Abstract

A viscometer measures the rheological properties of polymers over a wide range of temperature, shear-rate and cure conditions, so that it can be used with extremely fast-changing resinous materials such as fast curing thermosets and fast crystallizing thermoplastics. The viscometer uses a mold made of three plates, clamped together during testing, with the center plate having at least one cavity (reservoir) and a slit from each reservoir to the ambient conditions outside the viscometer. Resin is injected into the reservoir in a short period of time. After filling the reservoir, the sample is heated to a test temperature through heat conduction from the reservoir wall. The heating is rapid because of the small thickness of the reservoir. The rapid filling and heating properties of the apparatus makes the rheology measurement of fast changing polymers possible. The sample is put under pressure by a piston and forced to continuously flow through the slit. At this slit, various measurements, including flow rate, pressure, temperature, and degree of cure are made. Using this instrument, the relationship between the viscosity as a function of temperature, shear-rate, and degree-of-cure can be determined.