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This paper presents the foaming behaviors of high-density polyethylene (HDPE)-based and polypropylene (PP)-based wood fiber composites with a small amount of nanosized clay. Melt compounding was used to prepare various types of clay-filled, wood fiber composites, such as intercalated and exfoliated clay composites. Their morphology was determined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The extrusion foaming was conducted using N2 as the blowing agent. The cell nucleation and growth behaviors of composite foams were studied while varying temperature, pressure, wood fiber content, and clay content. The effects of clay content and exfoliation degree on the final cell morphology of wood fiber/polyolefin/clay nanocomposite foams were identified.

Polymers are often blended to create compounds with new or enhanced properties in order to compensate for an individual polymer's weakness or lack of inherent properties. In the field of polymer foaming, polymer blends are also used to generate fine-cell structures via heterogeneous nucleation. Recently, an interest in physical blowing agents, such CO2 and N2, has increased because of their low impact on the environment. It has thus become additionally important to pursue research on the foaming of polymer blends employing these particular physical blowing agents in an effort to keep up with the demand for environmentally friendly products. In this study, thermoplastic polyolefin (TPO) blends were prepared with polypropylene (PP) and a metallocene-based polyolefin elastomer (POE) using twin-screw extruders and a batch mixer.

This research presents a fundamental study of the interaction between chemically modified wood fibers and high density polyethylene (HDPE) to develop wood fiber/HDPE composites with satisfactory performance. This paper investigates the effects of the interfacial properties of HDPE and wood fibers on the rheological properties and foaming behavior of the composites. The surface characteristics of wood fiber were modified by treating the fiber with trialkoxy silane. The effectiveness of chemical surface modifications of wood fiber was characterized using FT-IR. The effect of the interfacial interaction on the foaming behavior was studied via extrusion foaming with a physical blowing agent. The rheological property of the composites with a different interfacial structure were also evaluated by using dynamic oscillatory rheometer.

This study compared the mechanical properties of rice hull/high density polyethylene composites with those of maple wood-based counterparts. In addition, the effects of maleated polymers on the mechanical properties of rice hull and maple wood composites were investigated. Six types of maleated polymers (coupling agents) were used to improve mechanical properties, of the composites, especially notched Izod impact strength. The results suggested that the maple wood composites showed higher strength, modulus and impact strength than the rice hull composites. The results also indicated that maleated thermoplastic elastomers increased notched Izod impact strength of both composites dramatically. However, it was found that Maleated metallocene polyethylene was the most effective coupling agent that increased notched impact strength without sacrificing tensile and flexural strength.

One of the key challenges of the wood polymer composites (WPC) is the inadequate toughness partly due to the incompatibility of the natural fibres and PP matrix. In this work, we performed the surface modification of the natural fibre by either in-situ grafting polymerization of butyl acrylate (PBA) or adsorbing matrix-compatible cationic PBA latex on the fibre surfaces. The results indicated that the mechanical properties of the polypropylene (PP) composites containing the modified fibres, unnotched Izod impact strength in particular, have been improved significantly. The influencing factors and the mechanism of toughening process have also been preliminarily investigated.

This research investigated the intercalation and exfoliation behaviors of polypropylene (PP)/clay nanocomposites. Different samples were prepared by melt blending with various combinations of PP, maleic anhydride grafted PP (PP-g-MAn), and nano-clay. The effects of key processing variables such as the mixing time, mixing temperature and screw rpm were investigated from the thermodynamic and kinetic point of view. The morphology was determined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effective strategies for controlling intercalation and exfoliation of PP/clay nanocomposites are proposed and evaluated.

Thermoplastic Vulcanizate (TPV) is a special class of Thermoplastic Elastomers (TPEs) made of a rubber/plastic polymer mixture in which the rubber phase is highly vulcanized. It is prepared by melt mixing a thermoplastic with an elastomer and by in-situ crosslinking of the rubber phase. Currently, TPV is replacing EPDM rubber dramatically because of the impressive advantages for automotive sealing applications. Some of the advantages of TPV compared to that of EPDM rubber are good gloss, recyclability, improved colorability, shorter cycle time and design flexibility. The development of TPV foaming technology is to fulfill the requirement of achieving lower cost, lighter weight and better fuel economy. Foaming of TPV has not been investigated extensively.

The use of natural fibers for polymer composite materials has increased tremendously in the last few years. This type of reinforcements offers many advantages such as low density, low cost, high specific strength and low environmental impacts. The performance of the natural fiber composites are affected by the fiber loading, the individual mechanical properties of each component (fiber and matrix), and the fiber and matrix adhesion. Concerning the interfacial interaction, natural fibers present a major drawback because of poor compatibility of fibers with most hydrophobic thermoplastic and thermoset matrix. Hemp fiber/acrylic composites were manufactured with sheet molding technique recently. Although mechanical tests give promising results, they exhibit low tensile strength resulting from a poor fiber/matrix adhesion. The moisture resistance property of the sheet molded composites also needs further improvement.