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Both better mechanical and rheological properties are pursued for composite solid propellant. In this work, varying proportions of a modified hyperbranched polyester (MHBPE) were added to HTPE/AP/Al propellant. The static tensile property as one kind of mechanical properties of MHBPE/HTPE/AP/Al propellant were found to be superior to those of blank HTPE/AP/Al propellant as a result of the entanglement and interpenetration of molecular chains caused by the introduction of the hyperbranched structure. Evaluations on the related improved creep resistance and stress relaxation performance further demonstrated the advantages of introduction of MHBPE to HTPE/AP/Al propellant. Rheological properties of HTPE/AP/Al propellant with and without MHBPE during the casting process were investigated and compared and the results confirmed the improvement benefiting from low viscosity and loose void structure. Thus, modified hyperbranched polyester provided a novel route to potentially meet the requirements for propellant manufacturing and applications. [ABSTRACT FROM AUTHOR]

The mechanical properties of hydroxyl‐terminated polyether/poly(ϵ‐caprolactone) (HTPE/PCL) propellant applying to the wide temperature range of −50 °C to 70 °C were investigated by uniaxial tensile test with different strain rates varying from 0.5 min−1 to 10 min−1. The scanning electron microscopy (SEM) was used to observe the fractured surface of HTPE/PCL propellant, and the dynamic mechanical analysis (DMA) was employed to analyze its strain induced crystallization at low temperature. It reveals that the temperature and strain rate have great influence on the mechanical properties of HTPE/PCL propellant. As the temperature increasing or the strain rate decreasing, the maximum tensile strength gradually reduces, but the elongation at break increases first and then decreases. The fracture of HTPE/PCL propellant changes from the part dewetting and brittle fracture at low temperature to the fracture caused by dewetting at high temperature. The master curves for mechanical properties of HTPE/PCL propellant at the wide temperature of −50 °C to 70 °C with the strain rate of 0.5 min−1 to 10 min−1 were obtained, the prediction of maximum tensile strength and elastic modulus can be achieved. [ABSTRACT FROM AUTHOR]

Composite solid propellants demand fine and stable mechanical properties, creep resistance and stress relaxation performance during their long storage and usage time. In this study, modified hyperbranched polyester (MHBPE) was prepared and introduced into HTPE/AP/Al/RDX (HTPE, hydroxyl‐terminated polyether; AP, ammonium perchlorate; RDX, cyclotrimethylenetrinitramine) solid propellant as an effective additive. The static tensile and dynamic mechanical properties of this propellant before and after the introduction of MHBPE were evaluated. The elevated interfacial interaction by using MHBPE between the binder and RDX fillers improved the toughness and elasticity of the propellant. The enhancement mechanisms were also confirmed by the influence on the fracture surface morphology of the binder which was investigated by SEM. In addition, some influence on the dynamic mechanical properties of HTPE/AP/Al/RDX propellant caused by MHBPE was investigated by dynamic mechanical analysis. The creep behaviors of the HTPE/AP/Al/RDX propellants with and without MHBPE were also investigated at different stresses and temperatures. Reduced creep strain rate and strain were obtained for the modified propellant, implying enhanced creep resistance performance. The creep properties were quantitatively evaluated using a six‐element model and the long‐term creep performance of the propellant was predicted using the time–temperature superposition principle. A creep behavior of nearly 106 s at 30 °C could be acquired in a short‐term experiment (800 s) at 30–70 °C. Moreover, the stress relaxation investigation of the propellants with and without MHBPE at −40 °C, 20 °C and 70 °C suggested that MHBPE/HTPE/AP/Al/RDX propellant possessed better response ability to deformation. Thus, the application of MHBPE provides an efficient route of reinforcement to enhance the creep resistance and stress relaxation properties. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Modern composite solid propellants must exhibit excellent mechanical properties together with high energy outputs, and the binder system plays a vital role in establishing these characteristics. In the present work, varying proportions of a novel hyperbranched multi‐arm azide copolyether (POG) were combined with a hydroxyl‐terminated polyether (HTPE) to prepare crosslinked elastomeric binders. The compatibility of the POG and HTPE was demonstrated before a series of HTPE/POG blend binders were prepared based on a urethane reaction using hexamethylene diisocyanate (HMDI) as the curing agent. The mechanical properties of HTPE/POG/HMDI elastomers were found to be superior to those of traditional HTPE/N100 crosslinked binders as a result of the formation of a hyperbranched crosslink structure. Evaluations of the local motions of polymers chains and parameters related to the cured network structure demonstrated the advantages of introducing the hyperbranched POG. Hydrogen bonding in the HTPE/POG/HMDI binder was investigated and the results confirmed that these elastomers also benefited from hydrogen bonding, as well as the entanglement and interpenetration of molecular chains. Decomposition behavior was studied by thermogravimetric analysis, differential thermogravimetry and differential scanning calorimetry, and the new binders exhibited good thermal stability and superior energetic performance that could potentially meet the requirements for military applications. [ABSTRACT FROM AUTHOR]