06/08/2011

www.gupta-verlag.de/polyurethanes

Pot life and curing monitor for PU formulations, epoxy and polyester resins

The SubCASE HT (fig. 1) combines dielectric polarisation measurement and temperature measurement of reactive test samples. The dielectric polarisation reveals the electro-chemical process during compound formation and crosslinking. From this conclusions can be drawn regarding the pot life and the curing behaviour of the material. The heatable CMD sensor (Curing Monitor Device), introduced by the measuring instrument specialists from Karlsruhe, is measuring the dielectric features of the reactive components by applying an alternating voltage of different frequencies. The heat release from the polymerisation reaction is recorded as the core temperature by a thermocouple centrically positioned inside the sample. A further temperature sensor is integrated into the CMD sensor for measuring the contact temperature of the sample and for controlling the heater power. Providing starting temperatures as high as 150 °C, the test device is especially suitable for measuring the reaction profile of epoxy resins. Production near testing conditions can be achieved by heating the CMD sensor to any reaction relevant temperature. The reactive test material is poured into a cardboard cylinder, the bottom of which is the heated CMD sensor. The test set-up is covered by an insulation hood with a bushing for the thermocouple. Fig. 2: Reaction profile of an epoxy resin measured with SubCASE HT. The pot life and the curing are determined by the dielectric polarisation measurement. The master indicates the margins for quality assurance testing.The software SubCASE continually records the measurement data and displays them in an online graph. After completion of a test, the results are shown as diagrams (fig. 2) and in a parameter list. The pot life is defined as a certain value of the polarisation curve. The software calculates the curing from the dielectric polarisation gradient. Due to a protection foil on the CMD sensor the cured sample can be removed easily from the device. SubCASE HT can be used in quality assurance as well as in production control applications.

www.gupta-verlag.de/polyurethanes