PREPARATION OF TOUGHENED PMMA THROUGH PEG-MODIFIED URETHANE ACRYLATE PMMA CORE-SHELL COMPOSITE-PARTICLES/

Poly( urethane acrylate) (PUA)/poly (methylmethacrylate) (PMMA) core-s hell composite particles were prepared by two-stage emulsion polymeriz ation. The sizes of composite particles could be varied from 25 to 210 nm by introducing polyoxyethylene (POE) groups to the urethane acryla te molecular backbone. Core-shell morphology was identified by investi gating the polarity of the surface of the core and shell polymer parti cles and by measuring the contact angle of the composite particles. A composite particle prepared with relatively small particles (about 20 nm) did not show the core/shell morphology, because the high polar sur face of the core polymer particle and the low-stage ratio of the core to the shell cause the formation of a core/shell two-stage latex to be more thermodynamically unstable. The fracture toughness of rubber-tou ghened PMMA containing PUA/PMMA composite particles increased as the p article sizes decreased and the shell thickness of the composite parti cles increased. In particular, when the average size of the composite particle was about 43 nm and the stage ratio was 50/50, the fracture t o toughness of the rubber-toughened PMMA increased more than three tim es compared with that of pure PMMA. Furthermore, the transparency of t oughened PMMA could be maintained up to 91% in the visible spectra ran ge. (C) 1998 John Wiley & Sons, Inc.