Nihon Reoroji Gakkaishi 

About: Nihon Reoroji Gakkaishi is an academic journal published by Society of Rheology, Japan. The journal publishes majorly in the area(s): Viscoelasticity & Viscosity. It has an ISSN identifier of 0387-1533. It is also open access. Over the lifetime, 651 publications have been published receiving 2834 citations. The journal is also known as: Journal of Society of Rheology, Japan & Journal of the Society of Rheology, Japan.

Effect of Fiber Concentration and Axial Ratio on the Rheological Properties of Cellulose Fiber Suspensions

Abstract: The steady flow and the dynamic viscoelastic properties of cellulose fiber suspensions were investigated as functions of the suspension concentration and the fiber shape using a parallel-plate type rheometer. Various concentrations of the suspensions were made from various types of cellulose fibers, i.e., microcrystalline cellulose, bacterial cellulose, and fibrillated cellulose fibers. All the suspensions showed non-Newtonian flow even at very low concentrations. The flow property of each suspension showed a plateau of the shear stress, i.e., the yield stress, over a critical concentration. The critical concentration obtained from the experiment agreed well with the value theoretically calculated from the axial ratio of the fibers. The dynamic moduli of the suspensions were almost independent of the angular frequency, and they increased with the fiber concentration. The dynamic storage moduli increased in proportion to the 9/4th power of the fiber concentration. This power of 9/4 is coincident with that theoretically required for polymer gels. This fact suggests that the rigidity of the suspensions has appeared by the same mechanism from the order of cellulose fibers to microcrystalline cellulose fibers, and even to polymer molecules.

Effect of Particle and Salt Concentrations on the Rheological Properties of Cellulose Fibrous Suspensions

Abstract: Rheological properties of cellulose fibrous suspensions were measured with a cone-plate type rheometer. Effect of particle concentrations, c, and salt concentrations of the systems on the properties were studied. The flow curve of the fully dialyzed system showed Newtonian flow at a particle concentration of 0.1 wt%. However, it showed plateau regions of shear stress over a particle concentration of ca. 0.3 wt%, which is consistent with the critical concentration c0 calculated from the aspect ratio of the fiber particle. The dynamic moduli of the systems were almost independent of angular frequency. They were in proportion to c9/4. The absolute value of zeta potential of the cellulose particle was decreased with increasing salt concentration of the suspension. When the particle concentration was lower than c0, salt concentration had no influence on the flow properties of the system. At higher particle concentration, however, the yield stress was exponentially decreased with decreasing the absolute value of zeta potential of the particle. These facts indicate that the shear stress consists of two different contributions: one is caused by friction of the effective volume of the particles and the other arises from overlapping of the electric double layer of the particles.

A Model of Neck-in Phenomenon in Film Casting Process

Abstract: We propose a theory to predict the neck-in behaviour of polymer materials in the film casting process. To calculate the neck-in length, we employ the Dobroth-Erwin model 2) which assumes that the film deformation is planar in the central part, and uniaxial at the edge. We derive an equation for the edge line of the film and an expression for the neck-in length. For Newtonian fluid, the neck-in length is shown to be given by L/√2 , where L is the length of the air gap. For viscoelastic fluid, the neck-in length depends on the draw ratio. As an example, the neck-in length is calculated for Maxwell model, and the result is compared with experimental data.

Differences in rheological properties of solutions of plant and bacterial cellulose in LiCl/N,N-dimethylacetamide

Abstract: Differences in molecular properties of celluloses from different biological origins were investigated chiefly in terms of the rheological properties of their solutions in 8 wt % LiCl/N,N-dimethylacetamide (DMAc). Cotton linter (CC) and dissolving pulp (DP) were used as cellulose samples derived from plant, and a cellulose from Acetobacter xylinum was also used as a bacterial cellulose (BC). For the three kinds of cellulose solutions, the values of η0 − ηs (η0: zero shear rate viscosity of solution, ηs: solvent viscosity) were in proportion to the weight fraction of polymer, φw, in the dilute region. On the other hand, they were in proportion to φw 4 for the CC and the DP solutions and φw 3 for the BC solution in the semidilute or concentrated region. This φw-dependence of η0 − ηs shows that CC and DP, celluloses from plants, behave as a flexible polymer and that BC behaves as a rodlike polymer, according to several molecular theories. Plateau modulus, GN, was in proportion to φw 2 for the CC solution, signifying that network structure by entanglement was formed in the CC solution, as is often observed for solutions of flexible synthetic polymers. On the other hand, the concentrated solution of BC showed the typical small-angle X-ray scattering (SAXS) profile of two-phase systems, which can be well approximated by Debye-Bueche equation. This fact indicates that the structure of the BC solution apparently differs from the network structure.

Viscoelastic Relaxation of Linear Polyisoprenes : Examination of Constraint Release Mechanism

Abstract: Linear viscoelastic behavior was examined for a series of binary blends of linear polyisoprenes (PI). These blends contained high molecular weight (M) component chains (probe chains) that were dilute and entangled only with the lower-M matrix chains. The PI probe exhibited the Rouse-like constraint release (CR) relaxation in the matrix chains much shorter than the probe, but this CR-dominance vanished on a moderate increase of the matrix molecular weight because of the competition with other mechanisms (such as reptation). These features are qualitatively similar to, but quantitatively different from, those noted for binary blends of linear polystyrenes (PS): The CR-dominance was more easily achieved in the PI/PI blends than in the PS/PS blends, which suggests that the entanglement dynamics is not uniquely determined by the number of entanglement segments per chain and the relaxation time within this segment but is affected by additional molecular factors such as the local CR gate number considered by Graessley (Adv Polym Sci, 47, 67 (1982)).