The effect of trialkoxysilane coupling agent coatings on E-glass fibers on the flexural properties of fiber-reinforced composites
Abstract-The adhesion performance of five different trialkoxysilane coatings on E-glass fibers to an experimental bis-GMA-based resin was evaluated by measuring flexural properties of continuous fiber-reinforced composites. E-glass fibers were silanized with the following silanes: 3methacryloyloxypropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 1,2-bis-(triethoxysilyl)ethane and ureidopropyltriethoxysilane. The fibres were embedded into the bis-GMA resin system and light-polymerized to form test specimens with dimensions 2 mm¥2 mm¥25 mm (n=6). One sample group was without silane and the control group was with the original silanization by the manufacturer. The three storage conditions used for test specimens were: dry, 30 days or 6 months in water. Flexural strength of test specimens was measured. Fresh silane solution hydrolysis (activation) on E-glass fibers was monitored by Fourier transform infrared spectroscopy. After flexural testing, fracture surfaces were imaged with a scanning electron microscope. Statistical analysis (ANOVA) showed that the highest flexural strength for storage in water for 6 months, 399 ± 91 MPa, was obtained for the control sample (with the original silanization), and the lowest flexural strength value, 296 ± 25 MPa, was obtained for 1,2-bis-(triethoxysilyl)ethane. The highest flexural strength for storage in water for 30 days, 370 ± 63 MPa, was obtained using 3-methacryloyloxypropyltrimethoxysilane, and the lowest value, 278 ± 59 MPa, for ureidopropyltriethoxysilane. The hypothesis was that silanization with other trialkoxysilanes than 3-methacryloyloxypropyltrimethoxysilane might provide better flexural properties for E-glass fiber-reinforced composites (based on a bis-GMA resin system).