Effect of curing agent on Tg of epoxy resin III

Through the establishment of some simple molecular models of cured epoxy resin, in the study of the change of glass transition temperature (TG) of epoxy resin with the structure of curing agent, the simulated value is in good agreement with the calculated value, although there is a large deviation from the experimental value, the effect of curing agent on TG can be qualitatively obtained by MD simulation The proposed method has potential significance for the development of curing agents with improved curing effect A simple and feasible method is proposed to predict the glass transition temperature of epoxy resin cured with different curing agents This method consists of two steps: building molecular model and operating molecular simulation The method is verified by comparing simulation results with calculation or experiment results Then the effect of curing agent on the thermosetting resin of the corresponding cured epoxy resin was investigated 3 Results and discussion: make V-T curve for the data set obtained from the simulation of two epoxy systems The data points above and below Tg are approximately in a straight line The glass transition temperature is determined as the inflection point of the curve At the corresponding temperature of the point, the volume of the system changes dramatically (Fig 3, 4) Compared with the calculated value and the experimental value (the calculated value comes from the QSPR prediction of cerius2.synthia, and the experimental value comes from the literature), it is obvious that the results of molecular dynamic simulation agree well with the predicted value of QSPR, but deviate greatly from the experimental value (see Table 1) The theory on which these methods are based may be a reasonable explanation for these differences Compared with the general group contribution method, QSPR method uses connection index correlation prediction, MD simulation method studies the movement of molecular conformation, while DSC method commonly used in experiments is based on the mutation principle of heat flow in the system near the glass transition temperature (TG).