D.C.-electrical conductivity as a method for monitoring radiation curing of unsaturated polyester resins-II. Influence of electrical field and dose rate

The course of radiation crosslinking of unsaturated polyester resins was followed by measuring electrical conductivity change. Both the electrical field strength and dose rate influenced the crosslinking. The electrical field somewhat increased the reaction rate possibly due to the orientation of a polar polyester chains. To investigate the effect of electrical field, the samples were irradiated to different doses at different field strengths, from 2.5 to 250 kV/m and then extracted in benzene to determine the extent of crosslinking. The extraction analysis of irradiated samples confirmed the influence of electrical field observed in conductivity measurements. The electrical field effect depended on the dose rate. Three dose rates were applied 3.05, 0.354 and 0.096 kGy/h. The medium dose rate gave the highest reaction rate (on dose scale). Faster decrease of free styrene content with radiation dose than increase of gel content at higher dose rate implies partial styrene graftng or homopolymerization. The higher the electrical field the more pronounced were the effects of dose rate.