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Mechanical Properties and Microstructures of Exfoliated Graphite Nano Platelet Reinforced Thermoplastic Nanocomposites



Exfoliated graphite nano platelets (EG) were fabricated and processed with high density polyethylene (HDPE) to produce EG/HDPE composites. Different compositions of EG/HDPE were prepared: 0%, 1%, 2.5%, and 5% weight of EG. The mechanical properties and microstructures of the composites were investigated. EG was fabricated using natural flake graphite (NFG) with 300μm diameter size. NFG was then intercalated using a Perchloric Acid and Potassium Permanganate (KMnO4) system. The intercalated graphite was expanded at 800oC, and then was sonicated for 6 hours. The produced exfoliated graphite possessed a mean diameter of 38.5μm and a thickness of around 15nm. It was called EG1. Asreceived and ball-milled EG with mean diameters of 9μm and 2μm and thicknesses of 8nm and 4nm, respectively, were also used, designated as EG2 and EG3. EG and HDPE were pre-mixed by a mechanical disperser in the presence of an isopropyl alcohol (IPA) solvent and then dried. EG/HDPE composites were then fabricated using a twin-screw extruder, followed by injection molding. Hardness, tensile and impact tests were carried out to evaluate the performance of these composites. 5% EG1 increased the tensile modulus of elasticity of the EG/HDPE composite by 24% and the yield stress by 5.5%. The ultimate tensile strength, on the other hand, experienced a reduction of 4.7%. A bigger particle sized EG1 resulted in a higher increase of the tensile modulus in a 1% EG loading compound, compared to EG2 and EG3. EG3 with the smallest particle size showed lower tensile properties, due to an EG agglomeration in the HDPE Matrix. The hardness exhibited no changes in all composition, whereas impact strength decreased in general.

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