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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.

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.

Foaming of a thermoplastic polyolefin (TPO) is gaining interests because of its superior mechanical properties of foamed automotive parts, such as lightweight and high performance to weight ratio, etc. In this context, understanding of the thermophysical properties of PP/gas and TPO/gas mixtures is critically important. This paper will present the newly developed experimental technique to accurately measure the swelling of PP and TPO due to gas dissolution at elevated temperatures and pressures. Our technique measures the geometry of the pendent drop accurately from the captured images to obtain the volume swelling data. It determines the boundary location of the polymer/gas sample accurately by magnifying the sample drop locally along its edge before capturing the image. The automated high-precision XY stage is chosen as the platform to control the motion of the CCD camera.

Foaming of thermoplastic polyolefins (TPO) and thermoplastic elastomers (TPE) is gaining interest because of the lightweight and high performance to weight ratio of foamed automotive parts. Since foaming will occur mainly in the PP matrix in these PP-based automotive materials, understanding of the thermophysical properties of PP/gas mixtures is critically important. This paper will present a proposed methodology for measuring the swelling of polymer/gas mixtures. The preliminary experimental measurement of PP/N2 swelling at elevated temperatures and pressures will be discussed.