Water-sorption kinetics of dental polymeric resin under tensile stressing conditions
Titel:
Water-sorption kinetics of dental polymeric resin under tensile stressing conditions
Auteur:
Y. Oshida J. Gorthy
Verschenen in:
Bio-medical materials and engineering
Paginering:
Jaargang 9 (2001) nr. 2 pagina's 125-133
Jaar:
2001-04-01
Inhoud:
Water sorption tests were conducted on unfilled poly(methyl methacrylate) samples in distilled water at 5, 37, and 60\,^{\circ}C under three different tensile stress ratios (\sigma_{\rm appl}/\sigma _{\rm ys}= 0%, 5%, and 10%). Each sample was placed in a modified Hoffman open-side tubing clamp and subjected to four-point bending at pre-determined stress level for 1 day, 3 days, 1 week, 2 weeks, and 4 weeks. Water sorption was measured by weight change calculations, without accounting for any weight loss due to solubility of uncured monomer. A generalized diffusion equation can be used to express both stress-free and stress conditions; D=D_{\rm o}\exp[-E(\sigma)/kT]. It was found that the activation energy for water sorption diffusion was linearly related to applied stress ratios; i.e., E=1.15\ \sigma_{\rm appl}/\sigma_{\rm ys} + 10.76 (kJ/mol), with the correlation coefficient r =0.97. Since the proportional pre-exponential constant, D_{\rm o}, is independent of temperature, it is speculated that the loading percentage of reinforcing filler elements in composite resin materials can be related to this constant.
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