Investigating the Effect of Molecular Weight on Chemorheology of Hydroxyl Terminated Polybutadiene gum stock
Volume Title: 1
1Chemical Engineering group, Technical Department, Imam Hossein Comprehensive University, Iran
2Chemical Engineering Group, Technical Department, Imam Hossein Comprehensive University
Long pot life for the HTPB-based gum stock (binder system) is essential to simplify the processing and manufacturing of non-defect grains, especially large size grains. The HTPB microstructural parameters such as Mn, Mw, PDI, functionality distribution and the type and relative concentration of cis/trans/vinyl affect the kinetics of step polymerization of HTPB gum stock. Chemorheological behavior of binder systems based on three different number-averaged molecular weight HTPB samples (HTPB-A, HTPB-J, and HTPB-AJ), DOS plasticizer and TDI curing agent, is investigated using a rotational viscometer at a constant temperature of 40 ºC. In this paper, the influence of the number-averaged molecular weight of HTPB on high-filled composite HTPB-based binder system pot life is investigated and the possibility of controlling pot life by microstructure tailoring has been investigated. The viscosity of the curing system at any given time can be changed with respect to time as an exponential function. Viscosity build-up results showed a linear relationship between number-averaged molecular weight (Mn) and pot life (t) of HTPB-based binder system, [t = - an Mn + b] therefore, it can be said that when the Mn of the HTPB sample increases, the viscosity increases, resulting in a decrease in the pot life of the HTPB-based binder system due to increasing of hydroxyl content.