Extraction and modification of lignin resin for rubber compounds

Abstract

The aim of this work was related to development of economically viable method of extraction of lignin from sawdust in order to produce additive capable to improve physical mechanical and aging properties of rubber compounds. Five methods were developed and performed to isolate lignin from sawdust. They were delignification, acidolysis with 5M Hydrochloric acid, acidolysis with 10M Hydrochloric acid, ethanolysis and extraction with acetone. Chemical structure of produced lignin samples was identified with Furior Transform Infra Red spectrometer (FTIR). Analysis of FTIR spectra showed good' conformity of all wave numbers at which specified peaks of experimented and reference lignin samples were observed. Acidolysis of sawdust with 10M hydrochloric acid was found the most efficient for lignin extraction. This lignin was proceeded as a filler for rubber compounds. Properties of rubber compounds extended with produced lignin samples were determined. The test results showed that lignin was capable to improve properties of rubber compounds to the level achieved with carbon black and imported lignin filler samples, as well as resistance of rubber to prolong heat aging. An attempt was made to synthesize commercial antioxidants for rubber from extracted lignin sample. Methodology was developed and performed. Synthesized products were 2,4,6 three-tert-butyl phenol and 2,6 di-tert butyl paracresol. Alcoholic and methoxyl groups present earlier in extracted lignin samples were replaced with methyl and tertiary butyl groups. These groups are particularly capable to donate hydrogen to an alkyl peroxy radical. The effects of substituent groups in the transition state involved not only electron transfer to the peroxy radical but electron delocalization in the aromatic ring. So synthesized products were expected to act as effective antioxidants in rubber compounds. Rubber compounds with experimented antioxidants were prepared and their properties carefully investigated. Test results showed excellent resistance of rubber compounds to heat aging, that proved with high level of confidence antioxidation activity of synthesized products.