Modified lignin for composite and pellet binder applications

Lignin is a naturally occurring polymer that is present in all vascular plants. It binds together the cell walls, thus being one of the main structural components of vegetable tissue. In this project, alkali and dealkali lignins have been chemically modified in order to incorporate reactive fragments for subsequent free radical co-polymerisation with n-butyl methacrylate, styrene, or divinylbenzene (DVB). The thermal properties of regular and modified lignins were assessed and compared. The cross-linking of modified lignins with DVB yields materials with properties suitable for applications as a pellet binder, as well as a bio-based resin for the preparation of biocomposites. The chemical modification of alkali and dealkali lignin has been verified by Raman and infrared spectroscopies. The thermo-mechanical properties of the final materials prepared have been assessed by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA), and are reported and discussed in this work.