Polymer Bead Foams: A Review on Foam Preparation, Molding, and Interbead Bonding Mechanism

Abstract

The diverse physical appearances and wide density range of polymer bead foams offer immense potential in various applications and future advancements. The multiscale and multilevel structural features of bead foams involve many fundamental scientific topics. This review presents a comprehensive overview of recent progress in the preparation and molding techniques of bead foams. Firstly, it gives a comparative analysis on the bead foam characteristics of distinct polymers. Then, a summary and comparison of molding techniques employed for fabricating bead foam parts are provided. Beyond traditional methods like steam-chest molding (SCM) and adhesive-assisted molding (AAM), emerging techniques like in-mold foaming and molding (IMFM) and microwave selective sintering (MSS) are highlighted. Lastly, the bonding mechanisms behind these diverse molding methods are discussed.

Microwave-Induced Facile Molding of Lightweight and High-Strength Segregated-CNTs/Polycarbonate Foams

“…For the physical foaming process, the polymer and foaming agent are mixed to form a homogeneous system, and then the cell growth is completed by rapid depressurizing or rapid temperature rising to achieve the foaming expansion . Supercritical CO 2 (scCO 2 ) or supercritical N 2 (scN 2 ) is widely used in physical foaming processes owning to its stability, environmental friendliness, availability, and notably low cost features. − At present, the mainstream polymer foaming technologies include autoclave foaming, injection mold foaming, extrusion foaming, and vapor-based bead foaming. − The autoclave foaming process is characterized by simple operation. The polymer foam material with a significantly high foaming ratio can be achieved by precisely adjusting the foaming parameters such as temperature, pressure, impregnation time, depressurization rate, etc .…”