Evaluation of Branched Glycidyl Azide Polymer Purified by Solvent Extraction

Abstract

Dimethyl sulfoxide (DMSO), a polar liquid of low volatility, was used as solvent in the synthesis of branched glycidyl azide polymer (GAP) which is a potential energetic binder for rocket propellants. Branched GAP product was purified by an extraction method using dichloromethane to create an organic phase and a mixture of methanol−brine (50:50 in weight) as the extracting solution. The extraction was carried out in four steps, leaving only less than 1% DMSO in the purified branched GAP. The DMSO concentration remaining in the organic phase was deduced from the 1H NMR spectra taken after each extraction step. Finally, the physical performance of branched GAP was evaluated through the tensile properties, the glass transition temperature, and the thermal degradation of the energetic polyurethanes obtained after curing branched GAP with different isocyanate compounds. The effect of residual DMSO in branched GAP on the tensile properties of polyurethanes was also investigated.

Effect of Solvent and Functionality on the Physical Properties of Hydroxyl-Terminated Polybutadiene (HTPB)-Based Polyurethane

“…Chung et al discussed the effect of Lewis acid on the mechanical properties of PUs. Bui et al reported that the presence of low-volatile solvent such as dimethyl sulfoxide in the polymerization reaction mixture increases the tensile properties of the PUs. In our latest report, , we observed that the functionalized HTPB at the terminal carbon with nitrogen-rich molecules significantly improved the tensile property due to the presence of strong hydrogen bonding and electrostatic interactions in the PUs chain.…”

Core–shell type multi‐arm azide polymers based on hyperbranched copolyether as potential energetic materials in solid propellants

“…Although GAPs were first reported in the 1970s, work on GAPs is an ongoing effort worldwide, especially in the area of synthesizing new structural GAPs. GAPs with various topological structures have been designed and prepared (branched GAPs, star‐type GAP oligomers, diblock or triblock copolymers of GAPs, grafting compounds of GAPs, etc.) in order to overcome some problems of general linear GAPs in application, such as low molecular weight (2000–5000 g mol −1 ), short polyether main chain, poor low‐temperature properties and so on .…”

Simultaneous Improvement of Tensile Strength and Elongation: An Unprecedented Observation in the Case of Hydroxyl Terminated Polybutadiene Polyurethanes

“…Lewis acid treatment of lignin enhances the concentration and reactivity of hydroxyl groups available to react with diisocyanate monomers which results in better integration of lignin into the urethane network; hence, the mechanical properties improve significantly . PUs obtained from glycidyl azide polymer (GAP), an alternative energetic binder to HTPB for rocket propellants, displayed tunable tensile properties depending upon the amount of residual dimethyl sulfoxide solvent which was used to synthesize the GAP prepolymer . Zhang et al reported simultaneous improvement of tensile strength, Young’s modulus, and elongation at break in the case of a polyurethane hybrid obtained from functionalized modified hexamethylene diisocynate trimer and dihydroxyl propyl-terminated siloxane oligomers .…”