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Preparation And Properties Of PYDF/BN Thermal Insulati On Composites

Posted on:2020-01-03Degree:MasterType:Thesis
Country:ChinaCandidate:Y L TuFull Text:PDF
GTID:2381330575454475Subject:Polymer Chemistry and Physics
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With the rapid development of microelectronics,5G communication,semiconductor and other industries,it is inevitable to generate a large amount of heat in a continuous high-power working environment Therefore,it is urgent to develop new and efficient thermal management materials to ensure the normal and stable operation of electronic equipment.In this work,boron nitride(BN)and polyvinylidene fluoride(PVDF),which have been chemically modified by dopamine,were simultaneously hot-pressed into the composites and boron nitride@silver nanowires(BN@AgNWs)were synthesized by one-pot solvothermal method Subsequently,the hybrid fillers were added to the PVDF matrix to shape the composites.In order to improve the interfacial compatibility between BN and P VDF,they were non-covalently modified by dopamine chemistry at the same time,and the PVDF composites with in-plane orientation were prepared by hot-pressing later,which not only improve the transmission of phonons at the interface and simplify the process but cater to the green chemistry ideal.TEM,XRD and XPS characterizations indicated successful modification of the BN and PVDF surfaces.By means of regulating the dopamine polymerization time,it was found that the most favorable polymerization time was 4 hour.Analysing non-isothermal crystallization of the composites,at lower BN content(within 17 wt%),BN was equal to heterogeneous nucleating agent in the matrix which could promote the increase of crystallinity,while the BN at high content,dense directional distribution of BN hindered the movement of the PVDF segment toward the crystal,which was not beneficial to the increase of crystallinity.In addition,the results of XRD and SEM cross-section analysis also showed that BN was in-plane.The thermal conductivity of the composites was obviously correlated with the content of BN.The thermal conductivity reached 1.466 W/mK when the BN content is 50 wt%,which was 2.3 times than that of PVDF@PDA.Using a thermal imager to analyze its heat dissipation performance,it could be seen that the(PVDF+BN)@PDA composites had good heat dissipation performance.Afterwords,the dielectric properties of the composites were improved obviously,which expanded its application in electronic devices.In order to construct an effective filler network,BN@AgNWs hybrid filler was simplely synthesized by one-pot solvothermal method.The SEM,TEM,XPS and XRD characterization were used to prove the BN@AgNWs hybrid filler.It was found that the hybrid fillers synthesized by different ratios of AgNO3 and BN had different synergistic effect on the composites.When the ratio of AgNO3:BN=1:1 the thermal conductivity was the largest.The non-isothermal crystallization,rheology,mechanics,dielectric and thermal conductivity properties of the composites were investigated in depth.As the content of hybrid filler increases,the crystallinity and crystallization rate of the composite increased firstly and then decrease,which was attributed to the heterogeneous nucleation of the hybrid filler,but the crystal growth was also limited at higher filler content.The dynamic rheological behavior of the composites were analyzed.At 20 wt%,the internal filler network of the composites gradually began to appear in the low frequency region.The Han curve also proved the formation of the filler network.Analysing of the mechanical properties of the composites showd that as the proportion of AgNO3:BN increases,the mechanical strength of the prepared composites also increased.Compared with the comparison sample,the addition of BN@AgNWs hybrid filler could form a denser filler network in the matrix to increase the Young's modulus of the composite,and the overall mechanical properties changed little.With the increase of BN@AgNWs hybrid fillers,the thermal conductivity of PVDF composites reached 1.19 W/mK at 30 wt%.which is 236%higher than that of pure PVDF matrix,and the thermal conductivity of composite with equivalent BN content is only 1.06 W/mK.The thermal imaging characterization also proved that the PVDF/BN@AgN Ws composite had good heat dissipation performance.In addition,the composites with BN@AgNWs hybrid filler obtained good dielectric properties compared with the comparative sample,which could expand its application range.At the frequency of 100 Hz,the highest conductivity of composites with hybrid filler was 2.9110-11 S/m,indicating that AgNWs had little effect on conductivity,and the composites were still in the insulation category.
Keywords/Search Tags:polyvinylidene fluoride, boron nitride, dopamine, silver nanowire, thermal conductivity
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