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 polye ster resin using benzoyl peroxide as an initiator. The isothermal kine tic 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 k now the rate equations. The results obtained through this adjustment w ere compared with those obtained by applying an autocatalytic model. T he kinetic parameters obtained by both methods permitted the simulatio n of the curing process inside and outside the experimental range of t emperatures. From the experimental results and the kinetic analysis, i t was possible to elucidate the dual mechanism of inhibition and retar dation exerted by hydroquinone. With the knowledge of the inhibition m echanism, we proposed a method for using the induction times to determ ine the kinetic parameters associated with the decomposition of the in itiator and/or the instantaneous inhibitor content in unsaturated poly ester resins.