| Because of it's excellent optical,electrical,gas and liquid barrier properties,Micro-/nano layered polymer composites have been widely used in many fields.By assembling the layered polymer,the composite materials expresses better performance.Micro-/nano multilayer coextrusion processing is currently one of the most economical and effective processing technologies for preparing micro-/nano layered polymer composites.During which the interfacial effect and spatial confinement between components may affect the structural evolution of the material and the overall performance of the product,but the mechanism behind these phenomena is not yet clear.In view of this,based on the micro-/nano multilayer coextrusion technology,this paper systematically studied the influence of the space constraints and interlayer interface effects on the structural evolution of micro-nano multi-layer coextruded composite materials,and clarifies the dielectric properties of the materials Influence mechanism.The research content and main conclusions of this article are as follows:?1?First,based on the incompatible polyvinylidene fluoride-hexafluoropropylene copolymer?PVDF-HFP?/polycarbonate?PC?micro-/nano multilayer composite material system,the layer structure of the composite material under the constraints of geometric space and the evolution of the aggregate state structure in the layer and its influence mechanism on the dielectric properties have been explored.Results show that as the thickness of the single layer decreases,the layer structure of the composite material loses stability when the the single layer film thickness is reduced to about 500nm,which the difference in the elasticity of the polymer melt and thermal fluctuation should be responsible;the crystallinity of PVDF-HFP increases under the competitive relationship of space limitation and interface interaction,from 13.9%to 20.4%;the layered structure effectively inhibits the composite material's electrical loss in low frequency region,whose loss angle is stable around 1×10-2;due to the space charge penetration behavior of the thin PC film,the dielectric storage permittivity of the composite material gradually weakens after the single-layer film thickness decreases to a certain extent.Sample 8L expresses the optimal value of dielectric performance,whose dielectric storage permittivity as high as 70 p F/m under 1000 Hz.?2?Based on the compatible polyvinylidene fluoride?PVDF?/polymethyl methacrylate?PMMA?micro-/nano multilayer system,the influence of the interlayer diffusion and space confinement effect on the layer structure,the aggregation structure in the layer,and the change of the dielectric properties of the multilayer films are studied.The results show that as the thickness of the single-layer film decreases,the composite material has excellent layer stability and continuity due to the highly matched viscoelasticity of the component polymer melt,and the interface profile gradually diffuses under the effect of polymer interdiffusion;PVDF occurs two-dimensional orientation parallel to the film thickness direction under space constraints,generating?electroactive phase,and for the equipartition system,the total crystallinity of the material gradually decreases under the combined effect of space constraints and rigid molecular chain topology constraints,from 60.46%to 20.65%;the layered structure effectively suppresses the dielectric loss of the composite material in the low-frequency,and its loss angle is stable near 8×10-3.Due to the increase in the number of carriers and the two-dimensional orientation of the crystal which facilitate deformation polarization,the dielectric storage permittivity of the composite material increases within a certain range as the thickness of the single-layer film decreases.Sample 32L expresses the optimal value of dielectric performance,whose dielectric storage permittivity as high as 140 p F/m under 1000 Hz. |
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