Determination of the Softening Point of Novolac Resins Used for Shell Process

The softening point is taken as the sign to differentiate the license tag of the novolac resins used for shell process in our country. Although the softening point is determined by the ringand瞓all method, the heating medium and the rate of heatingup are various. In this paper, It is found that the significant effect of the rate of heatingup on the softening point by a series of experiments. The more higher the softening point the more obvious the distinction. There is the effect of the heating medium on the determination of the softening point too. The softening point in the bath glycerin is the less higher than the softening point in the bath water. The water used in bath water should be the lately boiled and cooled down to 5℃'s distilled water, or be pure water for drinking. The rate of the heatingup should be (5±05℃)/min to determine the softening point of the novolac resins used for shell process.