Chanchal Kumar Kundu

In recent years, terahertz (THz) technology emerges as a promising research area in materials science, driven by its potential for vast applications. Notably, its unique characteristics – being nonionizing, safe for human health, and nondestructive‐ set it apart from conventional techniques like X‐ray radiation, particularly in the characterization of nonconducting materials. This study explores the potential of THz technology in investigating various material properties relevant to pure textiles and textile‐based composite structures. The findings demonstrate the effectiveness of THz technology in identifying textile types, determining blend ratios, detecting defects and damage in textile goods, and inspecting internal defects such as delamination, debonding, and porosity in fiber‐reinforced composites. This review also highlights the future insights of THz technology in the textile and composite industry and concludes that, despite existing challenges, it can unlock new opportunities across industries.

The global flame retardant industry is transforming significantly, shifting from petroleum‐based products to environmentally friendly alternatives derived from renewable natural sources. This transition aligns with the growing emphasis on sustainability and the development of biodegradable polymers aimed at mitigating the negative impacts of nonrenewable substrates. Consequently, the innovation of green flame retardants and sustainable polymer materials has emerged as a pivotal research area within the scientific community. This review synthesizes recent advancements in this field, focusing on the application of green flame retardants sourced from plants, animals, and microorganisms in biodegradable polymer substrates, such as textiles and plastics. Their performance, mechanisms of action, and additional functionalities beyond flame inhibition are examined. Furthermore, the inherent limitations of these bio‐derived compounds are discussed, which warrant further investigation to fully realize their potential. This review aims to provide a comprehensive overview of current developments and future directions in the pursuit of sustainable flame retardant solutions.

Bio-derived polysaccharides, namely, chitosan (CS) and sodium alginate (SA) were considered in a layer-by-layer (LbL) deposition to construct flame retardant coatings onto the polyamide 66 (PA66) fabric surfaces. The as-prepared coatings were further modified in the impregnation process with a number of inorganic salts containing boron, nickel, and iron elements. Obtained results revealed that the simultaneously LbL-assembled and metal salt-treated fabric samples exhibited superior flame retardant performance compared to the only LbL-deposited fabric samples. The limiting oxygen index (LOI) value reached up to 25.5% of the CS-SA-iron salt treated fabric sample and the dripping tendency was completely diminished only for the LbL-metal salt modified fabric samples. Among the treated fabric samples, the CS-SA-iron-salt-modified fabric sample exhibited a maximum reduction in the peak heat release rate by 34% and handed improved and higher quality char residues, indicating a possible condensed phase flame retardant mechanism of this applied finishing. Moreover, metal salt-induced cross-linking could enhance the coating stability and durable finishes against regular home laundering where an iron-salt-treated fabric sample could retain anti-dripping properties even up to 10 laundering cycles. Thus, this pairing of bio-macromolecules (i.e., charring agent) with the metal salts in a hybrid system showed efficacy in improving the fire performance of polyamide textiles via the synergistic involvement between them.

Among the synthetic polymeric textiles, Nylon (Polyamide) textiles (Nylon66/Nylon 6) are one of the most widely used materials, especially as apparel and industrial uses for their excellent properties, namely higher strength and good wear resistance. Unfortunately, due to their organic structures, they show the relative ease of burning, which poses a great risk to fire. For the flame retardant (FR) treatment of nylon textiles, several strategies have been developed throughout the years and the earlier studies show the enormous uses of petroleum-based flame retardant compounds via energy intensive application methods. However, the rapid improvement in living standards as well as the recent call for a reduction of environmental impacts during manufacturing and use have been pushed researchers to come up with environmentally benign chemistries and processes. Therefore, the challenges in search of the most sustainable, efficient and durable flame retardant treatments for nylon textiles still remain as a hot topic to be addressed. This chapter discusses the eco-friendly approaches that have been taken in escalating the fire performance of these novel nylon textiles, especially focusing on the applied compounds and the application techniques along with the durability issues of such applications.