The Role of Co-Units in Polymer Crystallization and Melting: New Insights from Fast Scanning Calorimetry on Poly(ethylene-<i>co</i>-octene)

The effect of noncrystallizable units on the crystallization and melting of polyethylene was studied for three ethylene octene copolymers [1]. Using fast scanning calorimetry (FSC) at cooling rate 100,000 K/s allows isothermal crystallization at 62 °C for all three samples. Heating at 10,000 K/s provides the melting curves of the isothermally formed crystals. At slow DSC cooling rates crystallization is determined by the ethylene sequence length distribution and the melting point of the corresponding crystals depends on crystal thickness [2]. Contrary, for the isothermally at 62 °C crystallized samples of different co-unit content the melting behavior is very similar. Under this particular conditions co-unit content only influences crystallization kinetics but not crystal thickness.
[2] Zhuravlev, E., V. Madhavi, A. Lustiger, R. Androsch and C. Schick (2016). "Crystallization of Polyethylene at Large Undercooling." ACS Macro Letters 5: 365-370.
[3] Hauser, G., J. Schmidtke and G. Strobl (1998). "The role of co-units in polymer crystallization and melting: New insights from studies on syndiotactic poly(propene-co- octene)." Macromolecules 31(18): 6250-6258.