Development And Application Of A Mixer Dominated By Volume Elongation Deformation In Synergy With In-situ Ball Milling For Lightweight Dielectric Composite Materials

Polymer-based composite materials are widely used in the field of energy storage and communication due to their high-power density,high breakdown voltage and other excellent properties,but their low dielectric constant limits their further applications.Filling modification is a common method to improve the dielectric constant of polymers.The commonly used screwtype melt mixing technology dominated by shear laminar flow needs to increase the shear strength and the residence time to improve the mixing effect,resulting in damage to the filler and degradation of the matrix,and affecting the functional effect and mechanical strength of the product.In this subject,based on the principle of high efficiency mixing under the influence of tensile deformation and the in-situ ball milling effect,an in-situ ball milling assisted tensile deformation melting mixing technology and volume stretching deformation mixing device were developed.The following research results were obtained.The volume stretching deformation mixing device has been developed.The key components,working principle and mixing process of the device were introduced in detail.And the physical and mathematical models of the mixing unit were established.The theoretical analysis proved that the material is mainly subjected to tensile deformation during the mixing process.The relationship between the ball mill pressure and the structural parameters of the mixing unit and the characteristics of the materials and process parameters were established.The influences of the Brabender rotor internal mixer dominated by shear flow field and the volume stretching deformation mixing device dominated by the extensional flow field on the morphology and performance of PVDF/HGMs blends were compared and analyzed.The results showed that the interfacial bonding strength between HGMs and PVDF matrix in the blends prepared by the volume stretching deformation mixing device is higher,the dispersion and distribution morphology is better,and the damage rate of HGMs is lower.When the HGMs content was 15 wt%,the density of blends decreased by 30% compared to that prepared by Brabender rotor internal mixer.The effect of in-situ ball milling assisted tensile deformation on the morphology and properties of PVDF/graphene(RGO)/HGMs composites was studied based on the volume stretching deformation mixing device.The results showed that the in-situ ball milling effect of HGMs can make the RGO uniformly dispersed in the matrix and cause a high degree peeling of RGO.When the RGO content was 4 wt%,the dielectric constant of PVDF/RGO/HGMs composites increased by 28% and the dielectric loss decreased by 25% compared with those of PVDF/RGO composites.When the HGMs content was 15 wt%,the thermal conductivity of the blend was 118% higher than that of pure PVDF.The experimental results showed that the smaller the particle size of HGMs was,the more obvious the stripping effect of RGO was,and the dielectric properties and thermal conductivity of the blends were improved.The research results of this thesis provide a new design idea and theoretical basis for the tensile deformation mixing equipment,and provide new equipment and new technology for the processing and preparation of lightweight filled dielectric polymer-based composites.There are important academic significance and industrial application value to enrich and develop the theory of polymer forming and melting mixing.