Water sorption, solubility and effect of post-curing of glass fibre reinforced polymers

Different polymer matrices are used for dental glass fibre composites. The aims of this study were to determine water sorption and solubility of glass fibre composites with different polymer matrices. In addition, the effect of post-curing of matrix polymers with heat on the water sorption and solubility values was investigated. Commercial one-phase and two-phase (powder–liquid) monomer systems were used in polymer matrix of E-glass fibre composite. Rhombic unreinforced and fibre reinforced test specimens were polymerized by autopolymerization or by light only, or additionally post-cured with heat. Water sorption and solubility determination method was based on ISO/DIS 1567–1997 draft for international standard with 7 d immersion time. In addition, water sorption was measured at second time for 30 d immersion time to determine saturation time of test specimens by water. Five test specimens of unreinforced polymer and reinforced polymer were tested and the quantity of fibres was determined by combustion analysis. Water sorption values of different brands of polymer matrices ranged from 0.9 to 8.3 wt% (P<0.001, ANOVA). High sorption values were explained by microscopic voids in the polymer matrix and by composition of polymer matrix. Solubility values ranged from 0.02 to 2.5 wt% (P<0.001, ANOVA). Generally, fibre inclusion and post-curing of polymer matrix reduced water sorption and solubility. The results of this study suggest that the water sorption and solubility of fibre composites varies according to the brand of polymer matrix and homogenity of polymer matrix. Water sorption of polymer matrix might influence hydrolytic stability of polymer–glass fibre composite.