首页|A Dual-Phase Approach to Reveal the Presence and Impact of the TLL Transition in Polymer Melts. Part II. The Theoretical and Practical Relevance of the TLL Existence and Characteristics on the Understanding of the Melt Thermal Analysis and Rheological Properties of Polymers: Duality and Cross-Duality of the Interactions
A Dual-Phase Approach to Reveal the Presence and Impact of the TLL Transition in Polymer Melts. Part II. The Theoretical and Practical Relevance of the TLL Existence and Characteristics on the Understanding of the Melt Thermal Analysis and Rheological Properties of Polymers: Duality and Cross-Duality of the Interactions
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NSTL
Taylor & Francis
In Part I of these 2 parts article, we derived mathematically the existence of a unique state for polymeric melts, occurring at a specific temperature above T_g, which we recognized to be the liquid-liquid transition, T_(LL), observed and described by Boyer and others. T_(LL) is the temperature at which the melt is in an iso-free-volume and isoenthalpic state independent of the molecular weight. It is a fundamental property of the material. The purpose of part II is to examine and explain the following: 1) the elusive character of T_(LL) (at the origin of the controversy about the existence of T_(LL) in the past), 2) the increase of free volume at T_(LL), and 3) the endothermal change of heat capacity on heating across T_(LL). Finally, our objective is to provide an explanation of T_(LL) and emphasize its importance as an example of a self-dissipative dynamic process that converts, at T_(LL), into a classical thermally activated process. In this article, the experimental evidence found in the literature for T_(LL) is critically examined to point out the often biased reviews offered by the antagonistic authors of a controversy, here the pros and cons T_(LL). We propose a Dual-Phase origin of the interactions in polymers to explain the weak and elusive manifestations of T_(LL) and show, by DSC, that the T_(LL) manifestations are made much more visible and prominent when the samples' state has been brought out of equilibrium. We analyze, in detail, the thermally activated depolarization of samples which have been submitted to a polarization stage by a voltage field.
NSTL
Taylor & Francis
