Synthesis and characterization of epoxy/methacrylic acid-based vinyl ester resin for corrosion resistance properties

The vinyl ester resin (VER) was synthesized using di-glycidyl ether Bisphenol A epoxy resin (E), methacrylic acid (MAA), and maleic anhydride (MA) as a catalyst and crosslinker. Benzoyl peroxide and hydroquinone were used as catalyst and inhibitor, respectively. The reaction was performed in a 3-neck round-bottom flask using a condenser at 128 °C for four hours to complete the polymerization reaction until the acid value became less than 10. Four different formulations E90MAA4MA6, E92MAA6MA2, E90MAA6MA4, and E88MAA6MA6 of E/MAA/MA were prepared to check the curing, mechanical, thermal, and corrosion resistance behavior of VER. FTIR analysis of the vinyl ester resin showed that the synthesis process involved an addition esterification reaction between the carbonyl and epoxy functional groups, proceeding selectively without the occurrence of side reactions. The resins were cured using 35 wt% styrene, 0.5% cobalt, and 1% methyl ethyl ketone (MEKP). Differential scanning calorimetry (DSC) was used to study curing behavior. The E90MAA4MA6 and E88MAA6MA6 samples show maximum Ti and Tg temperatures 89.4 °C, 104.7 °C and 47.8 °C, 95.3 °C, respectively. The sample E88MAA6MA6 shows maximum tensile strength of 12.05 MPa and E90MAA6MA4 maximum flexural strength of 65 MPa due to increased concentration of MAA and MA, which improves the crosslink density checked through universal testing machine (UTM). The samples were immersed in 25 wt% NaOH, 35 wt% HCl, 50 wt% H₂SO_4, and distilled water to evaluate their corrosion resistance. Among these four synthesized VER samples, E88MAA6MA6 and E90MAA6MA4 exhibited superior mechanical and corrosion resistance properties. These synthesized resins may be used for commercial applications like coatings of storage tanks, and base materials for pipe systems.