Time periodic structures and instabilities in shear thickening polymer solutions

• Type: Article in International Scientific Journal
• Date: 2002

Authors

Loic Hilliou (Author) FEUP; Dimitris Vlassopoulos (Author) Other

Journal

Title: Industrial & Engineering Chemistry Research

Vol. 41 No. 25

Pages: 6246 -6255

ISSN: 0888-5885

Publisher: American Chemical Society

Scientific classification

FOS: Engineering and technology

Other information

DOI: 10.1021/ie0110078

Abstract (EN): We revisit the problem of flow-induced structural changes in semidilute polystyrene/dioctyl phthalate (PS/DOP) solutions below their theta temperature by focusing on the high-shear-stress regime where thickening occurs. We observe a strong coupling of flow instabilities to the induced structure resulting from the enhanced concentration fluctuations. This behavior is manifested as a time-periodic signal of both the optical (birefringence and dichroism) and mechanical responses and represents an identifying signature of the strong-thickening region, being enhanced by shear stress and disappearing at low stresses or above the theta point. At the higher stresses, macroscopic rings are formed throughout the sample and sustained over the duration of the shearing. The emerging picture suggests that flow-enhanced fluctuations and eventually phase separation are the cause of shear thickening.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10