Vinyl ester resins (VERs) are high-performance unsaturated resins derived by the addition reaction of various epoxide resins with α-β unsaturated carboxylic acids. These resins have always been classified under unsaturated polyester resins. However, VERs have remarkable corrosion resistance and superior physical properties as compared with these conventional polyester resins, which make VERs a class of their own and hallmark of today's resin industries. Hence, there is a need to review the available literature on this important class of thermosetting resins separately. In this article, an attempt is made to review the state of the art of VERs, including synthesis, characterization, curing, thermal, chemical, oxidative properties, and applications. The main focus is on the latest developments in this area.

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Multifunctional bio-based epoxy resin (PEMPAE) was synthesized by reacting Diels-Alder adduct of gum rosin and maleic anhydride (MPA) with pentaerythritol to get the esterified product (PEMPA) which was further epoxidized using epichlorohydrin and potassium hydroxide. This paper includes the synthesis of bio-based imidoamine curing agent (IAEDK) by reacting diamino diphenyl ether (DDE) with dimaleopimaryl ketone (DMPK), a dehydrodecarboxylated derivative of MPA. The synthesized products were characterized by Fourier transform infrared Spectroscopy (FTIR), proton and 13 C nuclear magnetic resonance spectroscopy ( 1 H-NMR and 13 C-NMR). Curing dynamics of rosin-based epoxy cured with rosinbased imidoamine crosslinker were evaluated using differential scanning calorimetry (DSC) and were compared with resin cured with synthesized DMPK and commercial DDE curing agents. The mechanical properties and thermal stability of the cured epoxy samples were evaluated using a universal testing machine (UTM) and thermogravimetric analyzer (TGA), respectively. The chemical resistance of the samples was determined in terms of % weight loss when immersed in NaOH, HCl and NaCl solutions. The morphological changes were also evaluated via scanning electron microscopy (SEM). Results revealed that rosin-based epoxy cured with imidoamine curing agent gave preeminent properties over the commercial one. The studies suggested that curing properties were greatly affected by the molecular topology and kind of curing agent used.

Rosin‐modified o‐cresol novolac epoxy resin (AEOCN) was synthesized by condensation of rosin acid with o‐cresol formaldehyde novolac resin (AOCN). The AEOCN resin was further epoxidized using epichlorohydrin and sodium hydroxide. Rosin‐based imidoamine curing agents (IAMDK, IASDK, and IAEDK) were also prepared by reacting dimaleopimaryl ketone (DMPK), a dimerized rosin product with aromatic diamines. The chemical structures of all synthesized products were confirmed by FTIR, 1H‐NMR, 13C‐NMR, and DEPT‐135° spectroscopic techniques. The curing process of rosin‐modified epoxy cured with imidoamine crosslinkers was studied using differential scanning calorimetry (DSC) and the results were compared to o‐cresol novolac epoxy resin (EOCN) and some previously reported commercial‐based systems. The thermal and mechanical properties of the cured epoxy thermosets were determined using a thermogravimetric analyzer (TGA) and a universal testing machine (UTM), respectively. The chemical resistance analysis was carried out by immersing cured epoxy coated panels in 1M NaOH, 1MHCl, and 1M NaCl solutions. The results were evaluated in terms of % weight loss method and the morphological changes that appeared due to chemical exposure were also investigated via scanning electron microscopy (SEM). This study presents the economical synthetic approach towards high‐performance bio‐based epoxy coating materials impending to replace some of the petrochemical compounds in coating industries.

Methacrylated lignin model compounds (LMCs, i.e., eugenol and guaiacol) monomers are ideal candidates as styrene replacements because they have low volatilities and can free-radically polymerize with vinyl ester resins. This article reports the synthesis of methacrylated eugenol (ME), methacrylated guaiacol (MG) using LMCs and methacrylic anhydride in the presence of 4-dimethylaminopyridine (DMAP) as a catalyst. ME and MG were characterized using FT-IR, 1 H-NMR and 13 C-NMR. The thermal and mechanical properties of the samples prepared at 30°C from o-cresol epoxy based vinyl ester resin (VEOCN) using MG and ME, respectively, as reactive monomers, in the presence of benzoyl peroxide (2 phr) as initiator were further investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA/DTG/DTA) and universal testing machine (UTM). Chemical and corrosion resistance of cured VEOCN samples coated on steel panels were also evaluated as a function of percentage weight loss and with the help of scanning electron microscopy (SEM), upon immersing the VEOCN samples in 1 m HCl, 1 m NaOH and 1 m NaCl solutions for 90 days. Thermal, mechanical and chemical performance of VEOCN using ME and MG was also compared with VEOCN samples containing styrene and methyl methacrylate (MMA) as reactive monomers.

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Vinyl ester resin (VEOCN) was prepared from o-cresol epoxy resin (EOCN) and methacrylic acid in the presence of triphenyl phosphine as catalyst and hydroquinone as inhibitor with acid value of ~ 7 mg of KOH per gram of solid. O-cresol based novolac resin (OCN), OCN based epoxy resin (EOCN) and VEOCN were characterized by Fourier transform infra red spectroscopy (FT-IR), 1 H-NMR and 13 C-NMR. The thermal and mechanical behavior of the samples prepared at 30°C from VEOCN using styrene and methyl-methacrylate respectively as reactive diluents, in the presence of benzoyl peroxide (2 phr) as initiator was studied using Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA) and Universal Testing Machine (UTM). Chemical resistance of above VER samples was also evaluated as a function of % weight loss and with the help of Scanning Electron Microscopy (SEM), upon immersing the VEOCN samples in different solutions for 90 days.

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