Ecofriendly VERs using renewable sources, e.g., cardanol from cashew nut, can be synthesized to reduce viscosity, curing time, and concentration of styrene. VERs prepared from rosin-acid-based epoxy resin have been reported, with improved coating abilities of VERs due to faster drying and better chemical resistance. Carbohydrate-derived isosorbide can be used as core scaffold to synthesize novel and innovative VERs with extremely low viscosity. These can fulfill the requirement of high-performance composite resin since these have higher cross-link density and give a high Tg value of 245 ± 9 ° C compared with any other commercially available VERs. These have the potential to be used as viscosity modifiers without adversely affecting any other qualities of the matrix material for high-performance composite resin.
Aliphatic matrix resins derived from cycloaliphatic VER and glutaric acid showed reduced UV absorption. These can be used to obtain coatings and fiber-reinforced composites with extreme durability to sunlight. Photostabilization of VER was also reported by synthesized interpenetrating polymer network modified lignin. These resins also show excellent thermal stability and good shore hardness. Attempts have also been made to obtain VE bio-copolymer derived from dimer fatty acid polymerized with glycidyl methacylate and maleic anhydride modified dimer fatty acid polymerized with glycidyl methacrylate resin. These were further copolymerized with styrene and have been shown to exhibit superior mechanical and thermal properties.
The use of VERs as coating material has gained increasing popularity since the 1990s. Nowadays, VER are being used as new-generation self-healing coatings. These coatings have a self-protective ability to smartly resist mechanical and chemical damages caused by external aggressive environment. VERs containing TiO 2 particles have been reported as a self-healing coating material for aluminum alloy 5083, which guard the metal surface. In case of abrasion to the coating, the aluminum is said to react with BPA, which is a chemical precursor of VER, and forms a barrier at the damaged part, where these rutile particles serve as receptacles for the BPA. This diminishes the damage by the external hostile conditions on the surface.
E-glass and Kevlar-49 fiber-reinforced VE laminates have been reported to be used in ballistic applications. It has also been described that by optimization of loading of short aramid fibers and external variables (standoff resistance, impingement angle, erodent size, impact velocity, etc.), erosion or wear performance enhancement of short aramid-fiber-reinforced VER composite can be successfully achieved.