Influence of talc on crystallization behavior and cellular structure of microcellular foamed wood flour/PP composites

The microcellular foamed wood flour/polypropylene composites were prepared by a microcellular batch foaming process using talc as the nucleating agent and supercritical CO₂ fluid as foaming agent. The crystallization behavior and microcellular structure of impact fractured of microcellular foamed composite were investigated by differential scanning calorimeter (DSC), X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The results indicate that talc increases the crystallization rate and temperature of microcellular foamed wood flour/polypropylene composites and induces imperfect α crystal. The addition of talc improves the melt viscosity of the polymer matrix. The talc also decreases the size of the cellular, inhibit the formation of big cellular, cellular coalescence and collapse. The cellular density of wood flour/polypropylene composites can be up to 1.0×10⁹/cm³, the average radius is 16.4 μm, and the expansion ratio can reach 18, the apparent density is 0.055 g/cm³.