Effects of Fluorinated Additives on Physical Properties of Composite Resins

Fluorinated monomer-containing composites reported so far have limited use due to their generally moderate strength resulting from the low-cohesive energy of fluoropolymers. Our previous research has shown that use of fluorinated additives, e.g., silane agent Fluorolink (S10), fluorinated monomers, and/or the silane-derived oligomeric 3-(methacryloyloxy)-propyltrimethoxysilane (OMPTMS) or the fluorinated oligomer OMPTMS-heptadecafluoro-decyltrimethoxysilane (O-F17DMTS), resulted in high-strength composites with certain formulations having reduced polymerization shrinkage stresses.

Objectives: Here we tested the hypothesis that the fluorine in S10 and/or O-F17DMTS would affect water sorption (WS), degree of conversion (DC), and/or flexure strength (FS).

Methods: Ethoxylated-bisphenol-A-dimethacrylate (EBPADMA) was modified with (0, 5, or 10) mass% of OMPTMS or O-F17DMTS. Composites were prepared from photo-activated resins and 75 mass-% BaO-glass fillers silanated with 3-[methacryloyloxypropyl]trimethoxysilane (MPTMS) or MPTMS+1mass-% S10. Composite bars [(2x2x25)mm] were light-cured for 1min/side. FS and corresponding DC of composites measured by FT-NIR were determined after 1d, 1w and 4w storage in water (n=5). Water sorption/solubility were determined following ISO#4049.

Results: FS ranged from 78±17MPa to 141±22MPa and DC from 72% to 97%; they were not correlated. Mean WS ranged from 0.34 to 0.43 and mean solubility from 0.007 to 0.029 mass-%, respectively. For FS 2-way-ANOVA found no differences between times, but highly significant effects from resin composition with oligomer-containing composites having higher FS (p<0.001), whereas DC was affected by both time and composition (p<0.001).  S10 had a small but significant strength-lowering effect (p=0.016).  There was no significant difference in water sorption due to monomers or the presence of S10 (2-wayANOVA; p>0.05). The solubility was, however, affected with EBPADMA+O-F17DMTS having significantly lower solubility than EBPADMA alone (1-way-ANOVA, Holm-Sidak, p<0.05).

Conclusions:  While the fluorine added through S10 or O-F17DMTS did not reduce WS, addition of the silane-based oligomers OMPTMS or O-F17DMTS increased FS compared to EBPADMA-based composites and O-F17DMTS reduced the solubility.

Support: ADAF; NIST; NIDCR-Grant-DE13298.