Influence of the Prepolymer Structure of Glycidyl Azide Polymer (GAP) on Binder Properties - Some Theoretical Considerations (original) (raw)
Related papers
Molecules, 2019
Glycidyl azide polymer (GAP), an energetic binder, is the focus of this review. We briefly introduce the key properties of this well-known polymer, the difference between energetic and non-energetic binders in propellant and explosive formulations, the fundamentals for producing GAP and its copolymers, as well as for curing GAP using different types of curing agents. We use recent works as examples to illustrate the general approaches to curing GAP and its derivatives, while indicating a number of recently investigated curing agents. Next, we demonstrate that the properties of GAP can be modified either through internal (structural) alterations or through the introduction of external (plasticizers) additives and provide a summary of recent progress in this area, tying it in with studies on the properties of such modifications of GAP. Further on, we discuss relevant works dedicated to the applications of GAP as a binder for propellants and plastic-bonded explosives. Lastly, we indica...
The glycidyl azide polymer (GAP), known as an energetic, thermally stable, low sensitive, hydroxyl-terminated prepolymer, was synthesized using different diol and triol initiator units. GAP was prepared by azidation of poly(epichlorohydrin) (PECH) with different polyol units in the polymer chain. PECH was obtained by cationic ring-opening polymerization of epichlorohydrin, with BF 3-etherate as a catalyst and polyol as a co-catalyst. The synthesized polymers have been characterized using IR-spectroscopy, while the prepolymers structure was confirmed by proton NMR spectroscopy. Additionally, glass transition temperature (Tg) and sensitivity to thermal stimuli were determined. Physico-chemical and rheological performances were carried out towards: end groups analysis, as well as density and molecular mass determination
Propellants, Explosives, Pyrotechnics, 2013
Glycidyl azide polymer (GAP) is an energetic binder commonly used in solid propellant formulations [1-3] in combination with oxidizers such as ammonium perchlorate (AP), ammonium dinitramide (ADN), hydrazinium nitroformate (HNF), and hexanitroheaxaazaisowurtzitane (CL-20). The energetic property of GAP originates from the azide group, which decomposes exothermically with an associated enthalpy change of 1170 kJ kg À1 [1]. GAP is conventionally cured by reaction with diisocyanates like toluene diisocyanate (TDI) and isophorone diisocyanate (IPDI) to form a polyurethane network. However, curing of GAP with an isocyanate leading to polyurethane has the drawback of extraneous reactions with moisture causing evolution of gaseous products that induce voids in the system. An alternate approach appeared to exploit the 1,3 dipolar addition reactions between azide groups of GAP and triple bonds of alkynes yielding 1,2,3 triazoles. This has opened access to a plethora of synthetic reactions, which are an important part of "click" chemistry [4-9]. Earlier studies have reported the curing of GAP, with an alkyne such as bispropargyl succinate (BPS) and 1,4-bis(1hydroxypropargyl) benzene (BHPB) to form triazole networks. These reports elaborate on the mechanical properties , swelling characteristics, and crosslink densities of the system [10, 11]. However, there have been no reports on the detailed characterization of this system with respect to the cure kinetics, mechanical, dynamic mechanical, and thermal decomposition mechanism. In this paper, the above properties of GAP based triazole networks are investigated and compared with the urethane Abstract: Glycidyl azide polymer (GAP) was cured through "click chemistry" by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3-dipolar cycloaddition reaction to form 1,2,3-triazole network. The properties of GAP-based triazole networks are compared with the urethane cured GAP-systems. The glass transition temperature (T g), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher T g in comparison to the GAP-urethane system (T g À20 8C) and the networks exhibit biphasic transitions at 61 and 88 8C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)-based theoretical calculations implied marginal preference for 1,5-addition over 1,4addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP-triazole and the mechanism of decomposition was elucidated using pyrolysis GC-MS studies. The higher heat of exothermic decomposition of triazole adduct (418 kJ • mol À1) against that of azide (317 kJ • mol À1) and better mechanical properties of the GAP-triazole renders it a better propellant binder than the GAP-urethane system.
Binder model system to be used for determination of prepolymer functionality
1969
Development of a method for determining the functionality distribution of prepolymers used for rocket binders is discussed. Research has been concerned with accurately determining the gel point of a model polyester system containing a single trifunctional crosslinker, and the application of these methods to more complicated model systems containing a second trifunctional crosslinker, monofunctional ingredients, or a higher functionality crosslinker. Correlations of observed with theoretical gel points for these systems would allow the methods to be applied directly to prepolymers.
Polymers
We provide fundamental guidelines in the form of a tutorial to be taken into account for the preparation and characterization of a specific class of poly(ethylene glycol) (PEG) derivatives, namely azide-terminated PEGs. Special attention is given to the effect of these chain end groups and their precursors on properties affecting the PEGylation of proteins, nanoparticles and nanostructured surfaces. Notwithstanding the presence of 13C satellite peaks, we show that 1H NMR enables not only the routine quantitative determination of chain-end substitution, but is also a unique method to calculate the absolute number average molecular weight of PEG derivatives. In the use of size exclusion chromatography to get molecular weight distributions, we highlight the importance of distinguishing between eventual secondary reactions involving molecular weight changes and the formation of PEG complexes due to residual amounts of metal cations from reactants. Finally, we show that azide end groups ...
Understanding the performance of polymer-modified binders
Jack Youtcheff, Kevin Stuart, Ghazi Al-Khateeb, Aroon Shenoy, 2004
An investigation of the performance of asphalt binders of identical grade but varied chemistries was conducted to determine if binder performance is captured by the Superpave binder specification. The emphasis of this effort was on polymer modification of asphalt binders and their type and mode of incorporation. A single crude was used in the production of nine modified binders that included air blowing, chemical modification (e.g., polymer grafting), and polymer blending. Both plastomeric and elastomeric polymers were evaluated in this study. The materials selected represented a divergent group of modifiers that have been placed in pavements. The initial target grade was a PG 76-28. The modified asphalts came within 1ºC of the high temperature target and 2ºC of the low temperature target. Continuous grading specification values were determined on all the materials in addition to generating rheological mastercurves, and Black Diagrams. The rut resistance of mixes containing these binders was tested using the French Pavement Rut Tester at 70ºC and Superpave Shear Tester (SST) at 50ºC and 70ºC. Fatigue testing was conducted using the Four Point Bending Beam Test at 19ºC and 500 and 1000 microstrains. Moisture sensitivity of the mixes was evaluated using the Hamburg Wheel Tracking Device at 58ºC. The relationships between binder characteristics and mix results were evaluated. The performance of these systems with respect to fatigue and moisture sensitivity is markedly different, whereas the rutting and low temperature cracking tendencies were quite similar. Validation of these results is currently being conducted on pavements incorporating a number of these modified binders at our Accelerated Loading Facility.
Effect of composition and processing on the linear viscoelasticity of synthetic binders
European Polymer Journal, 2005
The influence that composition and processing variables exert on the linear viscoelastic properties of model synthetic binders has been studied in a wide range of temperature and frequency. Model synthetic binders were prepared by blending a non-modified colophony resin (40-65%), a process aromatic oil and a styrene-butadiene-styrene (SBS) triblock copolymer (5-15%). At high SBS content (11% and 15%) and gentle processing conditions (i.e. 150°C and 60 rpm), a plateau region in G 0 is found in the mechanical spectrum. The microstructure of this binder is characterized by a continuous SBS-rich phase. On the contrary, a shoulder in G 0 is found at low polymer content. The resulting microstructure consists of a continuous resin-rich phase and a dispersed polymer-rich phase. Under severe processing conditions (180°C and 1200 rpm) and low polymer concentration, the polymer influence is dampened and the glassy region appears at higher temperatures or lower frequencies. At high polymer concentration, a phase inversion can be induced by processing (i.e. 180°C and 1200 rpm.). Both resin oxidation and SBS degradation may explain such microstructural changes.
Kinetics of glycidyl azide polymer-based urethane network formation
Journal of Applied Polymer Science, 2008
Reactions between hydroxyl-terminated glycidyl azide polymer (GAP) and different isocyanate curatives such as toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and methylene diicyclohexyl isocyanate (MDCI) at various temperatures viz. 30, 40, 50, and 608C were followed by Fourier transform infra red spectroscopy. The reactions were found to follow second-order kinetics. With TDI and IPDI at 308C, a two-stage reaction was observed. For GAP-TDI system, the second stage was slower than the first while for GAP-IPDI system, the second stage was faster than the first indicating dominance of autocatalytic effect. The stage separation occurred due to the difference in reactivity of the isocyanate groups and was found to narrow down with increase in temperature. The viscosity build up due to the curing reaction was followed for GAP-TDI system for comparison. The stage separation was evident in the viscosity build up also. Rheokinetic analysis done based on data generated showed a linear correlation between viscosity build up and fractional conversion. The kinetic and activation parameters evaluated from the data showed the relative difference in reactivity of the three diisocyanates with GAP. Both the approaches suggested that the reactivity of the isocyanates employed for the present study could be arranged as TDI > IPDI) MDCI. V
DECOMPOSITION KINETICS OF GAP BINDER IN THE PRESENCE OF AN ENERGETIC COMPONENT
Glycidyl Azide Polymers (GAP) are promising candidates as energetic binders for future solid composite propellants. They produce minimum smoke, cause reduced pollution, and have low sensitivity. In our hands, we have undertaken a study of the decomposition kinetics of energetic binder in the presence of the energetic oxidizer, to assess the stability of the composite formulation. We now report the decomposition kinetics of GAP binder in the presence of two high performance and environment friendly oxidizers like Ammonium Dinitramide (ADN) and 4, 10-dinitro-2,6,8,12-4,10-diazatetracyclo-[5.5.0.0 5,9 0 3,11 ]dodecane (TEX). Thermal gravimetric analyses (TGA) and differential scanning calorimetry (DSC) were used to investigate the decomposition characteristics and heat of decomposition of TEX/GAP and ADN/GAP gum formulations. Addition of GAP has improved the thermal stabilities of both AND and TEX. GAP has been found to be more vulnerable to thermal decomposition in the presence of TEX than in the presence of ADN.