A new micro-sample instrument for isothermal gel time determinations

An instrument developed to measure the gel time of solventless, thermally polymerizable compositions with speed, accuracy, and reproducibility is described. The instrument features and theory of operation are presented. By way of example, experimental results of gel times with a commercial electrical varnish measured at different temperatures and catalyst concentrations are reported. The commercial composition (Dolph´s cc-1105), which comes pre-catalyzed, is often used with additional catalyst as a further accelerator. New information is reported that concerns risky catalyst additions in which large variations in cure time could result.<>