Polyurethane Elastomers With Improved Thermal Conductivity Part I: Elaborating Matrix Material For Thermal Conductive Composites
Cross-linked polyurethane elastomer matrix was evaluated for thermal conductive composites with magnesium oxide powder (MgO). MgO as one of the cheapest materials for high thermal conductivity,seems to be useful for incorporation in polyurethane elastomer increasing thermal conductivity of the composites. Possible matrix polyurethane elastomers were fabricated. The effect of MgO contents from 1 to 30 %wt were investigated bothin flexible and in rigid polyurethane elastomers. First experimental aim is investigating the structure of the polymer intended for application. Improving thermal conductivity was first not achieved but the causesof the poor results were discovered. After that differential scanning calorimetry (DSC) and thermally stimulated discharge (TSD) methods were used to examine the structure of polyurethane elastomers. Furthermore, hardness measurements were carried out for estimating the effect on mechanical properties. Then, morphology of theMgO particles was observed using scanning electron microscope (SEM). Resultsshowed that thermal conductivity of the composites both of flexible and rigid polyurethane elastomers did not significantly change with loading MgO contents less than 30 %wt. In case of structure examinations, DSC thermogramsregistered a small transition around -62 °C of flexible polyurethane elastomers and their composites while the small transition of rigid polyurethane elastomers were hard to evaluate because the DSC technique is not sensitive enough for detecting a glass transition in these rigid polyurethane elastomer chains. Therefore, TSD technique was used to investigate chain relaxation. Pure flexible and rigid polyurethane elastomers show the same glass transition temperatures of soft segments around -65 °C. The incorporation of MgO less than30 %wt in both flexible and rigid polyurethane elastomer did not significantlyaffect hardness properties. Moreover, the smallest MgO particle observed were around 400 nm by SEM technique.
Keywords - Polyurethane Elastomers, Magnesium Oxide, Thermal Conductivity