Preparation And Properties Of Polyarylene Ether Nitrile-based Barium Strontium Titanate Nanocomposite

Polyarylene ether nitrile(PAEN)has the characteristics of low creep,high rigidity,good electrical insulation,good heat resistance,high mechanical strength,etc.It can be used as a polymer matrix to compound with high dielectric constant fillers to prepare polyarylene ether nitrile-based flexible high-dielectric composites,which have broad application prospects in aerospace,military,machinery,electronics and other fields.In this thesis,firstly,barium strontium titanate nanoparticles were synthesized by the sol-precipitation method,and the optimized process conditions for preparing barium strontium titanate nanoparticles were obtained.Then a series of Ba_1-xSr_xTi O₃(x=0.1,0.33,0.5,0.74,0.8)nanopowders were prepared by combining the molten salt-assisted heat treatment.The crystal structure and performance test of the sample were carried out through X-ray diffractometer(XRD),scanning electron microscope(SEM),impedance analyzer and dielectric test system.The effect of barium-strontium ratio on the crystal structure,particle morphology and dielectric properties of barium strontium titanate was explored.The results showed that the average particle size of barium strontium titanate nanoparticles was 70?100 nm,and the dielectric constant of Ba_0.67Sr_0.33Ti O₃ reached 1680(1 k Hz),which had the best dielectric performance and could be used as dielectric ceramic filler of subsequent polyarylene ether nitrile-based barium strontium titanate nanocomposite material.Then,Ba_0.67Sr_0.33Ti O₃(referred to as BST)nanoparticles with the best dielectric properties were selected as filler,and the BST surface was hydroxylated(BST-OH)and then combined with the polyarylene ether nitrile matrix to prepare polyarylene ether nitrile-based titanium strontium barium nanocomposite material.Infrared spectroscopy results showed that the number of hydroxyl groups on the surface of BST-OH had been effectively increased.The thermal properties,mechanical properties,dielectric properties and microscopic morphology of polyarylene ether nitrile-based barium strontium titanate nanocomposites were investigated by thermogravimetric analyzer(TGA),differential scanning calorimetry analyzer(DSC),universal testing machine,impedance analyzer,dielectric test system and SEM.The results showed that the dielectric constant of the composites gradually increased with the increase of BST-OH content,while the tensile strength showed a slight downward trend with the increase of BST-OH content.When the content of BST-OH was 40 wt%,compared with pure polyarylene ether nitrile,the dielectric constant of the composite was increased by 80%to 5.87(1 k Hz)and the tensile strength still reached 65 MPa.Moreover,the microscopic morphology results showed that poor compatibility between the BST-OH nanofiller and the polyarylene ether nitrile matrix,resulting in a significant increase in the dielectric loss of the composites.In order to improve the interface compatibility between the barium strontium titanate nanofiller and the polymer matrix and further increase the dielectric constant of the composite material,we designed and prepared a series of new barium strontium titanate-silver(BST-Ag)hybrid particles with silver nanoparticles on the surface.Firstly,the surface of BST-OH was grafted by silane coupling agent(MPTMS)to form a small molecular layer with sulfhydryl groups on the surface of BST particles,and then silver nanoparticles were generated by in-situ reduction of silver ions,and through infrared spectroscopy,TGA,SEM and other means carried out structural characterization and microscopic morphology of BST-Ag hybrid particles.Then PAEN/BST-Ag composites were prepared by compounding BST-Ag hybrid particles with PAEN matrix,and the mechanical,thermal and dielectric properties of PAEN/BST-Ag composites were systematically studied.Microscopic morphology analysis showed that the new-type BST-Ag hybrid particles had better compatibility with the PAEN matrix,which enabled the composites to increase the dielectric constant while maintaining a low dielectric loss(<0.03).Compared with the PAEN/BST-OH composite material,the PAEN/BST-Ag composite material not only improved the dielectric constant,but also increased the tensile strength,which was mainly due to the better compatibility of the hybrid particles with the matrix.In addition,the PAEN/BST-Ag composite material also has high-temperature resistant and good dielectric-temperature stability.Therefore,it has potential application value in the field of high-temperature resistant dielectrics under demanding conditions.