Lignin as Alternative Reinforcing Filler in the Rubber Industry: A Review

Abstract

Lignin has potential as a reinforcing filler and to become an alternative to carbon black in the rubber industry. This is because it is formed from cheaper materials with abundant annually renewable sources and has low weight, high biological efficiency, and wide ecological adaptability. The utilization of bio-filler in the rubber industry has garnered increasing attention from researchers due to increasing environmental concerns over the toxic effects of carbon black on health and the environment. This article is intended to summarize current efforts in the development of a green and sustainable rubber product. Instead of focusing on silica and alternative rubber matrix-like guayule and Russian dandelion, it looks at lignin, which also has potential as a reinforcing filler and can enable the development of competitive green rubber composites. Lignin has several special characteristics such as good mechanical, physico-chemical, biodegradability, and antioxidant properties and excellent thermal stability. However, the incorporation of lignin in a rubber matrix is not straightforward, and this needs to be overcome with certain suitable solutions because of the polarity of lignin molecules, which contributes to strong self-interactions. Consequently, chemical modification of lignin is often used to improve the dispersion of lignin in elastomers, or a compatibilizer is added to enhance interfacial adhesion between lignin and the rubber matrix. This review attempts to compile relevant knowledge about the performance of lignin-filled rubber composite using different approaches such as mixing method, surface modification, hybrid fillers, etc. This study is expected to gain significant interest from researchers globally on the subject of lignin-based rubber composites and the advancement of development in green rubber products.

Techno-Economic Analysis and Life Cycle Assessment of Waste Lignin Fractionation and Valorization Using the ALPHA Process

“…LignoBoost, LignoForce, and SLRP (Sequential Liquid Lignin Recovery and Purification) technologies − have all been developed to recover raw bulk lignin from the alkaline black-liquor byproduct of a Kraft pulp mill. Although the resulting, so-called Kraft lignin has found application as a low-cost filler, , its use for higher-value applications such as carbon fibers and PU foams indicates that product performance with this bulk lignin can be subpar.…”

Recent developments in lignin modification and its application in lignin‐based green composites: A review

“…However, due to the polarity of lignin molecules, which causes significant aggregation, lignin integration in such a matrix material is difficult, and this must be addressed using specific appropriate approaches. [ 83 ] To achieve good dispersibility in elastomers, lignin can be chemically changed or a compatibilizer added to the system to achieve great interfacial adhesion between lignin and rubber matrix. Methoxy, phenolic, hydroxyl, and carbonyl groups are reactive functional groups connected to aromatic lignin structures that can chemically change structures.…”

Cellulose and lignin as carbon black replacement in natural rubber

“…Various lignocellulosic fillers, such as maple, 14 hemp, 15 flax, 16 wheat straw, 17 aspen wood flour, 18 rattan powder, 19 bamboo fiber, 20 jute, 21 cotton, 22 sisal, 23 oil palm, 24 coir, 25 pineapple leaf, 26 isora, 27 grass, 28 silk, 29 peanut shell powder, 30 and coconut shell powder, 31 have been used as fillers in NR composites. In addition to natural fibers, several studies have been conducted on the use of cellulose, 32,33 lignin, 34 and regenerated cellulose 35–39 on the properties of rubber composites. The mechanical properties of selected composites with different lignocellulosic fillers are listed in Table 1.…”