Key words: supercritical carbon dioxide, metacrylates, co-polymerization, composites
Methyl metacrylate and ethylene glycol di-metacrylate are co-polymerized in plastified ultahigh molecular weight polyethylene (UHMWPE) matrix in supercritical carbon dioxide (SC-CO2) medium. Composites with varied ratio of components are obtained. The mechanism of co-polymerization is determined by the way of attaining the supercritical conditions and does not depend on monomer ratio. If temperature is increased in closed volume (initial pressure 3÷4 MPa) from -20 to 120 °C with a subsequent addition of liquid CO2 (20 °C) to final pressure 20 MPa, a «block» polymerization in mass is taking place. On the contrary, if temperature and pressure are risen simultaneously from the initial values (room temperature, 6÷7 MPa) to the same final values (120 °C, 20 MPa), a dispersion polymerization occurs. The data obtained by differential scanning calorimetry demonstrate that metacrylate-impregnated UHMWPE samples have lower degree of crystallinity and reduced crystallization temperature. Atomic-force microscopy is utilized to study the surface structure and micro-mechanical properties of polymer samples. The results demonstrate the possibility of obtaining nano-scale uniform composites of the studied type.