| In this study, it was found that the activation energy spectrum could be calculated from the relaxation modulus and we demonstrated that the activation energy spectrum is a characteristic material function. Therefore by combining it with the relaxation spectrum at the reference temperature, viscoelastic properties at different temperatures can be predicted.; The thermorheological complexity of long chain branched polymers is caused by a particular relaxation mechanism called arm retraction. An equivalent relaxation mechanism is exhibited by linear polymers at short time scales. According to this theory, linear polymers should be thermorheologically complex in the time range that this mechanism is active, however this has never been observed experimentally. The primary reason for the lack of experimental proof of that theory is the difficulty in accessing experimentally the necessary time scales. In order to make it possible to observe this behavior within the experimental window, a very high molecular weight, monodisperse linear polyethylene was studied. (Abstract shortened by UMI.)... |
