(59c) Low Density Microcellular Foam Wholly Thermoplastic Composite

Supercritical carbon dioxide has been utilized to foam various amorphous polymers, such as polystyrene and poly(methyl methacrylate), in an environmentally friendly process. Saturation of the polymer matrix, followed by a rapid depressurization, leads to a closed microcellular structure of low density. This technique is used to improve the properties, such as increased impact strength, toughness, and stiffness to weight ratio, of a wholly thermoplastic composite. Spectra® fiber and low density polyethylene fibers are combined in a wet-lay process to form a thermoplastic composite. Through the use of supercritical carbon dioxide, the low density polyethylene matrix is foamed to produce a microcellular structure without affecting the physical properties of the Spectra® fiber. The closed cells of the microcellular foam and the reinforcing Spectra® fibers combine to yield a lightweight thermoplastic composite. Being an all thermoplastic composite, the resulting material is processable by compression molding and thermoforming.