Standard Test Method for Assignment of a Glass Transition Temperature Using Thermomechanical Analysis: Tension Method

Abstract

5.1 The glass transition is dependent on the thermal history, softening agents or additives of the material to be tested. For amorphous and semicrystalline materials the assignment of a glass transition temperature may lead to important information about thermal history, processing conditions, stability, progress of chemical reactions, and mechanical and electrical behavior. 5.2 Thermomechanical analysis provides a rapid means of detecting changes in hardness or linear dimensional change associated with the glass transition. Dimensional changes measured as a specimen is heated over the glass transition region may include the interaction of several effects: an increase in the coefficient of expansion, a decrease in the modulus, which under a constant stress leads to increased extension, stress relief leading to irreversible dimensional change (shrinkage in one dimension, expansion in another dimension), and physical aging effects which change the kinetics of the dimensional change. 5.3 This test method is useful for research and development, quality control, and specification acceptance testing; particularly of films and fibers.