Study on the effect of isocyanates on the PGN cure reaction

摘要

Composite propellant binders are typically cross-linked polyurethanes providing a matrix that hold together a charge of finely divided particles and help the friendly processing of the energetic materials. The raw polymers are liquid prepolymers with functionally hy-droxyl terminated groups. These terminal hydroxyl groups are used for curing with isocyanates to form a polyurethane linkage. The presence of energetic functional groups in the polymer structure allows the composition to have comparatively less explosive filler, thereby rendering less sensation formulation to external stimuli. It is also possible to obtain enhanced performance and improved the energetic properties of propellant formulations, by using energetic binders instead of the inert ones. PGN is one of the new types of energetic polymer which is developed solely for using in propellants. Regarding to the importance of PGN as a suitable candidate for energetic binder purposes, we attempted to follow the course of curing reaction at our study. The purpose of this work is to improve the polymer technology knowledge by studying mechanical properties and thermal behavior of PGN elastomer in presence of different isocyanates. Four different types of curing agents have been discussed in this work, along with their effects on curing reaction and mechanical properties (maximum stress and strain). PGN was cured with four isocyanate curatives generally employed in composite propellants, viz, Desmudar N-100, TDI, IPDI and HDI, is studied using DSC. Reactions are carried out in presence of DBTDL as catalyst. The tensile properties of the polyurethane elastomers are determined in the different systems is also measured simultaneously and compared with the results from the thermo-analytical DSC method.