Modification Of Poly(vinylidene Fluoride) Heat Conducting Property

Heat exchanger is an important kind of energy recovery in industrial areas. Metalheat exchangers are the most common at present, but they have large volume and arenot corrosion resisting. As the development of industry, the demand of heatexchanging materials develops. Although polymers are corrosion resisting, they havelow thermal conductivity. In this study, different materials are used to fillpoly(vinylidene fluoride)(PVDF) to mollify their thermal conductivity and otherproperties.In this study, Polyaniline (PANI) nanofibers doped with hydrochloric acid (HCl)were synthesized in aqueous solution using Dodecyl Benzene Sulphonic Acid (DBSA)as surfactant. The PANI nanofibers were dispersed in DMF with ultrasonicating.PVDF was dissolved in the homogenous PANI nanofiber solution to fabricatePVDF/PANI nanofiber films by mean of the evaporation of DMF. Scanning electronmicroscope (SEM) was employed to study the morphology of PANI nanofibers andthe surface and cross-section of the films. The crystalline structure of PVDF andPVDF/PANI nanofiber films was characterized with XRD (X-ray diffraction) andDSC (differential scanning calorimetry) was used to study thermal stability of thefilms. The results showed that PANI nanofibers were well dispersed in PVDF matrixand the fabricated films were very stabile. As the weight fraction of PANI nanofibersincrease, tensile strength first increase and then decreases. When the PANI is2wt%,the tensile strength reaches maximum, and it is55.27MPa,29.53%higher than PVDF.As the weight fraction of PANI nanofibers increase, the thermal conductivity firstincreases and then decreases. When the concentration of PANI reaches5wt%, thethermal conductivity of PVDF/PANI nanofiber film is45%higher than that of thepure PVDF film.The graphite oxide was synthesized by Hummers method. Graphene oxide wasprepared by sonicating the graphite oxide solution. Graphene oxide/PVDF films werefabricated by mean of the evaporation method. The morphology and structuralanalysis were carried out by using TEM, FTIR and XRD. The tensile strength andthermal conductivity of graphene oxide/PVDF films with different content ofgraphene oxide were studied. The results suggest that graphene oxide has various oxygen-bearing functional groups. Graphene oxide is well dispersed in PVDF matrix.And the graphene oxide in the films can improve the tensile strength and thermalconductivity. The thermal conductivity increases with increasing content of grapheneoxide first, and then it gradually decreases. When the content of graphene oxide is0.4wt%, the thermal conductivity reaches maximum. When the content of grapheneoxide is higher than0.4wt%, the thermal conductivity increases slowly.Electric field was applied for membranes structure orientation in the process ofthe membranes formation. The results showed that the compatibility between thegraphene oxide and PVDF matrix was significantly improved. The thermalconductivity of the films is higher than that of the films without electric field.