Mercedes Fernandez, Arrate Huegun, Maria Eugenia Munoz, Anton Santamaria
Nonlinear oscillatory shear flow as a tool to characterize irradiated polypropylene/MWCNT nanocomposites
Appl. Rheol. 25:4 (2015) 45154 (12 pages)

Abstract: The relative intensity and phase of the third harmonic, I_3/1 and Φ₃-Φ₁, deduced from Fourier Transform analysis of Large Amplitude Oscillatory Shear (LAOS ) experiments were used to differentiate the effect of irradiation and the effect of multiwalled carbon nanotubes (MWCNT) concentration in PP/MWCNT nanocomposites. Alternatively, studies of elastic and viscous non linearities that give shear thinning and thickening or strain softening and hardening were carried out for the same purpose. Using both methods to analyse LAOS data, the conclusion was the same: The influence of MWCNTs is noticed at low/intermediate γ_o strains (10 - 100 %), whereas the effect of irradiation is rather observed at strains above 100 %. This marks a difference with respect to small amplitude oscillatory flow measurements, which are not valid to distinguish between the respective rheological effects of irradiation and MWCNT in polymer nanocomposites. SEC-MALLS-IR-VI analysis was used to determine the long chain branching degree λ of irradiated polypropylene, but this technique is very difficult to be applied for nanocomposites. Face to this shortcoming, an empirical correlation between λ and the value of the I_3/1 plateau when γ_o tends to infinite, found for irradiated neat PP, was used to evaluate the long chain branching degree of nanocomposites. © 2015 Applied Rheology.

DOI 10.3933/ApplRheol-25-45154

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