Study On Thermal Conductivity Of PVDF-based Plastic Film

Compared with metallic heat exchange elements,polymer-based composites have the advantages of corrosion resistance,light density and easy processing and moulding in heat exchange processes below 100°C,which can effectively avoid many of the drawbacks of metallic materials in heat exchange process applications.Polymer-based composites have great application prospects.However,the low thermal conductivity of polymers is one of the main technical obstacles for heat exchangers made of polymeric materials due to their limited thermal diffusion capability.To address this issue,the composite material based on polyvinylidene fluoride(PVDF)was prepared in this experiment.And then the effects of its microscopic morphology,crystallization behavior,and filler network structure on the thermal conductivity and mechanism of action were explored in order to find the PVDF plastic composite film material with excellent thermal conductivity and other comprehensive performance.Some of the main investigations are as follows:(1)The base film of PVDF plastic film was preparad by solvent evaporation method.The effects of matrix solid content,evaporation temperature,holding time and other process parameters on the microstructure,crystal structure and thermal conductivity of PVDF plastic film were systematically investigated in the process of solvent evaporation.The research indicacated that the PVDF plastic film prepared by solvent evaporation had good overall tensile strength and good transparency.With a solid content of 15%,a solvent evaporation temperature of 60?,and a holding time of 4 h,the PVDF plastic film could guarantee a dense morphological structure and good mechanical strength.At the same time,it was mainly dominated by?-PVDF without producing other complex crystal forms.The thermal conductivity of PVDF plastic film was 0.19 W·m^-1·k^-1,and the breaking strength was 38.59 MPa.(2)PDA@CNTs-NH₂ after mussel co-modification of multi-walled carbon nanotubes(CNTs)with dopamine(DA)and 3-aminopropyltriethoxysilane(APTMS)was used as a thermally conductive filler,and the PDA@CNTs-NH₂/PVDF composite films were prepared by solvent evaporation method.The microscopic morphology and thermal conductivity of the composite films were analyzed to investigate the effect of the polydopamine formed on the surface of CNTs after DA polymerization on their uniform dispersion and interfacial thermal resistance.When the amount of PDA@CNTs-NH₂ was 8%,the thermal conductivity of the plastic composite film is up to 0.3379 W·m^-1·k^-1.The thermal conductivity of the composite plastic film was enhanced by improving the dispersion of the filler and adjusting the interface interaction between nano-filler CNTs and polyvinylidene fluoride.(3)PDA@T-Zn Ow was obtained by modifying T-Zn Ow with mussel,and then a hybrid filler system was formed by adding GO.PDA@T-Zn Ow/GO/PVDF composite plastic films were prepared by the solvent evaporation method.The thermal conductivity,morphological structure,mechanical properties and thermal stability of PVDF composite plastic films were investigated.It was shown that the hybrid filler system of PDA@T-Zn Ow/GO improved thermal conductivity,because reactive groups such as-NH₂ on the surface of PDA interacted with a large number of oxygen-containing groups on GO to promote dispersion and build a more dense and effective thermal conductivity path with PDA@T-Zn Ow,which reduced the interfacial thermal resistance and facilitates phonon transport channels.When the amount of PDA@T-Zn Ow/GO was 4%,the thermal conductivity of the plastic composite film was up to0.3321 W·m^-1·k^-1,and this was a 175%improvement over pure PVDF plastic film.