Automated Dynamic Mechanical Testing

Abstract

During the past 10 years a number of fully automated instruments for the dynamic mechanical testing of polymers became commercially available. Our purpose is to provide an introductory survey that covers key references, the goals of such test methods, general but not specific differences between the several types of instruments, and factors to consider in choosing an instrument. These latter topics include fixed vs. variable (resonant) frequency, frequency range, resolving power, types of specimens that can be handled, and maintenance costs. We also emphasize that all suppliers and users of such instruments are striving to improve and/or extend the range of capabilities of their respective instruments. A special section discusses the problem of determining activation enthalpies for any loss process. Finally, we point out that parallel developments are occurring in dielectric testing via new techniques: automated self-balancing dielectric bridges, and new methods of treating dielectric data. Thermally stimulated creep and thermally stimulated current are relatively new methods. We consider these alternate techniques as both competitive with, and complementary to, dynamic mechanical methods. Possible artifacts introduced by the use of porous substrates to support fluid polymers are discussed and dismissed.^JENERAL ASPECTS OF DYNAMIC MECHANICAL and dielectric testing, automated or not, are discussed in this chapter. Background material is given in References 1-10. For many years I collected transition and relaxation temperature data from the literature, whether obtained by static methods such as thermal expansion or by dynamic methods including both mechanical and dielectric loss. This endeavor pro-0065-2393/83/0203-0003$06.75/0