Investigation of the curing kinetics of polyurethane/nitrocellulose blends through FT‐IR measurements

Abstract

Polyester (HTPS) based polyurethane (PU) elastomers were currently established to be effective binders for high-energy composites with improved performances. Conventional PU binders are mostly non-energetic materials, and consequently reduce the energy performance significantly. Nitrocellulose (NC), is an energetic polymer widely used as an ingredient in propellants, explosives, fireworks, and gas generators, it may be introduced in PU-based compositions to overcome their performance drawback. Kinetic parameters must be specified in order to build PU binders with the most convenient and appropriate features. Therefore, the cure kinetics of polyester based polyurethane binder systems were investigated by Fourier transform infrared spectroscopy (FT-IR) isothermal method.The polyester prepolymer (Desmophen R 1200) was cured with hexamethylene diisocyanate (HDI: Desmodur R N100) at various molar ratios (R [NCO]/[OH] = 0.6, 1, 1.25, and 1.5) and under different isothermal conditions (T = 60 • C, 80 • C, 100 • C, and 120 • C). In addition, the effect of the addition of nitrocellulose on the kinetics of polymerization of PU was investigated. The progression of the reaction was followed based on the decrease of the peak intensity of -NCO group at 2271 cm −1 as a function of the reaction time. The curing kinetic model and the apparent activation energy (E α ) were determined by the use of Kamal autocatalytic model and Friedman isoconversional method, respectively.

Preparation of high‐performance polyurethane elastomers via direct use of alcoholyzed waste PET by high molecular weight polyester diols

“…The urethane group can be seen through the FT‐IR spectra analysis in Figure 9, and it proved that PUEs have indeed been successfully prepared. The absorption peak at 1725 cm −1 is due to the asymmetric stretching vibration of CO 39,48 . The absorption peak at 3350 cm −1 is attributed to the NH stretching vibration and the tiny peak at 1575 cm −1 is caused by the NH bending vibration 49 .…”

“…The absorption peak at 1725 cm À1 is due to the asymmetric stretching vibration of C O. 39,48 The absorption peak at 3350 cm À1 is attributed to the N H stretching vibration and the tiny peak at 1575 cm À1 is caused by the N H bending vibration. 49 The absorption peak at 1370 cm À1 is due to the stretching vibration of C N. 50,51 In addition, there are slight differences between two types of PUEs, one PUEs are prepared with the participation of the alcoholysis products and the another are prepared directly with original polyester diols.…”

Review on energetic copolymer binders for propulsion applications: Synthesis and properties

“…It was used as a highly effective explosive in military and industrial applications and is also used as a binder in some solid rocket propellants. [78][79][80][81] NC is produced by the nitration of cellulose, a natural polymer found in plants, using nitrating agents such as sulfuric and nitric acids. 82 NC is a solid binder with a high-energy content, making it effective as a fuel for rocket propulsion.…”

“…The curing kinetics of PU and PU/NC blend systems were also analyzed using FTIR. 104 The activation energy and the curing kinetic model were determined. The results showed that in the case of PU systems, the addition of excess isocyanate groups had a significant autocatalytic effect.…”

“…Cellulose nitrate, commonly referred to as nitrocellulose (NC), is a versatile compound with a multitude of uses despite its highly flammable nature. It was used as a highly effective explosive in military and industrial applications and is also used as a binder in some solid rocket propellants 78–81 . NC is produced by the nitration of cellulose, a natural polymer found in plants, using nitrating agents such as sulfuric and nitric acids 82 .…”