Surface wettability modification of poly(vinyl siloxanes) with nonionic surfactants

Abstract

Poly(vinyl siloxanes) are widely used as dental impression materials because of their superior dimensional accuracy and stability in comparison with the other elastomeric impression materials. However, the materials have low surface free energies, making them difficult to wet with the gypsum slurries which are subsequently poured into the impressions. The resultant bubble entrapment discourages their use. In this study, polyy(vinyl siloxane) impression materials were modified by the incorporation of members of a homologous series of nonylphenoxypoly(ethyleneoxy)ethanols and selected surfactants of substantially different chemistries. Contact angles with saturated aqueous gypsum and bubble counts in critical impressions were determined. The resultant contact angles fit a bilinear regression curve when angle is plotted against surfactant HLB number. For members of the homologous series, contact angles for surfactant blends were as predicted by the results for the pure components. Blends of surfactants with markedly different chemistries produced neither a clear minimum contact angle nor a bilinear curve of contact angle versus HLB. For the optimal surfactant, the improved wetting was substantially unaffected by rinsing. The improved wettability for optimally surfactant modified elastomer was reflected by the marked decrease in bubble counts in gypsum pours. The surfactant addition did not significantly degrade either dimensional accuracy or stability.