Vacuum Infusion for Processing Thermosetting Composites Containing High Loading Solid Fillers

A new processing route for making thermosetting materials and products containing high loading solid fillers including waste solid scraps and natural mineral fillers was investigated. Traditionally, solid fillers are incorporated into thermosetting polymers by liquid-state mixing. However, due to the high viscosity in mixing, high loading above 50% by weight is difficult to achieve. The new process overcomes this hurdle by a two-step processing strategy. First, solid fillers are placed in the mold and compacted to conform to the mold shape. Next, with the mold closed, a thermosetting resin is infused by vacuum into the particulate preform and after curing to form the desired product. In the exploratory study, epoxy and mineral particles including sand were chosen as material systems for feasibility demonstration. Thermal analysis and rheology were performed to assist in understanding of the fluid flow in heated porous media to achieve an optimized process window for rapid infusion. The results indicated that epoxy matrix composites with extremely high solid filler loading exceeding 70% by weight, as well as with complex external geometry, can be successfully produced. The resulting material is structurally uniform and its mechanical properties can be adjusted by changing the composition and makeup of the filler materials.