Eco Friendly Filler Modified Sustainable Polymer Composites for Improved Mechanical Performance

Abstract

This work presents a systematic investigation of kraft lignin as a sustainable bio-filler for elastomeric composites, focussing on chemical modification (nickel coordination), comprehensive physico-chemical characterisation, formulation into nitrile butadiene rubber (NBR) compounds, and comparison with conventional inorganic fillers. Motivated by the environmental and resource supply problems of petrochemical fillers, the study situates lignin within the circular bioeconomy paradigm and reviews current approaches to compatibility enhancement and performance optimisation of bio-fillers. The work details a reproducible protocol to synthesise nickel-coordinated lignin nanoparticles, and applies FTIR, UV–Vis and Raman spectroscopy to verify metal chelation and preservation of lignin’s aromatic backbone. Dispersion, thermal stability and interfacial behaviour are quantitatively and qualitatively evaluated; modified lignin demonstrates reduced hydroxyl accessibility, characteristic spectral shifts consistent with Ni²⁺ coordination, and absorption features indicative of discrete chelate complexes rather than metallic aggregates. When incorporated into NBR matrices under controlled mixing and cure conditions, chemically modified lignin particularly following hydrophobization/compatibilisation strategies yields composite property profiles (hardness, abrasion resistance, and modulus) comparable to, and in specific metrics competitive with, carbon black and silica filled analogues. The manuscript identifies key process windows for filler loading and highlights residual challenges (agglomeration, polarity mismatch, thermal-processing limits) that determine the practical ceiling for lignin substitution in high-performance elastomers