EFFECT OF STRUCTURE ON PROPERTIES OF VINYL ESTER RESINS

The paper describes the synthesis of vinyl ester resins based on digly cidyl ether of bisphenol-A (epoxy equivalent = 450-465 g/eq) (VR resin ) and tetrabromobisphenol-A (epoxy equivalent = 380-420 g/eq) (VR-1 re sin). The viscosity of styrenated VR resin was higher than VR-1 resin. The effect of styrene and a-methyl styrene on curing of VR resins was studied. An increase in styrene from 30 to 50 wt% resulted in an incr ease in gel time and a decrease in exothermic peak. Addition of a-meth yl styrene delayed and depressed the exotherm. The mechanical properti es of VR resin sheets and glass fabric reinforced laminates were bette r than VR-1 resins; whereas LOI of VR-1 was higher. A resin formulatio n containing 20-30 wt% of VR:VR-1 showed optimum mechanical properties and LOI.