Influence of filming process on macromolecular structure and organization of a medical segmented polyurethane



A medical segmented polyurethane, Tecoflex®, based on methylene bis(p-cyclohexyl isocyanate) and 1,4-butanediol as hard segments (HS), and poly(tetramethylene glycol) as soft segments (SS), was studied to evaluate the influence of different filming procedures on macromolecular structure and organization. Size-exclusion chromatography (SEC) and Fourier transform infrared (FTIR) spectroscopy were used to highlight differences between solvent-cast and hot compression-molded films (160 to 200°C). For compression-molded films, FTIR spectra showed weakened vibration bands attributed to HS and SS groups; SEC results indicated a decrease of Mn and Mw molecular weights that was dependent on processing time and temperature. These modifications were the result of both thermooxidation of soft segments and thermal dissociation of urethane linkages. Concerning solvent-cast films, no chemical or molecular modifications were observed. Moreover, we have highlighted that this procedure enhanced macromolecular organization: the carbonyl stretching region presented several bands assigned to free carbonyls and H-bonded carbonyls with different environments. Particularly, we observed a band at 1660 cm− 1 reported in only one publication; we demonstrated that it originated from a bonded carbonyl in a well-ordered structure. We have concluded that solvent casting has to be preferred because it enhances macromolecular ordering without chain degradation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1970–1979, 2002