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Heavy-duty epoxy coatings are utilized in a vast amount of applications from flooring to anti-corrosive protection of marine structures in harsh environments. The binders in these epoxy coatings are generally derived from fossil-based diglycidylether bisphenol A due to their thermomechanical contribution in cured networks stemming from high aromaticity, but are known to have high toxicity profile. In the context of a green transition and the potential future legislation, finding renewable and less toxic alternatives is therefore of high interest. Lignin, which constitutes 20-30 wt% of wooden biomass, is the most abundant aromatic biopolymer available and could be an attractive alternative, but its high molar mass and heterogeneity limit compatibility, solubility, and its overall viability as a renewable feedstock for coating components. This thesis employed several strategies to transform lignin into coating components of epoxy binders and curing agents. Initially, binders were synthesized directly from kraft lignin by esterification with epoxidized fatty acids, yielding a fully bio-based epoxy binder. The modification with long aliphatic chains enabled good solubility and film formation properties but led to softer and ductile epoxy networks, which could be strengthened by the addition of low molecular weight epoxy additives. Improvement of thermomechanical properties required pre-treatment of lignin to enable better solubility and molecular mobility during cross-linking. Subsequent epoxy derivatization targeted lower molar mass lignin species of liquid nature, which were obtained from a combined pre-treatment process of solvent fractionation followed by depolymerization. The reduced molar mass facilitated short-chain epoxy modification, which, by subsequent amine curing, resulted in better thermomechanical properties with Young moduli above 1.1 GPa and glass transition temperatures above 68°C. These liquid aromatic building blocks from lignin we

In the context of a green transition, alternatives to fossil-based aromatic compounds have to be implemented. In this study, the combination of sequential solvent fractionation followed by depolymerization via catalytic hydrogenolysis of lignin led to liquid oligomeric lignin structures with chemical properties governed by the choice of lignin soluble fraction. Lignin species of increasing molecular weight (MW) were obtained with MW reduction up to 72% compared to the parent lignin, with a corresponding increase in total hydroxyl content up to 18% obtained through cleavage of lignin ether bonds. Hydrogenolysis led to lignin depolymerization oils comprising macromolecular lignin fragments and app. 15–18 wt % lignin monomers, resulting in a liquid product mixture. The lignin species were epoxidized to show their potential as a bio-based aromatic substitute to fossil-based bisphenol A. Liquid epoxy resins were obtained with viscosities between 2 × 103 and 4 × 105 Pa·s, which after curing resulted in thermoset networks with Young’s moduli between 0.9 and 1.4 GPa depending on the lignin fraction. Optimal viscosity to mechanical performance was obtained for ethyl acetate and ethanol solvent fractionated and depolymerized lignins as lower viscosity allows for reduced use of volatile organics.

Det biobaserede alternativ til fossile aromater.

Combining drugs is an efficient tool in fighting bacterial infections. It has been proven to enable an increased antimicrobial activity compared to mono-drug therapies. Current commercial dressings for treatment of infected wounds provide delivery of one drug only. Therefore, there is an obvious need to develop a technology enabling incorporation and release of two and more actives. Ideally, such technology should prevent potential cross-reactions between the drugs during long-term storage. Here, a concept of drug compartmentalization within distinct glycerol domains of glycerol-silicone elastomer membranes is presented. Multiple drugs are encapsulated within different types of glycerol domains hampering any cross-reactions. The drugs are simultaneously released upon contact with aqueous media and the release kinetics can be precisely adjusted by tuning various material parameters, such as glycerol content and membrane thickness. Ultimately, the drug release capabilities and the antimicrobial potential are evaluated against a variety of bacteria in an agar diffusion assay. The membranes are proven effective against different bacterial species, which confirms the efficiency of release even at minimum moisture levels. The glycerol-silicone platform technology enables delivery of virtually unlimited combinations of drugs from different drug families (e.g., antimicrobial, anti-inflammatory, and pain relief agents) facilitating new ways of treating wound disorders.

Controlling drug delivery from medical dressings to wounds remains a challenge despite the presence of multiple drug-containing wound dressings on the market. The dressing should ideally be effective immediately after application and still show no burst effect, and must also be comfortable for an extended period of time. Here, a silicone-based membrane is shown to offer an adjustable, constant release of various drugs even at a minimum moisture level resembling that of dry wounds. The drugs are dissolved in glycerol, which is speed-mixed with silicone and subsequently cured to yield a solid membrane with evenly distributed glycerol microcontainers housing the drug. The drugs are released immediately upon contact with moisture, enabling efficient treatment with short response time and no burst. Drug delivery capability is evaluated using a classical drug release experiment, as well as by performing an antimicrobial susceptibility test on ten bacterial strains in agar diffusion assays. Results show that glycerol–silicone membranes are promising candidates for fighting bacterial infections. Moreover, the addition of glycerol domains to a silicone matrix is proven to have a positive impact on water vapor transmission rate and moisture handling capabilities, resulting in a more skin compliant dressing.

To realize the commercial potential of dielectric elastomers, reliable, large-scale film production is required. Ensuring proper mixing and subsequently avoiding demixing after, for example, pumping and coating of elastomer premix in an online process is not facile. Weibull analysis of the electrical breakdown strength of dielectric elastomer films is shown to be an effective means of evaluating the film quality. The analysis is shown to be capable of distinguishing between proper and improper mixing schemes where similar analysis of ultimate mechanical properties fails to distinguish.

Dielektriske elastomerer (DE) er en relativ ny type materiale, som har stort potentiale blandt andet inden for medico- og energiteknologi