The Effect of Metal Reinforcement of a Polymer Matrix Composite

The development of novel and more durable amalgam alternatives is an ongoing strategic goal of the NIDCR. Here, we investigate the use of metal particulate and novel coupling mechanisms for improving polymer-matrix composite perfomance. OBJECTIVE: To evaluate the effect of metal particle reinforcement and functionalized thiol couplers on the fracture strength of a polymer matrix composite. METHODS: X-ray Photoelectron Spectroscopy was used to determine optimal cleaning protocols for deposition of a functionalized thiol on silver particles. Cleaned silver was immersed in an experimental thiol solution, rinsed, and dried. A composite made by dispersing the silver-thiolate in a comonomer was placed into a mold for fabricating samples for DTS measurements and polymerized (Group A). In addition, samples consisting of resin reinforced by neat silver particles (Group B), resin only (Group C), and resin reinforced by silanated ceramic particles (Group D) were fabricated (n=10 per group). A separate set of samples for Groups (A) and (D) were stored in water at 37 degrees C for 7 days, and submitted to fracture tests. RESULTS: The mean stress at failure (MSAF) in MPa and (SD) for each of the air-stored groups was: (A) 123.1 (22.6); (B) 81.1 (11.5); (C) 32.3 (15.3); (D) 62.1 (13.0). For water-stored samples, MSAF for Groups (A) and (D) were respectively 121.5 (29.2) and 43.9 (12.0). ANOVA and post-hoc tests were used for data analysis. MSAF for the silver-thiolate composite was significantly greater (p<0.01) than that of the other groups. Additionally, water storage did not degrade DTS. CONCLUSION: Silver particles coupled to a resin via a thiol linkage reinforce a polymer matrix composite. Compared to a silane-coupled ceramic composite, the metal-thiol bond is stable in water. Further, a metal-polymer composite may have utility as a more durable amalgam alternative compared to conventional ceramic reinforced composites. Supported by NIH/NIDCR grant R43DE013464.