Chemorheological Investigation on The Effect of Three Polymerization Retardants on Hydroxyl Terminated Poly butadiene-based Polyurethane-Forming Rate

Research subject:

 The binder system based on of hydroxyl-terminated polybutadiene resin (HTPB), consist of dioctyl sebacate as a plasticizer (DOS), and toluene diisocyanate as the curing agent. Reaction between the HTPB hydroxyl resin group and the curing agent isocyanate group produces a polyurethane mesh to produce a rubber with the desired properties. In this research, the rheological and mechanical properties of the binder system were investigated and Physical properties compared in the presence of three chemicals retarder polymerization Polyurethane, oxalic acid, maleic acid and tetracycline.

Research approach:

 Oxalic acid, maleic acid and tetracycline alter the properties of the binder system by specific mechanisms. Oxalic acid and maleic acid react with the isocyanate group of the curing agent to produce amides and reduce the viscosity of the binder system. Due to its chemical structure, tetracycline reacts with the curing agent and prevents the development of the main reaction between the HTPB resin and the curing agent TDI and reduces the viscosity. Infrared Fourier transform (FT-IR) test was also used to investigate the functional mechanism of these compounds. In this test, the intensities of the spectra related to each sample were compared with each other and the type of function and mechanism of each of the oxalic and maleic substances and tetracycline were determined.

The structure of the reaction product between HTPB resin and oxalic acid, maleic acid and tetracycline with curing agent was determined and confirmed by FT-IR spectrum. In-situ FT-IR study showed reduction in isocyanate peak intensity after 60/90 min. Chemorheological investigation showed best performance at 0.05% concentration for all retardants, among them tetracycline, oxalic acid and maleic acid depicted 54%, 48% and 47% reduction in viscosity build-up; respectively. Adding 0.05% of tetracycline to binder system resulted in about 20% decrease in cross link density probably due to better interaction with curing agent which emphasized the best performance of 0.05%-tetracycline as retardant.