Nano Particle and Fiber Reinforced Injection Molded Polymeric Materials

Abstract

Fiber reinforced polymers have been widely used for many years. Despite of their higher cost of production compared to metals, their improved properties make them widely used. Modeling of fiber reinforced polymers is necessary to predict the final product properties, and to decide on production conditions and material properties to be used in manufacturing. In 1987, Fukushima and Inagaki who were researchers in Toyota investigated the effects of nano sized clay on the strength properties of timer belts. Their trial started the nanocomposite era. The discovery of carbon nanotubes and fullerenes gave more options for nanocomposites production. Due to the difference between nano scale and micron scale, nanocomposites have different properties compared to conventional composites. In this study, polypropylene (PP) is reinforced with elastomers, fibers and nanoclay. To improve the toughness of PP, two thermoplastic elastomers were added separately. Tensile tests were conducted according to the ASTM D638-3 standard test method on Instron universal testing machine. Rubber particle distributions were observed on SEM. Tensile test results give an increase in energy at break which is the toughness of the material. Increase in toughness proves that adding thermoplastic elastomers toughens the PP. For fiber and nanoclay reinforcement, polypropylene based composites having glass fiber, carbon fiber, and nanoclay reinforcements at 1 wt%, 4 wt% and 7 wt% are produced. The fibers are in the micron scale while the clay is in nano scale. Pure polypropylene samples are used as control samples. The effect of compatibilizer on nanoclay/polypropylene is also investigated using a montmorillonite nanoclay. The mechanical properties (tensile strength, flexural strength and impact strength) of the samples are tested. The cross-sections of the samples are studied using scanning electron microscopy. Fiber length distributions are studied using scanning electron microscopy and light microscopy. The processing characteristics of PP/F1 and PP/F2 blends have been studied. Addition of thermoplastic elastomers F1 and F2 to PP decreased the yield stress of the blend and decreased its modulus. Toughening of polypropylene was achieved by blending of PP with the thermoplastic elastomers. Tensile tests show that brittle characteristics of PP turns to be ductile both in PP/F1 and PP/F2 blends. Addition of carbon fibers and glass fibers to PP matrix, enhances tensile, flexural and impact properties of the composite; while the addition of nanoclay decreases the composite properties. This may be due to poor dispersion of nanoclay, for this reason compatibilizer is added to the nanoclay/polypropylene composites and improvement in properties is achieved. Models are developed for predictions of tensile strength, impact energy and flexural strength depending on the fiber volume content, interfacial shear strength, void volume, matrix volume, fiber volume, fiber orientation degrees and total fiber area of glass and carbon fiber reinforced samples. The difference between measured and calculated values does not exceed 10%; model predictions for tensile strength, impact energy and flexural strength give good correlation between measured and calculated values.