Preparation Of Self-polarized PVDF-HFP Porous Composite Film And Research On Its Mechanical-electrical Conversion Performance

As polar fluorine-containing polymers,PVDF and its copolymers have high flexibility as well as piezoelectric and triboelectric properties.The design and preparation of self-powered devices using PVDF and its copolymer,which can collect energy in the environment and convert it into electric energy,have attracted extensive attention.In this paper,a series of self-polarized power generation films based on polyvinylidene fluoride-hexafluoropropene(PVDF-HFP)were designed and prepared to improve the conversion of mechanical energy to electrical energy.The self-polarized PVDF-HFP porous piezoelectric thin film was prepared by the interaction between the substrate and PVDF-HFP.The high?-phase fraction and good crystal orientation of porous PVDF-HFP were obtained due to PVDF-HFP forms hydrogen bond with the hydroxyl group and the imino group in PVA and CTS respectively and electrostatic interaction with polar groups such as carbamate group in waterborne polyurethane(PU).The short circuit current and open circuit voltage of the porous PVDF-HFP based on PU reached 0.51?A and 6.3 V,respectively,under the action of 7 N,which can be used to monitor human motion.The electrode-free self-polarized porous CB/PVDF-HFP composite film was prepared by compositing with conductive carbon black(CB)particles.Hydrogen bonding between water,CB and PVDF-HFP,electrostatic interaction between positively charged aluminum foil and PVDF-HFP,and strong upward evaporation of solvent acetone contribute to the formation and orientation of?-phase,which simultaneously undergoes the above three self-polarization processes.When the CB content is 5 wt%,the?-phase content of the composite film reaches 70%.CB particles can effectively collect and transfer piezoelectric charges through the induction effect,without additional electrodes.Under the action of 7 N,the short circuit current,open circuit voltage and charge of 0.66?A,17.6 V and 4.7 n C can be obtained,and the finger bending angle and flow velocity can be effectively sensed.Self-polarized porous PVDF-HFP films with different pore structures were obtained by controlling the proportion of water to acetone in the precursor solution.The higher the porosity of the film is,the more sufficient the charge exchange is when the film is rubbed with the cathode material,and the more additional charges are induced on the surface of the hole,so as to obtain higher power generation performance.Compared with pure PVDF-HFP films without pores,the friction short circuit current between porous PVDF-HFP and CTS films increases from 0.15?A to0.86?A with the increase of porosity.Among them,the maximum output power of the 10 vol%H₂O porous PVDF-HFP and CTS friction nanogenerator under the force of 30 N reaches 3.63?W.