Microstructural, mechanical, and thermal-insulation properties of poly(methyl methacrylate)/silica aerogel bimodal cellular foams

Thermal insulation properties of lightweight, self-healing, and mesoporous carrageenan/PMMA cryogels

The development of new bio-based cryogel materials with low environmental impact and various properties such as self-healing, flame-retardancy, low thermal conductivity has emerged as a cutting-edge research topic in special-purpose materials and a significant challenge. Herein, we report a simple processing methodology for preparing new mesoporous light weight thermal insulation biomass hybrid cryogels based on natural and biocompatible polymers, including marine glycosaminoglycan carrageenan moss (CM) and polymethyl methacrylate (PMMA) abbreviated as CM/PMMA under cryo conditions. The mechanical, thermal, and physicochemical characterization of the obtained hybrid cryogel was studied. The effect of increasing thickness on thermal conductivity and compressive strength was investigated. The results show that the thermal conductivity increases from 0.068 W m-1 K-1 to 0.124 W m-1 K-1 with increasing thickness. Also, the compressive strength changed from 89.5% MPa to 95.4% MPa. The results revealed that cryogel has a wrinkled surface and interconnected pores and exhibits high flexibility, self-healing ability, flame retardancy, and low thermal conductivity.

Poly(methyl methacrylate) Nanocomposite Foams Reinforced with Carbon and Inorganic Nanoparticles—State-of-the-Art

Polymeric nanocomposite foams have attracted increasing research attention for technical reasons. Poly(methyl methacrylate) is a remarkable and viable thermoplastic polymer. This review highlights some indispensable aspects of poly(methyl methacrylate) nanocomposite foams with nanocarbon nanofillers (carbon nanotube, graphene, etc.) and inorganic nanoparticles (nanoclay, polyhedral oligomeric silsesquioxane, silica, etc.). The design and physical properties of poly(methyl methacrylate) nanocomposite foams have been deliberated. It has been observed that processing strategies, nanofiller dispersion, and interfacial interactions in poly(methyl methacrylate)–nanofiller have been found essential to produce high-performance nanocellular foams. The emergent application areas of the poly(methyl methacrylate) nanocomposite foams are electromagnetic interference shielding, sensors, and supercapacitors.

Advances in precursor system for silica-based aerogel production toward improved mechanical properties, customized morphology, and multifunctionality: A review

Conventional silica-based aerogels are among the most promising materials considering their special properties, such as extremely low thermal conductivity (~15 mW/mK) and low-density (∼0.003-0.5 g.cm^-3) as well as high surface area (500-1200 m². g^-1). However, they have relatively low mechanical properties and entail extensive and energy-consuming processing steps. Silica-based aerogels are mostly fragile and possess minimal mechanical properties as well as a long processing procedure which hinders their application range. The key point in improving the mechanical properties of such a material is to increase the connectivity in the aerogel backbone. Several methods of mechanical improvement of silica-based aerogels have been explored by researchers such as (i) use of flexible silica precursors in silica gel backbone, (ii) surface-crosslinking of silica particles with a polymer, (iii) prolonged aging step in different solutions, (iv) distribution of flexible nanofillers into the silica solution prior to gelation, and, most recently, (v) polymerizing the silica precursor prior to gelation. The polymerized silica precursor, as in the most recent approach, can be gelled either by binodal decomposition (nucleation and growth), resulting in a particulate structure, or by spinodal decomposition, resulting in a non-particulate structure. By optimizing the material composition and processing conditions of materials, the aerogel can be tailored with different functional capabilities. This review paper presents a literature survey of precursor modification toward increased connectivity in the backbone, and the synthesis of inorganic and hybrid systems containing siloxane in the backbone of the silica-based aerogels and its composite version with carbon nanofillers. This review also explains the novel properties and applications of these material systems in a wide area. The relationship among the materials-processing-structure-properties in these kinds of aerogels is the most important factor in the development of aerogel products with given morphologies (particulate, fiber-like, or non-particulate) and their resultant properties. This approach to advancing precursor systems leads to the next-generation, multifunctional silica-based aerogel materials.