Study On Preparation And Properties Of Crosslinkable Crystalline Polyarylene Ether Nitrile

Polyarylene ether nitrile(PEN)is widely used in electronics,automobile manufacturing and other fields due to its excellent thermal properties,mechanical properties,dielectric properties and radiation resistance.PEN can be divided into amorphous PEN and crystalline PEN according to its crystallization ability;it can be divided into non-crosslinked PEN and crosslinkable PEN according to whether the PEN can undergo cross-linking.For crystalline PEN,the presence of crystals makes the molecular chain arrangement more regular,-CN is arranged on one side of the main chain,the polarity of the PEN system increases,and the dielectric constant increases slightly.For cross-linkable PEN,the phthalonitrile group at the end of the PEN molecular chain can undergo a cross-linking reaction at high temperatures to form a thermally stable triazine ring or phthalocyanine ring realized thermoplastic processing thermosetting application of polyarylene ether nitrile.Based on the above background,crystalline PEN and crosslinkable crystalline PEN was prepared in this paper.The effects of crystallization and crosslinking on polymer properties were studied.And combined with the temperature resistance characteristics of cross-linkable polyarylene ether nitrile,a dielectric composite with high thermal stability was prepared.Firstly,the crystalline polyarylene ether nitrile(HQ/BPA-PEN)with different crystallization ability was obtained by adjusting the ratio of hydroquinone and bisphenol A in the raw materials,its structure and molecular weight were characterized by infrared spectrum,intrinsic viscosity and other test methods.Then the effects of different bisphenol A contents on the thermal,crystallization,mechanical and dielectric properties of HQ/BPA-PEN were studied.The results show that with the increase of the content of bisphenol A,the thermal,crystalline,mechanical and dielectric properties of HQ/BPA-PEN are slightly reduced,but the overall performance remains good.In addition,by observing the synthesis phenomenon and testing the intrinsic viscosity of the polymer,it can be concluded that the introduction of flexible segment bisphenol A can effectively solve the problems of precipitation,small molecular weight and low yield of hydroquinone type polyarylethernitrile in the synthesis process.Based on the above results,HQ/BPA-PEN10 with excellent comprehensive properties was selected,and phthalonitrile groups were introduced at both ends of the molecular chain of HQ/BPA-PEN10 to obtain a crosslinkable crystalline polyarylene ether nitrile(PEN-Ph).Next,the effects of heat treatment temperature and time on the crystallization properties of HQ/BPA-PEN10 were investigated,and the effects of the crystallinity of HQ/BPA-PEN10 on the thermal,mechanical,and dielectric properties of polymers were further explored.According to X-ray diffractometer,differential scanning calorimeter,mechanical property and dielectric property test,as the crystallinity of HQ/BPA-PEN10increases,the mechanical strength of the polymer increases,the elongation at break decreases,and the thermal and dielectric properties are improved.Compared with HQ/BPA-PEN10 without isothermal crystallization,its comprehensive performance has been greatly improved,and finally a crystalline polyarylene ether nitrile material with enhanced dielectric properties has been obtained.However,the crystalline PEN can only be used under the glass transition temperature of 190 ~oC.Therefore,based on the above research,the appropriate temperature and time were selected to process PEN-Ph to prepare a single-component polyarylene ether nitrile composite material(CSC-PEN)with self-enhanced thermal and dielectric properties.The thermal properties,degree of cross-linking,dielectric properties at room temperature,and high-temperature dielectric properties of the prepared single-component polyarylene ether nitrile composite materials were sequentially characterized.From the dielectric frequency and temperature diagram of CSC-PEN,it can be obtained that the polymer has good dielectric constant and temperature stability,which makes CSC-PEN have potential application value in the field of high-temperature film capacitors.Finally,using the cross-linking properties of PEN-Ph,MWCNTs-CN was filled into the PEN-Ph matrix to prepare a composite with dielectric enhancement.This composite was then treated at high temperature to cross-link the cyano group in MWCNTs-CN with the phthalonitrile group in PEN-Ph to prepare MWCNTs-CN/PEN-Ph hybrid.The material eliminates the interface between the filler and the matrix,and solves the compatibility problem between the filler and the matrix.The glass transition temperature of the formed hybrid material can be increased to about430 ~oC,and it still maintains good dielectric properties.When the content of MWCNTs-CN is 7%,the dielectric constant of the hybrid material is 22.08 at 1 KHz.From the dielectric constant-temperature dependence diagram of the MWCNTs-CN/PEN-Ph hybrid material,it can also be seen that the material can be used in high temperature environments above 350 ~oC while maintaining its dielectric properties without being affected too much.These data show that MWCNTs-CN/PEN-Ph hybrid materials have excellent thermal stability,which is of great significance in practical applications.