Hard phase plastic flow stress

The higher compression set data are due to the couples BDO-DBDI or EG-DBDI, where the variable geometry of DBDI favors the polymer crystallization. In polymers based on the couples BDO-DBDI or EG-DBDI (especially polyether PUs) there perform high phase separations and differences in hard phase plastic flow stress, resulting from crystallinity in the DBDI phase. 

It is now well established that formation of hard or stiff gels is the result of association of micelles into cubic phases. The notation hard gel follows Hvidt and co-workers (Almgren et al 1995 Hvidt et al. 1994) and refers to a micellar solution with a dynamic elastic shear modulus G > 103Pa. The correlation between the formation of a cubic phase and the onset of plastic flow (i.e. formation of a gel with a finite yield stress) was first made for PS-PI solutions in... 

Plasticizers Which Reduce Cohesive Strength. Plasticizers which are readily compatible with the polystyrene endblocks prevent the formation of strong crosslinks between the rubber molecules. Endblock domains will form as a separate phase, but instead of being hard and rigid at room temperature, they will be soft and fluid. Stress applied to the network will cause irreversible flow. 

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