Cross-linking kinetics of hyperbranched epoxy cured hyperbranched polyurethane and optimization of reaction conversion by central composite design

Study on cure kinetics and optimization of various curing parameters of thermosetting polyurethane are very important for its industrial utility. Hence, an attempt has been made to study the cure kinetics of hyperbranched polyurethane by using a hyperbranched epoxy with and without poly(amido amine) as a cross-linker. The kinetics study was conducted by Differential Scanning Calorimetric (DSC) measurements. Different kinetic parameters were evaluated by fitting the DSC data to an autocatalytic kinetic model using Advanced Pyris® 10.1 analytical software. The results clearly indicated the efficacy of the used cross-linker. The study witnessed greater conversion of curing with reduction in activation energy from 44.78 kJ/mol to 30.05 kJ/mol by hyperbranched epoxy and poly(amido amine), as a combined cross-linker. Dynamic calorimetric measurements suggested the effect of cross-linker on on-set, peak and end-set temperature of the curing reaction. The cross-linker effectively reduced the on-set curing temperature. Further, exothermic heat flow and other kinetic parameters such as order of reaction, rate constant, pre-exponential factor were found to be influenced by the cross-linker. A response surface model was also employed to optimize the conversion of curing with variation of time and temperature. A significant quadratic influence of the variables on the response was observed with model co-efficient >0.93. Thus, the cure kinetics and optimization of curing parameters of a hyperbranched polyurethane by a hyperbranched epoxy in the presence of a poly(amido amine) was demonstrated for the first time.