Expansion and shrinkage of fibers. Load- and temperature modulated TMA measurements temperature calibration of fiber attachments

The thermal behavior of a drawn PET fiber has been investigated by thermome chanical analysis, TMA, and by differential scanning calorimetry, DSC. Abov e the glass transition temperature of 79 degrees C, the fiber shrinks to a maximum of 8% of the initial length. Temperature modulated TMA enabled the separation of the thermal expansion from the overlapping shrinkage during t he first heating and to calculate the expansivity, alpha(e) and the shrinka ge coefficient, alpha(s), independent of each other. Young's modulus, E, wa s measured by TMA with modulation of the tensile stress. Hence, it was poss ible to record the behavior of alpha(e), alpha(s) and E during the structur al changes by combining both modulations in a single measurement. A new technique was developed to calibrate the sample temperature. With thi s, accurate control of the modulated temperature of the specimen was achiev ed, independent of the changing heating rate.