Energy Release Characteristics and Reaction Mechanism of PTFE/Al/Bi2O3 Reactive Materials under Drop-Hammer Test

Abstract

To obtain the influence of the Bi2O3 particle content of a PTFE/Al/Bi2O3 reactive material (later referred to as PAB) on its shock-induced chemical reaction (SICR) characteristics, five kinds of PAB with different Bi2O3 contents were prepared; the reaction process in a drop-hammer test, recorded using a high-speed camera, was analyzed. The ignition and reaction mechanisms of PAB under mechanical impact were analyzed based on the thermochemical reaction characteristics and the microstructure. The results show that with an increase in Bi2O3 content, the shock-induced chemical reaction duration and the sensitivity of PAB increase, and then decrease. When the Bi2O3 content is 9%, the impact sensitivity is the highest and the reaction duration is the longest. The heating at the crack tip is responsible for PAB ignition under long-pulse low-velocity impact. During ignition, PAB undergoes several physicochemical changes such as the melting of PTFE, a PTFE/Bi2O3 reaction, an Al/Bi2O3 reaction, pyrolysis of the melted PTFE, and a C2F4/Al reaction; moreover, the presence of Bi2O3 decreases the excitation threshold of the reactive material, which facilitates the propagation of the reaction and improves the degree of the reaction and overall energy release of the reactive material.

Effects of different mass ratios on mechanical properties and impact energy release characteristics of Al/PTFE/W and Al/PTFE/CuO polymer composites

“…2 Thus, PTFE is usually mixed with active metal particles and subjected to a special heat treatment to prepare polymer composites with a high mechanical strength, high energy density, and good insensitivity. 3 In PTFE-based polymer composites, PTFE acts both as the oxidizer, which undergoes a fluorination reaction with the active metals, releasing a significant amount of reaction heat, and as the binder, which closely wraps metal particles during the sintering process to increase the overall compressive strength. 4 Among all metal/fluoropolymer composites, Al/PTFE is becoming a hot research topic, and researchers have achieved important results both experimentally and through numerical simulations.…”

“…PTFE also has a high thermal stability, high chemical resistance, and low friction coefficient 2 . Thus, PTFE is usually mixed with active metal particles and subjected to a special heat treatment to prepare polymer composites with a high mechanical strength, high energy density, and good insensitivity 3 . In PTFE‐based polymer composites, PTFE acts both as the oxidizer, which undergoes a fluorination reaction with the active metals, releasing a significant amount of reaction heat, and as the binder, which closely wraps metal particles during the sintering process to increase the overall compressive strength 4 .…”

Effect of CF on mechanical properties and ignition characteristics of Al/PTFE reactive materials under quasi-static compressive

“…The results show that the appropriate addition of metal hydrides can not only improve the mechanical strength of the material, but also participate in the chemical reaction of the sample under quasi-static pressure, Hydrogen is released and combusted, which achieves the purpose of being a high-energy additive. Jiang et al [13] added metal oxide as filler to Al/PTFE, and conducted a drop weight test and thermal decomposition test on Al/Bi 2 O 3 /PTFE with different Bi 2 O 3 content. Through analysis, they believed that the hot spot at the crack tip of impact loading was the cause of ignition, and speculated the physical and chemical reaction process.…”