Torsional Braid Analysis (TBA) of Polymers

Abstract

A review is presented of the development and application of an adaptation of the freely hanging and freely decaying torsion pendulum (TP) which uses supported specimens to characterise polymeric materials. A composite, well-aligned specimen is easily prepared by impregnating a substrate such as a glass braid (TBA) with a polymer solution and thermally removing the solvent from the mounted specimen in the apparatus. The technique is particularly suitable for characterisation of materials which are available in limited quantities, of liquids which solidify on cooling or heating, and of thermohysteresis effects. The major topics discussed are instrumentation and automation, including methodology for control and data processing using a desktop digital computer; experimental technique; structure-property relationships in linear polymers; the Tu (i.e. T > Tg) relaxation in styrene polymers; and analysis of the thermosetting process in terms of a time—temperature—transformation (TTT) state diagram which relates the process of cure to properties of the cured state. The automated instrument is an analytical tool which can be used to examine most polymeric and oligomeric materials by using either supported specimens (TBA) or unsupported specimens (TP).