Measurement of spherulite growth rates using tailored temperature programs

A method recently proposed for measuring spherulite growth rates (G) using temperature programs, tailored for each polymer, is reviewed. This method, compared to the conventional isothermal procedure, permits to expand the temperature range where spherulite growth rates can be measured. Examples of application of this method are reported, in particular, the spherulite growth rates of isotactic polypropylene (iPP) and poly(l-lactic acid) (PLLA) are analyzed. For iPP, growth rates were obtained from 112 to 148 °C using different cooling rates and a self-nucleation procedure. For PLLA, measurements in both isothermal and non-isothermal conditions allowed to overcome the difficulties due to the very high nucleation density that prevent determination of growth rates at low crystallization temperatures. For this polymer the entire curve of G vs. T was obtained.