Controllable synthesis and characterization of 4HTPI-Si liquid rubber with high 1,4-structure content applied to rocket solid propellant matrix

In this study, a new type of star multifunctional polyisoprene liquid rubber 4-arm star hydroxyl terminated polyisoprene (4HTPI-Si) that can be used for rocket solid propellant matrix was designed and synthesized by anionic polymerization method. It was characterized by Fourier Transform Infrared Spectroscopy (FT-IR), 1H Nuclear Magnetic Resonance Spectroscopy (1H-NMR) and Gel Permeation Chromatography (GPC), and the mechanical properties of the cured product obtained by blending with hydroxyl-terminated polybutadiene (HTPB) liquid rubber, a traditional solid propellant matrix, were studied. The results show that the aliphatic alkyl lithium initiator with silane-protected hydroxyl group and silicon tetrachloride coupling agent can polymerize isoprene monomers to obtain 4HTPI-Si with narrow molecular weight distribution (Mw/Mn = 1.14). The molecular weight of the polymer can be precisely designed, the average functionality is very close to 4. In the polymer synthesized in nonpolar solvent, 1,4- structure accounts for the majority. By proper blending, the tensile strength and elongation at break of the cured product of commercial HTPB can be improved by 281% and 66.7%.