A PRA customer requested synthesis of a set of high solids hybrid alkyd resins to a literature recipe, and their subsequent formulation into a clearcoat for metal substrates, using cobalt-free driers. The baseline resin was a standard long oil alkyd based on isophthalic acid, pentaerythritol and soybean oil.
PRA initially carried out the synthesis according to the literature recipe, but some unexpected results were achieved, and further optimisation of the recipe was needed to meet our customer’s requirements. Following this work, a set of 3 resins were prepared for testing in formulations, incorporating different quantities of the hybridising resin.
The resins were formulated into a pigment-free coating to investigate differences in drying and adhesion performance.
The issue with the literature recipe was found to be a combination of recipe and process factors, which once resolved, allowed us to achieve acid values of <8 mg KOH g‑1 for both the alkyd control and the hybrid resins.
Hybridisation of the alkyd chemistry with the new resin produced coatings that dried faster than the standard long oil alkyd. Results are shown for the tack-free time determined using a drying recorder test.
In addition, better adhesion was observed for the coatings based on hybrid resins to both steel and aluminium substrates using the cross-cut test.
These experiments provided our customer with data to support marketing campaigns for their products.
Published polymer recipes are not always easily replicated, and specialist knowledge is often needed to fill in the gaps. Contact [email protected] for more information on how PRA can help you with your alkyd (or other) resin synthesis and testing.