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2 Archives of Materials Science and Engineering

2 2011

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Preparation and mechanical properties of graphite filled HDPE nanocomposites

Sarikanat M., Sever K., Erbay E., Güner F., Tavman I., Turgut A., Seki Y., Özdemir I.

Archives of Materials Science and Engineering

2011

Vol. 50, nr 2

120-124

Purpose: The design and manufacture of lightweight polymer composites with high electrical and thermal conductivity have been a research focus in recent years. In this study, tensile strength and modulus of elasticity of nanocomposites formed by high density polyethylene (HDPE) matrix and graphite powder filler material were determined. Design/methodology/approach: In this study the conductive filler was graphite with an average particle size of 400 nm and purity of 99.9%, the matrix material was high density polyethylene (HDPE) with a density of 0.968 g/cm3 and a melt index of 5.8 g/10 min, supplied by Petkim A.Ş.- Izmir. Nanocomposites containing up to 30 weight percent of graphite powder filler material were prepared by mixing them in a Brabender Plasticorder at 180°C for 15 minutes. Tensile strength and modulus of elasticity of nanocomposites formed were determined as functions of graphite powder content. Findings: An increase in tensile strength and modulus of elasticity was observed with increasing graphite powder content from 0 to 6%. However, for further increasing the graphite content, tensile strength decreases while modulus of elasticity continued to increase in the composite. Practical implications: Since natural graphite (NG) has a high electrical conductivity at room temperature, it is considered an ideal candidate for manufacturing conductive polymer composites. The recent advancement of nano-scale compounding technique enables the preparation of highly electrically conductive polymeric nanocomposites with low loading of conductive fillers. Nanocomposites may offer enhanced physical features such as increased stiffness, strength, barrier properties and heat resistance, without loss of impact strength in a very broad range of common synthetic or natural polymers. Originality/value: To see the effect of conducting fillers on mechanical properties of HDPE based nanocomposites, graphite particle 400 nm in size were used.

Measurement of heat capacity and thermal conductivity of HDPE/expanded graphite nanocomposites by differential scanning calorimetry

Tavman I., Aydogdu Y., Kök M., Turgut A., Ezan A.

Archives of Materials Science and Engineering

2011

Vol. 50, nr 1

56-60

Purpose: In this study, heat capacity and thermal conductivity of nanocomposites formed by high density polyethylene (HDPE) matrix and expanded graphite (EG) conductive filling material were investigated. Design/methodology/approach: Nanocomposites containing up to 20 weight percent of expanded graphite filler material were prepared by mixing them in a Brabender Plasticorder. Two grades of expanded graphite fillers were used namely expanded graphite with 5 ěm (EG5) and 50 ěm (EG50) in diameter. Heat capacity and thermal conductivity of pure HDPE and the nanocomposites were measured using differential scanning calorimetry (DSC). Findings: A substantial increase in thermal conductivity was observed with the addition of expanded graphite to HDPE. Thermal conductivity increased from 0.442 W/m.K for pure HDPE to 0.938 W/m.K for nanocomposites containing 7% by weight of expended graphite. Heat capacity increases with the increase in temperature for both pure HDPE and the nanocomposites filled with expanded graphite and no appreciable difference in the values of heat capacity were detected due to particle size. Heat capacity decreased with increasing graphite particle content for both particle size, following the low of mixtures. Practical implications: Layers of expanded graphite have become of intense interest as fillers in polymeric nanocomposites. Upon mixing the expanded graphite intercalates and exfoliates into nanometer thickness sheets due to their sheet-like structure and week bonds normal to the graphite sheets. That way they have very big surface area and high aspect ratio (200.1500) what results in a formation of percolating network at very low filler content. The nanoparticles usage results in significant improvement in thermal, mechanical, and electrical properties of polymers even with very low loading levels compared with microparticles. Originality/value: To see the effect of conducting fillers on thermal conductivity and heat capacity two different sizes of expanded graphite were used.