Abstract
Rheological investigations aim to provide an understanding of the stress-strain-time-temperature relationships for materials; our current understanding results from numerous studies illustrating various approaches to the problem. Although each approach reflects the interests of the investigator, the nature of the materials being studied, and the general state of development of the field at the time, an underlying objective is to relate observed rheological behavior to molecular structure and molecular processes. Toward this end, the two general approaches mentioned by Professor Lazan are important: the phenomenological or macroanalytical, and the solid-state or micromechanistic. (When considering materials such as polymers the latter can be called the molecular theory approach.)