Cryogenic mechanical alloying of poly(methyl methacrylate) with polyisoprene and poly(ethylene-alt-propylene)

Mechanical alloying is performed at cryogenic temperatures to incorporate p olyisoprene (PI) or its hydrogenated analogue poly(ethylene-alt-propylene) (PEP) into poly(methyl methacrylate) (PMMA) as an example of high-energy so lid-state blending. Morphological characterization of the blends by X-ray a nd electron microscopies confirms that the degree of dispersion of the cons tituent polymers improves with increasing milling time. Such dispersion in the PEP/PMMA blends is, however, ultimately compromised by phase coarsening when the materials are postprocessed above the PMMA glass transition tempe rature in the melt. Milling-induced PI cross-linking serves to suppress pha se coarsening in PI/PMMA blends, which remain relatively well-dispersed eve n after postprocessing. These blends are generally less fracture-resistant than the as-received PMMA due mainly to the accompanying reduction in PMMA molecular weight. Their optical transparency is observed to decrease dramat ically with increasing PEP or PI concentration until they appear opaque. An overall improvement in blend properties by mechanical alloying is, however , anticipated upon judicious selection of more degradation-resistant polyme rs.