Kinetics of glycidyl azide polymer‐based urethane network formation

Abstract

Reactions between hydroxyl-terminated glycidyl azide polymer (GAP) and different isocyanate curatives such as toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and methylene diicyclohexyl isocyanate (MDCI) at various temperatures viz. 30, 40, 50, and 608C were followed by Fourier transform infra red spectroscopy. The reactions were found to follow second-order kinetics. With TDI and IPDI at 308C, a two-stage reaction was observed. For GAP-TDI system, the second stage was slower than the first while for GAP-IPDI system, the second stage was faster than the first indicating dominance of autocatalytic effect. The stage separation occurred due to the difference in reactivity of the isocyanate groups and was found to narrow down with increase in temperature. The viscosity build up due to the curing reaction was followed for GAP-TDI system for comparison. The stage separation was evident in the viscosity build up also. Rheokinetic analysis done based on data generated showed a linear correlation between viscosity build up and fractional conversion. The kinetic and activation parameters evaluated from the data showed the relative difference in reactivity of the three diisocyanates with GAP. Both the approaches suggested that the reactivity of the isocyanates employed for the present study could be arranged as TDI > IPDI ) MDCI.

Optimization of Curing Agents for Linear Difunctional Glycidyl Azide Polymer (GAP), with and without Isocyanate, for Binder Applications

“…The comparative mean values of the Shore hardness are listed in Table 2. It is well known that the degree of cross linking or polymerization in a polymer may be affected by the amount of curing agent used to cure the polymer [9][10][11]. These results indicated that the hardness of the samples increased with the increase in percent of acrylate.…”

“…Azido polymers can undergo dipolar cycloaddition reactions with acrylates resulting in a cross-linked network of polymer containing triazole rings. GAP cured with polyfunctional acrylate has been reported as a binder for gas generating compositions [10][11][12].…”

Synthesis and Characterization of Poly(glycidyl nitrate-block-caprolactone-block-glycidyl nitrate) (PGN-PCL-PGN) Tri-Block Copolymer as a Novel Energetic Binder

“…New energetic polymers such as glycidyl azide polymer (GAP), polyglycidyl nitrate (PGN), polynitromethyloxetane (PLN) and 3,3-bis(azydomethyl)oxetane (BAMO) have become one of the promising materials that could satisfy these requirements [3,4]. Among them, glycidyl azide polymer (GAP) is one of the most thoroughly studied energetic binder which its synthesis, performance, and applications have been reported in detail by several researchers [5][6][7][8][9][10][11][12].…”

Structure and mechanical properties of crosslinked glycidyl azide polymers via click chemistry as potential binder of solid propellant

“…As a result, the curing temperature, an important factor to curing kinetics process, must be matched with the type of curing agents. When the GAP were cured with different diisocyanates at 30°C, both GAP/TDI and GAP/IPDI systems obviously showed a two‐stage reaction due to the difference in the reactivity of two isocyanate groups in the same curing agent, resulting in the instability of curing kinetics process. Although increasing curing temperature can make such two‐stage reaction narrow down and even vanish, too fast and severe curing kinetics process under higher temperature usually leads to the decrease in the quality of composite solid propellant.…”