Evaluation of the particle size of organosolv lignin in the synthesis of resol resins for plywood and their performance on fire spreading

Abstract

Scientists today are intensively seeking alternatives to petrochemical materials. Among others, lignin is a promising candidate because it is available in large quantities while its chemical structure makes its use possible in a variety of chemical reactions. Lignin, received by numerous methods from various feedstocks, is a promising material for the synthesis of many products like active carbon, thermosetting and thermoplastic polymers, surfactants, phenolic chemicals, etc. In this paper, the potential of using Biolignin – a trademarked organosolv lignin from straw prepared by Compagnie Industrielle de la Matière Végétale (CIMV; Neuilly-sur-Seine, France) – in the synthesis of phenol-formaldehyde (PF) resins was studied by CHIMAR HELLAS S.A. (Kalamaria, Greece). Before its use, Biolignin was further purified and subjected to mechanical treatment for the reduction of its particle size in order to increase its reactivity. The effectiveness of the treatment was verified by atomic force microscopy (AFM) measurements that were carried out by SYNPO Company (Pardubice, Czech Republic). Resol phenolic resins were prepared with various substitution levels of phenol up to 80%. However, their synthesis process was smooth only up to the substitution level of 50%. The properties of the resins were determined with typical lab analysis. Their thermal behavior was studied with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements that were conducted by the Aristotle University of Thessaloniki in Greece. Their bonding ability was evaluated by CHIMAR HELLAS via their application in the production of plywood panels of three layers that were prepared following a simulation of the industrial process. The panels were tested for their properties according to the relevant European standards, while their performance relative to fire was studied with cone calorimetry measurements that were performed by the Latvian State Institute of Wood Chemistry (LIWC; Riga, Latvia). All results were compared with that of a typical PF resin. It was found that the particle size of lignin affects the performance of the resins, while lignin-based PF resins are suitable for the production of plywood panels and have somewhat better performance relative to fire than typical PF resins. This study has been performed within the framework of the European project BIOCORE (biocommodity refinery for biofuels, chemical intermediates, polymers and materials).