DEVELOPMENT AND FLAMMABILITY BEHAVIOR OF FOREST/CROP RESIDUE-BASED POLYMERIC COMPOSITES

Abstract

Throughout human civilization, the role of materials has been paramount, shaping technological advancements and driving progress. In this context, polymer matrix composites (PMCs) have emerged as versatile and promising materials, offering a unique blend of mechanical properties. However, their widespread adoption faces challenges, notably in terms of sustainability. To address these challenges, the incorporation of biobased fibers and fillers derived from forest and agricultural waste has gained substantial attention. Incorporating biobased fibers and fillers in biopolymers signifies a critical shift towards sustainable material development. Despite these advancements, one significant limitation that hinders the broader application of natural fiber reinforced polymer composites (NFRPCs) is their inherently poor flame retardancy. Natural fibers, while offering an array of advantages, tend to be highly flammable when exposed to heat or flame. This susceptibility to combustion poses a critical constraint on their potential utility across various industries, particularly in applications where fire resistance is an essential criterion. Conventional flame-retardant (FR) materials, typically based on halogenated compounds and other hazardous chemicals, have addressed this challenge effectively. However, they often counteract the sustainability goals sought using natural fibers. Consequently, developing flame-retardant biobased composites becomes a pressing imperative, as it aligns sustainability with fire safety. Hence, the current research endeavor aims to tackle the issue by exploring various underutilized agricultural/forest waste as potential filler/fibers for the development of polymer matrix composites via conventional routes, such as extrusion, injection, and compression molding techniques. It is followed by developing flame-retardant-based composites using non-halogenated flame retardants, thereby broadening the application spectrum of these sustainable materials. The present research investigation is divided into four broad areas. The first phase explores a feasibility check and process parameter optimization for processing NFRPCs using various forest/agricultural waste (such as, finger millet husk, barnyard millet husk, and corncob). The processing is followed by investigation of the mechanical, thermal, and morphological behavior of developed NFRPCs using standard characterization techniques. The tensile and flexural strength varies for all the composites in the range of 22-30 MPa and 45-63 MPa, respectively. The tensile and flexural modulus varies in the range of 550-900 MPa and 1700-2700 MPa, respectively. The results established the potential candidacy of the selected waste materials as a filler/reinforcement in developing composite materials for non-structural applications. The second phase explore the woven (continuous) fiber (such as, jute, sisal, and jute-sisal intra hybrid fabric) based polypropylene composites. The analysis involved the investigation of fiber orientation, hybridization, and stacking sequence and their effect on the static and dynamic mechanical behavior of the developed composites. The results revealed that the combined and alternative orientation of the jute and sisal fibers resulted in better stress transfer efficiency. Therefore, hybridization and orientation of the fibers significantly improved the static and dynamic mechanical properties of developed composites. The third phase explored the FR additives, treatment of fibers with FRs, and hybrid FR approaches to develop flame-resistant NFRPCs. The findings provide an in-depth analysis of the development and utilization of FR-based natural fibers for developing flame-resistant NFRPCs employing detailed characterization. The results revealed that the hybrid approach utilizing FR additives and treated fibers exhibited superior flame retardancy as compared to the additive and treated fiber approaches adopted independently. The fourth phase explored the detailed analysis of the degradation behavior of the jute-sisal fibers and their polypropylene based composites when exposed to three different environmental conditions. The results have been thoroughly analyzed and discussed in detail. The results revealed that the lowest durability was observed with alkali aging, followed by water and oil aging. The current experimental research gives insight into the importance of fiber hybridization, orientation, stacking sequence processing, flame retardancy behavior, and environment aging behavior of polymeric composites. The research findings from the current work can certainly help the industrial and research fraternity working in the broad area of sustainable composites.