Effect of molecular weight on spherulite growth rate of poly(ethylene terephthalate) via real‐time small angle light scattering

Abstract

The effect of molecular weight on the spherulite growth rate of poldethylene terephthalate) (PET) has been determined using a real-time small angle light scattering (RTSALS) device equipped with a two-dimensional position-sensitive detector. This detector, the design of which was previously reported, incorporates a CCD camera, a personal computer, and a n imaging board as the major hardware components. The device performs real-time analysis of the light scattering pattern and calculates the average spherulite radius as a function of time during the crystallization experiment. Growth rate data were obtained for PET having number-average molecular weights of 18,000, 24,700, and 33,100. Samples were crystallized isothermally following a temperature jump from the glass at room temperature to the desired crystallization temperature, which ranged from 130 to 200°C. Both the temperature and molecular weight dependence were found to be well described by the Hoffman equation. The temperature dependence agrees well with that found by previous workers, but the molecular weight dependence is somewhat different.

Crystallisation kinetics of novel branched poly(ethylene terephthalate): a small‐angle X‐ray scattering study

“…Typically, with an increase in molecular weight (or correspondingly an increase in the IV) there should be a decrease in the rate of crystallisation, due to the time required for longer chain lengths to disentangle and reorient. 32,33 However, in the case of the branched PET produced in the present study, it was clear that the rate of crystallisation was increased. Also, L p at time zero for the branched PET (160Å) was significantly smaller than that observed for the unprocessed PET (180Å).…”