Objective: When filler is silanated, silane coupling agent forms a bi-layer, consisting of the chemisorbed and physisorbed layer. However, the effect of physisorbed silane on composite has not clearly confirmed. The objective of this study was to clarify the effect of physisorbed silane on flexural properties of composite. Methods: A spherical silica filler of a diameter of 1.5mm was silanated with to γ-methacryloxy-propyltrimethoxysilane at 0.66, 2.64 and 5.28 mass%. Silane physically adsorbed on the filler when more than 0.66 mass% was employed. Half of silanated filler was then subjected to tetrahydrofuran (THF) washing in order to remove physisorbed silane. Therefore, six groups of filler were prepared, and used for photopolymerized experimental composites at a filler loading of 65 mass% with UDMA/TEGDMA. Six bar-shaped specimens, 2x2x25mm, of each composite were photopolymerized, and tested after immersion in 37°C water for 24 hours. All specimens were subjected to a 3-point bending in 37°C water. Data were analyzed using 2-way ANOVA and Tukey HSD at p<0.05. Results: Means±s.d.s of flexural strength (FS) and flexural modulus (FM) are summarized in table.
|
Amount of silane |
0.66 |
2.64 |
5.28 |
|||
|
THF washing |
- |
+ |
- |
+ |
- |
+ |
|
FS/MPa |
93.6±7.2 |
95.5±4.9 |
99.4±8.3 |
97.6±6.2 |
103.3±9.3 |
100.9±8.2 |
|
FM/GPa |
4.1±0.1 |
4.1±0.3 |
4.3±0.3 |
4.4±0.2 |
4.1±0.2 |
4.3±0.3 |
No significant difference was found with respect to both 2 main factors and their interaction regarding FS; however, a significant difference was detected only the main effect of the amount of silane coupling agent regarding FM. Conclusions: These results suggest that physisorbed silane did not strongly affect on flexural properties of composites.