Recent Progress in Electromagnetic Interference Shielding Performance of Porous Polymer Nanocomposites—A Review

Exploring the Potential of Sustainable Biopolymers as a Shield against Electromagnetic Radiations

The increasing demand for biodegradable and environmentally friendly materials is shifting the focus from traditional polymer composites to biocomposites in various applications, especially in electromagnetic shielding. Effective utilization of biopolymers demands improved properties and can be achieved to a certain extent by functionalization. Biopolymers such as cellulose, polylactic acid, and starch are some of the potential candidates for mitigating electromagnetic pollution in next-generation electronic devices because of their high aspect ratio, flexibility, light weight, high mechanical strength, thermal stability, and tunable microwave absorption to the electromagnetic interference (EMI) shielding composites. This Review provides an overview of the current advancements in EMI shielding materials and outlines recent research on EMI shielding composites that utilize various biodegradable polymer structures.

Structural Design for EMI Shielding: From Underlying Mechanisms to Common Pitfalls

Modern human civilization deeply relies on the rapid advancement of cutting-edge electronic systems that have revolutionized communication, education, aviation, and entertainment. However, the electromagnetic interference (EMI) generated by digital systems poses a significant threat to the society, potentially leading to a future crisis. While numerous efforts are made to develop nanotechnological shielding systems to mitigate the detrimental effects of EMI, there is limited focus on creating absorption-dominant shielding solutions. Achieving absorption-dominant EMI shields requires careful structural design engineering, starting from the smallest components and considering the most effective electromagnetic wave attenuating factors. This review offers a comprehensive overview of shielding structures, emphasizing the critical elements of absorption-dominant shielding design, shielding mechanisms, limitations of both traditional and nanotechnological EMI shields, and common misconceptions about the foundational principles of EMI shielding science. This systematic review serves as a scientific guide for designing shielding structures that prioritize absorption, highlighting an often-overlooked aspect of shielding science.

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.

Experimental Studies of the Effective Thermal Conductivity of Polyurethane Foams with Different Morphologies

Polyurethane foam (PUF) is actively used for thermal insulation. The main characteristic of thermal insulation is effective thermal conductivity. We studied the effective thermal conductivity of six samples of PUF with different types and sizes of cells. In the course of the research, heat was supplied to the foam using an induction heater in three different positions: above, below, or from the side of the foam. The studies were carried out in the temperature range from 30 to 100 °C. The research results showed that for all positions of the heater, the parameter that makes the greatest contribution to the change in thermal conductivity is the cell size. Two open-cell foam samples of different sizes (d = 3.1 mm and d = 0.725 mm) have thermal conductivity values of 0.0452 and 0.0287 W/m⸱K, respectively, at 50 °C. In the case of similar cell sizes for any position of the heater, the determining factor is the type of cells. Mixed-cell foam (d = 3.28 mm) at 50 °C has a thermal conductivity value of 0.0377 W/m⸱K, and open-cell foam (d = 3.1 mm) at the same temperature has a thermal conductivity value of 0.0452 W/m⸱K. The same foam sample shows different values of effective thermal conductivity when changing the position of the heater. When the heater is located from below the foam, for example, mixed-cell foam (d = 3.4 mm) has higher values of thermal conductivity (0.0446 W/m⸱K), than if the heater is located from above (0.0390 W/m⸱K). There are different values of the effective thermal conductivity in the upper and lower parts of the samples when the heater is located from the side of the foam. At 80 °C the difference is 40% for the open-cell foam (d = 3.1 mm).