Distinguishing Linear from Star‐Branched Polystyrene Solutions with Fourier‐Transform Rheology

Abstract

Summary: Fourier‐Transform rheology (FT rheology) was used to study the influence of the degree of branching on the nonlinear relaxation behaviour of polystyrene solutions. The results were compared with those obtained under oscillatory shear and step‐shear conditions. The different topologies could be distinguished using FT rheology where the other rheological measurements failed. Significant differences occurred under large amplitude oscillatory shear (LAOS) conditions as particularly reflected in the phase difference of the third harmonic, Φ3, which could be related to strain‐softening and strain‐hardening behaviour. Currently, this work is extended towards different topologies in polyolefins (e.g. long chain branched).Phase difference Φ3 as a function of the Deborah number De at γ0 = 2 for the polystyrene solutions measured at temperatures from 295 to 350.5 K.magnified imagePhase difference Φ3 as a function of the Deborah number De at γ0 = 2 for the polystyrene solutions measured at temperatures from 295 to 350.5 K.

Analytical Rheology of Polymer Melts: State of the Art

“…The bulk of literature on analytical rheology relies on linear viscoelasticity, because experiments are more convenient to perform and less prone to experimental error like wall-slip and shear-banding. However, quite a few studies have considered the difference in the nonlinear shear or extensional response of LPs and BPs [91,[307][308][309][310][311][312][313][314] as a probe of LCB.…”

A Novel and Straightforward Methodology to Analyze Materials Under Constant-Structure Oscillatory Motion (Saos and Ql-Laos)

“…However, a few macroscopic material properties that may be obtained through rheological experiments provide indirect and qualitative information about microscopic structural state (33). Other techniques such as light scattering (SANS, SALS and SAXS) and microscopy are necessary in order to obtain direct information about microscopic properties (22).…”

“…Information about elasticity and characteristic times can only be obtained with transient flow experiments, and oscillatory experiments are recommended to obtain indirect information about the material microscopic state (33). Oscillatory experiments at large stress amplitudes are important to assess the macroscopic effects of changes in the microscopic state.…”

“…The simple experimental setup was clearly beneficial for a broader adoption of the technique. (56) FT-Rheology was used for various complex fluids, such as polymer melts (35,20,54), polymer solutions (36,34), polymer blends (3), dispersed systems (55) and industrial elastomers (28, 27).…”

Szilikonolaj nemlineáris viszkoelasztikus tulajdonságainak mérése és modellezése

“…A Fourier transzformációs reológiai (FTR, Fourier Transform Rheology) módszer lényege [35], összhangban más Fourier transzformációs módszerrel az, hogy vesszük a mért nyers periodikus nyírófeszültségi jel Fourier felbontását, amely a következő alakú lesz [36]: A Fourier transzformációs módszer számos különböző típusú komplex folyadékra alkalmazható, többek között emulziókra [39], szuszpenziókra [40], híg és koncentrált polimer oldatokra, valamint polimer olvadékokra [41][42][43][44][45][46].…”