Investigation of the Compatibility of a Novel Copolymer Based on Polypropylene Glycol/Polyglycidyl nitrate (PPG/PGN) with Plasticizers: Thermal, Rheological, Solubility Parameter and SEM

Plasticizers were added to the polymeric networks to improve the performance of the composite solid propellants. Energetic plasticizers were used to increase the energy content, in addition to improving the glass transition temperature and mechanical properties. The compatibility between polymer and plasticizer is an important criterion for obtaining the best thermomechanical properties. In this research, the compatibility of the novel PPG/PGN based copolymer with three energetic plasticizers was studied. Firstly, the polypropylene glycol-poly glycidyl nitrate (PPG/PGN) based copolymer (M_n = 2.3 × 10³) was synthesized and characterized by FTIR, gel permeation chromatography (GPC), and ¹H and ¹³C NMR spectroscopy, then to choose the appropriate plasticizer, we performed experimental studies on the compatibility of this copolymer with energetic plasticizers such as n-butyl nitroxyethylnitramine (BuNENA), trimethylolethanetrinitrate (TMETN) and butanetrioltrinitrate (BTTN). Compatibility in different copolymer-plasticizer systems was studied using the scanning electron microscope (SEM) technique, the solubility parameter as well as thermal and rheological analyses. Observation of the scanning electron microscope (SEM) indicated that BuNENA had better miscibility with this copolymer than other plasticizers. This plasticizer reduced the glass transition temperature of its mixture with a copolymer to –64°C. Moreover, the rheological analysis and solubility parameter confirmed the superior compatibility of BuNENA with the copolymer.