Synthesis, characterization, and curing of propylene oxide and glycidyl nitrate random copolymer (GN-ran-PO) and investigation of its compatibility with different energetic plasticizers

Abstract

In this research, arandom copolymer of propylene oxide and glycidyl nitrate (poly [GN-ran-PO]) (Mn = 1152 g.mol−1) was synthesized via ring-opening polymerization of epoxides in the presence of boron trifluoride etherate (BF3.OEt2) as the catalyst. This copolymer has a potential use as a binder in the propellant industries. The obtained product has characterized by 1H and 13C NMR spectroscopy, FTIR, and gel permeation chromatography (GPC). The thermal behavior of the random copolymer was determined by differential scanning calorimetry (DSC). Energetic polyurethane was synthesized by curing of the random copolymer with different curing agents such as toluene-2,4-diisocyanate(TDI), isophorone diisocyanate(IPDI), desmodurN100, (IPDI/N100) and different NCO/OH ratios. To evaluate the plasticizing effect of the different plasticizers on the thermo-mechanical properties of the polyurethane, the compatibility of the copolymer with three energetic plasticizersincludingn‐butyl nitroxyethyl nitramine (BuNENA), trimethylol ethane trinitrate (TMETN), and 1,2,4-butanetriol trinitrate (BTTN) has studied using the solubility parameter, rheological and thermal analysis. The solubility parameter differences indicate that the BuNENA has better miscibility with this copolymer than others. This plasticizer reduced the glass transition temperature of its composition with copolymer from -47 °C to -58 °C. Moreover, the rheological analysis also confirms that BuNENA is more compatible with the copolymer. The mechanical properties effect of the BuNENA plasticizer on the polyurethane network has investigated using dynamic mechanical analysis (DMA) as well as the tensile test. The IPDI/N100 curing agents-polyurethane mixture, demonstrate appropriate mechanical properties (0.6 MPa stress and 109% elongation) that make it a suitable binder system comparison with pure PGN (unstable and de-cured). Also, the mechanical properties of the prepared polyurethane containing 20 wt.% BuNENA showed 0.42 MPa stress and 124% elongation.