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Nonlinear behavior of PP/PS blends with and without clay under large amplitude oscillatory shear (LAOS) flow

Salehiyan, Reza; Song, Hyeong Yong; Hyun, Kyu


Reza Salehiyan

Hyeong Yong Song

Kyu Hyun


Dynamic oscillatory measurement, i.e., small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) test was used to investigate linear and non-linear viscoelastic properties of Polypropylene (PP)/Polystyrene (PS) blends with and without 5 wt.% clay (C20A). Fourier transform (FT-Rheology), Lissajous curves and stress decomposition methods were used to analyze non-linear responses under LAOS flow. Composition effects of blends were investigated prior to compatibilization effects. Elevated concentrations of dispersed phase (PS) increased the moduli G'(ω) from SAOS test and G*(γ0) from LAOS test of the blends as well as strain thinning behavior. Interestingly, addition of 5 wt.% clay (C20A) boosted moduli of the blends as well as led to similar strain thinning behaviors among the PP/PS/C20A blends, except for the (90/10) PP/PS blend. The latter did not show improved rheological properties despite morphological improvements, as shown by SEM. Results from SEM and improved rheological properties of PP/PS/C20A blends revealed the compatibilization effects of clay (C20A) particles regardless of size reduction mechanisms. Third relative intensities (I3/1) from FT-rheology were found to be sensitive to clay (C20A) additions for the (70/30) and (30/70) PP/PS blends. Similarly, Lissajous curves could detect changes upon clay (C20A) addition, specifically at lower strain amplitudes whereupon addition of 5 wt.% clay resulted in the closed loops of Lissajous curves showing a more ellipsoidal shape due to increased elasticity in the blends. However, detection of these changes at larger strain amplitudes was more challenging. Therefore, stress decomposition (SD) method was applied for more precise characterization as it decomposes the total stress (σ) into elastic stress (σ′) and viscous stress (σ″). Using SD method, elastic stress was more distorted, especially, strain hardening, while the total stress response remained almost unchanged at larger strain amplitudes.

Journal Article Type Article
Acceptance Date Mar 16, 2015
Online Publication Date May 27, 2015
Publication Date 2015-05
Deposit Date Jan 30, 2023
Journal Korea-Australia Rheology Journal
Print ISSN 2093-7660
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 27
Issue 2
Pages 95-103
Keywords linear and non-linear viscoelastic properties, PP/PS/C20A blends, FT-rheology, composition ratio, compatibilization