Development of a reaction injection molding encapsulant system. I: Kinetic studies of butyllithium-catalyzed styrene polymerization

Differential scanning calorimetry (DSC) was used to study the isothermal bulk polymerization of styrene, initiated by either n-butyllithium or 2-butyllithium, over the temperature range 20-50 deg C. At higher temperatures, the rates of polymerization initiated with either n-butyllithium and 2-butyllithium were the same within experimental error. The polymerization reaction order with respect to initiator and monomer concentrations was found to be 0.5 and 1.0, respectively. The heat of reaction was found to be 16 plus/minus 0.5 kcal/mol, and the activation energy for polymerization was determined to be 14.4 plus/minus 0.6 kcal/mol, with the corresponding prefactor A = 4.5 x 10 exp 8 s exp --1 (L /mol) exp 1Maps2 . Nearly adiabatic polymerizations were carried out using 2-butyllithium-initiated styrene to simulate the reaction injection molding (RIM) operation. The reactor system was found to have a time constant for heat transfer of 48 s. Numerical calculations based on these kinetic and heat-transfer parameters were found to agree well with experiment. Graphs. 26 ref.--AA