FTIR studies of the curing reactions of palm oil alkyd-melamime enamels

Three alkyds of high hydroxyl numbers with oil lengths of 21, 30, and 41 were prepared from crude palm oil. The excess hydroxyl groups provided good compatibility with melamine resins, and also served as sites for crosslinking reactions. They were made into baking enamels by blending with 20% of a commercial melamine resin. All of them could be cured at temperatures below 200 degreesC although thermodecomposition might occur above 290 degreesC. The dry-hard time of these enamels cured at temperatures between 140-180 degreesC ranged from 10 to 180 min. Fourier transform infrared spectroscopy could be used to follow the major curing reactions. The absorbance of-O-H and -N-CH2-OCH3 groups showed significant reduction. The changes in the absorbance of these peaks with time and temperature were investigated. The predominant reaction was identified as the formation of methylene ether linkages. However, the self-condensation reactions of the amino resin and ester linkages did not occur to any noticeable extent. (C) 2001 John Wiley & Sons, Inc.