Progress in the Foaming of Polymer-based Electromagnetic Interference Shielding Composites by Supercritical CO2

Recent Trends in Polymeric Foams and Porous Structures for Electromagnetic Interference Shielding Applications

Polymer-based (nano)composite foams containing conductive (nano)fillers limit electromagnetic interference (EMI) pollution, and have been shown to act as good shielding materials in electronic devices. However, due to their high (micro)structural complexity, there is still a great deal to learn about the shielding mechanisms in these materials; understanding this is necessary to study the relationship between the properties of the microstructure and the porous structure, especially their EMI shielding efficiency (EMI SE). Targeting and controlling the electrical conductivity through a controlled distribution of conductive nanofillers are two of the main objectives when combining foaming with the addition of nanofillers; to achieve this, both single or combined nanofillers (nanohybrids) are used (as there is a direct relationship between electrical conductivity and EMI SE), as are the main shielding mechanisms working on the foams (which are expected to be absorption-dominated). The present review considers the most significant developments over the last three years concerning polymer-based foams containing conductive nanofillers, especially carbon-based nanofillers, as well as other porous structures created using new technologies such as 3D printing for EMI shielding applications. It starts by detailing the microcellular foaming strategy, which develops polymer foams with enhanced EMI shielding, and it particularly focuses on technologies using supercritical CO2 (sCO2). It also notes the use of polymer foams as templates to prepare carbon foams with high EMI shielding performances for high temperature applications, as well as a recent strategy which combines different functional (nano)fillers to create nanohybrids. This review also explains the control and selective distribution of the nanofillers, which favor an effective conductive network formation, which thus promotes the enhancement of the EMI SE. The recent use of computational approaches to tailor the EMI shielding properties are given, as are new possibilities for creating components with varied porous structures using the abovementioned materials and 3D printing. Finally, future perspectives are discussed.

Advances in Graphene-Polymer Nanocomposite Foams for Electromagnetic Interference Shielding

With the continuous advancement of wireless communication technology, the use of electromagnetic radiation has led to issues such as electromagnetic interference and pollution. To address the problem of electromagnetic radiation, there is a growing need for high-performance electromagnetic shielding materials. Graphene, a unique carbon nanomaterial with a two-dimensional structure and exceptional electrical and mechanical properties, offers advantages such as flexibility, light weight, good chemical stability, and high electromagnetic shielding efficiency. Consequently, it has emerged as an ideal filler in electromagnetic shielding composites, garnering significant attention. In order to meet the requirements of high efficiency and low weight for electromagnetic shielding materials, researchers have explored the use of graphene-polymer nanocomposite foams with a cellular structure. This mini-review provides an overview of the common methods used to prepare graphene-polymer nanocomposite foams and highlights the electromagnetic shielding effectiveness of some representative nanocomposite foams. Additionally, the future prospects for the development of graphene-polymer nanocomposite foams as electromagnetic shielding materials are discussed.

Modification of Hollow Expanded Microspheres with Superior Thermal Insulation Properties and Their Applications

Thermally expandable microspheres (TEMs) are hollow polymeric particles in which a blowing gas has been encapsulated. This property makes them excellent for thermal insulation applications, such as lightweight fillers. This study has developed a viable technology for further improving thermal insulation properties in the field that needs excellent thermal insulation of textile fabrics. The ATO/TEMs composites were designed and prepared to reduce sunlight radiation by the charge gravity method. The test results showed that the ATO-coated TEMs effectively block thermal radiation from sunlight. The temperature difference between ATO/TEMs treated cotton and the uncoated cotton fabric was 9 °C, and the thermal conductivity coatings were 0.0432 W/m⋅K. The UPF value of ATO/TEMs (ILs) coated cotton fabric is 440, significantly higher than pure cotton. This approach can provide insight into the design of high-performance solar insulation composite structures.