Review of the Effects of Polymer Binder Properties on Microstructure and Irreversible Volume Growth of Plastic Bonded Explosives Formulations

Abstract

The rational design of effective polymeric binders for the formulation of plastic-bonded explosives (PBX) is challenging due to their inherent compositional complexity. The composites comprise irregularly shaped energetic material (EM) powders coated with low weight fractions of polymer via non-equilibrium processes such as slurry coating. Defects can deleteriously affect PBX stability and performance: nano-to micrometer-scale voids can act as loci for hot spots, lowering deflagration and detonation temperatures in unpredictable ways. Furthermore, some nominally desirable polymer properties are at odds with each other: e. g. good flow characteristics are desirable for coating and adhesion, but mechanical stiffness is needed to prevent deformation and cracking of PBX under mechanical stress. Good binder adhesion is critical, but the best means to predict and measure adhesion in PBX is not obvious. Experimental methods of determining binder adhesion on model surfaces may not capture polymer structural config-urations relevant to deposition during coating. Molecular dynamics-based computational models have predicted key observables in PBX formulation, suggesting that they may be powerful tools for binder selection. In this review, primarily recent (~2006 and later) literature on polymeric binders for insensitive HE (IHE) is surveyed. We focus on how binder properties influence observable PBX properties as resistance to irreversible volume growth and void formation in PBX formulations mainly (but not exclusively) featuring 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as the EM (e. g. PBX 9502, LX-17 and others). Conclusions from these studies yield useful guidelines for choosing HE binder candidates, as well as for the general design of highly-filled polymer composite materials. Finally, studies describing challenges in PBX formulation with the newer and more energetically dense high explosive, LLM-105, will be discussed.

Shock Hugoniot Calculations of Newly Designed Thermoplastic Elastomers and Comparison with Classical Binder Estane

“…Estane 5703 is ideal for use in IMs as binders. ,,, Here, due to the lack of an absolute standard to determine the shock performance from Hugoniot curves, we used Estane as a benchmark to select new TPEs that are close to it. In fact, Estane 5703 is the copolymer of the hard segment (MDI, m = 1–3) and soft segment (PBA, n = 4–6).…”

“…Regulating the shock response of polymers is of great significance for polymer-bonded explosives (PBXs). 1,2 Obtaining the Hugoniot curve of binders is critical to the dynamic modeling of PBXs ranging from shock initiation to detonation and the design of insensitive munitions (IMs). 3,4 In the development of PBX binders (e.g., polysulfides, polystyrenes, and epoxy resins), thermoplastic elastomers (TPEs) gain attention for their notable advantages, including uncomplicated preparation, remarkable cost-effectiveness, robust cohesion, and exceptional shock resistance.…”

“…Regulating the shock response of polymers is of great significance for polymer-bonded explosives (PBXs). , Obtaining the Hugoniot curve of binders is critical to the dynamic modeling of PBXs ranging from shock initiation to detonation and the design of insensitive munitions (IMs). , In the development of PBX binders (e.g., polysulfides, polystyrenes, and epoxy resins), thermoplastic elastomers (TPEs) gain attention for their notable advantages, including uncomplicated preparation, remarkable cost-effectiveness, robust cohesion, and exceptional shock resistance. , One of the most commonly used TPEs in PBX formulations, such as PBX 9501 and LX-14, is commercially available Estane 5703, which contains “hard” segments composed of 4,4′-methylenediphenyl-1,1′-diisocyanate (MDI) and a 1,4-butanediol (BDO) chain extender and the “soft” segments of poly­(butylene adipate)…”

Compressive strength of the plastic-bonded explosive surrogate idoxuridine under quasistatic and dynamic compression

“…The same binder is used in these Mock IDOX samples as in PBX 9501, but the binder may interact differently with the surface of IDOX crystals than with HMX crystals due to chemical and surface energy effects. Binder-crystal adhesion energy is an ongoing area of study, [49][50][51][52] including a recent single-crystal delamination study with HMX and an HTPB binder, 53 which though different from the PBX 9501 binder system should have similar parameters at play. 54 Another contributing factor could be anisotropic responses of how the crystals are being loaded.…”

A Solvent-free Processed Low-temperature Tolerant Adhesive

“…The ever-growing practical demands and sustainable development for society and industry within a wide temperature range, for example, research at the poles of the Earth (e.g., South Pole, 20.7 to -94.2 ℃) and human space exploration (e.g., Moon, 127 to -183 ℃; Mars, 20 to -140 ℃; Saturn, -130 to -191 ℃; Neptune, -210 to -218 ℃), call for high-strength adhesive at low temperature [4][5][6][7][8] . Up to now, a majority of traditional adhesives are based on polymer as the main component [9][10][11] , for example, commercially available hot melt adhesives include ethylene-vinyl acetate copolymer (EVA), polyamide (PA) and polyether sulfone (PES), etc. Despite their widespread use in daily life, they still have some bottlenecks [12][13][14][15][16][17] , especially at low temperature: 1) high crosslinking density and low surface energy lead to di cult bonding and easy debonding between substrate surface and adhesive; 2) poor interfacial in ltration effect with easily formed thicker adhering layer, resulting in undesired residual stress; 3) the traditional polymer molecules tend to be frozen at low temperature, leading to volumetric contraction, enhanced fragileness, weakened mechanical force transmission across the substrates, and reduced resistance to crack propagation and 4) the long-term stability in low temperature is generally unmet, and the adhesion mechanism especially that under low temperature has been less investigated.…”