Synthesis and characterization of solvent-free hybrid alkyd resin with hyperbranched melamine core

In this study, a new hybrid alkyd resin was formulated using melamine-based hyperbranched polymer having 24 hydroxyl groups on its structure and relatively low molecular weight alkyd. The alkyd was synthesized using an oil mixture (40% linseed + 60% sunflower). Melamine was used as the core molecule for the hyperbranched polymer due to its excellent properties such as greater hardness, alkali and solvent resistance, and thermal stability. Melamine was first hydroxylated using formaldehyde and changed into hexamethylol melamine. This product was then twice hydroxylated with dimethylol propionic acid to obtain a hyperbranched polymer with 24 hydroxyl end groups. It was then reacted with low molecular weight alkyd resin at different proportions. The product had a low viscosity and could easily flow like oil. It is a solvent-free and water-free liquid. The ‘hyperbranched polymer/alkyd’ ratio affected physical properties of the liquid polymer and also the mechanical properties of the hardened polymer, which can be used for surface coating. The viscosity of the liquid resin decreases from 148 to 8.84 Pa.s as the hyperbranched-polymer-to-alkyd ratio is decreased from 1:3 to 1:24. On the other hand, the hardness of heat-treated resin decreases from 198 Persoz to 43 Persoz, respectively. That is, the increase in the amount of hyperbranched polymer in the resin increases hardness, whereas the increase in the amount of alkyd decreases it. The mechanical tests of hardened resins showed that all specimens passed conical mandrel bending test, and they all depicted high adhesion, and high abrasion and impact resistance. The specimens also had excellent gloss properties.