New Promoter System for the Oxidative Curing/Drying of Unsaturated Polyester Resin Based on Ascorbic Acid Metal Complexes of Cobalt and Copper
Unsaturated polyester resin (UPR) can be transformed into valuable and high quality industrial parts like gears, spools, pipes, etc. Curing/drying of UPR required organic peroxide as a source of radical flux. Most commonly used organic peroxide is methyl ethyl ketone peroxide, MEKP. At ambient temperature MEKP provides the flux of radicals very slow, therefore, certain active transition metal salts are added as promoters. These promoters catalyzed the oxidative decomposition of peroxide into radicals hence curing/drying of UPR increases. The efficiency of the promoters depends on the stability of metal salts. In this paper we synthesized ascorbic acid complexes of cobalt and copper with different ratio of metal to ligand and investigate their curing/drying property in comparison with cobalt naphthenate a conventional promoter. The results showed that all complexes are promoters in drying/curing of UPR. The complex with 2:1 ligand to metal ratio is found to be more active in drying/curing of UPR in comparison with 1:1 ligand to metal ratio.