NIR-spectroscopic investigation of water sorption characteristics of dental resins and composites

✍ Scribed by Venz, S. ;Dickens, B.

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 842 KB
• Volume: 25
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/jbm.820251005

✦ Synopsis

Abstract

A near infrared (NIR) method using the 5200 cm^−1^ absorption of water has been employed to examine water absorbed in photopolymerized dental resins and composites in the form of 0.01‐cm‐to 0.15‐cm‐thick specimens. The concentration, c [mol L^−1^], of absorbed water in specimens of thickness t [cm] was calculated by means of Beer's law, A = ϵct. A is the NIR absorbance and ϵ is the absorptivity of absorbed water. ϵ depends on the environment of the water molecule and it is necessary to estimate ϵ for water in each material. Water sorption was determined gravimetrically and correlated to the absorbance in the NIR spectrum. Once the relationship between ϵ and water content was known for a material, water sorption was determined rapidly on very thin specimens for faster equilibration. Where dissolution of the specimen occurred, the solubility behavior of the specimen was evaluated from a comparison of NIR and gravimetric measurements. The NIR absorptivity, ϵ, of water absorbed in a polymeric medium was found to be inversely related to the degree of hydrophilicity and hydrogen bonding capability of the polymer. The presence of water clusters in a polyethylene oxide methacrylate polymer was inferred from convex‐up curvature in the plot of ϵ vs. water content.