Preparation And Properties Of Poly(Vinylidene Fluoride) Composites With High Thermal Conductivity And Mechanical Performance

Heat exchange material is the core of heat exchangers,which is expected to be excel ent for thermal conduction,corrosion resistance,mechanical properties and scale resistance.Currently,traditional metal heat exchangers cannot meet the requireme nts in fierce conditions during industrial production.Thermal conductive polymer ic materials are strategically supplementary materials owing to their excel ent corrosion resistance,scale resistance,easy-processing.Therefore,polymer-based materials with high thermal conductivity are highly valued in scientific research and industr ia l application.In the dissertation,the present research progress and the development tendency of thermal conductive polymer are discussed and analyzed,and then two kinds of poly(vinylidene fluoride)(PVDF)composites with high thermal conductivity are prepared.Thermal conductivity,mechanical properties,morphology,crystal iza t io n behavior,and heat transfer performance of PVDF composites are studied.The results are summarized as follows:Due to hard dispersion problem of fillers in polymer matrix,especially in high filler loading,the uniform and continuous network of(3-Aminopropyl)trimethoxysi la ne(APTMS)modified carbon nanotubes(A-CNTs)in poly(vinylidene fluoride)(PVDF)is built up via solution compounding method.The obtained A-CNTs/PVDF composites possess the excel ent thermal conductivity and mechanical properties simultaneous ly.The thermal enhancement of 877%and the high tensile strength(47.88 MPa)are attained for 40vol%A-CNTs/PVDF.In contrast,thermal conductivity and tensile strength of pure PVDF are 0.22 Wm^-1K^-1 and 35 MPa,respectively.APTMS can effectively tailor CNTs positively charged and promote the uniform dispersion at a high content.This is not only beneficial for the establishment of point-to-point phonon interconnected network,but also important to promote mechanical properties.The plate heat exchangers made of A-CNTs/PVDF composite show high heat transfer efficie nc y and durability in corrosive water.In order to further eliminate the interfacial thermal resistance between fillers and polymer matrix,a new hierarchical three-dimensional(3D)framework is built by electrostatic self-assembly between A-CNTs and graphene oxide(GO)in poly(vinylidene fluoride)(PVDF).Thermal conductivity enhancement of 628%and tensile strength enhancement of 120%are achieved at 10 vol%GO-A-CNT hybrid filler loading compared with that of pure PVDF.Compared with 20vol%A-CNTs/PVDF in the first stage,the filler content is reduced by 1/2.This is because GO-A-CNT hybrid fillers are beneficial for interconnected 3D point-plane network,decreasing the interfacial thermal resistance.In the future,PVDF composites owe great potential in new heat transfer materials.