Microwave‐assisted rapid fabrication of robust polyetherimide bead foam parts

Abstract

Polyetherimide (PEI) is an important candidate for fabrication of highperformance 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-mmthickness 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.

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

“…During the molding process, the loading weight, power, and sintering time are the three key parameters that should be optimized for the preparation of the final parts with sound weld strength and surface quality. Using carbon nanotubes [68,87,88] or graphene nanoplatelets [89] as the conductive materials, Feng et al have conducted much work on fabricating EPEI parts using MSS, which is also used to prepare bead foam parts from PS [25,90] and PVA [91]. Using water as the dielectric material, Liu et al [25] fabricated EPS parts with enhanced weld strength.…”

Progress in preparation of high‐performance and multi‐functional polymer foams

“…To investigate the behavior of microwave heating, graphite, known for its ability to rapidly absorb microwave energy, was used as a microwave absorber and wrapped around PEI beads (Figure 8A1). 79 This resulted in an increase in the temperature of the surface in close contact. Within 50 s of microwave irradiation, the surface temperature of the beads reached over 350°C, meeting the fusion temperature requirement of PEI beads (Figure 8A2).…”

Interfacial Sintering of PU/MXene Foam for Piezoresistive Sensor with Superior Sensitivity, Mechanical Performance, and Durability

“…Recently, microwave sintering (MW) has been reported to fabricate 3D poly(ether imide) (PEI) bead foams via selectively sintering the interface between graphene nanoplatelets (GNP) and PEI by using GNP as the microwave absorbent. 30 In general, polymers are transparent to MW, whereas conductive fillers such as carbon nanotubes, 31,32 graphene, 33−35 and MXene 36,37 are excellent MW absorbers that can be heated vigorously upon MW irradiation. In this work, for the first time, a piezoresistive sensor derived from anisotropic PU foam with a tightly adhered MXene conductive layer (MXene@PU) is fabricated by microwave sintering and unidirectional freezing.…”

“…Recently, microwave sintering (MW) has been reported to fabricate 3D poly­(ether imide) (PEI) bead foams via selectively sintering the interface between graphene nanoplatelets (GNP) and PEI by using GNP as the microwave absorbent . In general, polymers are transparent to MW, whereas conductive fillers such as carbon nanotubes, , graphene, − and MXene , are excellent MW absorbers that can be heated vigorously upon MW irradiation.…”