THERMAL AND THERMOPHYSICAL PROPERTIES OF EPOXY-SILICA NANOCOMPOSITES OF CATIONIC POLYMERIZATION

The polymer and composites were received using epoxy resin EPONEX 1510 – diglycidyl ether of dicyclohexylolpropane and 15 % solution of boron trifluoride in diethylene glycol. The silica particles were formed in situ via the sol-gel method using hydrolytic polycondensation of tetraethoxysilane. The silica sol was obtained in acetone as the organic solvent. Silica filler content in the composites varied from 0.5 to 3 wt%. The effect of the nanofiller on the thermophysical and thermal properties of the obtained polymers was studied. Thermophysical characteristics were determined by differential scanning calorimetry on a TA Instruments DSC Q2000 apparatus at a rate of heating of 20 °С/min in the temperature range from 5 to 190 °C. With the objective of decreasing the influence of the technological (kinetic) and thermal prehistory of the sample on its thermophysical characteristics, the scanning was done twice. The glass transition temperature and heat capacity jump of the composite coatings based on epoxy-silica prepared by cationic polymerization were studied. It was established that with an increase of filler content the glass transition temperature of composites increases, and the value of the heat capacity jump remains almost unchanged. Parameters of thermostability of polymer and composites were determined by thermogravimetric analysis on a TA Instruments Q50 apparatus at a rate of heating of 20 °С/min in the temperature range from 20 to 1000 °C in an atmosphere of oxygen. The destruction process of epoxy-silica composites proceeds in several stages. In the deep stages of the thermo-oxidative destruction of obtained composites the effect of the silica filler is insignificant. The obtained polymer coatings were subjected to a long-term (100 hours) isothermal aging at 160 °C in an atmosphere of oxygen. It was determined that the maximum rate of mass loss rate of epoxy-silica composites is 1.5 times lower than that of unmodified polymer