A multifunctional mechanical Fourier spectrometer

Abstract

A multifunctional instrument for measuring viscoelastic characteristics of polymeric materials is described. The operational principle of this instrument is based on the method of mechanical Fourier spectrometry. An incoming signal represents white noise that, like an outgoing signal, is expanded into a Fourier series in frequency. The use of a highly sensitive displacement transducer and a high-precision electromagnetic actuator makes it possible to collect spectral functions in a broad frequency range with a fair level of reliability. For the tests of flowable media, deformation is performed so that the test sample is compressed between two plane-parallel plates. In the tests of rubbery and solid samples, loading is accomplished via a three-point bending procedure or deformation of a membrane. The instrument makes it possible to perform tests on small samples (a volume less than 0.25 μl) and solid films with a thickness of 10–300 μm. The interval of complex elastic-modulus measurements ranges from 10 Pa to 50 MPa in the regime of a rheometer and from 10 kPa to 100 GPa in the regime of a solid-body spectrometer. The frequency interval is 0–1 Hz, and the temperature interval ranges from −100 to +300°C under the isothermic regime or under scanning at a heating rate from 0.1 to 10 K/min. Examples of the experimental results are presented.