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Study on the Modification of FEP with High Thermal Conductivity and Insulating

Author: ZhaoHongQiang
Tutor: JiangLiQiang
School: Zhejiang University of Technology
Course: Materials Science
Keywords: FEP Al2O3 insulation thermal conductivity mechanism
CLC: TB332
Type: Master's thesis
Year: 2009
Downloads: 51
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Abstract


Using alumina （Al2O3） particles modified by coupling agents as filler, a series of Al2O3/FEP composites with high thermal conductivity and insulation were achieved by blending and hot molding process. The effects of different Al2O3 contents on the thermal conductivity, volume resistance, mechanical properties and rheological behavior of the Al2O3/polymer composites were studied. The thermal-conducting model and mechanism of Al2O3/FEP were discussed. The effects of alumina shape and size on thermal conductivity of composite were also studied. The blending modification of FEP matrix was investigated to get high rheological behavior.The effects of PPS addition on the flowing rate, mechanical properties and microstructure of the PPS/FEP system prepared by physical blending method were studied. The results indicate that the PPS addition in FEP obviously increases the flowing rate of PPS/FEP system compared with the single FEP. However, the tensile strength drops with increasing PPS. A mechanism was proposed to explain the growth of the flowing rate that the liquid PPS particles dispersed in FEP offer FEP the large deformation space under the shearing force during the process. The SEM observation shows that the weak compatibility between FEP and PPS surface results in the decrease of the tensile strength and elongation of PPS/FEP system. However, a small mount of PPS addition obviously improves the flowing property of FEP, which is good for machining process.The bulk resistance of the composite was between the matrix and aluminium nitride. It gets closed to AlN while the addition of AlN increases. Different polymer matrixes play the important role on the bulk resistance of composties.PPS/FEP-based composite filled with Al2O3 was prepared by physically blending and hot molding. The result shows that the thermal conductivity increases with increasing Al2O3 content and reaches 0.99 W/m·K when Al2O3 addition is 30wt%. It has increased in four times compared with the single FEP. The tensile strength of the composite slightly changes. However, the elongation at break and flowing ability decreases with the increase of Al2O3 addition. Using PPS/FEP system, the similar flowing ability can be achieved even though Al2O3 addition reaches 10wt% compared with the single FEP.FEP-based composites filled with alumina platelets were prepared by physical blending method. The thermal conductivity and elongation of the composites containing Al2O3 platelets were studied in comparison with Al2O3 particles as filler. The microstructure of the composites was also observed by SEM. The results show that the Al2O3 fillers with low mass fraction display an island distribution in the FEP matrix and cannot form the continuous thermal conduction chains. However, the thermal conductivities of the composites greatly increase compared with the single FEP. The tensile strength and the elongation at break of the composites decrease with the increase of the Al2O3 contents. The increasing thermal conductivity of the composites containing fine alumina platelets is associated with the prolonged heat conducting path and the interface between the fillers and FEP.The action between FEP and silane coupling agent KH550 was studied using scanning electronic microscope, Fourier Transform Infrared Spectrometer and Differential Scanning Calorimeter. The results show that a good bonding interface begins to form between KH550 and FEP when they are heated to 190℃. The combination comes from the reaction of-CF3 group in the long chains of FEP and -NH2 group of KH550. The reaction increases the melting point of FEP from 258℃to 266℃. The strong combination makes it possible that the FEP-matrix composites improved by fillers are prepared by the proper surface treatment on the filler particles.

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