Degradation of crosslinked poly(ester-urethanes) elastomers in distilled water: Influence of hard segment

摘要

Polyurethane elastomers are frequently used in wet conditions. Crosslinked polyurethanes based on poly(ethylene adipate) diol, 4,4′-diphenylmethane diisocyanate, 1,6 hexane diisocyanate-with different hard-segment compositions but with the same molecular weight soft segment-were degraded in distilled water at 37°C, in a specific environment; in the dark without exposure to enzymatic conditions and under the continuous circulation of water. The incubation of polymer samples took place over a period of maximum 30 days. The degradation process was evaluated by the changes in mechanical properties and surface relief observed by optical microscopy. The changes in hydrogen bonding were collected through attenuated total reflectance infrared (ATR-FTIR) spectroscopy which indicated that aliphatic diisocyanates allow for a better formation of hydrogen bonds. The mechanical properties of the degraded films show that the crosslinked polyurethanes containing aromatic diisocyanate suffer a decrease in tensile strength between 33 and 56% depending on the chain extender and hard segment content. The hydrolytic degradation behavior of crosslinked polyurethanes was found to be dependent on the diisocyanate and chain extender structure, as well as on the hard segment content and chemical crosslinks.