Kurzbeschreibung
(Englisch)
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The goal of the project is to provide a complete modification process for solid wood, including the synthesis of a treatment agent based on biopolymers from the biomass. The treatment will improve the wood properties, mostly dimensional stability, durability and hardness. It will be based on the association of lactic acid and other monomers like glycolic or succinic acids, respectively basis components of poly(lactic acid) (PLA), poly(glycolic acid) (PGA) and poly(butylene succinate) (PBS). Those biopolymers are nowadays well-known and more and more largely distributed on the market, however never used so far as wood preservatives. As polar polyesters, they are expected to show a good affinity to wood. Furthermore, as carboxylic acids, they are able to be grafted on the hydroxyl groups of wood before polymerizing in the cell walls and lumens. Besides, the so-modified wood will be a completely green composite, since entirely based on agro-resources and fully biodegradable at the end of its life cycle.
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Abstract
(Englisch)
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Current social and environmental context highly encourages the use of bio-based materials. In this frame, through carbon dioxide storage, wood constitutes a remarkable natural material, not only being a sustainable alternative to other materials, but also combining many advantages, like high and easy availability, good workability, high specific strength, bw price and pleasant appearance. Unfortunately, wood discloses serious drawbacks as weil: hygroscopicity leading to dimensional changes, and limited durability due to its sensitivity to biological aftacks. Historically, for wood protection against insects, moids and fungi, creosote and salts solutions were dominating but were however more and more restricted due to their significant impact on the environment, either during production or service life. Another approach leading to both dimensional stabilization and improvement of biological resistance is the chemical modification of wood stwcture. This is achieved by impregnation of chemicals, able to react or interact with hydroxyl groups of wood, in order to hinder water affinity. Reaction between treatment agent and wood structure can be a covalent chemical grafting or weaker linkage leading to a bulking effect that can also be amplified by eventual in-situ polymerization of well-chosen chemical monomers. Nowadays, research has to focus on the development of environmentally friendly and/or bio-based treatments for wood stabilization to take up the challenge to generate stable and durable bio-treated wood entirely coming from bio-based resources. The COST project “Bio-modiflcation of wood“ deals with Hie impregnation, grafting and in situ polymehzation of bio-oligomers of lactic acid, glycolic acid, polybutylene succinate and polybutylene adipate, as weil as their ca-oligomers. Historically deveboped as bio-based and/or biodegradable piastics for the packaging industry, these polar bio polymers are considered here as treatment agents for wood stabilization. lndeed, as carboxylic acids, these bio compounds showed a good chemical affinity with wood components, allowing high weight up-take of their oligomers by vacuum impregnation, and a possible chemical grafting. The process used is a usual vacuum impregnation step of oven dned wood samples folbowed by a heating step of impregnated samples, dedicated to chemical grafting and/or further in-situ polymerization. The evaluation of physical and mechanical performances of such treated wood revealed very promising resuits. lndeed, all oligomeric treatments confer very different properties to wood. Mechanical performances are either increased, stable or decreased by the treatment considered, while dimensional stability against moisture and water are almost always improved. This observation is iinked to the treatment penetration into wood cell wall, which is not achieved in every case. Assessed in the second part of the project, the co-polymerization of monomers did not iead to significantly improved properties. Besides, the natural weathering revealed a very good behaviour of some systems, the same systems that showed clear optimization potential by adjusting the treatment conditions, namely polybutylenesuccinateoNgomers.
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