Method for measurement of polymer molecular weight based upon a temperature difference

A method for the measurement of a molecular weight of a polymer during a present polymerization thereof which comprises the steps of:

• heating a polymer portion with heating means,
• measuring, with temperature measuring means, a difference between temperatures of at least two points of the polymer portion thereby determining an empirical point, each of said points being thermally influenced by said heating means differently from the other of said points, and
• establishing the molecular weight of the polymer which corresponds to the difference between the temperatures obtained by the measuring step according to a predetermined relationship between the temperature difference and the molecular weight of the polymer, wherein
• the predetermined relationship is obtained by first obtaining a calibration curve between the temperature difference and the molecular weight of the polymer in an earlier polymerization process, and then moving the calibration curve in parallel, while maintaining the shape of the calibration curve, so that the curve contains said empirically determined point measured during the present polymerization.