Crystallization of PET fractions: Comparison between the scaling laws of PE and PET

It is shown that polyethylene and polyethylene terephthalate fractions, quenched from the melt, crystallize in a similar manner; the long periods in these materials obey the general law where lc is the crystalline lamella core thickness independent of the molecular weight M, and α is a parameter dependent on the rigidity of the chain in the liquid state before crystallization. In annealed linear and branched PET materials, the similar dependence of the long periods on the supercooling above the temperature T∗ = 200°C is explained by the dynamic flexibility of the chains in the solid state; according to the rule of O'Leary and Geil, this temperature corresponds to the temperature Tα of mechanical relaxation.