[article]
| Titre : |
How to optimize coating surfaces by using specialty modified siloxanes |
| Type de document : |
texte imprimé |
| Auteurs : |
Heike Semmler, Auteur ; Roger Reinartz, Auteur ; Ingrid K. Meier, Auteur ; K. Michael Peck, Auteur |
| Année de publication : |
2021 |
| Article en page(s) : |
p. 122-125 |
| Note générale : |
Bibliogr. |
| Langues : |
Anglais (eng) |
| Catégories : |
Bois -- Revêtements protecteurs
Formulation (Génie chimique)
Jaune
Pigments
PolydiméthylsiloxaneLe polydiméthylsiloxane —[O-Si(CH3)2]n—, ou poly(diméthylsiloxane) selon la nomenclature systématique, communément appelé PDMS ou diméthicone, est un polymère organominéral de la famille des siloxanes souvent présent dans les shampoings. On l'y ajoute pour augmenter le volume des cheveux mais il peut également aller boucher les pores du cuir chevelu et rendre les cheveux gras. C'est une des raisons pour lesquelles se laver les cheveux tous les jours est très déconseillé avec un shampooing contenant des silicones.
Il existe également de l'amodiméthicone, qui est un dérivé du diméthicone.
Le polydiméthylsiloxane est un additif alimentaire (E900), utilisé comme antimoussant dans les boissons (Coca-Cola BlāK).
La chaîne de poly(diméthylsiloxane) forme également la structure de base des huiles et des caoutchoucs silicones.
Résistance à l'abrasion
Revêtements en phase aqueuse -- Additifs
Vernis en phase aqueuse -- Additifs
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
Siloxane-based additives are critical tools in coating applications: their structures can be varied in order to provide a broad range of performance benefits in many types of formulations. Surfactants and defoamers are commonly recognised additive classes, but also many other functionalities can be derived from siloxane chemistries, particularly attributes related to surface control, such as flow and levelling, slip, scratch resistance and haptic properties. This extensive range of performance is achievable due to the broad flexibility inherent in siloxane chemistry, allowing a fine-tuned balance of compatibility, incompatibility and surface activity. As with many additive types, a broad range of functionalities creates many options for improvement and innovation, but also presents challenges in finding the right additive and optimising molecular structure to achieve the desired performance. In order to clarify some general structure-property relationships, a study was carried out.
Due to their unique interfacial activity, siloxane-based surface control additives have become invaluable tools in the coating formulator's tool box. Many surface control additives are capable of mitigating surface energy gradients that can exist within a liquid film immediately after application ; thus, they can improve flow, prevent retraction, minimise cratering, enable better surface levelling and ensure a flawless surface appearance. As their surface activity increases, surface control additives can also render special properties to the surface of the coating. For example, depending on their chemical structures, certain surface control additives can impact surface slip, affect haptic properties (surface 'feel'), impart scratch resistance, act as anti-blocking agents and even create a release effect on the surface of the cured coating. This is of great importance in many areas of application, but especially for wood coatings, which typically have to combine very good aesthetics with high mechanical resistance.
The property of 'slip' is characteristic of a smooth sliding motion across the coating that results from a reduced coefficient of friction. lt is quantified as the force needed to slide a mass across the coating surface. The material properties of both the substrate and the object to be moved are reflected in the static and dynamic coefficients of friction with contributions from the chemical composition of the coating and the interactions arising from it, as well as surface roughness. Surface control additives with large polydimethylsiloxane segments and a high degree of surface activity can ensure particularly slippery surfaces. Additionally, coatings with a high slip often feel smooth and silky. Coatings may also resist scratching when the scraping object slips off the surface rather than penetrating the coating film ; however, force-dependent scratch resistance of a coating can only be significantly improved if the surface control additive used contains functional groups that do not interact strongly with one another. Organo-modified siloxanes, with a high percentage of polydimethylsiloxane domains, exhibit particularly weak interactions both with each other and with other materials. This can make them ideal for this purpose. Moreover, during the drying process, organo-modified siloxanes continually migrate to the air-liquid interface, producing a lubricating film that significantly reduces the coefficient of friction of the coating. When a cured coating surface has a strong polydimethylsiloxane character due to the use of a surface control additive, it is also more likely to resist blocking — adhesion of the dried coating to another freshly coated surface or other substrates.
While it is possible to achieve a variety of desired benefits by using siloxane-based surface control additives that have large polydimethylsiloxane segments, most coatings eventually need to be recoated. The downside to employing strongly hydrophobic and oleophobic surface control additives is the tendency for the resultant coating to have a very low surface energy and to be very difficult — if not impossible — to recoat. Even if a second coating layer can be applied to such a surface, lack of adhesion and the tendency for the second coating layer to show craters are true problems. |
| Note de contenu : |
- Design of surface control additives
- Properties in two wood coating formulations
- Test of emulsion-type additives in clear coat formulation
- Table 1 : Characteristics of siloxane-based surface control additives in this study
- Table 2 : Waterborne self-crosslinking modified acrylic clea wood coating based on NeoCryl XK-12
- Table 3 : Performance of surface control additives when post-added to a waterborne self-crosslinking modified acrylic wood coating (based on NeoCryl XK-12)
- Table 4 : Pigmented waterborne acrylic wood coating based on ACRONAL LR 9014 and Pigment Yellow 42 concentrate
- Fig. 1 : Scratch resistance testing and ratings
- Fig. 2 : Comparison of the effects of surface control additives on the blocking properties of a pigmented waterborne acrylic wood coating
- Fig. 3 : Comparison of cross-cut areas of panels that have been coated twice with pigmented waterborne acrylic wood coatings containing 05 wt% surface control additives |
| En ligne : |
https://drive.google.com/file/d/1LAnKlTYPYRTilx7GwkMEANR6lSywT8qi/view?usp=drive [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35999 |
in SURFACE COATINGS INTERNATIONAL > Vol. 104.2 (03-04/2021) . - p. 122-125
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How to optimize coating surfaces by using specialty modified siloxanes in SURFACE COATINGS INTERNATIONAL, Vol. 104.2 (03-04/2021)
