Preparation And Performance Study Of Temperature-resistant Polyarylether Dielectric/thermal Conductive Composite Materials

With the rapid development of electronic information technology,electronic devices have been developing towards miniaturization,integration and portability,which needs us to create fresh advanced dielectric materials to meet the requirements of electronic devices for raw materials.So far,inorganic nanoparticles/polymer composites have been recognized as the most possible advanced materials to replace of traditional ceramic dielectric materials due to the combination of advantages of both functional fillers and matrix.As a special engineering resin,poly(aryl ether nitrile)(PEN)is often used as the matrix of advanced functional composites because of its excellent dielectric properties,such as low dielectric loss,excellent temperature resistance,processability,etc.In this paper,HNTs@Ag,HNTs@Fe3O4 and h-BN@Ag were used as fillers to prepare the dielectric compisites with different properties by solution casting method in order to expand their application.Meanwihile,the dielectric properties,thermal stability and mechanical properties of the composites were systematically investigated.The main work includes following three parts:(1)At first,silver nanoparticles(Ag)were deposited on the surface of poly dopamine(PDA)coated HNTs(HNTs@Ag)by redox method,followed by the surface modification of HNTs@Ag with dopamine(DA)and y-aminopropyl triethoxysilane(KH550),so as to improve the dispersion of HNTs@Ag in PEN matrix.Finally,the surface-modified HNTs@Ag was compounded with PEN by solution casting method,thus obtaining the HNTs@Ag/PEN composite materials.The morphology,dielectric properties,mechanical properties and thermal stability of the composites were studied.The results showed that HNTs@Ag had a good dispersion in the PEN matrix by the SEM.At 100 Hz,the dielectric constant of the HNTs@Ag composite film with 9 wt%filler content was about 10.6,which was 3.2 times that of pure PEN film under the same condition,while the dielectric loss was about 0.14.Moreover,the dielectric performance of composite film remained stable at a filler content below 7 wt%throughout the testing range.The glass transition temperatures of all composite films were above 150?,showing good thermal stability.When the content was 7 wt%,the Tg of the composite film increased by about 14.4?,compared with pure film(159.5?),indicating that the filler made an outstanding contribution to the thermal stability of PEN film.The mechanical properties test showed that the composite film had the best mechanical properties at a filler content of 5 wt%HNTs@Ag.(2)Although the HNTs@Ag/PEN dielectric composite films with significant improvement in comprehensive properties were obtained,they have the drawbacks of low dielectric constant,high dielectric loss and complex preparation method.To overcome these shortcomings,ferric oxide nanoparticles(Fe3O4)were loaded on the surface of HNTs coated by PDA through chemical co-precipitation method.Then,HNTs@Fe3O4 and PEN were compounded by solution casting method to prepare HNTs@Fe304/PEN dielectric composite films.The morphology,dielectric properties,mechanical properties and heat resistance were studied.Experimental results showed that HNTs@Fe3O4 can effectively enhance the comprehensive properties of the composite films.The HNTs@Fe3O4 was dispersed evenly in the PEN matrix by the SEM,indicating that there is a strong interfacial effect between the filler and the matrix.As the content of HNT@Fe3O4 increased from 0 to 7 wt%,the dielectric constant of the composite film rose to 11(100 Hz),and the dielectric loss increased to 0.08,showing the property of high dielectric constant and low dielectric loss.As the filler content increased from 0 to 7 wt%,the tensile strength of composite film increased to 111 MPa and then decreased to 90.6 MPa,but was still higher than that of pure PEN.With the addition of HNTs@Fe3O4,Tg of the composite film rose to 162?,which was increased by 8 0C compared with that of pure PEN film.(3)Considering that heat accumulation of electronic equipments in the working process have the adverse effects on equipments,the dielectric composites with good thermal conductivity and low dielectric loss were prepared.Firstly,silver nano particles(Ag)were loaded on the surface of DA-treated hexagonal boron nitride(h-BN)by redox method,thus obtaining the h-BN@Ag hybrid.Then,h-BN@Ag/PEN dielectric composite films were prepared by solution casting method and their comprehensive properties were studied.h-BN@Ag has a good dispersion in PNE matrix by the SEM,because PDA on the surface of h-BN enhances interfacial effect between the h-BN and PEN.As a result,the composite film has low dielectric constant and low dielectric loss.For example,the dielectric constant of the composite film with a 30 wt%filler content at 1000 Hz is about 6.5,while the dielectric loss is just only 0.12.The thermal conductivity of the composite film increases from 0.274 W/mk to 0.921 W/mk with an increasing content of h-BN@Ag from 0 to 30,wt%,which is 3.4 times that of pure PEN film.Therefore,h-BN@Ag has a great strengthening effect on the thermal conductivity of composite film.As the filler content increased from 0 to 30 wt%,the decomposition temperature(T10)of the composite film increased from 440? to 511?,indicating h-BN@Ag can improve thermal stability of PEN.