Biopolymers & Bioplastics

Biography

Biography: Lydia Heinrich

Abstract

The biopolymer lignin, recovered as a byproduct from pulp and paper mills in large amounts, consists of a densely connected network of phenolic units and functional groups such as hydroxyl groups, carboxylic acids and aldehydes. This makes its incorporation into polymeric binders desirable both in terms of the valorization of waste materials leading to a more circular economy, and in terms of the novel properties that it can introduce in binders. While lignin has already successfully been used to replace phenol in phenol-formaldehyde resins in various adhesive applications including particle boards, plywood and laminated veneer lumber, its covalent incorporation into other binders not cured through condensation mechanisms remains underexplored. The reason for this lies on one hand in the difficulty of processing lignin, which is a non-melting solid with low solubility in common solvents, and on the other hand in its heterogeneity and multi-functionality, which make it difficult to produce a chemically exactly defined material from it. In this work, lignin was chemically modified with different renewable building blocks, such as succinic acid, 1,2-propanediol and fatty acids, and non-renewable building blocks, such as polyethylene glycol and ε-caprolactone, to give products suitable for use as binders in applications such as adhesives, coatings and printing inks. Different methods are explored that allow the targeting of specific properties, such as the variation of the melting point and viscosity of the binders, as well as the tuning of the polarity to allow formulation in different solvents and for applications that require certain hydrophobicity. Application examples which utilize the specific properties of lignin show that it is a very promising starting material for binder synthesis, and that many different products can be obtained through appropriate chemical modification.