Effects of temperature and pressure on the glass transitions of plastic bonded explosives

Abstract

Various plastic bonded explosives (PBXs) contain about 5 wt.% polymer, plasticizer, and stabilizer as binder. The glass-transition temperature ( T g) determines, in part, if the binder will reduce or increase the sensitivity of the PBX to impact. A soft binder reduces the impact sensitivity; however, too soft a binder compromises the mechanical strength below that desirable for dimensional stability. Glass transitions were measured by temperature modulated DSC for PBXs before and after pressing. Pressing temperature was 90°C. The T g of Estane, a polyester/polyurethane used in some PBX binders, was investigated. Only small changes were observed in the low temperature T g of the soft segments but larger changes were seen in the higher temperature transitions due to the relaxation of the hard segments. The T g of Kel F 800, a binder used in insensitive PBX 9502, was observed near ambient temperature. The PBX 9502 had a lower T g than the neat polymer. Mechanical strength was measured for the samples of PBX 9502.