PA46 Matrix Composites For High Thermal Conductivity

In the electro-optical conversion efficiency of light-emitting diode(LED),85%of the energy is converted into heat.The heat dissipation becomes one of the main problems which limits the lifetime of LED with the development of high power LED.So the new type of polymer composites have the wide usage in this filed.Spherical aluminum and alumina powders with different particle sizes were chosen to mix with PA46 by twin screw extruder to prepare Al/PA46 and Al2O3/PA46 composites respectively for the application in the LED encapsulation.Thermal conductivity,flow property,mechanical property and microstructure of the composites were measured.The influence of filler content,particle size and coupling agents on the composites were studied in this article.In the PA46 composites filled with spherical aluminum powders,the thermal conductivity of composites increases with the increase of the filler content.When the filler volume fraction reaches the critical value of 55%,the thermal conductivity of composites increases dramatically.The thermal conductivity is 2.242 W/(m·K)and the melt flow rate drops to 41.8g/10min when 60vol%Al powder is added.The tensile strength of composites increases but the impact strength first increases and then decreases with the increase of the filler contents.The thermal conductivity of composites not only relates to the filler content but also has a lot to do with the particle shape and size distribution.Using the Al2O3 particles with different sizes to mix with PA46,the results show that the thermal conductivity of composites filled with small Al2O3 particles is higher and the saltation point appeares earlier than the composites filled with large particles.But the result of melting fluidity is opposite.The interfacial adhesion between the fillers and the polymer matrix can also affect the thermal conductivity of composites.When the optimal amounts of KH-550 and titanate coupling agent are separately 0.5%and 1%respectively,the Al/PA46 composites display good microstructure and properties.The best dosage of KH-550 was 0.25%for Al2O3/PA46 composites.The coupling agents can improve the interface between the fillers and the polymer matrix from the observation on the SEM photos of the fractural surfaces.The double melting behavior in the PA46 matrix composites can be found in the experiments.DSC,XRD,TG were adopted to analyse the melting behavior of the PA46 matrix composites.The results shows that the double melting behavior is associated with the different crystalline regions formed in the extruding process based on the experimental data.