STUDY OF POSTGELATION REACTION BY DIFFERENTIAL SCANNING CALORIMETRY

Determination of conversion in the polycondensation of polyfunctional monomers above the gel point is complicated by insolubility of the polymer. The use of d.s.c. can overcome this difficulty if it affords sufficient accuracy. The aim of this work was to estimate the accuracy of the d.s.c. determination of conversion in the reaction of tris(4-isocyanatophenyl) thiophosphate and polypropyleneglycol of MW = 1000 model system. The calibration of the d.s.c. conversion values was carried out by titration of the isocyanate groups at different conversions in the pre-gel state. The results were then used to compare the conversion measured by d.s.c. with that from sol fraction measurements in the post-gel state. The relationship between the sol fraction and the degree of conversion for our system was obtained from cascade theory. Reasonable agreement between the d.s.c. and sol fraction methods was found below 90% conversion. © 1990.