SOLUTION BLENDS OF POLYACRYLONITRILE WITH SEGMENTED POLYURETHANES - EFFECT OF SOFT SEGMENTS

Solution blends of a modified polyacrylonitrile (PAN) with polyurethane (PU) obtained from 4,4'-diphenylmethane diisocyanate (MDI) and two different types of polyols-i.e., ether-linked polytetramethylene ether glycol (PTEG) and ester-linked polytetramethylene adipate glycol (PTAG)-were prepared in N,N-dimethylformamide (DMF). The domains in the PTAG-PU blends were much finer than those in the PTEG-PU blends. Shift of the soft segment transition temperatures (T-g's) of PU toward lower temperature with increasing PAN was more significant for PTAG-PU blends. Miscibility was also examined through Fourier transform infrared spectra. These showed clear carbonyl peak shifts due to the different types of hydrogen bonding, The PTAG-PU/PAN (30/70) blend had the maximum draw ratio at failure, measured in 100 degrees C water; it was over 2.5 times that of pure PAN.