A DEVICE FOR STUDY OF POLYMER CRYSTALLIZATION KINETICS VIA REAL-TIME IMAGE-ANALYSIS OF SMALL-ANGLE LIGHT-SCATTERING

A two-dimensional position-sensitive detector for real-time small-angle light scattering (RTSALS) of polymers is described. The device performs real-time image analysis of the evolving light-scattering pattern during crystallization. Such an approach provides a means of simultaneously measuring the rate of spherulite growth and the overall rate of crystallization, allowing calculation of nucleation density and/or rate. Although separation of nucleation effects from growth effects typically requires the application of two different experimental techniques, this device is unique in that it, allows these two effects to be easily separated using only time-dependent light-scattering data. The device incorporates a CCD camera, a personal computer, and an imaging board as its major hardware components. Software designed specifically for this application performs real-time analysis of the light-scattering pattern at a rate of 1-3 images per second, thus allowing study of even moderately rapidly crystallizing polymers. (More recent software modifications have resulted in a speed enhancement to 5 images per s and further improvement is expected.) Intensities at various scattering and azimuthal angles are plotted at each time. In addition, the average spherulite radius is calculated and plotted. Application of the device is illustrated by measuring the spherulite growth rate of poly (ethylene terephthalate) as a function of temperature.