Polymer nanocomposites have a wide application in automotive and airplane industries, shipbuilding, household appliances and medical apparatus due to their excellent mechanical, thermal and chemical properties. In this research, Polypropylene (PP) / Ethylene-Propylene Diene Monomer (EPDM) nanocompositeswith 5%wtnanoclayare fabricatedby Friction Stir Processing (FSP) and compared to those obtained via a conventional Twin Screw Extruder (TSE) and) in order to determine the effects of process parameters on morphology and mechanical properties.The mixtures and dispersion of nanoclay in PP/EPDM have been characterized by X-ray diffraction, transmission electron microscopy and mechanical property tests.Comparison of the results of these methods indicated that PP/EPDM/clay nanocomposite fabricated by FSP had a better dispersion of nanoclay and mechanical properties. The results show that by addition of 5% wt nanoclay to base material, the tensile strength and tensile modulus increased and elongation at break and impact strength decreased.Under optimal conditions of rotational speed of 1200 rpm, traverse speed of 50 mm/min, shoulder temperature of 100 °C and number passes of 3, simultaneous maximization of tensile strength (19.35 MPa), tensile modulus (643 MPa), impact strength (63 J/m) and elongation at break (101 %) can be obtained.
Keywords: Nanocomposite, Clay, Friction Stir Process, Twin Screw Extruder, Mechanical Properties.
Thermoplastic elastomeric materials (TPEs) aredefined as a group of polymer blends which consist of two-phase materials exhibiting both thermoplastic and elastomeric properties[1, 2]. TPE blends can be divided into dynamically vulcanized blends (TPVs) and polyolefin blends (TPOs). TPOs blendare widely used in airplane, shipbuilding and automotive industries and medical apparatusdue to their excellent mechanical, thermal and chemical properties[3, 4]. Polypropylene (PP) as one of the most important commodity thermoplastic polymer have useful properties such as high thermal stability, low density, chemical resistance, good processability and high strength. The industrial use of this polymer is still limited because of its low tensile modulus and poor impact resistance, especially at high strain rate and low temperatures.Blending PP with rubbers such as ethylene-propylene diene monomer (EPDM) give thougher materials suitable for automotive, aerospace and medical applications where excellent mechanical, thermal and chemical properties are needed [7, 8]. The addition of a small amount of clay (less than 10% w/w) further enhances mechanical, thermal and barrier properties [9, 10]. The development of polymersnanocomposite and their manufacturing technologies is one of the important advances in the recent history of plastics. Lately, various process have been developed for fabricating polymer nanocomposites which includes solvent blending, in-situ polymerization and melt compounding[8, 11, 12]. Studies on the preparation and properties of thermoplastic Elastomer (TPEs) nanocomposites based on PP, EPDM and nanoclay are readily available [2, 7].
Friction stir process (FSP) is a novel process developed based on the principle of friction stir welding (FSW) for the fabrication of composites, nanocomposites and microstructural modifications[13, 14].According to Fig. 1(a), in this process, a groove with defined dimensions is machined in the base material sheet and nano particles are placed into this groove.
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