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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 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.