A New Approach to Capillary Extrusion Rheometry

A capillary extrusion rheometer has been developed which circumvents many of the problems of traditional hypodermic principle rheometers. The capillary is enclosed in a hollow plunger driven at a series of fixed rates into a barrel containing the test sample. Drawbacks observed with traditional viscometers have been obviated, for example, entrapment of air between the sample and the plunger leading to gas compression effects, gross motion of the fluid in the barrel leading to fluid structure breakdown and difficulties in determining plunger/barrel friction contributions. With strict temperature control, it has been shown that absolute values for fluid flow properties could be determined on small samples quickly and easily with an accuracy of ±0.5%.