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Wood surface functionalisation using photoinitiators

English title Wood surface functionalisation using photoinitiators
Applicant Grützmacher Hansjörg
Number 136688
Funding scheme NRP 66 Resource Wood
Research institution Laboratorium für Anorganische Chemie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Inorganic Chemistry
Start/End 01.01.2012 - 31.12.2014
Approved amount 289'714.00
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All Disciplines (2)

Discipline
Inorganic Chemistry
Material Sciences

Keywords (5)

photoinitiator; wood modification; cellulose nanofibres; solid wood; surface functionalisation

Lay Summary (German)

Lead
Behandlung von Holzoberflächen mit Hilfe von Photoinitiatoren Die Oberflächeneigenschaften von Massivholz und Holzpartikeln bestimmen, wie gut diese Materialien beschichtet und verklebt oder in Verbundwerkstoffen eingesetzt werden können. Mittels Photoinitiatoren, die Lichtenergie in chemische Energie umwandeln, lässt sich die Reaktivität der Holzoberflächen steigern und so die Anwen-dungsmöglichkeiten von Holz erweitern.
Lay summary

Hintergrund
Um Massivholz und Holzpartikel zu beschichten oder mit anderen Materialien zu verkleben, braucht es eine erhöhte chemische Reaktivität der beteiligten Oberflächen. In diesem Projekt entwickeln die Forschenden dafür neuartige Methoden. Dabei binden sie an die Oberflächen aus Lignocellulose, dem Strukturgerüst verholzter Pflanzen, neue funktionelle Gruppen, die die Oberflächen reaktiver machen und diesen neue Eigenschaften verleihen. Dafür setzen die Forschenden phosphorbasierte Photoinitatoren ein, welche Lichtenergie über reaktive Zwischenprodukte in chemische Energie umwandeln.

Ziel
Die Forschungsarbeiten in diesem Projekt konzentrieren sich auf Oberflächenbehandlungen für zwei Formen von holzbasierten Materialien: für Cellulose-Nanofasern (CNF) als faserartige, strukturelle Holzkomponenten und für Massivholzoberflächen im naturbelassenen Zustand. Die unterschiedliche Oberflächenbeschaffenheit sowie die verschiedenen Anwendungsgebiete der beiden Materialien ermöglichen es den Forschenden, verschiedene Modifi-zierungsstrategien zu verfolgen. Bei der Behandlung von CNF geht es darum, die Oberflä-cheneigenschaften besser aufeinander abzustimmen, um z. B. die Adhäsion (Aneinanderheften) zu verstärken oder um Holzpartikel in Polymermatrizen von Verbundwerkstoffen besser einzubetten. Die Behandlung von Massivholzoberflächen hat hingegen zum Ziel, die Oberflächen beispielsweise wasserabweisend oder gegen Licht unempfindlich zu machen.

Bedeutung
Die Erkenntnisse aus dem Projekt könnten es ermöglichen, die Reaktivität oder Funktionalität von Holzoberfläche massgeschneidert zu verändern. Solche Oberflächenmodifikationen haben ein hohes Innovationspotential (z. B. durch Einbezug von Nanotechnologie) und sind besonders wichtig für hochwertige Holzanwendungen wie beschichtetes Holz im Aussenbe-reich, Holzwerkstoffe für den Holzbau, oder Holz-Kunststoff-Verbundmaterialien.

Direct link to Lay Summary Last update: 25.01.2013

Lay Summary (French)

Lead
Traitement des surfaces en bois à l'aide de photo-initiateurs Le degré de qualité des solutions de revêtement, de collage et de combinaison à des matériaux composites dépend des propriétés de surface du bois massif et des particules de bois. Des photo-initiateurs transformant l’énergie lumineuse en énergie chimique augmentent la réactivité des surfaces de bois et élargissent l’éventail d’applications du bois.
Lay summary

Contexte
Revêtir le bois massif et des particules de bois, ou encore coller ces derniers à d’autres matériaux requiert une réactivité chimique élevée des surfaces impliquées. A ces fins, les chercheurs de ce projet développent de nouvelles méthodes. Elles consistent à lier de nouveaux groupes fonctionnels aux surfaces en lignocellulose, l’armature structurelle des plantes arborescentes, pour rendre les surfaces plus réactives et leur conférer de nouvelles propriétés. A cet effet, les chercheurs utilisent des photo-initiateurs à base de phosphore, qui transforment l’énergie lumineuse en énergie chimique sous l’effet de produits intermédiaires réactifs.

But
Les travaux de recherche de ce projet se concentrent sur les traitements de surface de deux formes de matériaux ligneux : les nanofibres de cellulose (CNF), composantes structurelles du bois de type fibreux, et les surfaces de bois massif à l’état naturel. Les différents types de surfaces ainsi que les divers champs d’application des deux matériaux permettent de poursuivre différentes stratégies de modification. Le traitement des CNF a pour enjeu une meilleure harmonisation des propriétés de surface entre elles, par ex. pour renforcer l’adhérence ou mieux intégrer les particules de bois aux matrices de polymères dans le cas des matériaux composites. Pour sa part, le traitement des surfaces en bois massif a pour objectif de rendre les surfaces imperméables ou insensibles à la lumière.

Portée
Les conclusions tirées du projet pourraient permettre d’adapter à la demande la réactivité ou la fonctionnalité des surfaces en bois. Les modifications de surfaces de ce type présentent un fort potentiel d’innovation (par ex. par l’intégration des nanotechnologies) et sont particulièrement importantes pour les applications faisant intervenir le bois, telles que les revêtements en extérieur, les dérivés du bois pour les ouvrages ou encore les matériaux composites bois-polymères.

Direct link to Lay Summary Last update: 25.01.2013

Lay Summary (English)

Lead
Wood surface functionalisation using photoinitiators Surface properties of solid wood and wood particles determine whether the materials can be coated, bonded or used in composite materials. By using photoinitiators which can turn light energy into chemical energy, the reactivity of wood surfaces can be increased and the uses of wood widened.
Lay summary

Background
Many processes for modern, high-value applications of solid wood and wood particles—such as adhesive bonding, coating or compounding—depend on a defined and elevated chemical reactivity or functionality of the involved surfaces. This project aims to develop novel methods which bind the superficial lignocellulose, typical of ligneous plants, to new functional groups which render the surface more reactive and lend it new properties. This is achieved with the use of phosphorous-based photoinitiatiors which turn the energy of light into chemical energy.

Aim
Treatments will be developed for two forms of wood based materials with a different application spectrum: for cellulose nanofibres (CNF) as a fibrillar, structural wood component and for solid wood surfaces in their native state. As a result of the different surface properties and the different application spectrum, researchers can pursue various modification strategies. When treating CNF, the challenge is to better adjust the surface properties, for example to improve adhesion of integration of wood particles in polymer matrices of composite materials. The aim of solid wood treatment is to make the surface more water repellent and insensitive to light.

Significance
The results gained in the project will enable the tailoring of the reactivity and functionality of wood surfaces. Such surface modifications have a high potential for innovations (e.g. application of nanotechnology) and are particularly important for high value wood utilisation such as coated wood for external use, engineered wood products for timber constructions or wood-plastic composites.

Direct link to Lay Summary Last update: 25.01.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Phosphorous-Functionalized Bis(acyl)phosphane Oxides for Surface Modification
Huber Alex, Kuschel Andreas, Ott Timo, Santiso-Quinones, Stein Daniel, Bräuer Judith, Kissner Reinhard, Krumeich Frank, Schönberg Hartmut, Levalois-Grützmacher Joëlle, Grützmacher Hansjörg (2012), Phosphorous-Functionalized Bis(acyl)phosphane Oxides for Surface Modification, in Ang. Chem. Int. Ed. / Ang. Chem., 51, 4648-4652.
Snowballing Radical Generation Leads to Ultrahigh Molecular Weight Polymers
Laurino P., Hernandez H.F., Bräuer J., Krüger K., Grützmacher H., Gauer K. (2012), Snowballing Radical Generation Leads to Ultrahigh Molecular Weight Polymers, in Macromol. Rapid Commun., 33(20), 1770-1774.
Simple One-Pot Syntheses of Water-Soluble Bis(acyl)phosphane Oxide Photoinitiators and Their Application in Surfactant-Free Emulsion Polymerization
Müller Georgina, Zalibera Michal, Gescheidt Georg, Rosenthal Amos, Santiso-Quinones Gustavo, Dietliker Kurt, Grützmacher Hansjörg, Simple One-Pot Syntheses of Water-Soluble Bis(acyl)phosphane Oxide Photoinitiators and Their Application in Surfactant-Free Emulsion Polymerization, in Macromol. Rapid Commun.

Collaboration

Group / person Country
Types of collaboration
Fachhochschule Bern Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
1st Progress Report Meeting NRP 66 Talk given at a conference Wood surface functionalisation using photoinitiators 19.04.2013 Magglingen, Switzerland Low Jia En; Zimmermann Tanja; Tingaut Philippe; Arnold Martin; Grützmacher Hansjörg;


Abstract

Many processes for modern, high-value applications of solid wood and wood particles - such as adhesive bonding, coating or compounding - depend on a defined and elevated chemical reactivity or functionality of the involved surfaces. This project aims at the development of novel surface modification and functionalisation methods for lignocellulosic materials based on phosphorous-based photoinitiators. A broad range of potential industrial applications will be explored. Successful initiators and processes will be transferred to focused, application oriented follow-up projects.To protect inherent or achieve designed properties of wood surfaces for a superior performance, special treatments - preferably forming durable chemical bonds with the wood constituents - are often necessary. Because of the intimate association of the wood constituents cellulose, hemicelluloses and lignin in solid wood, reactivity towards chemical modifications is limited and heterogeneous. Thus, wood surfaces in their natural state are frequently not fully compatible with such treatments and rely more on physical than on chemical bonds. Therefore, pre-treatments are applied to enhance compatibility with functional treatments.Many different biological, chemical or physical methods are used for wood surface modification and functionalisation, which all have their specific advantages and limitations. A particularly versatile and effective method can be the use of photo-sensitive chemical compounds (so called photoinitiators), by which the chemical reactivity of wood surfaces can be controlled and enhanced. Given that these photoactive compounds can be anchored through suitable functional groups to the wood surface, a broad range of surface modifications is possible.Bisacylphosphaneoxid (RPO(COR1)2 = BAPO) and Monoacylphosphanoxid (R2PO(COR1) = MAPO) are efficient photoinitiators (PIs). Upon radiation with visible light, the acyl groups, COR1, are cleaved, yielding highly reactive RPO type radicals. In these, the R groups (one in BAPO, two in MAPO) shall be functionalised to allow the formation of durable bonds to the wood surfaces. This goal can be achieved either by binding to naturally occurring functional groups present in wood, especially hydroxy groups, or by a pretreatment of the wood surface, whereby suitable functional groups on the wood surface are generated.Treatments will be developed for two forms of wood based materials with a different application spectrum: 1) Cellulose Nanofibres (CNF) as a fibrillar, structural wood component, and 2) Solid wood surfaces of selected wood species in their native state. Besides their different application spectrum, the two materials also present different levels of challenges for modifications: CNF are regarded as a comparably well-defined model substance with a homogeneous chemical composition and a large surface area, while solid wood surfaces are known to be difficult substrates for uniform modifications.Regarding potential applications, two distinct modification goals will be followed: 1) Compatibilisation (for example to promote adhesion or to aid embedding in polymer matrices for composite materials), and 2) Functionalisation (to achieve advanced end-use properties of surfaces like hydrophobicity, UV protection, etc.).
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