Lignin modification to produce hydrophobic products

Abstract

Kraft lignin is not widely utilized for industrial applications. In this MSc work, kraft lignin was modified by grafting hydrophobic groups to produce hydrophobic materials. The main objective was to study the grafting of lipophilic long alkyl chains on kraft lignin to improve its hydrophobicity. Dodecyl glycidyl ether was grafted at various molar ratios on kraft lignin in the presence of dimethyl benzyl amine catalyst. The influence of the grafting ratio of long alkyl chain to kraft lignin and methylated kraft lignin was comprehensively studied. The effect of grafting on the structure and thermal properties of lignin was investigated. The modified kraft lignin based products were characterised using a variety of methods including NMR, FTIR, TGA, DSC, GPC and elemental analysis, all of which demonstrated remarkable changes in the chemical and physical structure of kraft lignin after modification. The results showed that by increasing the grafting ratio, an increasing fraction of the phenolic hydroxy groups of lignin reacted with dodecyl glycidyl ether. Moreover, alterations in the surface tension of solvents and water containing modified kraft lignin as well as on the wettability of surfaces coated with modified kraft lignin were studied in detail.