Minghui Wu

Polypropylene/carbon nanostructure (PP/CNS) nanocomposite foams with a void fraction as high as 78% were successfully prepared by foam injection molding (FIM) with core‐back operation. Rheological curves and differential scanning calorimetry results showed that the added CNS significantly improved the melt strength and accelerated the crystallization process of PP, respectively. A high mold temperature was applied to overcome the adverse effect of CNS, which had a high thermal conductivity and went against the preparation of high void fraction (VF) products. Thus, adding CNS could dramatically increase cell density by three orders of magnitude. With a CNS loading of 5 wt%, the PP/CNS nanocomposite foam with a cell size of about 60 μm, cell density over 10⁷ cells/cm³, and a void fraction of 78% was obtained. More interestingly, the specific flexural modulus of the PP/CNS composite foam with 50% void‐fraction was increased by 37% relative to the neat solid injection‐molded PP. PP/CNS composite foams with adjustable cell structure and good mechanical properties show great potential for electromagnetic interference (EMI) shielding and sensors applications.

Foam injection molding (FIM) is an advanced technology for preparing lightweight plastic foams, but its inferior mechanical performance remains a challenge. In this study, microcellular injection‐molded β‐polypropylene (β‐PP) foams with high ductility were successfully prepared by combing the β‐nucleating agent with controllable temperature field. Foaming results showed that the microcellular β‐PP foams exhibiting a cell size of about 8 μm and cell density over 10⁸ cells/cm³ were prepared with a crystalline diameter approximately 5 μm, while PP foams had a rather large cell size approximately 150 μm and low cell density of 10⁵ cells/cm³ with 30 μm crystalline size. As a result, this significant improvement in cell structure as well as the crystalline size lead to a significant increment of 86% for the ductility of β‐PP foams. This work offers a facile strategy to prepare injection‐molded foams with desirable mechanical properties for their wide range of applications, such as automotive construction and consumer electronics.

The objective of the present work was to study the sorption kinetics of open‐cell polypropylene/polyolefin elastomer (PP/POE) blend foams. First, open‐cell PP/POE foams of different cell structures were prepared by controlling the foaming temperature via a continuous extrusion foaming process. Second, the effect of the cell structures on the sorption process, rate, and capacity was studied. Pseudo‐first order and pseudo‐second order models were applied to study the sorption kinetics of the PP/POE foams for cyclohexane. Third, the sorption rate and sorption capacity by both volume and weight of the PP/POE foam for different oils and solvents were studied to show how the intrinsic properties of the testing oils and solvents affected the sorption performance. The results showed that the sorption with the PP/POE foams followed the pseudo‐second order kinetics model. Both the cell structures of the foams and the intrinsic properties of the testing oils and solvents affected the sorption performance. For the same testing oil, a higher open‐cell content in the foam was favorable for a higher sorption rate, and a higher void fraction was favorable for a higher sorption capacity. For the same foam, a lower viscosity of the testing oil was favorable for a higher sorption rate. The sorption capacity by volume was closely related to the viscosity of the testing oil, while both the viscosity and the density of the testing oil determined the sorption capacity by weight.