A Piezoelectric Minirheometer for Measuring the Viscosity of Polymer Microsamples

This paper describes the electromechanical design, operating principles and performance of a rheometer able to characterize the rheological behavior of microsamples of viscoelastic materials, such as polymer solutions, melt, and rubbers. It was developed with a view to portability, robustness, and ease of operation for very small samples. The rheometer operates by subjecting the samples to small-amplitude sinusoidal strain rates via an inverse piezoelectric actuator and detecting the stress response of the material via a direct piezoelectric sensor. The device operates under frequency-sweep mode in a very wide range of frequencies. Required sample sizes are typically three orders of magnitude smaller than for conventional rheometers. Owing to its lack of moving parts, the rheometer has an extremely simple design and is insensitive to vibration. Measurements on pressure-sensitive adhesives and other polymeric systems are presented and validated against a standard cone-and-plate rheometer.