Effects of reaction and cure temperatures on morphology and properties of poly(ester-urethane)

Poly(ester-urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4-toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110 degrees C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU-90, PEPU-100, and PEPU-110. Then the PU prepolymers were crosslinked by 1,1,1-tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80 degrees C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide-angle X-ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100 degrees C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (T-g) of soft domain and tensile strength. When the cure temperature was above 60 degrees C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment T l and tensile strength. On the whole, all of the PEPU-90, PEPU-100, and PEPU-110 films cured above 60 degrees C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. (c) 2006 Wiley Periodicals, Inc.