Metallurgical By-Product Transformation and Its Plasma Modification to Increase HDPE Thermal Conductivity
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Metallurgical By-Product Transformation and Its Plasma Modification to Increase HDPE Thermal Conductivity Olivares-Maldonado Y.1, F Ramírez-Vargas E.1, Ramos-deValle L.1, Perera-Mercado Y. A.2, Neira-Velázquez M. G.2 1 Department of Polymer Processing, Research Center for Applied Chemistry, Saltillo, México. 2 Department of Advanced Materials, Research Center for Applied Chemistry, Saltillo, México. ABSTRACT A metallurgical by product mostly constituted of Wustita (FeO) was transformed to Magnetite (Fe3O4) spheres using a flame treatment. Then magnetite spheres surface was modified by cold plasma treatment with ethylene, where a thin polyethylene film was deposited on the spheres surface. Finally, HDPE composites with modified spheres were obtained by melt mixing and its thermal conductivity was determined by MDSC. It was found that spheres surface modification helps to increase composites thermal conductivity. INTRODUCTION Polymers thermal conductivity is an important property for its processing and applications. Polymers have very low thermal conductivity, e.g. high density polyethylene (HDPE) has a conductivity of 0.35 W/m·K. During processing, polymers are manipulated at temperatures above its melting temperature, and then have to be cooled down in order to obtain the final article, which results in longer processes [1]. Having polymers or polymer composites with higher thermal conductivity would make it possible to reduce the cycle time process. Also, there are some applications that require high thermal conductivity in order to dissipate heat generated during functioning of an appliance [2]. One way frequently used to increase polymers thermal conductivity is through the addition of high thermal conductivity particles. In this sense, the metallurgic industry produces slag that can be used as precursor to obtain magnetic, high conducting, particles, which can be used in polymer composites to increase its thermal conductivity. One of the most important factors that can affect the final thermal conductivity of the composite is heat resistance at the interphase [3]. Modifying the particle surface could improve polymer-particle interactions [4]. Plasma is a versatile and clean technique for this purpose. When a polymerizable gas is used, a nanometric film layer is deposited on the particle surface. In this study, magnetic spheres were obtained from the metallurgic industry slag. Spheres surface was modified by plasma with polyethylene, and finally thermal conductivity of final composite was determined.
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EXPERIMENTAL DETAILS Materials A high density polyethylene (HDPE) was used with melt flow index of 5g/10 min, density of 0.9665 g/cm3 and melting point of 130°C. Magnetite spheres preparation A Metallurgical Industrial by product rich in wustite was used as precursor. A flame process was used to project particles into a recollecting camera. A common flame gun was used with an oxygen:gas relation of 6:1, feeding distance was 2 cm. During this process wustite was oxidized into magnetite. Plasma treatment A copper
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