[article]
| Titre : |
Flexible formulation : Eliminating external plasticizer can improved performance in waterborne caulks and sealants |
| Type de document : |
texte imprimé |
| Auteurs : |
Rick Miner, Auteur |
| Année de publication : |
2017 |
| Article en page(s) : |
p. 18-21 |
| Langues : |
Américain (ame) |
| Catégories : |
Assemblages (technologie)
Formulation (Génie chimique)
Liants
Plastifiants -- Suppression ou remplacement
Produits d'étanchéité
|
| Index. décimale : |
668.3 Adhésifs et produits semblables |
| Résumé : |
A caulking sealant has three basic functions: filling a gap between two or more substrates; forming a barrier through the physical properties of the sealant itself and by adhesion to the substrate; and maintaining sealing properties for the expected lifetime, service conditions, and environments. To help maintain flexibility at low temperatures and to retain performance, most pigmented acrylic latex sealants on the market today are formulated with a supplementary external plasticizer. When properly chosen and formulated, plasticizers such as benzylbutyl phthalate, dipropylene glycol dibenzoate or others effectively lower the glass-transition temperature (Tg) of acrylic polymers and thus “soften” the composition.
At the same time, heavy reliance on plasticizers in a sealant formulation can result in negative side effects, such as mildew growth or glossing. In addition, the use of phthalate plasticizers has recently come under scrutiny due their poor toxicological profile. For these reasons, product developers are beginning to look at new latex binders that allow for the elimination or significant reduction of plasticizers from the formulation. New technologies in this area offer many benefits and may help formulators improve product performance while still achieving the flexibility of high-plasticizer products.
It is first important to understand the historical importance of plasticizers and how they are used today. Waterborne acrylic latex sealants generally offer excellent durability in terms of ultraviolet light resistance and chemical resistance. Further, they offer desirable application properties such as ease of gunning, tooling and cleanup; the elimination of solvent odors and flammability; and the ability to be painted shortly after joint placement. Highly plasticized systems yield flexible sealants with movement capability of ± 35% and the ability to meet the performance requirements of high-performance sealants such as ASTM C 920. |
| Note de contenu : |
- Plasticizer migration
- Reducing or eliminating external plasticizers
- FIGURES : 1. Comparison of the tensile-elongation of externally plasticized (30% based on polymer solids) and plasticizer-free sealant formulated with the latex - 2. Comparison of dirt pickup and mildew resistance of externally plasticized (30% based on polymer solids) and plasticizer-free sealants after 24 months of north vertical exterior exposure in Cary, N.C. - 3. Comparison of dirt pickup, mildew and crack resistance of externally plasticized (caulk samples A and B) and plasticizer-free (caulk samples C and D) after 48 months of north vertical exterior exposure in Cary, N. C. - 4. formluation guidelines for achieving adequate low-temperature flexibility
- TABLES : 1. Suggested formulation ASTM C834/-17°C caulking sealant - 2. Suggested formulation ASTM C920 class 25 caulking sealant |
| En ligne : |
http://www.adhesivesmag.com/articles/95594-flexible-formulation-of-waterborne-ca [...] |
| Format de la ressource électronique : |
Web |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28954 |
in ADHESIVES & SEALANTS INDUSTRY (ASI) > Vol. 24, N° 7 (07/2017) . - p. 18-21
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