A study of heat transfer during molding of elastomers

Heat transfer is often of a great importance in several elastomer processing unit operations and even more so in the case of any variety of vulcanization process although it is seldom treated equally important as the cross-linking kinetics. Heat transfer in several elastomers was studied on a pilot scale mold utilizing various expressions for description of temperature dependent elastomer densities, heat capacities and thermal conductivities, which were applied in the governing heat equation. The latter was solved by means of quasi-exact and explicit finite difference algorithms. Molding experiments were performed for natural rubber, polybutadiene, hydrogenated butadiene–acrylonitrile copolymer, polychloroprene and polyisoprene. Whereas the molding experiments were applied for determination of the temperature dependent thermal conductivities, the temperature dependent densities and heat capacities were determined separately using pycnometry and differential dynamic calorimetry, respectively. The experimental and the predicted temperatures were in good agreement throughout the entire examined temperature range between 20 and 200∘C. Moreover, the determined parameters of the temperature dependent thermodynamic quantities may be correlated to the parameters of other, non-elastomeric polymers. The developed model along with its determined parameters may be readily applied for a wide range of elastomers and processing operating conditions or even combined with other aspects of a certain operation, such as kinetics or mechanics.