[article]
| Titre : |
Enhancing exterior performance of clear coatings through photostabilization of wooden surfaces. Part 1 : treatment and characterization |
| Type de document : |
texte imprimé |
| Année de publication : |
2008 |
| Note générale : |
Bibliogr. |
| Langues : |
Américain (ame) |
| Catégories : |
Applications extérieures
Bois -- Revêtements protecteurs
Bois -- Vernis
Caractérisation
Peracétique, AcideL'acide peracétique ou acide peroxyacétique (formule chimique: C2H4O3) (ou PAA) est un acide et agent oxydant très puissant utilisé dans l'Industrie pharmaceutique et le domaine médical comme oxydant, biocide désinfectant ou "stérilisant à froid" de certains dispositifs médicaux5. Ses propriétés oxydantes sont connues depuis 1902.
Cette molécule est très soluble dans l'eau, l'alcool et l'éther.
Fabrication : Il est le plus souvent produit en faisant agir de l'anhydre mixte boroacétique sur du peroxyde d'hydrogène (eau oxygénée).
Dégradation : En condition normale, ce produit se dégrade en sous-produits non toxiques (acide acétique, oxygène et eau).
Efficacité comme biocide : Utilisé seul ou avec du chlore ou des formaldehydes, sous forme liquide8 ou gazeuse (vapeur d'acide peracétique), il tue la plupart des micro-organismes libres en libérant de l'oxygène avec production d'hypochlorite ou de radicaux hydroxyles. Il est le plus efficace des désinfectants du marché sur les bactéries Gram-positives et Gram-négatives (moins de 5 minutes à faibles concentrations sur des bactéries libres), sur Mycobacterium tuberculosis et sur les spores.
Photostabilité
Pins et constituants
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
The aim of this work was to produce a less photodegradation-prone substrate for clear coating by partially delignifying the surface cells of Pinus radiata boards to a depth of 2-3 mm while maintaining the integrity of the wood surface tissues in the delignified zone. To achieve this, several surface oxidative delignification treatments were trialled in the method development process and paracetic acid was chosen as the method for refinement and deployment. The treatment method was optimized to yield a significant degree of delignification compatible with the aim of producing a photostabilized yet intact wooden surface. A preweathering technique was also used as a second delignification method for producing photostabilized boards. Microscopic and chemical techniques were used to characterize the effects of chemical and preweathering treatments, which produced delignified surface envelopes 2-3 mm and 100 [micro]m deep, respectively. Acetyl bromide lignin analyses, infrared spectroscopic analyses, and density changes of 30 [micro]m-thick sections of peracetic-acid-treated samples, as a function of depth from the wood surface, suggested that a partial delignification had occurred that diminished with depth. Light and transmission electron microscopy rovided evidence of delignification at the cellular level. In the surface layers of peracetic-acid-treated boards, all cell wall regions were delignified, with the middle lamella being the most severely affected. Lignin appeared to be completely removed from the cell corner middle lamella regions, but tracheids were still joined in other parts of the middle lamella. The[S.sub.1] [Ssub.2] and [S.sub.3] walls were also delignified. In subsurface layers, cell walls were only partially delignified and the tissues held their integrity. In contrast, in the preweathered boards, cell walls in the outermost layers were completely separated at the middle lamella from photodegradation. Preferential lignin removal over that of hemicelluloses was achieved via oxidative treatment of solid wood. The outcome of this was the successful fulfillment of our aim to produce partially delignified wooden surfaces that retained sufficient strength and aesthetic appearance and were suitable for application in wooden structures, provided that the necessary protection measures were carried out. Due to the narrow surface zone produced, machining of such surfaces would not be recommended as the most delignified zone would be removed first. In Part 2 of this series, the photostability of treated boards, which had been clear coated and weathered, will be considered. |
| DOI : |
10.1007/s11998-008-9089-5 |
| En ligne : |
https://link.springer.com/content/pdf/10.1007%2Fs11998-008-9089-5.pdf |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2996 |
in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 5, N° 2 (06/2008)
[article]
|
Aller sur edunet
Accueil
Enhancing exterior performance of clear coatings through photostabilization of wooden surfaces. Part 1 : treatment and characterization in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 5, N° 2 (06/2008)
