| Irradiation at a dose of 3.21 Mrad caused polystyrene matrix to crosslink, which enhanced rheological properties. Irradiation of PS matrix filled with synthesized monodisperse crosslinked poly(methyl methacrylate) microparticles caused these properties to decrease. At low frequency, in dynamic mechanical analysis and at small shear rate, in steady shear measurement, a higher degree of crosslinking of PMMA increased elasticity and led to higher values of rheological properties. Two cases were compared: (A) unirradiated PS matrix filled with pre-irradiated PMMA microparticle powders; (B) filled composite of PMMA and PS irradiated together. Effects of oxygen were examined. For case A, irradiation in air caused rheological properties to decrease less due to more efficient oxidation and generation of peroxy radicals; for case B, irradiation in air caused rheological properties to decrease more due to less peroxide generated, cage recombination of PMMA scission fragments, and reaction of oxygen with radical precursors of crosslinking in PS. |
