International. A study conducted by an Indian paint manufacturer investigated the effect of branching in hyperbranched alkyds on the performance of alkyd polyurethane coatings.
The hyperramified alkyld was synthesized by a one-step approach using trimethylolpropane, monopentaerythritol as the core material, and propionic acid (DMPA) 2,2-bis (methylol), a combination of fatty acid from dehydrated castor oil and fatty acid from coconut oil as a chain extender.
A series of hyperbranched alkydes in different degrees of branching was prepared by changing the amount of DMPA in the resin formulation. The alkyds became polyurethane coating after reaction with hexamethylene diisocyanate trimer in the presence of dibutyltin dilaurate as a catalyst.
The effect of branching and entanglement of the polymer chain on the glass transition temperature Tg of the alkyd polyurethane coating (APUC) was studied. The performance of such APUC in terms of brightness, brightness retention under accelerated QUV radiation, natural outdoor exposure condition, mechanical properties and corrosion resistance was improved with increased entanglement of polymer chains, i.e. compactness or higher branching order in the alkyd resin structure.
Source: Applied Polymer Science.
