Understanding the dispersion state of nanocarbon particles in water is essential in the manufacturing technology of various products, including a secondary battery. When an excess amount of dispersant is added to the particle dispersion, the rheological properties of the dispersion are considered to change due to rheological changes in the aqueous solution of the excess dispersant without changing the dispersion state of the particles. In such cases, the relative viscosity, which is the ratio of the viscosity of the dispersion to that of the dispersant solution, should be consistent. In the present study, we proposed a method to investigate the composition of the dispersant solution and the amount of adsorption on the particles using the relative viscosity as an index. The validity of the adsorption amount of the dispersant was validated from various aspects, and the influence of the preparation method of the particle dispersion on the adsorption behavior of the dispersant was also discussed.

Particle deposition, occurring during the transport of colloidal suspension through process streams, can degrade the processing performance by increasing pressure drop and inducing channel clogging. In this study, we examine the particle deposition phenomena in an expansion-contraction microchannel visualize by a microfluidic observation system. Image processing techniques are employed to analyze the effect of fluid viscosity qualitatively and quantitatively on the deposition phenomena in both Newtonian and non-Newtonian fluids. Glycerin aqueous solution and poly (ethylene oxide) (PEO) solution are utilized as the Newtonian and non-Newtonian fluid, respectively, with viscosity manipulated by changing the concentration of glycerin as a thickening agent. Polystyrene (PS) latex particles are suspended in each medium and flows through the expansion-contraction microchannel. Particles deposit more readily in the downstream region compared to the cavity region for both Newtonian and non-Newtonian fluids. As fluid viscosity increases, the quantity of deposited particles decreases in both media. Notably, particle deposition in the non-Newtonian fluid occurs more extensively in the cavity region due to the fluctuating flow behavior and particle-polymer interactions.

This paper aims to establish a theoretical framework linking the macroscopic in-plane isotropic laminated structure of fiber-reinforced resin materials, such as sheet molding compounds (SMC) and randomly oriented strand (ROS) composites, to their flow behavior. These materials exhibit plug flow-like behavior during compression molding. However, conventional models for SMC’s flow behavior have inherent limitations, necessitating improvements by thoroughly examining the relationship between the laminated structure and flow modes. In this work, we introduce a decomposition of the strain rate tensor and derive an anisotropic stress tensor tailored to the material’s symmetry and anisotropy. Furthermore, we propose an effective shear viscosity model that integrates the anisotropic stress induced by the laminated structure into general-purpose computational fluid dynamics (CFD) software. To assess the characteristics of the proposed viscosity model, we conduct numerical simulations of the compression molding process, systematically varying the ratio of out-of-plane compression viscosity to out-of-plane shear viscosity. Without arbitrary modifications to the wall boundary conditions, simulations with a high viscosity ratio successfully predict the formation of layers with variable viscosities and velocity distributions indicative of plug flow-like behavior. This behavior is attributed to the out-of-plane shear flow region adjacent to the walls, acting as a low-viscosity lubricating layer.

The Rouse-Ham model is a simple yet useful dynamics model for an unentangled branched polymer. In this work, we study the normal modes of the Rouse-Ham type coarse-grained symmetric star polymer model. We model a star polymer by connecting multiple arm beads to a center bead by harmonic springs. In the Rouse-Ham model, the dynamics of the bead positions can be decomposed into the normal modes, which are chosen to be orthogonal to each other. Due to the existence of degenerate eigenvalues, the eigenmodes do not directly correspond to the normal modes. We propose several methods to construct the normal modes for the coarse- grained symmetric star polymer model. We show that we can construct the normal modes by using a simple permutation or the Hadamard matrix. These methods give simple and highly symmetric orthogonal modes, but work just for a special number of arms. We also show that we can construct the normal modes by using the discrete Fourier transform (DFT) matrix. This method is applicable for an arbitrary number of arms.

The influence of mixing ultra-high molecular weight polyethylene (UHMWPE) on the morphology and mechanical properties of solid-state high-density polyethylene (HDPE) was investigated using various analytical methods. The dispersion of UHMWPE chains within HDPE improved with longer mixing times. However, increased mixing time also led to a decrease in molecular weight, particularly affecting the high molecular weight component because of the degradation of molecular chains. The strain-hardening modulus and strength of UHMWPE/HDPE blends significantly surpassed those of pure HDPE and continued to improve with increasing UHMWPE fraction. In particular, the strain-hardening modulus of all samples was predominantly influenced by the fraction of tie molecules connecting more than six lamellar crystals, irrespective of the degree of degradation.