The variational principle, which allows the deduction of the basic equation system of continuum mechanics from the local form of Gyarmati’s integral principle is presented in this paper. Following the approach of irreversible thermodynamics, the principle the kinetic energy is described like the fundamental equation of thermodynamics as the internal energy change, namely intensive quantity multiplied by the changing of extensive quantity. As the internal energy is objective so that is an independent quantity from the coordinate system, this description to the internal energy can be done. However, the kinetic energy is coordinate-dependent quantity. To resolve this contradiction the stress tensor can be divided into elastic and dissipative stress components by using the laws of thermodynamics.
Contributions of modern, temperature-modulated calorimetry
are qualitatively and quantitatively discussed. The limitations are summarized,
and it is shown that their understanding leads to new advances in instrumentation
and measurement. The new thermal analysis experiments allow to separate reversing
from irreversible processes. This opens the irreversible states and transitions
to a description in terms of equilibrium and irreversible thermodynamics.
Amorphous systems can be treated frommacroscopic to nanometer sizes with weak
to strong coupling between neighboring phases. Semicrystalline, macromolecular
systems are understood on the basis of modulated calorimetry as globally metastable,
micro-to-nanophase-separated systems with locally reversible transitions.
Authors:B. Wunderlich, A. Boller, I. Okazaki, and S. Kreitmeier
Temperature-modulated differential scanning calorimetry (TMDSC) is based on heat flow and represents a linear system for the measurement of heat capacity. As long as the measurements are carried out close to steady state and only a negligible temperature gradient exists within the sample, quantitative data can be gathered as a function of modulation frequency. Applied to the glass transition, such measurements permit the determination the kinetic parameters of the material. Based on either the hole theory of liquids or irreversible thermodynamics, the necessary equations are derived to describe the apparent heat capacity as a function of frequency.
This review traces the development of thermal analysis over the last 40 years as it was experienced and contributed to by the author. The article touches upon the beginning of calorimetry and thermal analysis of polymers, the development of differential scanning calorimetry (DSC), single run DSC and other special instrumentations, up to the recent addition of modulation to calorimetry. Many new words and phrases have been introduced to the field by the author and his students, leaving a trail of the varied interests one can have over 40 years. It began with “cold crystallization” and most recently the term “oriented, intermediate phase” was coined, creating in-between: “extended chain crystals,” the “irreversible thermodynamics of melting of polymer crystals,” “dynamic differential thermal analysis” (DDTA), “the rule of constant increase ofCp per mobile bead within a molecule at the glass transition temperature,” “superheating of polymer crystals,” “melting kinetics,” “crystallization during polymerization,” the “chain-folding principle, “molecular nucleation,” “rigid amorphous phase,” a “system of classifying molecules,” “macroconformations,” “amorphous defects,” “rules for the entropy of fusion based on molecular shape and flexibility,” “single-molecule single-crystals,” “a system of classifying phases and mesophases,” and “condis phase.”
This review traces the development of thermal analysis over the last 50 years as it was experienced and contributed to by
the author. The article touches upon the beginning of calorimetry and thermal analysis of polymers, the development of differential
scanning calorimetry (DSC), single-run DSC, and other special instrumentations, up to the recent addition of modulation to
calorimetry and superfast calorimetry.
Many new words and phrases have been introduced to the field by the author and his students, leaving a trail of the varied
interests over 50 years. It began with cold crystallization and more recently the terms oriented, intermediate phase, glass
transitions of crystals, and decoupled chain segments were coined. In-between the following phenomena were named and studied:
extended-chain crystals, irreversible thermodynamics of melting of polymer crystals, zero-entropy-production melting, dynamic
differential thermal analysis (DDTA), the rule of constant increase of Cp per mobile bead within a molecule at the glass transition temperature, superheating of polymer crystals, melting kinetics,
crystallization during polymerization, chin-folding principle, molecular nucleation, rigid amorphous phase, system of classifying
molecules, macroconformations, amorphous defects, rules for the entropy of fusion based on molecular shape and flexibility,
single-molecule single-crystals, systems for classifying phases and mesophases including condis phases, and the globally metastable
semicrystalline polymers with reversible, local subsystems.
thermodynamics” (1971) up to the recent books by, e.g., C. Truesdell, S. Bharatha “Concepts and Logic of Classical Thermodynamics as a Theory of Heat Engines” (1988); D. Jou, J. Casas-Vazques and G. Lebon “Extended IrreversibleThermodynamics” (1993); R. F
Authors:Urs von Stockar, Ian Marison, Marcel Janssen, and Rodrigo Patiño
be negative, as the entropy generation rate can only be positive. The former then reflects directly the rate of entropy generation, which according to irreversiblethermodynamics is the driving force for the process. The higher the entropy generation
documented by proper thermal analysis at its zero-entropy-production limit as described by irreversiblethermodynamics. Equilibrium thermodynamics, which describes the equilibrium zero-entropy-production process on melting, does not apply to the