After cellulose, lignin is the second most abundant natural polymer in the world. It has multiple functional groups, providing great potential for polymer production. In this project, we explored the use of this renewable and valuable resource in two different adhesive applications to displace petroleum-based additives, thereby providing a more sustainable and “green” product. In this regard, two types of lignin, water-soluble (Amalin LPH) and non-water-soluble lignin (Amalin HPH) provided by the British Columbia Research Institute (BCRI) were used. In the first case, lignin was added to a pressure-sensitive adhesive (PSA) formulation via in-situ seeded semi-batch emulsion polymerization. It was seen that lignin does not readily take part in the polymerization reaction; rather, its presence results in reaction inhibition. Therefore, Amalin LPH lignin was modified via acrylation to overcome this issue. In another modification approach, maleic anhydride was used to produce maleated Amalin HPH lignin. Both the acrylated and maleated lignins were used in butyl acrylate/methyl methacrylate emulsion copolymerizations to produce PSA films. A series of controlled experiments with different lignin loadings was conducted. Adhesive properties of the PSA films were measured and compared with the corresponding acrylic base case formulation. The incorporation of lignin in the PSA formulation was a “green” solution to conventional PSA production and led to a simultaneous increase in tack and shear strength. Further characterization of the latex films via transmission electron microscopy (TEM) showed that lignin was successfully incorporated into the polymer particles. It also showed that the use of maleated lignin at a higher concentration led to a core-shell morphology. In the second application, unmodified Amalin LPH lignin was used to create a starch-based adhesive through the Stein-Hall process, a two-step process involving a “carrier” portion and a “slurry” portion. Several formulations with lignin loadings up to 35 wt% distributed in varying ratios in the carrier and slurry portions were prepared. It was shown that the addition of lignin to the starch-based adhesive formulation increases the water-resistance of the adhesive. Therefore, lignin addition is a solution for a common issue in starch-based adhesives, their lack of water-resistance due to the high affinity of starch toward water. Lignin incorporation solely in the slurry portion significantly increased the strength of the glued joints in a paper board adhesive test. The use of lignin as a renewable replacement of petroleum-based components in two different adhesive formulations was demonstrated successfully. This research strongly suggests that lignin can be used as a high value-added property modifier in adhesive applications.

Le cadre industriel de ce projet est de trouver une alternative à la résine phénol-formaldéhyde (RFP) et à son durcisseur, utilisée actuellement en pneumatique pour améliorer les performances aussi bien des compositions de caoutchouc que celles des produits semi-finis. Un des aspects essentiels de la pneumatique est d’augmenter la rigidité à faible déformation des pneus sans augmenter l'hystérésis des élastomères durcis chargés de noir de carbone. Ainsi, l'objectif de ce travail de thèse est de proposer un système thermodurcissable alternatif aux résines RFP actuelles. Ce nouveau système doit être riche en carbone renouvelable et doit être chimiquement modifié au moyen de procédés écologiques. La lignine a été choisie comme source de carbone renouvelable. Une étude préliminaire a souligné les potentialités d'une classe de lignines époxy pour l'application visée. Notre approche consiste en la conception de lignines modifiées par des époxy par une méthode originale évitant l'utilisation de l'épichlorhydrine suivie de son durcissement par des agents de réticulation appropriés. Des tests préliminaires avec un composé modèle de lignine ont donné la gamme des composés époxy et les conditions à tester pour la réaction avec la lignine. Les expériences avec la lignine ont alors confirmé le potentiel de l’ester diglycidylique de l’acide 4, 5-époxytetrahydrophthalique, un composé époxy contenant à la fois un groupement cycloaliphatique et deux types de groupements époxy glycidyliques, comme alternative à l'épichlorohydrine pour la préparation de lignines modifiées. Dans les conditions que nous avons définies, la réaction donne des prépolymères de type lignine-époxy sous forme de poudre avec un niveau d’époxydation de 1,2 mol/kg déterminé par spectroscopie FTIR. La série de tests effectuée sur des mélanges de caoutchouc a montré que la nouvelle lignine époxy associée à la p-xylylènediamine peut être mélangée avec succès avec le caoutchouc naturel et peut atteindre les propriétés de notre mix de référence. / The industrial framework of this project is the substitution of phenol formaldehyde resin (RFP) and its methyl donor hardener currently used for improving the performances of rubber compositions of tires or semi-finished products for tires. A critical aspect is the need for an increase of rigidity at low deformation without enhancement of the hysteresis of the cured elastomers filled with carbon black. The specific aim of this PhD work was to propose an alternative thermosetting system to the current RFP resins. This new system should be rich in renewable carbon and chemically modified by environmentally friendly processes. Lignin was chosen as the source of the renewable carbon. A preliminary study emphasized the potentialities of a class of epoxy-modified lignins for the targeted application. The main approach was the design of epoxy modified lignin to be obtained by an original method avoiding the use of epichlorohydrine and to be subsequently cured by appropriate cross-linkers. A preliminary screening with a lignin model compound gave the range of the epoxy compounds and the conditions to be tested for the reaction with lignin. Then various experiments with lignin confirmed the potential of 4, 5-epoxytetrahydrophthalic acid diglycidylester, an epoxy compound containing both one cycloaliphatic and two glycidyl type of epoxy groups, as an alternative for epichlorohydrine for the preparation of modified lignin. In the conditions we have defined, the reaction yielded epoxy lignin-based prepolymers as a powder with epoxy level as high as 1,2 mol/kg determined by FTIR spectroscopy. The series of evaluation campaigns in rubber blends showed that the new epoxy-modified lignin associated with p-xylylenediamine can be successfully mixed with natural rubber and enable to reach the properties of our reference mix.

Development of biomass feedstocks with desirable traits for cost-effective conversion is one of the main focus areas in biofuels research. As suggested by techno-economic analyses, the success of a lignocellulose-based biorefinery largely relies on the utilization of lignin to generate value-added products, i.e. fuels and chemicals. The fate of lignin and its structural/compositional changes during pretreatment have received increasing attention; however, the effect of genetic modification on the fractionation, depolymerization and catalytic upgrading of lignin from genetically engineered plants is not well understood. This study aims to fractionate and characterize the lignin streams from a wild-type and two genetically engineered switchgrass (Panicum virgatum) species (low lignin content with high S/G ratio and high lignin content) using three different pretreatment methods, i.e. dilute sulfuric acid, ammonia hydroxide, and aqueous ionic liquid (cholinium lysinate). The structural and compositional features and impact of lignin modification on lignin-carbohydrate complex characteristics and the deconstruction of cell-wall compounds were investigated. Moreover, a potential way to upgrade low molecular weight lignin to lipids by Rhodococcus opacus was evaluated. Results from this study provide a better understanding of how lignin engineering of switchgrass influences lignin fractionation and upgrading during conversion processes based on different pretreatment technologies.