Rheo-optical characterization of the shear-induced non-isothermal crystallization of polyamide 6

Bernardo, Felipe Oliveira Campos and Canevarolo, Sebastiao Vicente (2025) Rheo-optical characterization of the shear-induced non-isothermal crystallization of polyamide 6. EXPRESS POLYMER LETTERS, 19 (6). pp. 636-650. ISSN 1788-618X

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Abstract

The use of rheo-optical techniques to evaluate crystallization in polymer processing has many advantages; however, it is still little seen. Shear-induced crystallization of polyamide 6 (PA6) was here proposed and studied with these techniques. Mixtures of PA6 in a polypropylene (PP) matrix were also studied. A polarized light optical microscope, with an AxioVision system attached to its top allowing the acquisition of photos at any time during the measurement and a Linkam hot stage device to control shear and temperature, was modified to receive a specially built quantitative rheo-optical detector. Temperature was variable, characterizing non-isothermal analysis. The experiments consisted of varying the shear rate on the polymer system while collecting the respective cross-polarized transmitted light intensity response by LabVIEW software. Shear rates of 1, 10, 100 and 180 s–1 were applied to all samples. Differential scanning calorimetry (DSC) analysis was also performed to predict crystallization behavior. PA6’s crystallization increased with the increase of shear rate; however, for the PP/PA6 mixtures under the highest rates, crystallization intensity falls from a specific temperature in which the polymer’s viscosity is not enough to maintain the structural integrity. Data related to PP/PA6 mixtures showed that shear increases crystallization if the polymer has time to organize itself.

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