A study on yield behavior and stress relaxation of α-gels

Abstract

The new rheometrical techniques are demonstrated to examine the yield behavior for α-gels. The yield behaviors and re-structuring process are observed by using the repeated stress ramp test and the stress relaxation experiment after the stress ramp test. In this specific test, continuously change from the stress control mode to the strain control mode, a newly developed high performance rheometer is used. The first yield behavior is strongly affected by the hysterical effect. The first yield stress is recovered during a certain interval time. Furthermore, when the interval time is longer, the first yield stress is increased gradually. The second yield stress is hardly affected by the hysterical effect. The relaxation process shows very complex behavior. This behavior is organized by the three mode Maxwell Model. The experimental results are in good agreement with the three mode Maxwell model. The first one of three Maxwell elements shows the short time relaxation time that is corresponding to the viscous nature generated by the first yield behavior. The second element is related with the second yield behavior and it exhibits the negative stress. The last element shows the long relaxation time that is corresponding to the first yield behavior and re-structuring behavior.