Flexoelectricity in fluoropolymer/aluminium reactives

Abstract

The development of smart reactive materials is of significant interest to the reactives community in order to tailor energy delivery and enable ON/OFF capability. Of the polymer bound reactives, those with fluoropolymer binder have shown potential as smart materials due to the polymer's strong electroactive characteristics. This could be due to piezoelectricity or flexoelectricity but has not been well characterized. This effort measures the flexoelectric coefficient for two fluoropolymer/aluminium (Al) reactive systems and details the role processing, configuration and fluoropolymer type have on their electroactive behavior. Specifically, poly(vinylidene fluoride) (PVDF) and tetrafluoroethylene‐hexafluoropropylene‐vinylidene fluoride (THV) were characterized with Al (fuel) loadings of 0, 20, 33 and 50 wt%. Two additive manufacturing routes, direct ink writing (DIW) and fused filament fabrication, were used to determine how processing and print direction may influence the electroactive behavior. A linear increase in flexoelectric coefficient as a function of Al loading was observed for both fluoropolymer systems ranging from 5.03 ± 0.7 nC m–1 to 7.83 ± 1.1 nC m–1. Processing via DIW resulted in samples with the highest flexoelectric coefficients, 8.48 ± 1.0 and 11.62 ± 2.5 nC m–1 for THV/Al and PVDF/Al, respectively, attributed to increased porosity. These results indicate that non‐piezoelectric polymer bound reactives have promise as smart reactives with calculated apparent piezoelectric coefficients up to 189 ± 12 pC N–1. © 2021 Society of Industrial Chemistry.

Additively Manufactured Micro‐ and Nano‐ Al/PVDF Ignition Sensitivity and Burning Characterization

“…Aluminum-fluoropolymer composites can be fabricated by dispersing particles in a solution, mechanical activation, coating aluminum particles in fluoropolymers, direct ink printing, electrospray deposition, or fused filament fabrication [9,10,12,14,[17][18][19]. Aluminum-fluoropolymer composites have been created to tailor the thermal conductivity and dielectric properties of various materials [20], and because fluoropolymers can be piezoelectric; composites such as Al/THV and Al/PVDF have been studied to improve their piezoelectric or flexoelectric properties [5,13,21]. A wide variety of fluoropolymers such as PVDF, Viton, THV, and PMF have been tested with aluminum to study their effect on burn rate, flame temperature, gas release, and agglomeration reduction [5,8,[10][11][12]22].…”

Large Curvature Sensors Based on Flexoelectric Effect in PEDOT:PSS Polymer Films

“…In other words, flexoelectricity may compete with piezoelectricity in flexible materials like soft polymer films with Young’s modulus lower than 1 GPa. , Marvan et al first studied flexoelectricity in dielectric polymers like rubber. Many other insulating polymers exhibit a significant flexoelectric effect when subjected to a deformation gradient such as polyurethane (PU), poly­(vinylidene fluoride) (PVDF), , etc. In their study, Chu et al characterized the flexoelectric coefficient of different polymers (such as PVDF, oriented polyethylene terephthalate (PET), PET, and epoxy).…”