Change in mechanical properties, composition, and structure of hydrated polyurethaneurea

Relative to the extensive study on the relationship between the structure a nd properties of polyurethane (PU) and polyurethaneurea (PUU), basic inform ation available on hydrated PUU is limited. In this study, PW films were im mersed in a saline solution (0.9 wt % NaCl, 37 degreesC) for periods of up to 60 days and evaluated by the change in static and dynamic mechanical pro perties, composition, and hydrogen-bonding structure. It was found that imm ersion in a saline solution could greatly increase the average molecular we ight and degree of phase separation, which enhanced the mechanical strength and reduced the flexibility. The increase in the average molecular weight is believed to come from the chain extensions or crosslink reactions betwee n intramolecules and/or between intermolecules and from the leaching out of poly(tetramethylene oxide) (PTMO) oligomers. FTIR analysis indicated that H2O molecules did not obviously alter the hydrogen-bonding structure of PUU . (C) 2001 John Wiley & Sons, Inc.