Avaliação dos processos de incorporação da lignina em composições de borracha nitrílica

Abstract

The search for sustainable materials with economic viability has driven the development of solutions that utilize natural and renewable resources for various technological applications. In the rubber industry, one of the main concerns is the replacement of petroleum-based reinforcing fillers in composites and the incorporation of renewable and biodegradable raw materials into their formulations. In this context, lignin stands out as the second most abundant biopolymer on Earth, surpassed only by celulose, and has emerged as a potential alternative due to its availability, biodegradability, mechanical properties, low density, and low cost. In this study, formulations based on NBR/Lignin and XNBR/Lignin with 40 phr (parts per hundred of rubber) of kraft lignin were investigated, using both latex co-coagulation and traditional mixing processes to incorporate the filler into the elastomeric matrix. Carboxylated nitrile rubber (XNBR) in the formulation aims to enhance interaction between the filler and nitrile rubber (NBR), as the difference in polarity and affinity between lignin and NBR makes efficient interaction challenging. The formulations were evaluated for their rheological, rheometric, mechanical, and morphological properties to assess whether the interaction of lignin with nitrile rubber provides technical advantages in composite properties. Morphological analysis indicated improved filler dispersion in the elastomeric matrix with the presence of XNBR and the use of the co-coagulation mixing process (masterbatch production). Overall, the use of lignin contributed to improvements in tensile strength, elongation at break, modulus at 100%, and Mooney viscosity, with more significant results observed in formulations with XNBR. Based on the results obtained, it was possible to concluded that carboxylated nitrile rubber can act as a compatibilizer between nitrile rubber and lignin, indicating enhanced interaction when XNBR is used in the formulations.