This study analyzes the fundamental principles and characteristics of the microcellular foaming process (MCP) to minimize warpage in glass fiber reinforced polymer (GFRP), which is typically worse than that of a solid polymer. In order to confirm the tendency for warpage and the improvement of this phenomenon according to the glass fiber content (GFC), two factors associated with the reduction of the shrinkage difference and the non-directionalized fiber orientation were set as variables. The shrinkage was measured in the flow direction and transverse direction, and it was confirmed that the shrinkage difference between these two directions is the cause of warpage of GFRP specimens. In addition, by applying the MCP to injection molding, it was confirmed that warpage was improved by reducing the shrinkage difference. To further confirm these results, the effects of cell formation on shrinkage and fiber orientation were investigated using scanning electron microscopy, micro-CT observation, and cell morphology analysis. The micro-CT observations revealed that the fiber orientation was non-directional for the MCP. Moreover, it was determined that the mechanical and thermal properties were improved, based on measurements of the impact strength, tensile strength, flexural strength, and deflection temperature for the MCP.

In this work, a high-magnification extrusion-foaming technique for biomass-based biodegradable composite materials using water vaporization was examined. Starch was selected as the biomass and polylactic acid was selected as a biodegradable matrix resin. No additional plasticizer or additives were used in this extrusion-foaming process. The foaming ratio was deduced according to the conditions of the extrusion-foaming process to confirm the forming characteristics of the foaming materials. Scanning electron microscopy was performed to examine the morphology of the composite foam. To investigate the potential of the foam cushion as an ecofriendly packing material, we conducted experiments on its static compression and dynamic cushioning properties and examined whether its biodegradability could be controlled by varying the mixing ratio of the materials. Thus, we developed a water-foaming process that is ecofriendly and whose products can be recycled as compost after use.

This study investigates the properties of a polymer–gas mixture formed through diffusion, based on the changes in the partial pressure and observed changes in the impact and tensile strengths owing to the gas dissolution. The high-pressure gas dissolves into a solid-state polymer through diffusion based on the difference in the partial pressure. This dissolved gas is present in the amorphous region within the polymeric material temporarily, which results in the polymer exhibiting different mechanical properties, while the gas remains dissolved in the polymer. In this study, the mechanical properties of amorphous polyethylene terephthalate (APET) specimens prepared by dissolving CO₂ using a high-pressure vessel were investigated, and the resulting impact and tensile strengths were measured. These experiments showed that the increase in sorption rate of CO₂ caused an increase in the impact strength. At 2.9% CO₂ absorption, the impact strength of APET increased 956% compared to that of the reference specimen. Furthermore, the tensile strength decreased by up to 71.7% at 5.48% CO₂ sorption; the stress–strain curves varied with the gas sorption rate. This phenomenon can be associated with the change in the volume caused by CO₂ dissolution. When the APET absorbed more than 2.0% CO₂ gas, sample volume increased. A decrease in the network density can occur when the volume is increased while maintaining constant mass. The CO₂ gas in the polymer acted as a cushion in impact tests which have sorption rates above 2%. In addition to the reduction in the network density in the polymer chain, Van Der Waals forces are decreased causing a decrease in tensile strength only while CO₂ is present in the APET. These observations only occur prior to CO₂ desorption from the polymer.

This study focuses on improving multifunctional product development. Instead of face-to-face or other survey methods, we used text mining of online reviews to confirm which characteristics consumers prefer. The reference probability (importance), and the difference between positive and negative opinions (satisfaction) were indexed. By linking “importance” and “satisfaction” with a product’s quantitative performance, the correlation between satisfaction and quantitative performance was confirmed, and the method of setting a product’s design requirements was presented. To verify the validity of the method, we used the subcompact SUV (Sports Utility Vehicle) market in South Korea as a case study. The average importance and satisfaction with each performance aspect of the cars in the market was extracted, and the successful entry of new products in the market, which reflects these market characteristics, was confirmed. The proposed methodology is meaningful in that it reduces the risk (biased, inefficient) of existing consumer survey methods by utilizing big data to identify consumer preferences. Companies can use these findings during the product development process to improve customer satisfaction. This study improves product development methods by combining them with the latest advances in big data-related technologies.

This study proposes a novel process that integrates the molding and patterning of solid-state polymers with the force generated from the volume expansion of the microcellular-foaming process (MCP) and the softening of solid-state polymers due to gas adsorption. The batch-foaming process, which is one of the MCPs, is a useful process that can cause thermal, acoustic, and electrical characteristic changes in polymer materials. However, its development is limited due to low productivity. A pattern was imprinted on the surface using a polymer gas mixture with a 3D-printed polymer mold. The process was controlled with changing weight gain by controlling saturation time. A scanning electron microscope (SEM) and confocal laser scanning microscopy were used to obtain the results. The maximum depth could be formed in the same manner as the mold geometry (sample depth: 208.7 μm; mold depth: 200 μm). Furthermore, the same pattern could be imprinted as a layer thickness of 3D printing (sample pattern gap and mold layer gap: 0.4 mm), and surface roughness was increased according to increase in the foaming ratio. This process can be used as a novel method to expand the limited applications of the batch-foaming process considering that MCPs can impart various high-value-added characteristics to polymers.