Catalyst Screening for Reaction of HTPB and IPDI in PBX Formulations

Abstract. HTPB-IPDI binder system generally used in polymer bonded explosive (PBX) formulations. Polyurethane structure is formed as a result of catalytic cure reaction of HTPB and IPDI. Therefore, catalyst plays a crucial role by facilitating the reaction through the formation of various complexes, thereby reducing the activation energy in PBX formulations. While DBTDL is commonly used due to its high catalytic efficiency, its environmental and health risks have prompted the search for alternative catalysts. Depending on the catalyst employed, the activation energy may decrease, the reaction rate may vary, and consequently, the properties of the resulting polyurethane structure may be affected. In this study, the reaction kinetics of the IPDI-HTPB binder system were investigated using catalysts; K-KAT 635, K-KAT 651, K-KAT 672 and DBTDL. The activation energies were calculated using both the Kissinger and Ozawa methods. The activation energies calculated using Kissinger and Ozawa methods were found to be lowest for K-KAT 672, followed by DBTDL, K-KAT 651, and K-KAT 635, respectively. Moreover, PBX samples were produced with these catalysts by using high shear planetary mixer and explosives were casted under vacuum conditions and cured at 50 ⁰C. The physical, mechanical and safety properties of PBX samples were evaluated with hardness and density measurement, tensile tests, and impact and friction sensitivity tests.