[article]
| Titre : |
Green wood protection |
| Type de document : |
texte imprimé |
| Auteurs : |
Dirk Mestach, Auteur ; Derrick Tweene, Auteur |
| Année de publication : |
2004 |
| Article en page(s) : |
p. 18-21 |
| Langues : |
Anglais (eng) |
| Catégories : |
Analyse thermomécanique dynamique
Bois -- Revêtements protecteurs
Chromatographie sur gel
Formulation (Génie chimique)
Polyacryliques
Polyaddition
Résistance à l'humidité:Résistance à l'eau
Résistance chimique
Stabilisants (chimie)
Surfactants
Vernis en phase aqueuse
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
The authors explain which acrylic dispersions with polymer bound coatings are suitable for wood finishes.
Emulsion free-radical polymerisation has proven to be an environmentally friendly method for the production of a wide range of polymeric dispersions. In the emulsion polymerisation process, monomer is polymerised in an aqueous medium containing surfactant micelles. Surfactant plays a dual role in the process; it not only provides the locus of polymerisation but also stabilises the polymer particles.
Recent changes in the regulations concerning the emission of organic solvents in the European Community have led to a growing interest in the use of polymer dispersions in high performance waterborne coating systems.
One-pack systems, using the current state-of-the-art technology of combining carbonyl-hydrazide crosslinking with control of the morphology of the particles in the polymeric dispersion, have been studied extensively.
These acrylic dispersions are synthesised using conventional surfactants as an integral part of recipe. Even though some grafting might occur during the polymerisation, the surfactants are predominantly adsorbed onto the surface of the polymer particles.
The presence of surfactant has an influence on the final properties of the paint film. During film-formation coalescence is caused by self-diffusion and results in polymer inter-penetration. This process requires the disappearance of surfactant from the surface of the polymer particles.
Because most surfactants are not fully compatible with the polymer matrix, surfactant will have the tendency to migrate to the film-air interface. Therefore, the surface structure of a film cast from a dispersion will be different from its internal structure.
Because of the non-volatile nature of the surfactent, a permanent reduction of surface hardness is observed. In coatings this effect can lead to bad blocking resistance, inferior sanding properties and dirt pickup. In some cases the surfactant is completely exuded from the film.
As a result resin chemists have been actively pursuing alternatives for conventional low molecular weight surfactants. |
| Note de contenu : |
- Surface active monomers
- Polymeric stabilisers
- Paint evaluation
- FIGURES : 1. Water whitening after soaking at 50°C for three hours. Left : dispersion with APEO surfactant, middle : dispersion with APEO-free surfactan, right : dispersion with anionic surfmer - 2. Carbonyl functional polymeric stabiliser - 2. Graft emulsion polymerisation process using a polymeric surfactant - 4. Clarity of clear-coat based on an acrylic dispersion made with a polymeric surfactant and a conventional surfactant - 5. Gel permeation chromatogram of the polymeric stabiliser (A) and the polymer dispersion (B). In B (1) is the second stage and (2) is the non-grafted polymeric stabiliser - DMTA of clear-coat based on polymer stabilised acrylic dispersion
- TABLES : 1. Typical properties of a polymer stabilised dispersion - 2. Formulation is made with polymers stabilised acrylic dispersion - 3. Hardness development - 4. Early water resistance - 5. Chemical resistance according to DIN NORM 68 861 1B |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=27728 |
in POLYMERS PAINT COLOUR JOURNAL - PPCJ > Vol. 194, N° 4477 (06/2004) . - p. 18-21
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