Characterisation and application of NovaFiber lignin

Abstract

Sulphur-free lignin coming from a novel alkaline-pulping process called NovaFiber, which has been developed by KIRAM AB, has been characterised and evaluated for potential applications. A Kraft lignin has been used for comparison. Considering the characterisation results of a NovaFiber softwood and Kraft lignin, it can be concluded that these lignins significantly differ in amounts of functional groups, molecular weight and acidity. This will affect their properties towards the potential applications studied in this project. The chemical composition and thermal stability to about 220 °C of both types of lignin are comparable. The “high molecular” NovaFiber lignin is totally different from the other lignins due to a high ash content, as a result of the different precipitation procedure used. This study has shown that NovaFiber lignin has a great potential as functional additive for UV stabilisation of thermoplastics and as part of a phenol formaldehyde-based wood adhesive. Initial results demonstrate that NovaFiber and Kraft lignin act as UV stabilisers in polyethylene with comparable or only slightly inferior product performance, with respect to UV exposure, compared to a relatively very expensive commercially applied stabiliser (HALS). This means that NovaFiber lignin has a very good price/performance ratio. Without loss of adhesive strength, 31% of phenol formaldehyde can be replaced by NovaFiber and Kraft lignin in a wood adhesive. The adhesive properties have been improved to a level substantially higher than the phenol formaldehyde resin by using modified lignin, after sodium dithionite treatment, and/or by using a higher curing temperature. Furthermore, the processing of NovaFiber lignin is easier compared to Kraft lignin in respect of the mixing/solubility of the lignin in the thermoplastic or glue matrix and the amount of released odour seems to be much less.