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DEFINITIONS

DEFINITIONS. transition:. Refers to a change of state induced by changing temperature or pressure (or volume) from one thermodynamic equilibrium to another. relaxation:. Refers to the time required to respond to the time required to respond

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DEFINITIONS

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  1. DEFINITIONS transition: Refers to a change of state induced by changing temperature or pressure (or volume) from one thermodynamic equilibrium to another relaxation: Refers to the time required to respond to the time required to respond To a change in temperature or pressure (or volume). It also implies Some measure of the molecular motion, especially near a transition Condition. Frequently, an external stress is present permitting the re- Laxation to be measured dissipation: Refers to the emission or absorption of energy – that is a loss peak – at a transition

  2. poly(dimethyl siloxane) (PDMS) heat flux or cp • glass transition • enthalpy relaxation • cold crystallization • melting

  3. T T(t) t slope: Cp can be calculated from the heat fluxQ Q is determined by the exactness of the signal M*is determined by the exactness of the program rates

  4. Consequently, a correction is needed that is independent of the parameters of the instrument: M. J. O`Neill, Anal. Chem. 38 (1966) 1331 Tg, Tm, Tcr, TS-N, TSA-SC,…TN-I…

  5. Classification of the thermodynamic transitions according to Paul Ehrenfest*): Discontinuity the derivative (1st, 2nd,…) of the Gibbs function G *)Ehrenfest P Proc Kon Akad Wetensch Amsterdam (1933) 36, 153

  6. First Order Transitions

  7. In a real experiment heat transfer requires time and a temperature gradient  and this is what we actually see: a (endothermal) melting peak

  8. Hoffman & Weeks Plot* slope stability parameter thermodynamic equilibrium melting temperature isothermal crystallization temperature experimental melting temperature J. D. Hoffman, J. J. Weeks, J. Res. Bureau Standards 66A (1962) 13 *(solution crystl.)

  9. At the glass transition Volume Enthalpy Storage modulus Expansivity Heat capacity Loss modulus

  10. Vspec Hspec high cooling rate CR1 low cooling rate CR2 Tg2 Tcr Tg1 T (dV/dT)~ a (dH/dT)p= cp Tg1 Ti2 Tg2 Te2

  11. Calculation of Tg according to M. J. Richardson, N. G. Savill, Brit. Polym. J. 11 (1979) 123 Tg determined independent of the heating rate

  12. integration

  13. time

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