Paper Number
SM12 

Session
Polymers Solutions, Melts and Blends

Title
Unentangled polystyrene melts in fast shear flows

Presentation Date and Time
October 10, 2022 (Monday) 3:45

Track / Room
Track 2 / Sheraton 3

Authors (Click on name to view author profile)

1. Ianniruberto, Giovanni (Federico II University, Department of Chemical, Materials and Production Engineering)
2. Marrucci, Giuseppe (Federico II University, Department of Chemical, Materials and Production Engineering)
3. Costanzo, Salvatore (Federico II University, Department of Chemical, Materials and Production Engineering)
4. Grizzuti, Nino (University of Naples Federico II, Chemical, Materials and Industrial Production Engineering)
5. Peponaki, Katerina (University of Crete, Department of Materials Science & Technology)
6. Alexandris, Stelios (FORTH, Institute of Electronic Structure and Laser)
7. Vlassopoulos, Dimitris (FORTH and University of Crete)

Author and Affiliation Lines (in printed abstract book)
Giovanni Ianniruberto¹, Giuseppe Marrucci¹, Salvatore Costanzo¹, Nino Grizzuti¹, Katerina Peponaki², Stelios Alexandris² and Dimitris Vlassopoulos^2
1Department of Chemical, Materials and Production Engineering, Federico II University, Naples, Italy; ²FORTH and University of Crete, Heraklion, Greece

Speaker / Presenter 
Ianniruberto, Giovanni

Keywords
experimental methods; theoretical methods; computational methods; polymer melts; rheometry techniques

Text of Abstract
Nonlinear start-up flow data on unentangled polystyrene (PS) melts (M<M_c˜35k) are rather scarce. A few years ago, transient extensional data were reported on a PS melt with M=27k [1] whereas shear data remain mostly limited to steady flows [2]. Here, new systematic start-up shear tests are performed on several nearly monodisperse unentangled PS melts (M=10k,20k,30k), encompassing start-up, steady state, and relaxation. Normal stress differences were also measured. Consistently with the analysis of the shear data in [3], and of the extensional ones in [4], most of these new shear data appear to be reasonably well described by a FENE-Rouse model, endowed with flow-induced friction reduction, provided that the glassy contribution is accounted for. However, exceptions can be noted. For example, non-zero second normal stress differences were measured for the 20k and 30k samples, which (as is well known) the Rouse model is unable to predict. This suggests that some effect of topological interactions is present in these unentangled melts. Hence, a mild topological interaction must be accounted for, possibly through an anisotropic Rouse model.

[1] Matsumiya et al. Macromolecules 2018, 51, 9710-9729.
[2] Santangelo and Roland, J. Rheol. 2001, 45, 583-594.
[3] Ianniruberto and Marrucci, Macromolecules 2020, 53, 1338-1345.
[4] Ianniruberto et al., Macromolecules 2019, 52, 4610-4616.