EFFECT OF THE INHIBITOR ON THE CURING OF AN UNSATURATED POLYESTER RESIN

Differential scanning calorimetry has been used to study the influence of hydroquinone as an inhibitor on the curing of an unsaturated polyester resin using benzoyl peroxide as an initiator. The isothermal kinetic analysis was performed by isoconversional adjustment ln t = A + E/RT. This adjustment makes it possible to predict the variations in the activation energy with the degree of conversion without the need to know the rate equations. The results obtained through this adjustment were compared with those obtained by applying an autocatalytic model. The kinetic parameters obtained by both methods permitted the simulation of the curing process inside and outside the experimental range of temperatures. From the experimental results and the kinetic analysis, it was possible to elucidate the dual mechanism of inhibition and retardation exerted by hydroquinone. With the knowledge of the inhibition mechanism, we proposed a method for using the induction times to determine the kinetic parameters associated with the decomposition of the initiator and/or the instantaneous inhibitor content in unsaturated polyester resins.