Effects of different ionizable groups on the thermal properties of waterborne polyurethanes used in bulletproof composites

The thermal stability of the resin matrix is an important factor affecting the safety performance of fiber-reinforced bulletproof composites (FRBCs) during their service period. In this study, two kinds of waterborne polyurethanes based on polyester diol (PEDL218) and isophorone diisocyanate were synthesized; these were used as the matrix of para-aramid FRBCs. Their thermal stability and thermal decomposition behaviors in a nitrogen atmosphere were studied by dynamic thermogravimetric analysis techniques. The kinetic parameters, including the activation energy (E) and pre-exponential factor (A), were calculated by the Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Kissinger, and Šatava-Šesták methods. The results show that the cationic waterborne polyurethane with quaternary ammonium groups has better thermal stability than the anionic waterborne polyurethane with carboxylate groups. Their nonisothermal decomposition mechanisms were studied, and the kinetic parameters were also calculated; this will offer theoretical reference for the manufacturing and application of FRBCs based on waterborne polyurethane.