Synthesis and curing of cardanol-based vinyl ester resins for applications in surface coatings -I

摘要

Cardanol-based vinyl ester resin was synthesized by reacting the epoxy resin and methacrylic acid at an equivalent ratio of 1.0/ 0.9 in presence of triphenylphosphine (TPP) catalyst (1% by weight of the epoxy resin) and hydroquinone (200ppm as inhibitor) at 85°Cin nitrogen atmosphere. The structural changes during the synthesis of VER were studied by Fourier-transform infrared spectroscopic (FT-IR) analysis. Gel permeation chromatographic (GPC) analysis gave the number - average molecular weight of cardanol-based epoxy resin (CNE) to be 780 gmole-1. A structure of synthesized cardanol - based VER was also proposed. A comparative study of vinyl ester resins (VERs), synthesized by using two different epoxy resins i.e. indigenous synthesized cardanol-based epoxidized novolac resin (CNE) and market procured 1138 EPN epoxy resin (EPN), was done in the present investigation. The resins were cured by using the mixture of resin, styrene and benzoyl peroxide in the ratio of 10:4:0.2 (w/w). Differential scanning calorimetric (DSC) technique was used to investigate the curing behaviour. It was found that the maximum peak temperatures for curing, in both the cases, were almost same. So, the cardanol-based VER may prove an alternative to EPN based VERs. Also, these resins may be environmentally friendly.