Effects of Different Surface Treatments of Woven Glass Fibers on Mechanical Properties of an Acrylic Denture Base Material

Silanized glass fibers are popular reinforcements of acrylic denture base materials. To increase the number of surface hydroxyl groups and to improve interfacial adhesion between the matrix and reinforcements, acid or base treatments of glass fibers are commonly performed before the silanization. However, limited data are available on the effect of these treatments on the mechanical properties of acrylic matrix composite materials used for denture base applications. In this work, before the silanization of a woven glass fiber fabric (GF) with 3-(trimethoxysilyl) propyl methacrylate, activation pretreatments using HCl and NH(4)OH aqueous solutions have been performed. To characterize the glass surface, FTIR spectroscopy was used. Specimens of cured acrylic denture base resin and composites were divided into five groups: (1) cured acrylic denture base resin-control group; (2) composite with non-silanized GF; (3) composite with silanized GF; (4) composite with NH(4)OH activated and silanized GF; (5) composite with HCl activated and silanized GF. The flexural and impact properties of specimens were evaluated by means of three-point-bending tests and Charpy impact testing, respectively. The residual reactivity of the samples was analyzed using differential scanning calorimetry. The results of mechanical testing showed that acid and base pretreatments of the glass fabric had a positive effect on the flexural modulus of prepared composites but a negative effect on their impact strength. Possible interfacial adhesion mechanisms and the diffusion control of isothermal cure reactions due to vitrification have been discussed.