Techniques for Studying Liquid State Transitions in Polystyrene

Abstract

Various instrumental methods applied or developed at MMI over the past ten years to study liquid state transitions are presented. T>T _g transition studies with an emphasis on polystyrene are discussed. Instrumental techniques cover the areas of dielectric relaxation, thermal methods, dynamic mechanical relaxation, and computer statistical analysis of tabulated literature data, as well as the spectroscopic methods of Fourier transform infrared and electron spin resonance.

Thermal methods include differential scanning calorimetry, thermomechanical analysis, hot stage microscopy, and a new technique referred to as “photo DSC.” Two dynamic mechanical analysis techniques have been developed, the first employing a perforated shim stock support, and the second utilizing polymer blend encapsulation.

Computer statistical analysis procedures involve the application of a series of curve-fitting models to a set of data and evaluating the goodness of fit. Linear, quadratic, and higher order polynomials, as well as multiple linear regression models are tested. Goodness of fit is judged by the randomness in the residuals pattern, the magnitude of the standard deviation, and comparison between models. The use of derivative treatments applied to dielectric and dynamic mechanical relaxation data is also discussed.