Compostos poliméricos con alúminainfluencia da reoloxía e amorfoloxía na condutividade térmica

Abstract

The current scientific-technological development demands high-performance materials, versatile in terms of properties, with ease of molding and a good cost-properties ratio. In this context, the main target of this thesis is to design new polymer composites with high thermal conductivity and easy processability at industrial scale. For that purpose, α-alumina short fibers (whiskers) and a combination of whiskers and nanoparticles of α-alumina (hybrid filler) were added to different immiscible blends of high density polyethylene and polyamide 6. During the thesis work, the morphology of the composites was analyzed and related with the material composition, the rheological properties and the thermal conductivity obtained. To optimize the properties (mainly the thermal conductivity) with the low filler amount, different strategies have been studied: modifying the composite morphology by inducing coalescence after preshear treatments or changing the sequence of incorporation of the hybrid filler in the polymeric matrices. From the obtained data, it can be concluded that the incorporation of α-alumina whiskers has improved the thermal conductivity of the matrices. The highest value was obtained with 50% short fibers, getting a threefold increase respect to polyethylene or polyamide values. In general, the application of preshear in compounds with 30% of whiskers, increased their thermal conductivity. With low alumina amounts (30%), generally, the preshear treatment increased the thermal conductivity of the composites with whiskers. Although the largest increase, it was obtained using the hybrid filler, with differences based on the composition of the polymer matrix and the processing method followed.