Coupled Orientation and Stretching of Chains in Mesoscale Models of Polydisperse Linear Polymers in Startup of Steady Shear Flow Simulations

Abstract

behavior of the polymer melt. [ 5 ] Fujiyama et al. [ 6 ] provide a comprehensive experimental work on the rheological properties of poly(propylene)s with different molecular weight distributions. According to their results many of the rheological properties depend on the polydispersity including the end correlation coeffi cient in capillary fl ow, the die swell ratio, the critical shear-rate and shear stress for the onset of melt fracture, the zero-shear viscosity, the characteristic relaxation time, and the oscillatory storage and loss moduli. The infl uence of polydispersity is not only limited to these properties. It also affects the fl ow patterns of the melt even in the simplest geometries. Studies have shown that a highly monodisperse sample partitions into two fractions with different local shear-rates in a sliding plate rheometer. [ 7 ] The polydisperse sample possesses a smooth spatial variation of the local shear-rates in the same experimental setup. Other reports on the polydisperse Polydisperse linear polymers are studied in startup of steady shear fl ow simulations using dissipative particle dynamics. The results show that with an increase in polydispersity the stress overshoot declines while the steady-state stress increases. Various physical characteristics of the systems are studied including frequency of nonbonded interactions, gyration radius data, fl ow alignment angles, and average bond lengths. The patterns in the data suggest higher forces are necessary to orient and stretch long chain fractions in the fl ow direction. Relaxation modulus data prove the broad range of relaxation mechanisms in polydisperse systems. Linear viscoelasticity theory is used to quantify the relaxation spectrum. The results indicate an increase in the longest relaxation time in systems with higher polydispersity. The steady-state shear viscosity results show higher viscosities with an increase in polydispersity at all shear-rates. The good agreement of the characteristic behaviors of modeled polydisperse polymers with experiments is encouraging for future work.

Predicting experimental results for polyethylene by computer simulation

“…Using this approach, crossover between Rouse for short chains and reptational dynamics for long chains were recovered. Although, the model has been successfully applied in some simulations [502,503], it has recently shown some deficiencies when applied to systems with many DPD beads, which could limit its application to PE systems [504]. A highly CG model has been proposed by Zhu et al [505] to simulate the entangled polymer melts.…”

Dissipative Particle Dynamics Models of Orientation of Weakly‐Interacting Anisometric Silicate Particles in Polymer Melts under Shear Flow: Comparison with the Standard Orientation Models

“…Moreover, it shows that the simulated system is experiencing shear‐thinning effects mainly due to the orientation of its components, i.e., polymer chains and silicate layers. Recently, the orientation and stretching of polymer chains was addressed in a paper . Here, we attempt to focus more on the orientation of layered silicates.…”

“…Recently, the orientation and stretching of polymer chains was addressed in a paper. [ 75 ] Here, we attempt to focus more on the orientation of layered silicates. Lastly, it is noteworthy that the error bars of the simulated data were not added to the fi gures.…”

“…Recently, Moreira et al have shown that the box‐size effects can be safely ignored for polymer systems if the gyration radius of the chains is smaller than or equal to the box size. In a recent paper, the gyration radius of polymer chains with 50 beads in each chain was simulated. According to the results, the gyration radius increases to values larger than 10 only at applied shear strains, , larger than 32.…”

Numerical and experimental investigations on polymer melt flow phenomenon in a vario‐thermal mold cavity

“…Gooneie et al . studied the coupled orientation and stretching of chains of polydisperse linear polymers in startup of steady shear flow utilizing mesoscale models . An increase in polydispersity the stress overshoot declines while the steady‐state stress increases.…”