An instrument for determining the rate of crystallization of polymer from melt by depolarized light intensity method is described

and satisfactory results were obtained for isotactic polypropylene and nylon 6 samples. This method possesses following advantages: (1) only a small amount of sample is needed; (2) the crystallization rate of (t1/2) not less than about 40 sec. can be me asured. Reliable and reproducible results can be obtained by the use of an automatic control circuit to supply a constant light intensity through the sample cell.