The purpose of this study was to investigate flow characteristics of four commercial polyaddition-type silicone impression materials (Regular Type) before mixing.
Base and catalyst pastes were filler and polymer separated by a centrifugal separator with benzene for component analysis. As a result, weight fraction of filler was 39-55% and the chief ingredient was silica. The main polymer of base and catalyst pastes was polydimethylsiloxane. Especially, base polymer included hydrogen polydimethylsiloxane which was a crosslinking agent. The molecular weight (Mw) of these polymer was mostly about 40, 000-70, 000.
The viscosities of these pastes before mixing were measured by a cone-plate viscometer. Both base and catalyst pastes demonstrated pseudoplastic behavior which is the non-Newton flow. Particularly, base pastes showed thixotropic properties because of their clear hysteresis curves and time dependency on the viscosity. One of the base pastes had a yield value.
The inorganic filler significantly affected on flow characteristics of impression materials. The results suggested a means to manufacture impression materials with superior characteristics for working.