Incorporating a POSS filler (isobutyl-POSS) into an isobutyl-POSS-PMMA copolymer causes a significant increase in viscosity at all loadings. The addition of POSS fillers to PMMA leads to an enhancement in the toughness in both slow-speed tension (strain rate = ... ) and high rate split-Hopkinson pressure bar tests (strain rate = ... ). In particular, the combined addition of two distinct POSS species - one miscible, one immiscible - led to the greatest enhancement in toughness and excellent reproducibility. A four-fold increase in tensile toughness was observed through the use of these two disparate POSS species.