Curing of Glycidyl Azide Polymer (GAP) Diol Using Isocyanate, Isocyanate‐Free, Synchronous Dual, and Sequential Dual Curing Systems

Abstract

a] 1I ntroductionIn solid propellant rocketry,p ropulsion units in fielded and currently operational missile systems are founded upon ar elatively small number of firmly established propellant technologies, most of which have an extensive historical track record. While propulsion systems with either limited or no restrictions with respect to exhaust plume signature have their basis in ammonium perchlorate (AP) composites with inert binder systems (preferably aluminized), smokeless systems are based on nitrate ester plasticized binders (nitrocellulose, polyethers, polyesters) with or without nitramine filler materials [1].C ombination of the two sorts gives rise to the high-performance propellant types important in domains such as submarine-launched ballistic missiles, applications where performance with regards to specific impulse is particularly critical [2].Although implemented propellant technology has now remained somewhat static for ac onsiderable period of time, new incentives have accelerated the development of new generations of solid rocket propellants. Increasingly stringent legislature associated with the handling and use of many chemical species traditionally used in rocket propellant formulations (heavy metal compounds, perchlorates, isocyanates), when assessed in conjuncture with at ightening export bureaucracy and the diminishing production base for many important raw materials (a result of plant closures and industry consolidation during recent decades), have all contributed to an increased willingness by relevant manufacturers to evaluate new propellant candidates.The bulk of contemporary research efforts directed towards new solid rocket propellant candidates is concentrated around new energetic binder systems and chlorine-free filler materials, as well as associated formulation additives (curing agents, bonding agents, burning rate modifiers) [3-Abstract:G lycidyl azide polymer (GAP) is an important energetic binder candidate for new minimum signature solid composite rocket propellants, but the mechanical properties of such GAP propellants are often limited. The mechanical characteristics of composite rocket propellants are mainly determined by the nature of the binder system and the binder-filler interactions. In this work, we report ad etailed investigation into curing systems for GAP diol with the objective of attaining the best possible mechanical characteristics as evaluated by uniaxial tensile testing of non-plasticized polymer specimens. We started out by investigating isocyanate and isocyanate-free curing systems, the latter by using the crystalline and easily soluble alkyne curing agent bispropargylhydroquinone (BPHQ). In the course of the presented study,w et hen assessed the feasi-bility of dual curing systems, either by using BPHQ and isophorone diisocyanate (IPDI) simultaneously (synchronous dual curing), or by applying propargyl alcohol and IPDI consecutively (sequential dual curing). The latter method, which employs propargyl alcohol as ar eadily available and adjustable hydroxyl...

Structure and mechanical properties of fluorine-containing glycidyl azide polymer-based energetic binders

“…Among energetic polymers, glycidyl azide polymer (GAP) and related energetic polymer binders are considered as the most promising candidates for energetic binders in future composite solid propellants. GAP was first reported in a patent in 1972 by Vandenburg, and stands unchallenged among azide polymers prepared during the last few decades . This is because it has a high positive heat of formation (+957 kJ kg −1 ), low detonation tendency and low glass transition temperature ( T g = −45 °C) .…”

Isocyanate‐Free Curing of Glycidyl Azide Polymer with Bis–propargylhydroquinone

“…Results presented in Table 3 showed that tensile strength increases in the range 0.79 to 10.65 kgf cm -2 and Emodulus 0.70-42.53 kgf cm -2 . The trend in changing the mechanical properties of our studies has good agreement with data published by T. H Hagen et al [12]. This is due to while increasing curative ratio, enhances in crosslinking density of binder (GAP/BPHQ).…”

“…In addition, as the amount of BPHQ increases toughness of the cured polymer matrix also increases. As reported by T. H. Hagen et al [12], we could not observe any issues such as partial precipitation, and solubility during curing of GAP with BPHQ. The mechanical properties of a composite propellant can be modified by relative ratio of curative, proportion of solid fillers and adding plasticizer in appropriate quantity [20][21][22].…”

“…3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 How Ghee Ang et al [11] suggested that with activated acetylenes, the curing takes place in the temperature range of 35-50 8C, which is suitable for processing of propellant formulations. Recenly, T. H. Hagen et al [12] have been studied that feasibility of dual curing systems, either by using isocyante-free BPHQ and conventioanl isophorone diisocyante (IPDI) with GAP prepopymer. The cured systems reported by authors still contain toxic ingredients such as isocyanates for the development of advanced propellants.…”

Fluorinated glycidyl azide polymers as potential energetic binders

“…5,6 Among the energetic polymeric binders, glycidyl azide polymers (GAP) and their related energetic polymer binders are considered as promising candidates for propellant binders. 7,8 It is well known that GAP has a high positive heat of formation (+957 J g À1 ), low detonation tendency, low glass transition temperature (T g ¼ À45 C), and also has good compatibility with high-energy oxidizers. However, GAP which has high polarity azide groups graed on the polymer backbone, possesses poor exibility of backbone resulting in lack of intermolecular interactions, exhibits inferior mechanical properties in propellants formulations.…”