VISCOELASTIC CREEP CHARACTERISTICS OF NEAT THERMOSETS AND THERMOSETS REINFORCED WITH E-GLASS

The long-term creep behavior of vinyl eaters and polyesters have been studied as a function of curing conditions using flexural creep tests at ambient temperature (23 degrees C). Vinyl esters that have been cur ed at room temperature had a greater creep exponent (n similar to 0.20 ) for power law creep (t(n)) than vinyl esters that were postcured to crosslink completion at 93 degrees C (n similar to 0.12). Reinforcemen ts using woven glass fabric in the room temperature cured vinyl ester and the vinyl ester postcured at 93 degrees C gave much lower complian ces, but with approximately the same time exponents (n similar to 0.20 and 0.13, respectively). The vinylester without reinforcement was tes ted in creep after a variety of curing conditions: one day, one week, one month at room temperature; 49 degrees C for 4 h, 71 degrees C for 4 h, and 93 degrees C for 4 h. The total creep compliance as well as t he time exponent n decreased systematically with increasing cure condi tion and time, with a creep compliance for room temperature cure for o ne day that is 250% more than that for a neat vinyl ester cured for 4 h at 93 degrees C.