THE INHOMOGENEITY OF CROSS-LINKING OF OLI GOMERS DUE TO CONVECTION

Experimentally studied were the inhomogeneities of various types in th e material obtained by photoinitiated and thermal polymerization of co mpositions based on epoxy resins. Primary effect discovered at one-sid ed initiation of reaction was the onset of convective flows, which des troy layered pattern of reaction. Under actual experimental conditions there superpose conversion- and temperature-induced inhomogeneities. It was possible to suppress the onset of thermal convection in chemica lly initiated polymerization by applying a stabilizing temperature gra dient (heating from above). The results obtained show that in the item s obtained from reactive oligomers by photoinduced polymerization (but for polymerization of thin films), there inavoidably is inhomogeneity related to convective flow and this predetermines the quality of such items.