Preparation And Properties Of Polyvinylidene Fluoride Composite Piezoelectric Films

Piezoelectric materials have become indispensable electronic component in smart devices due to their unique electro-mechanical conversion property recently.Piezoelectric materials can be divided into three categories: piezoelectric crystals,piezoelectric ceramics and piezoelectric polymers.Conventional piezoelectric ceramics and piezoelectric crystals have complicated preparation processes and poor plasticity,while intelligent devices are seeking portability and light weight.Piezoelectric polymers with good flexibility and plasticity have attracted increasing scientific attention recently.Polyvinylidene fluoride(PVDF),as one of the representative piezoelectric polymers,has been widely applied since it was reported in 1969 because of its high piezoelectric response,simple preparation process and good corrosion resistance.Aiming to select a relatively quick and simple fabrication method of PVDF piezo-film,we diligently investigated the preparation process,modification method and polarization method in this work.The main researches are listed as follows:1.PVDF films were prepared by different methods such as casting,melting,electrospinning and spin-coating.By comparing the properties of PVDF films prepared by different processes,various parameters were adjusted to give the best preparation process for PVDF films.2.PVDF films were modified by doping carbon nanotubes,hydrated rare earth salts and molecular ferroelectric materials.Besides the copolymer films were prepared by using PVDF binary and ternary copolymer resins.X-ray diffraction(XRD),Fourier Infrared spectropy(FTIR),scanning electron microscope(SEM)and other tests were conducted to analyze the crystallization property of the films in order to select effective doping methods that could improve the ?-phase content of the PVDF film.3.The effects of key process parameters such as polarization temperature,polarization field and polarization time on piezoelectric property of PVDF pizeo-films were studied.Then,these parameters were adjusted to give the best polarization process for PVDF pizeo-films.To summarize,we found that the ?-phase content of the PVDF film doped with 1wt% cesium chloride hexahydrate prepared by the casting method can be significantly improved.In addition,a polarization method of copper sheet covering double-layer films was investigated,which can effectively simplify the polarization process of PVDF piezo-films.