Measuring glass transition temperatures of polymers by using phase-stepping shadow moiré

Abstract The glass transition temperature (T g ) is a crucial factor in the applications of polymers. Therefore, various methodologies for T g measurement have been developed. However, although full-field optical methods have been used in a wide range of areas and provide the advantages of high sensitivity and noncontact measurement, they have not been applied to characterize glass transition behavior for T g measurement. Therefore, a full-field optical deflection measurement method, namely phase-stepping shadow moire (PSSM), was employed to observe the glass transition phenomenon of a polymer and determine its T g . The resolution of the PSSM system applied for deflection measurement in this study was 1.56 μm. A polystyrene (PS) strip was employed to demonstrate the suitability of PSSM for T g measurement. The results indicated that the glass transition of a PS strip could be clearly determined by PSSM; the T g was found to be 98 °C, which is close to the measurement result of other presently used methods. Therefore, this study shows that PSSM is a viable, low-cost, and easy-to-use technique that can be used to measure the T g of polymers.