Facile approach for largely refining phase domains of PMMA/PS blends and improving their properties during extrusion

The immiscible poly(methyl methacrylate)/polystyrene (PMMA/PS) blends with three composition ratios (80/20, 70/30, and 60/40 w/w) are prepared using water-assisted mixing extrusion (WAME). The injected high-pressure water during extrusion facilitates to significantly refine the phase domains without adding compatibilizer. Compared with the counterpart blend samples prepared without injecting water, the mean diameter of the PS droplet is decreased by approximately 50% for the PMMA/PS (80/20) sample; the co-continuous structure is obviously finer for the PMMA/PS (60/40) sample. The PS phase sizes in the PMMA/PS blends prepared by WAME in this work are smaller than those reported in relevant references. The mechanism is analyzed for promoting the phase domain refinement in the PMMA/PS blends during WAME based on high-pressure rheological tests. The phase domain refinement can improve the anti-creep property of the PMMA/PS blends, and simultaneously enhance their tensile strengths and elongations at break. This work gives a guidance for refining the phase domain of immiscible polymer blends by facilely injecting high-pressure water during extrusion instead of adding compatibilizer (e.g. block or graft copolymer, and fillers).