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Contenido archivado el 2022-12-23

High performance in wood coating

Objetivo

A.BACKGROUND

Coated wood is utilised in exterior application as sidings or siding details of buildings, window and door joinery, fencing and garden constructions. In interior applications coated wood is used in panels, flooring, furniture and fittings. Opaque and semi-transparent coatings are applied on wood either in factories or at a building site. Coating materials and systems vary according to tradition, means of application and end use.

Service life and maintenance of exterior wood are crucial aspects of the competition between wood and other materials such as plastics and aluminium in window joinery, plastics in garden furniture and brick and concrete in sidings; most of the competing materials are based on non-renewable resources. Generally, maintenance intervals of coated wood are regarded by users as too short which has increased the use of the competing materials. Because of this, proposals for specifications or quality assurance schemes for coatings and exterior wood products have been launched in many European countries or organisations independently.

Construction, wood quality and species, coating materials and systems, and climatic stress all contribute to the rate of ageing and deterioration of coatings. Moisture, sunlight and fungi are the external factors threatening the integrity of coated wood and some preliminary work has been undertaken to create a climatic index in order to obtain some correlation between the exposure conditions in the various European climatic zones. Dimensional changes lead to wood cracking and loss of adhesion, but also may lead to detrimental changes in the wood due to mould disfigurement and decay. Although there has been much research into this matter, both nationally and internationally, due to the complexity of the interactions between coatings and wood more attention should be paid to the problem, and there is a need for better cooperation between coatings experts, wood scientists, biologists and building engineers.

Pressure to develop coating formulations with lower levels of harmful organic solvents (volatile organic compounds or VOCs) has led to extensive development work on low VOC products based on water-borne, high-solids solvent-borne, UV-curable and powder coating technologies. The requirement to develop new types of coatings has been driven by safety concerns and current and future legislation restricting solvent emissions. There are also other driving forces to develop novel coatings, notably requirements for improved performance and application characteristics from end users. End users also require more environmentally friendly coatings, with reduced levels of solvents and, increasingly, with reduced or zero levels of fungicides to protect against mould disfigurement. Environmental impact is very closely related to the duration of service life and maintenance requirements, and in assessing these environmental issues, there is a need for an integrated approach that would also consider not just coating formulation, but the method of production of the coating and its constituent components, application process, maintenance and service life.

Development of improved coatings also requires consideration of the fundamental properties of coatings and of the coating-wood interface. Although adhesion of a coating to wood is essential, there has been little research on adhesion mechanisms of new types of coatings and the factors affecting their adhesion. It is known that the bonding between coating and wood substrate is formed by means of mechanical anchoring and weak physical-chemical forces and that the penetration of a coating into wood is dependent on the paint formulation and the properties of the wood itself, but basic knowledge of how, for example, stresses develop during ageing and how these affect adhesion and durability requires study.

Extensive research on wood modification by treatments with organic chemicals and polymers and preservatives is being undertaken at several European institutes in order to develop new kinds of wood material with improved properties such as increased dimensional stability or resistance to decay. These treatments produce totally different substrate conditions compared with untreated wood. The active research on wood modification and wood composites is a challenge both to the development of coatings and also in the research of performance of coatings on new types of wood substrates.

A new COST Action for high-performance wood coating will provide an open forum for dissemination of the national and international research and for interdisciplinary discussions, which many research and industry scientists and technologists have seen to be lacking in Europe. There are ongoing and completed international projects funded by EU programmes and moreover many national research programmes and projects on exterior wood coatings and related areas which can be exploited by European coating manufacturers, coating raw material producers and end use industry in their development activities in the circumstances where the directives of solvent emissions and solvent content of coating materials as well as new EN-specifications for wood coating systems and coating materials are coming in force in Europe. The proposed Action will initiate new types of networks covering interdisciplinary fields, but also strengthen existing networks in the exterior wood coating sector in order to overcome new challenges in the changing European environment.

Links to other European activities

The proposed action has links to the COST Actions E2 Wood Durability, E5 Timber Frame Building Systems, E8 Mechanical Performance of Wood and Wood products, E9 LCA Forestry, E10 Wood Properties for Industrial Use and other new COST Action E13 on Wood Adhesion and Glued Products. The proposed Action has also links to current but soon to end EU projects like Performance and Durability of Wooden Window Joinery painted with low VOC paints in the AIR programme and Novel Approach to Coating Testing in SMT programme, as well as on-going projects such as LIFE-SYS and NATRESINS in the FAIR programme and ARWOOD in SMT programme and to PROWOOD in EUREKA. Apart from these transient and specific projects, there are no established Networks for wood coating work at a European level.

B.OBJECTIVES AND BENEFITS

The main objective of the Action is to improve the performance, durability and environmental properties of coated wood structures and products by expanding, coordinating and integrating knowledge on wood coating.

Detailed objectives will be:

-to establish an interdisciplinary forum for coatings technologists, wood scientists, surface chemists, biologists, wood coating researchers and construction researchers

-to review and establish the present state of the art in order to improve understanding of the participants about interdisciplinary fields like:

-surface chemistry
-climatic stresses and indices

-influence of various constructions on durability influence of modification, new types of preservatives and surface activation on substrate properties for coatings
-environmental impact of coated wood during service future development of coating materials

-to identify gaps and to stimulate relevant and interdisciplinary research and development and to initiate new projects in the 5th Framework Programme

-to exchange knowledge and disseminate results obtained from national and international research concerning the performance of coated wood and related areas

-to disseminate results of the proposed Action as seminar proceedings.

The combined benefits of the Action will be:

-closer European networking on coated wood performance and durability in exterior use

-improved dissemination of information on national research programmes

-more effective exploitation of results obtained in several national and international projects

-improved understanding of factors influencing coating performance on wood in various structures and of environmental impacts of coated wood during service life

-clearer identification of future needs in research and development work

-improved competitiveness of wood products from European forests

-more effective collaboration in interdisciplinary areas between the industry and research participants.

C.SCIENTIFIC PROGRAMME

This Action is intended to encourage cooperation of ongoing and prospective European research work regarding coated wood. An interdisciplinary approach is needed to meet the objectives and experts will be drawn from various backgrounds including paint chemistry and technology, paint raw material chemistry, wood chemistry and science, surface and colloid chemistry, wood and construction engineering and wood biology. The experts will come from universities, institutes and industry.

To cover the topics listed below, working groups, research tasks and networks will be established. The areas have strong interactions between each other.

WG 1.Coating-wood interface

This Working Group covers topics related to interfacial phenomena between various types of wood substrates and coatings in application and during service life. The objective for this group is to focus participants in the Action on research work related to adhesion theories and measurements, surface and paint chemistry and wood chemistry and morphology. This will lead to a better understanding of theories and practice and improve mutual collaboration between the experts with different background expertise. Tasks are specified in detail below:

- adhesion and wetting
- penetration of a coating into wood substrate
- wood properties
- wood quality, defects in wood and quality assurance
- wood species
-modified and preservative treated wood as a substrate for a coating
-surface chemistry
-surface activation

WG 2.Performance and durability

This Working Group includes issues such as changes in coated wood due to ageing, moisture dynamics in coated wood, service life, weathering tests, climatic stresses, maintenance and environmental impact of coated wood. The objective of the Working Group is to obtain a better understanding of the wide range of interacting factors which affect performance and durability. The experts will come from coating research, wood science, construction engineering and environmental research. Tasks are specified in detail below:

-life time prediction
-weather stresses and climatic index
-exposure tests and assessments
-maintenance
-moisture dynamics, moisture content of coated wood and dimensional stability, influence of various types of wood substrate
-permeability and permeability tests
-micro-organisms and coated wood
-wooden structures
-environmental impact, LCA, VOC, etc.

WG 3.Paint chemistry and formulation

This Working Group links paint raw material producers, coating producers, technologists and researchers. The main objective is to review and exchange results and opinions on future trends in wood coating materials and systems. Tasks are specified in detail below:

-new types of binders
-novel coatings

-development of additives
-solvents
-application and film formation
-flexibility properties, glass transition temperature
-colloid and surface chemistry

Organisation and timetable

The proposed Action will be steered by a Management Committee. There will be 3 Working Groups, each led by a chairman. Participants of the Working Groups will come from institutes, universities, paint and raw-material companies and end use industry. The industry partners will participate actively in Working Group 3, but also in the seminars of Working Groups 1 and 2 in order to be able to exploit up-to-date results of European research of the field. The exchange of knowledge in interdisciplinary areas will be possible in arranging the meetings and seminars in a way that they are open for members of every Working Group. The duration of the action will be 5 years.
Knowledge will be exchanged in seminars, Working Group and network meetings, through publications and exchanges of scientists.

Dissemination plan: Presentations of the seminars will be published according to the schedule below

Seminar Proceedings No 1month22
Seminar Proceedings No 2month32
Seminar Proceedings No 3, finalmonth 52

Short-term scientific missions: Scientists will be exchanged in the proposed Action between laboratories in order to introduce methods, interchange knowledge and disseminate results on the performance of coated wood and related areas.

E.ECONOMIC DIMENSIONS

The following COST countries have actively participated in the preparation of the action or otherwise indicated their interest:

Belgium
Croatia
England
Finland
France
Germany
Italy
Netherlands
Sweden
Switzerland

On the bases of national estimates provided by the representatives of these countries and taking into account the coordination costs to be covered by the COST budget of the European Commission, the overall cost of the activities to be carried out under the Action has been estimated, on the basis of 1998 prices, at roughly EUR 12 million.

This estimate is valid under the assumption that all the countries mentioned above but no other countries will participate in the Action. Any departure from this will change the total cost accordingly.

Convocatoria de propuestas

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Régimen de financiación

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Coordinador

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Aportación de la UE
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Dirección


Finlandia

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