Viscoelastic rheology in the melting and crystallization domain: Application to polypropylene copolymers

The purpose of this article was to study the relationship between the rheological properties and the crystallization or melting of two polypropylene-based copolymers used in the welding of the coating of offshore pipelines. The materials microstructure was studied via X-ray diffraction, scanning electron microscopy, and optical microscopy. Differential scanning calorimetry was used to determine the crystallization and melting properties at different cooling and heating rates. Dynamic rheological analysis was used to define the rheological properties in the molten and in the transition zone from the molten to solid state and inversely. Both experiments (DSC and rheology) were performed under non-isothermal conditions to allow complete accessibility to the transition zone. Crystallization and melting are both complex processes in which coexist amorphous and crystalline phases in the sample. A correlation between the rheological properties and crystallization was proposed. (C) 2017 Wiley Periodicals, Inc.