Novel functional lignins as building blocks in preparation of polyurethane foams
M.Sc. Mareike Zieglowski (2015 – )
Lignin, a bio-based polymer carrying an abundant number of alcoholic functions, can be used as a substitute for petrochemical products. At the moment, only a small amount of lignin is used for materials applications (about 2 %). Most of the Lignin is being burned for energy production. Lignin contains a large number of hydroxyl groups and it can be used as a macromonomer in polyurethane foam-formulations, as a low-cost polyol. Polyurethane foams (PUs) are an important class of polymers, which are synthesized by a polyaddition reaction between polyols and polyisocyanate to form a urethanic linkage. The synthesis of such lignin-based PUs often follows two major strategies: (1) the Lignin is used directly without any previous chemical modification, with/without addition of further other polyols or (2) the lignin is chemically modified prior to the reaction to make hydroxyl functions available, which could increase the efficiency of binding the lignin into the PU polymer.
Lignin-substituted bio-based epoxy resins
Dr.-Ing. Sabrina Mehlhase
Lignin as one of the most abundant renewable resources is an excellent raw material for several applications due to its highly functional character and source of aromatic building blocks. Taking advantage of its hydroxyl moieties, it can be used in epoxy-based thermosets as a feasible polymeric building block bringing new interesting features.
Epoxy-based thermosets are a very interesting class of polymers due to the adjustability of their properties which depend on the large variety of easy available starting materials and an adjustable cross-linking density. Incorporating lignin, either unmodified using lignin as filler, as accelerator through its hydroxyl moieties or functionalized as novel bio-based curing agents, highly lignin-substituted epoxy resins with promising properties can be achieved. Further, the substitution of Bisphenol-A based epoxy resins with bio-based alternatives such as epoxidized soybean or linseed oil is from great interest.
Derivatization of Lignin and its application in 2-component thermosets
Dr. Marcus Ott
In order to replace petroleum-based chemicals in the production of resins Lignin has been chemically modified. The strategy is the incorporation of chemically reactive groups onto the ligin.
For this, Kraft Lignin was aminated via Mannich reaction with various amines. In a subsequent step, a curing reaction was performed using commercially available Bisphenol-A epoxide and amine-terminated polypropylene glycol as hardener. With this strategy up to 30 w-% of lignin were successfully incorporated into the resin formulations. The samples were investigated by a set of analytical techniques such as ATR-IR, Elemental analysis, REM and mechanical analysis (3-point bending test according to DIN EN 178). Comparison of the mechanical properties to neat resin showed, that resins containing 23 wt.-% modified lignin provided up to 74% of the flexural strength. Reference experiments with unmodified Lignin proved our hypothesis that the chemical modification of the lignin with amine groups has a significant impact on the reactivity during the curing reaction and therefore on the mechanical performance of the resulting resins.