1. Dielectric Thermal Analysis Duncan Price IPTME, Loughborough University © Copyright: D.M.Price@lboro.ac.uk (2006)

2. contents  Equipment  Thermally stimulated current analysis  Theory  Example – multi-frequency temperature sweep  Time-temperature superposition  Applications

3. equipment

4. dielectric relaxation

5. thermally stimulated current analysis

6. voltage-current relationship in a capacitor

7. theory The admittance of the sample (Y) given by: Y = / Y is a vector quantity and is characterised by its magnitude |Y| and direction . Capacitance (C) is the ability to store electrical charge and is given by: C = |Y| sin(  )/  Conductance (G) is the ability to transfer electric charge and is given by: G = |Y| cos(  )

8. theory (contd.) Data are presented in terms of the relative permittivity (ε’) and dielectric loss factor (ε”) – these are related to capacitance and conductance by: ε’ = C/(ε 0.A/D) & ε” = G/( .ε 0.A/D) where ε 0 is the permittivity of free space (8.86×10 -12 F m -1 ) and A/D (in m), is the ratio of electrode area (A) to plate separation or sample thickness, D for a parallel plate capacitor. ε’ & ε” are dimensionless quantities. The ratio ε”/ε’ is the amount of energy dissipated per cycle divided by the amount of energy stored per cycle and known as the dielectric loss tangent or dissipation factor (tan  ).

9. poly(ethylene terephthalate)

10.  ’ vs. frequency

11. master curve @ 130°C

12. Arrhenius plot

13. self adhesive film

14. base film

15. in-situ photodegradation monitoring Dielectric loss factor,  ” (0.1 Hz) for adhesive with different stabiliser packages during accelerated weathering Sample“standard”“poor”“good” initial3.002.863.14 after 600 hr8.5912.63.18 after 1200 hr10.471.06.45

16. online cure monitoring

17. dielectric thermal analysis of water in pores

18. summary  Similar to TMA/DMTA  Very sensitive for polar/ionic components  Ideal for thin films  Suitable for remote monitoring

19. recommended reading A. Blythe and D. Bloor; “Electrical Properties of Polymers”, Cambridge University Press, Cambridge (2005) D. Q. M. Craig; “Dielectric Analysis of Pharmaceutical Systems”, Taylor and Francis, London (1995) P. Hedvig; “Dielectric spectroscopy of polymers” Wiley, New York (1977) N. G. McCrum, B. E. Read and G. Williams; “Anelastic and Dielectric Effects in Polymeric Solids”, Dover, New York (1991) D. M. Price, “Thermomechanical and Thermoelectrical Methods”, in P.J. Haines (ed.) “Principles of Thermal Analysis & Calorimetry”, Royal Society of Chemistry, Cambridge (2002) J. P. Runt and J. J. Fitzgerald, ed., “Dielectric Spectroscopy of Polymeric Materials: Fundamentals and Applications”, American Chemical Society, Washington DC (1997)