Effect of crystalline structure on the cell morphology and mechanical properties of polypropylene foams fabricated by core‐back foam injection molding

Abstract

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 10 8 cells/cm 3 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 10 5 cells/cm 3 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.

Lightweight and tough PVDF foams via high‐pressure foam injection molding with core‐back operation

“…The core‐back FIM technology usually produced the microcellular foams with sandwich structures consisting of two skin layer (non‐foamed) and a cellular core layer, [ 25 ] and the cellular morphology in the core layer was mainly studied here. Figure 3 shows the cell morphologies of neat PVDF and PVDF 70 blend with different void fractions (30%, 40%, and 50%).…”

“…The schematic diagram of the machine was mentioned in our previous study. [25] The effect of PMMA and weight reduction on the foaming behavior and mechanical properties of PVDF were studied by the FIM with core-back operation. Unlike the regular FIM, the core-back FIM could achieve a high weight reduction (void fraction) by expanding the mold cavity in the foaming process.…”

Achieving low‐thermal conductivity and high β phase in PVDF/PMMA blend foams via low‐pressure microcellular foaming

“…Compared with solid counterparts, polymeric foams usually exhibit low density, high‐specific strength, good heat and sound insulation property 1–8 . Furthermore, microcellular foaming process using inert gas such as carbon dioxide (CO 2 ) or nitrogen (N 2 ) as a foaming agent has the characteristics of safety, energy‐saving, and environmental friendliness, which further promotes the wide application of plastic foam in packaging materials, transportation industry, aerospace, automobiles and functional materials 9–13 . Additionally, with the incorporation of functional filler, polymeric nanocomposites foams could be used as lightweight functional materials with excellent electromagnetic shielding and/or piezoelectric properties 14–17 …”

Effect of nano TiO2 on the cellular structure and mechanical properties of wood flour/polypropylene composite foams via mold‐opening foam injection molding

“…15,16 The foam injection molding (FIM) technique involves injecting foaming agent into the melt to form dense cells inside the polymer to balance the internal shrinkage, reduce the warping deformation, and produce lightweight products. [17][18][19] Mold-opening FIM (MOFIM), or core-back foam injection, can significantly enlarge the cavity volume by moving the mold for a certain distance along the parting direction after melt injection, while adjusting the mold shape can further reduce the weight of the part. Therefore, MOFIM technology shows a promising prospect for the production and application of WPC foams.…”

“…As a common molding method used in the production of polymer materials, injection molding produce polymer products with complex shapes through a simple, one‐step, highly efficient, and low‐cost molding process 15,16 . The foam injection molding (FIM) technique involves injecting foaming agent into the melt to form dense cells inside the polymer to balance the internal shrinkage, reduce the warping deformation, and produce lightweight products 17–19 . Mold‐opening FIM (MOFIM), or core‐back foam injection, can significantly enlarge the cavity volume by moving the mold for a certain distance along the parting direction after melt injection, while adjusting the mold shape can further reduce the weight of the part.…”