Analysis methods are discussed for polymer crystallization and melting with three different types of plots constructed by using fast-scan calorimetry and small angle X-ray scattering for the determination of the melting point TM, heat of fusion ΔHf and crystalline lamellar thickness ??c. Two of those plots are the well-known Hoffman-Weeks plot of TM against crystallization temperature Tc and the Gibbs-Thomson (G-T) plot of TM against 1/dc in terms of the data-sets obtained in the primary stage of polymer crystallization. The third plot is a newly proposed Thermal G-T plot of TM against 1/ΔHf, both of which shows a logarithmic time evolution in the secondary stage with reorganization, i.e. lamellar thickening and crystal perfecting, of existing crystals formed in the primary stage. By utilizing those plots, the zero-entropy-production melting point TM0 , folding surface free energy σe, and a thickening coefficient γ can be evaluated. Obtained results are self-consistent and agreed with prior literature values. Temperature dependent σe suggests curved melting and crystallization lines of the G-T plot. Application of fast heating is essential for the quantitative analysis of the melting behavior of chain-folded lamellar crystals in a metastable state.
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Keywords:polymer, crystallization, melting, fast-scan calorimetry, small angle X-ray scattering
Publication Date: 2020-07-25