Improving the Interfacial Bonding of Extruded Bead Foams by Introducing the Double-Crystal Peak and Pressure Compensation Technology

Improving the interfacial bonding of polymeric extruded bead foams during the steam chest molding process is an important, yet challenging task. In this work, by introducing the double-crystal melting peak and pressure compensation strategy, the problem of poor bonding of extruded bead foams during the molding process was effectively solved. Low-melting-point polyethylene was added to high-melting-point polypropylene to successfully construct double-crystal melting-peak foamed beads. Specifically, four extruded bead foams with double-crystal melting peak but with different expansion ratios (20.0, 16.9, 16.2, and 15.6) and closed-cell ratios (51.2%, 23.0%, 32.5%, and 26.0%) were prepared. It was found that the interbead bonding condition of the low closed-cell ratio foamed beads was not very optimistic because of the weak secondary expansion behavior during the molding process. Herein, a coordinated pressure compensation technology during the steam molding process was put forward to improve the bonding conditions of the beads. This work is conducive to understanding the influence of the microporous structure and matrix composition of foamed beads on their interfacial bonding effect.