Viscoelastic Creep Characteristics of Neat Thermosets and Thermosets Reinforced with E-Glass

Abstract

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