Nanoenergetic Composites with Fluoropolymers: Transition from Powders to Structures

Abstract

Over the years, nanoenergetic materials have attracted enormous research interest due to their overall better combustion characteristics compared to their micron-sized counterparts. Aluminum, boron, and their respective alloys are the most extensively studied nanoenergetic materials. The majority of the research work related to this topic is confined to the respective powders. However, for practical applications, the powders need to be consolidated into reactive structures. Processing the nanoenergetic materials with polymeric binders to prepare structured composites is a possible route for the conversion of powders to structures. Most of the binders, including the energetic ones, when mixed with nanoenergetic materials even in small quantities, adversely affects the ignitability and combustion performance of the corresponding composites. The passivating effect induced by the polymeric binder is considered unfavorable for ignitability. Fluoropolymers, with their ability to induce pre-ignition reactions with the nascent oxide shell around aluminum and boron, are recognized to sustain the ignitability of the composites. Initial research efforts have been focused on surface functionalizing approaches using fluoropolymers to activate them further for energy release, and to improve the safety and storage properties. With the combined advent of more advanced chemistry and manufacturing techniques, fluoropolymers are recently being investigated as binders to process nanoenergetic materials to reactive structures. This review focuses on the major research developments in this area that have significantly assisted in the transitioning of nanoenergetic powders to structures using fluoropolymers as binders.

Synergistic Enhancement on Ignition and Combustion Properties of Boron via Viton Core–Shell Coating

“…For example, HMX coating increased the combustion temperature from 960.27 to 1163.92 °C, and NQ coating reduced the ignition delay time and combustion time by 35 and 53%, respectively . In addition, fluoropolymers are considered to be attractive oxidants for enhancing the ignition and combustion of boron, , which can react with boron oxide to produce gas-phase products (BF 3 and BOF), , allowing underlying boron to be exposed more quickly and resulting in a reduced ignition delay time. At the same time, the volumetric (135.8 kJ cm –3 ) and gravimetric (105.01 kJ g –1 ) heat values of boron fluorination are much higher than those of boron oxidation .…”

Probing on Mutual Interaction Mechanisms of the Ingredients of Al/CuO/PVDF Nanocomposites

“…Therefore, the introduction of additives on the nanoscale or functional materials into conventional MICs is considered an effective way of tuning energy release and combustion behavior. Typically, there are currently three categories of commonly used modifying additives: energetic components such as ammonium perchlorate (AP) and nitramine, , fluorine-containing polymers (FCP) such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), − and functionalized carbon nanomaterials such as graphene oxide (GO) and carbon nanotubes (CNTs). , …”