Research On Melting Behaviors And Processing Properties Of Polyvinyl Fluoride Resin

PVF film has excellent corrosion resistance, wear resistance, self-lubrication, dielectric properties, weather resistance, ultraviolet resistance, and many other advantages. Therefore, PVF film is widely used in many fields, such as solar cells, etc. At present, there are many studies on processing methods of PVF film. Among all kinds of molding methods, melt extrusion method has many advantages to other molding methods. The method has short molding cycle and the advantage of continuous industrial production. Moreover, the prepared film has better mechanical performance. During the the preparation of PVF film by melt extrusion method, the solvent is an indispensable component. However, researches on effects of different solvent on the process of melting extrusion, melting point and rheological properties of PVF resin, crystallinity, mechanical properties and dielectric properties of PVF film are less. N,N-Dimethylformamide(DMF), N,N-dimethylacetamide (DMAC) and y-butyrolactone were introduced into polyvinyl fluoride(PVF) resin to improve the melt extrusion processing, separately.The effects of different solvent with different content(50%,60%,70%) on melting point of PVF resin were studied by the test of differential scanning calorimetry (DSC). The result showed that three kinds of solvent can reduce melting point of PVF resin, contribute to melt extrusion molding of PVF resin and improve the processing property of materials. Moreover, the higher the content of solvent, the greater the amplitude of melting point depression.The torque curve of different solvent with different content(50%,60%, 70%) under the same temperature(170℃) and the torque curve of different solvent with the same content(70%) under different temperature(160℃,170℃, 180℃,190℃) were tested by Huck torque rheometer. The result showed that the higher the content of solvent, the lower the melt torque values. When the temperature was 170℃ and solvent content was 70%, the PVF resin-solvent could fully plasticizing with no breakdown phenomenon. The melt index of different solvent with different content was tested by the melt mass flow rate(MFR) instrument. The result showed that the higher the content of solvent, the higher the melt mass flow rate(MFR).The crystallinity of PVF resin-different solvent with different content and the crystallinity of the prepared PVF film under the condition of different solvent with the same content(70%) were tested by X-ray diffraction(XRD). The result showed that the crystallinity of PVF resin-different solvent was not affected by the content. Their crystallinity were nearly the same. The crystallinity of the prepared PVF film under the condition of different solvent with the same content(70%) is less than the crystallinity of PVF resin-differ ent solvent with content of 70%.The mechanical properties of PVF film were tested by tensile prpperties test and dynamic mechanical properties test. The result showed that mechanical property of PVF membrane prepared by γ-butyrolact one was best. Moreover, the storage modulus, the loss modulus and the mechanical loss of the prepared PVF film were affected after the addition of different solvent.The dielectric constant and the dielectric loss of PVF film were tested by dielectric constant instrument. The result showed that the PVF film prepared by three solvent had high dielectric constant. Besides, with the increase of frequency, the dielectric constant changed smaller and the dielectric loss changed bigger.