THE APPLICATION OF STATISTICAL PROCESS-CONTROL TO RHEOLOGICAL MEASUREMENTS

This article presents data on and discusses the application of statist ical process control (SPC) to rheological measurements. With the help of case studies on capillary rheometry and dynamic oscillation, it is shown how SPC, coupled with careful calibration and maintenance of rhe ometers, can demonstrate significant improvement in the accuracy and p recision of rheological measurements. This improvement is evident on e xamination of the various control charts discussed and the narrowing o f their control limits. Specifically, individual and moving range cont rol charts for the apparent viscosity measured at an apparent shear ra te of 100 s(-1) using capillary rheometers are discussed. For the dyna mic oscillatory rheometer, the charts presented are for the magnitude of the complex viscosity measured at a frequency of 1 Hz. This article shows how SPC provides quality assurance by assuring that erroneous d ata will not be inadvertently reported. The issues discussed are of un iversal interest and relevance, not only to rheologists, but to all sc ientists and engineers who make and/or use measurements. (C) 1995 John Wiley and Sons, Inc.