Rubber Toughened Polyamide 6/ Polypropylene Nanocomposites: Mechanical, Thermal And Morphological Properties

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Date
2006-06
Authors
Wahit, Mat Uzir
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Universiti Sains Malaysia
Abstract
Rubber-toughened nanocomposites (RTNC) consisting series of compatibilized polyamide 6 / polypropylene (PA6/PP) blends, of composition 100/0, 70/30, 50/50, 30/70 and 0/100, polyethylene-octene elastomer (POE) and organophilic modified montmorillonite (organoclay) were produced by melt compounding followed by injection moulding. Polypropylene grafted maleic anhyride (PPgMA) was used as compatibilizer. Subsequently, for PA6/PP (70/30), the POE and organoclay loading was varied between 5 and 20 wt% and 2-6 wt%, respectively. For the optimum particles dispersed in the PA6 matrix, was characterized by scanning electron of a formulation, four different types of elastomer were incorporated into the blends i.e. ethylene-octene elastomer (POE), ethylene-propylene elastomer (EPR), maleated POE (POEgMAH) and maleated EPR (EPRgMAH). For the selected formulation, the nanocomposites were also prepared through different mixing sequence of melt intercalation i.e. direct, two times and two steps method. The mechanical properties were studied through tensile, flexural, Izod impact and fracture toughness testing. The morphology, essentially comprised of PP and POE microscopy (SEM). Wide angle X-ray diffraction (XRD) was used to characterize the formation of the nanocomposites. The thermal properties were characterized by using differential scanning calorimeter (DSC) and thermogravimetry analysis (TGA). The dynamic mechanical were analyzed by using dynamic mechanical thermal analyzer (DMTA). The results showed that, the incorporation of organoclay significantly increased the stiffness and strength but at the expense of the toughness. Conversely, the incorporation of the POE increased the toughness, while the strength and stiffness decreased. The PA6/PP nanocomposites containing 4 wt % of organoclay and 10 wt% of POE had the best balance of stiffness, strength and toughness. The results also showed that modulus and strength of the nanocomposites was not significantly affected by types of elastomer and their functionality and the blending sequence. However, the toughness of the nanocomposites toughened by maleated elastomer was higher than the unmaleated elastomer. Two steps method gave the best mechanical properties due to its good dispersion of the organoclays and elastomer in the matrix. XRD established that the organoclay was well dispersed (exfoliated) and preferentially embedded in the PA6 phase. The type of elastomer and functionality and method of processing did not significantly affect the dispersion of the organoclay in the system. Blend ratio and the presence of organoclay were found to influence the morphology (e.g. POE particle size and distribution) of the system. A finer particles size and better distribution of POE elastomer has been observed in higher PP concentration system. The SEM observation also revealed that rubber functionality and two steps method reduces the elastomer particle size in the PA6/PP matrix.
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Chemistry
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