2003 Volume 2 Issue 1 Pages 1-10
Purpose : This study investigated the effect of immersion temperature on the flexural strength of a pre-coated E-glass fiber reinforced, UTMA-based composite resin. In addition, the effect of coating the fibers and the bonding agents on the flexural strength of the composites at two different temperatures was evaluated.
Materials and Methods : Continuous pre-coated glass fibers (impregnated everStick and preimpregnated StickTM-fibers) were placed parallel to the longitudinal axis of the specimen. The fibers were covered with a UTMA-based composite resin. The specimens were light- and heat-polymerized and then stored in a water bath at 37°C for 24 hours as well as at 70°C for 24 hours and for 7 days. After immersion, the flexural strengths of the specimens were measured and the fracture surfaces studied using SEM. The results were analyzed using statistical methods.
Results : After 24 hours at 37°C, the flexural strength values were between 603 and 676 MPa. There was no significant difference between the different types of glass fibers. At the high temperature (70°C), the flexural strength of the specimens containing pre-impregnated fibers deteriorated but the specimens containing impregnated fibers retained their flexural strength.
Conclusion : Within the limitations of this study, the results suggest that in the impregnated fibers, the bonding agent is evenly spread around the fibers. It is not possible for water molecules to diffuse into the matrix. However, further studies are needed to confirm the reasons why the flexural strengths of either the wetted (pre-impregnated) fibers or the composite resin decreased after 7 days' immersion at 70°C.
