Hard segment Content

The choice of macrodiol influences the low temperature performance, whereas the modulus, ie, hardness, stiffness, and load-beating properties, increases with increasing hard-segment content. 

Figure 3. Stress versus % elongation behavior for siloxane-urea segmented copolymers from H-MDI as a function of molecular weight of oligomer used and the hard segment content at 25 °C. (Reproduced with permission from Ref. 25. Copyright 1984 IPC Business Press, Ltd.)...

Figure 3. Small-angle x-ray scattering intensity curves demonstrating the effect of soft-segment molecular weight for three polycaprolactone polyurethanes (MDI/BD) of approximately equal hard-segment content. (A) 57% by wt, FCL 2000-178 (S) (B) 53% by wt FCL 830-123 (S) and (C) 61% by wt, FCL 830-134 (S).

Table I. Soft-Segment, Glass-Transition-Temperature Dependence on Hard-Segment Content for PTMO/MDI/BD(ET) - and PTMA/MDI/BD (ES) -Segmented Copolymers...

Sample Hard Segment Content (Wt %) Soft Segme Tg (°C)... 

Figure 9. Effect of hard-segment content on storage modulus and loss tangent of compression-molded FTMO/FTMT-segmented copolymers...

Hesketh, et al. (99) have performed similar time-dependent Tg studies on a number of segmented copolymers, only samples were annealed for 4 hr at various temperatures (120°, 150°, 170°, or 190°C). All samples had similar hard-segment contents ( 50% by weight) and a poly(tetramethylene oxide) (mol wt 1000) soft segment, and differed only in hard-segment composition. Exponential decay to the steady-state... 

Figure 7. Transmission electron micrographs of solution-cast films of (upper left) 1/312, (lower left) 1/4/3, and (above) 1/6/5. Spherulite size decreases with decreasing hard-segment content.

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