Effects of inhibitors and retarders on low temperature free radical crosslinking polymerization between styrene and vinyl ester resin

Many composite manufacturing methods are room temperature processes, which require the resins to be cured at low temperatures. Examples are Seemann Co mposite Resin Infusion Molding Process (SCRIMP)-a vacuum assisted resin tra nsfer molding (VARTM) process, hand lay-up and spray-up. Vinyl ester resins have been widely used in this type of processes because of their versatili ty as a composite matrix. Low temperature polymerization between styrene an d vinyl ester tends to be complex because of the presence of different curi ng agents. This paper reports on 1) the effects of a promoter (cobalt napht henate) on the initiation at low temperatures, and 2) the effects of a reta rder (2,4-pentanedione) and an inhibitor (1,4-benzoquinone) on the pot life , gel time, and cure kinetics. A differential scanning calorimeter (DSC) an d a Fourier transform infrared (FTIR) spectrometer were used to investigate the reaction kinetics of vinyl ester resins. The influence of the retarder s and inhibitors on the theological changes of the resin during curing was also studied using a Rheometrics Dynamic Analyzer (RDA).