2005

Polymer Engineering and Science

Journal year: 2005 | Journal volume: vol. 45 | Journal number: iss. 2

scientific article

english

EN In the present work, the influence of well-defined simple shear flow histories on the isothermal crystallization of an isotactic polypropylene (i-PP) has been investigated. At first, the research of the flow conditions in terms of temperature, shear rate (γ̇) and shear strain (γ) has been performed by means of the rheological technique. The continuous shearing analysis enabled us to build the flow curve at 144°C showing a Newtonian region as well as a shear-thinning zone. Indeed, for γ̇ above a critical value, the molecular orientation occurring during flow provides a kinetic promotion of the crystallization process. In the rheological step-shear flow analysis, an in-crease of the flow sensitivity parameter, k_S/k_Q, with in-creasing the shear rate at a constant strain (γ = 150) is observed. The structure of the crystallized samples has been investigated by differential scanning calorimetry(DSC) and wide angle X-ray scattering (WAXS) methods. In agreement with the DSC, the WAXS results show that crystals with a certain bimodal distribution are generated in the samples crystallized under step-shear flow conditions. A small orientation of the (110) plane of the i-PP α-phase crystals is also detected.

153 - 162

10.1002/pen.20240

https://4spepublications.onlinelibrary.wiley.com/doi/10.1002/pen.20240

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