PHYSICOCHEMICAL STABILITY STUDY OF POLYUR ETHANES BY SIZE-EXCLUSION CHROMATOGRAPHY, DIFFERENTIAL THERMAL-ANALYSIS AND FTIR

The effect of exposure to buffer alone (pH = 2) and buffered pepsin on the chemical stability of three polyurethanes (PUR), namely PUR 1, PU R 2 and PUR 3, was studied. Three complementary polymer characterizati on techniques weve used: size exclusion chromatography (SEC) which sho res variation of averages of moleculars masses, differential scanning calorimetry (DSC) which verifies the thermal characteristic and Transf orm fourier infrared spectroscopy (FT-IR) which confirms the structura l modifications. It was shown that PUR 1 macromolecular chains were su sceptible to scission which followed post-reticulation. Scission is du e to pH = 2 (chemical degradation), and to dissociation of the urethan e linkage (-NH-COO-)- by pepsin (enzymatic degradation). Polyurethanes PUR 2 and PUR 3 exhibited only reticulations. DSC and FTIR, applied t o PUR 3, suggest that reticulation corresponds to nit increase of hydr ogen bonding which acts as cross-link into the polyurethane.