CHARACTERIZATION OF POLYETHER-POLYURETHANES BY SEC COUPLED WITH VISCOMETRY AND LALLS

Two- and three-component polyether-polyurethanes were characterized by means of size exclusion chromatography (SEC)-multidetector methods. S EC was coupled with three or two detectors in series, a continuous vis cometer (CVM), a low angle laser light scattering (LALLS) photometer a nd a differential refractometer (DR), or with CVM and DR. Molecular we ight (MW) averages were determined independently by SEC-LALLS and by S EC using universal calibration (SEC-UC). MWs obtained by SEC-UC agreed with the corresponding SEC-LALLS MWs up to 60,000, but were higher fo r MWs over 60,000. This apparent increase in MW was attributed to the non-linearity of the calibration curve in the range of MW over 7.10(5) . Due to high limiting viscosity number [eta] of polyurethanes as comp ared to polystyrenes with the same MW, there was a big influence of co ncentration effects upon SEC when using calibration curves. For an acc urate SEC-UC determination of the MW distribution, the parameter [eta] .c should be considered.