A review of thermoplastic polymer foams for functional applications

Abstract

Recently, functional applications of thermoplastic foams have received extensive attention from the research and materials communities, focusing on their various applications, key challenges, material systems designs, processing methods, and cellular structure characteristics needed for specific functional applications. This review paper starts with consideration of the microcellular foaming mechanism and basic concepts of microcellular foam processing, followed by polymer modification methods, and crucial factors that determine the performance of thermoplastic foams. Special emphasis has been placed on the synergies between foaming and reinforcements, including functional fillers and polymer blends; improvements in homogeneous, functional properties by achieving uniform cell structure and cell dispersion in polymer systems; and comparison of melt processing and solvent-based methods. Then, a wide array of advanced functional applications for foams-such as lightweight applications, heat and sound insulation, electromagnetic shielding, tissue engineering, oil spill cleanup, shape memory, and flexible materials-will be presented. In particular, the relationships between cellular structure and anticipated properties-including mechanical, barrier, dielectric, biomedical, and other properties required in advanced functional applications-will be discussed. Finally, we will outline a future perspective of lightweight and functional foams and suggest recommended future work regarding functional microcellular foams.

Polypropylene‐based in situ fibrillation‐reinforced ternary composite foams with improved filler‐phase dispersion

“…The initial goal of microcellular foams was to increase toughness by arresting cracks, which was associated with impact strength. [ 3 ] However, the impact strength of foamed pure PP and PP/talc composites was worse than the solid counterpart, relating to nonuniform cellular morphology. A significant difference was observed in composites before and after adding in situ fibrillated phase—the fibrillar network had a remarkable effect on the impact strength.…”

“…[1,2] Microcellular foams are thought to be the optimum material to achieve lightweight, which endows materials with elevated impact strength, toughness, and functional properties by tuning cellular structure. [3] Besides, foam injection molding (FIM) with physical blowing agents (PBAs) has received extensive attention, especially for preparing thermoplastic foams due to the advantages of eco-friendly, high efficiency, and flexibility. [4] ptPolypropylene (PP) is a promising thermoplastic polymer in the industry, with great potential for industrial and consumer products because of its excellent mechanical strength, easy processing, and low cost.…”

“…[ 1,2 ] Microcellular foams are thought to be the optimum material to achieve lightweight, which endows materials with elevated impact strength, toughness, and functional properties by tuning cellular structure. [ 3 ] Besides, foam injection molding (FIM) with physical blowing agents (PBAs) has received extensive attention, especially for preparing thermoplastic foams due to the advantages of eco‐friendly, high efficiency, and flexibility. [ 4 ]…”

Cold spray deposition of metallic coatings on polymers: a review

“…The deposition of metallic particles through cold spray is more successful with thermoplastic substrates due to their ductile nature [109]. The most used thermoplastic materials for CS applications are ABS, PEEK, PVC, HDPE, and PP.…”

Foamed bioplastics: a review

“…In all three cases the high porosity materials can be constructed from open or closed pores. One particularly exemplary and porous material is a hierarchically structured product (Geramipour and Oveisi, 2017;Su, 2012;Wu et al, 2021). They are defined as materials containing a structure of connected pores of different lengths.…”