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

Abstract

ABSTRACT:A medical segmented polyurethane, Tecoflex ® , based on methylene bis(pcyclohexyl 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 M n and M w 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 Ϫ1 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.

Oxygen permeability in thermoplastic polyurethanes

“…The internal organizations of hard and soft segments can be altered by temperature, adsorption of liquids, or mechanical strains, resulting in a modification of the material properties 14. Annealing is a simple process for favorably rearranging polymer chains, which can modify the material morphology and thermo/mechanical properties 15. Since the molecular structure and the dynamics of TPU polymer chains can be easily altered, the study of gas transport property through these materials should provide interesting insights into structural dynamics.…”

Laboratory investigation of biodegradability of a polyurethane foam under anaerobic conditions

“…The ranges of 3600e2600 cm À1 and 1800e700 cm À1 were of particular interest where the major absorption bands of PU are assigned [30]. The IR absorbance of the carbonyl group (C]O), urethane (NH), aryl (C]C), and ether (CeO) functional groups are indicated at 1720, 1630, 1600, and 1125 cm À1 , respectively [31].…”

Degradation of Polyurethanes for Cardiovascular Applications

“…Petrovic reported that the degradation temperature for these materials ranged from 120°C to 250°C depending on their structure [Petrovic et al 1994]; however, literature reports processing temperatures closer to 180°C [Guignot 2002].…”