Microwave-assisted rapid fabrication of robust polyetherimide bead foam parts

Polyetherimide (PEI) is an important candidate for fabrication of high-performance polymer foams. Nevertheless, the manufacture of PEI foamed parts with specific three-dimensional geometry shape and lightweight properties remains a big challenge worldwide. Herein, a microwave (MW)-assisted foaming and selective sintering approach was proposed towards rapid fabrication of robust PEI bead foams. During the process, compressed carbon dioxide/tetrahydrofuran was used as physical co-foaming agent, and the surface-coated graphene nanoplatelets (GNPs) was used as MW absorbent. Upon MW irradiation, the GNPs selectively heated and served as solders that effectively facilitated the foaming of expandable PEI (EPEI) beads, and strongly promoted the local polymer melt and entanglement across the surface of EPEI beads. The MW irradiation power and time were considered as the important parameters to achieve fine inter-bead bonding strength between foamed beads. As a model system, we successfully fabricated a 25-mm-thickness foamed part with an apparent density of 0.32 g/cm(3)and achieved excellent inter-bead bonding performance. Specifically, we also utilized the COMSOL Multiphysics simulations to study the MW selective heating mechanism. This MW-assisted fabrication strategy offers a new foaming approach toward high-performance polymer foamed parts for many advanced applications.

Automated summary

A microwave-assisted foaming and selective sintering approach was proposed for rapid fabrication of robust PEI bead foams, with important parameters being MW irradiation power and time. Graphene nanoplatelets were used as MW absorbent to promote inter-bead bonding strength, successfully fabricating high-performance foamed parts.