Analysis of Isothermal Crystallization Runs:

1. We want to make a Hoffman-Weeks Plot of Tm versus Tc in order to determine Tinf. The sample is first isothermally crystallized at temperatures between Tg and Tinf, then quenched to below Tg and a heating run such as shown above is recorded. Tm is always greater than Tc from the isothermal heating run and you should be able to explain why.
   In this case Tm is about 217°C and Tc was 200°C.
   Melting and heating occur simultaneously above Tg and below Tminf. The faster the heating rate and the lower the temperture the smaller is this problem. The plot above was for a 50°/min heating run.
2. We also desire the enthalpy of melting for the crystals formed during the isothermal crystallization. These are associated with the first endotherm. The second endotherm is associated with crystals that form during the heating run. You will have to make some assumptions and corrections to the data to obtain the enthalpy for the isothermal crystallization. Please state all assumptions and carefully describe the corrections you did to determine a value for the enthalpy of crystallization and the degree of crystallinity for the isothermal runs.