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The microcellular foam injection molding process for thermoplastic materials provides design flexibility and cost savings opportunities not found in conventional injection molding. This process allows for plastic part design with material wall thickness optimized for functionality. The combination of density reduction and design for functionality can result in material and weight savings of up to 20%. With the correct equipment configuration, mold design, and processing conditions, these microcellular voids are uniform in size and distribution. The use of microcellular foam molding provides significant reductions in cycle time, material consumption, injection pressure, and clamp tonnage. In this work, a physical foam molding process, MuCell, is applied to a polypropylene (PP) composite.

The long-term weathering behavior of three different 3D printable, non-stabilized, UV cure resin formulations (A and B with thiol-ene base, and C with acrylate chemistry) was studied using tensile testing, nano-indentation, and photoacoustic infrared (FTIR-PAS) spectroscopy. To this end, type I tensile bars were printed from each resin system using a 3D printer, and were post UV-cured under a broad spectrum source. Systems A and C showed a similar trend after weathering. They first experienced an increase in modulus and tensile strength, due to additional crosslinking of the residual unreacted species. This increase in mechanical properties was followed by a drop in modulus, tensile strength, and percent elongation, due to the over-crosslinking and consequent embrittlement. System B, however, showed remarkable retention of the mechanical properties before/after weathering.