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Over the past two decades, the use of microwaves for physical foaming of polymers has undergone significant advancements. Typically, the preparation of polymer foams during physical foaming relies on heat transfer heating, which results in temperature gradients and consumes significant time and energy. In contrast, microwave-assisted physical foaming offers a simple, convenient, fast, and cost-effective approach for obtaining polymer foams. These features render microwaves an alternative clean energy source that can replace or complement the conventional heating in various foaming processes. This review provides an overview of recent research on the application of microwaves to five different methods for preparing polymeric foams, namely batch foaming, bead foaming, steam foaming, salt immersion foaming, and 3D-printing. The study also highlights key challenges and opportunities for the development of microwave foaming processes and identifies potential areas for future research. [ABSTRACT FROM AUTHOR]

Compared to exploratory development of new structure types, pushing the limits of isoreticular synthesis on a high‐performance MOF platform may have higher probability of achieving targeted properties. Multi‐modular MOF platforms could offer even more opportunities by expanding the scope of isoreticular chemistry. However, navigating isoreticular chemistry towards best properties on a multi‐modular platform is challenging due to multiple interconnected pathways. Here on the multi‐modular pacs (partitioned acs) platform, we demonstrate accessibility to a new regime of pore geometry using two independently adjustable modules (framework‐forming module 1 and pore‐partitioning module 2). A series of new pacs materials have been made. Benzene/cyclohexane selectivity is tuned, progressively, from 4.5 to 15.6 to 195.4 and to 482.5 by pushing the boundary of the pacs platform towards the smallest modules known so far. The exceptional stability of these materials in retaining both porosity and single crystallinity enables single‐crystal diffraction studies of different crystal forms (as‐synthesized, activated, guest‐loaded) that help reveal the mechanistic aspects of adsorption in pacs materials. [ABSTRACT FROM AUTHOR]

With the development of radio technology, 5G electronic equipment has higher requirements for materials. This has become an imperative matter to realize the controllable preparation of Thermotropic liquid crystal polyester (TLCP) foams with homogeneous microcellular. Accordingly, the foaming behavior of TLCP in isotropic state is investigated. TLCP foams are prepared by a one‐step rapid depressurization foaming method at different temperature pressures, with cell diameter in the range of 67.5–283.9 μm and the material density in the range of 0.37–0.25 g/cm3. In order to broaden the distribution of cell diameter and the density of TLCP foams, the mixture foaming agent of N2 and CO2 is used in foaming process. When mixture foaming agents are used, the cell diameter is widened to the range of 40.5–283.9 μm, and the material density is widened to the range of 0.70–0.25 g/cm3, which realizes the controllable preparation of cell diameter and material density of TLCP. The dielectric constant and dielectric loss of TLCP foams can be as low as 1.35‰ and 0.85‰ at 10 GHz, respectively. The structural regulation of low‐dielectric TLCP microcellular materials is achieved for the first time by way of varying the temperature, pressure, and co‐blowing agent ratio. [ABSTRACT FROM AUTHOR]

The bubble growth process of epoxy resin foams has been evaluated through a combination of numerical simulation and chemorheology. It was discovered that rheological properties play an essential role in forecasting bubble growth during supercritical CO2 epoxy resin foaming. Time–cure superposition was conducted revealing that shear storage modulus increased from 10−3 to 106 Pa during the curing reaction process. The complex viscosity increased up to 105 Pa s and the characteristic relaxation time increased up to 53.1 s with the curing degree. The epoxy resin with high rigid modulus could effectively inhibit bubble growth. Furthermore, the simulation results indicated that the bubble growth process for epoxy resin foams was influenced by both the CO2 content and CO2 plasticization on rheology properties. [ABSTRACT FROM AUTHOR]