Dependence of Viscoelastic Properties on Segregation Degree

From what was said about the reaction kinetics of IPN formation it follows that the segregation degree depends on the ratio of rates of chemical reactions and, therefore, on the conditions of phase separation. We may think that the viscoelastic properties will be dependent on the reaction kinetics and segregation degree, which, in its turn, is also determined by reaction conditions. This represents a great difference in describing the properties of IPNs as compared with the properties of blends of linear polymers. 

The general picture of viscoelastic properties was considered when we discussed the method of determining the segregation degree. The majority of cases may generally be described by this scheme. However, it was shown that the viscoelasticity depends not only on composition, but also on the order of the network formation and the method of synthesis. All this is easily explained if we remember that all these factors affect the segregation degree. 

The dependence of the viscoelastic properties of IPNs based on PU and PUA on the segregation degree was shown in [88,256,257]. Taking into account the interconnection between the chemical kinetics and the kinetics of phase separation, various methods of IPN synthesis have been used, i.e., simultaneous and sequential methods. It is known that oHgourethane acrylate (OUA) in the presence of photoinitiators polymerizes at a high rate at room temperature, the reaction rate being much higher than that 

In the first stage of PU formation, some microgel particles are formed which serve as nuclei for the three-dimensional network formation and lead to the microseparation of the PU system. Thus, the OUA network is formed 

It was shown that the increasing curing temperature increases the degree of segregation, i.e., the completeness of phase separation in the system. For the system under consideration, the phase separation proceeds according to the spinodal mechanism. With an increase in the curing temperature, the rate 

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