Eiichi Takatori

Nonlinear viscoelastic behavior of aqueous detergent solutions

Abstract Nonlinear viscoelastic behavior of aqueous solutions consisting of a cationic detergent, cetyltrimethylammonium bromide, and sodium salicylate as an added salt was examined with varying salt concentration. The nonlinear properties varied markedly with varying C*S, the concentration of free salicylate ion not caught in the detergent-salt complex. The systems with low C*S exhibited a kind of strain-hardening: the shear relaxation modulus, G(t, γ), increased with increasing magnitude of strain, γ; the shear stress, σI(t, γ . ) increased enormously and exhibited a marked overshoot at the start of shear flow of high rate of shear, γ . . The nonlinear behavior of systems with high C*S is somewhat similar to those of polymeric liquids: G(t, γ) decreased with increasing γ; the ratio σI(t, γ . / γ . was always a decreasing function of γ . . On the other hand, σI(t, γ . ) at high γ . exhibited a damped oscillatory behavior, which has not been reported for most of the polymeric systems. Evidently the viscoelastic properties cannot be described by the integrated constitutive equation with strain-dependent memory function which are suitable for polymeric liquids.

Viscoelastic properties of semidilute poly(methyl methacrylate) solutions

Viscoelastic properties were examined for semidilute solutions of poly(methyl methacrylate) (PMMA) and polystyrene (PS) in chlorinated biphenyl. The number of entanglement per molecule, N, was evaluated from the plateau modulus, GN. Two time constants, τs and τ1, respectively, characterizing the glass-to-rubber transition and terminal flow regions, were evaluated from the complex modulus and the relaxation modulus. A time constant τk supposedly characterizing the shrink of an extended chain, was evaluated from the relaxation modulus at finite strains. The ratios τ1/τs and τk/τs were determined solely by N for each polymer species. The ratio τ1/τs was proportional to N4.5 and N3.5 for PMMA and PS solutions, respectively. The ratio τk/τs was approximately proportional to N2.0 in accord with the prediction of the tube model theory, for either of the polymers. However, the values for PMMA were about four times as large as those for PS. The result is contrary to the expectation from the tube model theory that the viscoelasticity of a polymeric system, with given molecular weight and concentration, is determined if two material constants τs and GN are known.

Thermal process-dependence of the mechanical properties and inner structures of pre-consumer recycled polypropylene

Recycled plastics are considered to have less-desirable mechanical properties and durability than virgin materials, and this is usually thought to be due to chemical degradation. However, we recently found that pre-consumer polypropylene (Pre-RPP) was not chemically degraded and had almost the same molecular properties as virgin polypropylene (VPP). In this study, we subjected recycled pre-consumer polypropylene to various thermal treatments and found that we could obtain properties similar to those of virgin polypropylene. We also investigated the fracture surfaces by SEM. The results showed that the mechanical properties were closely related to the inner structure, and if we can control the inner structure of Pre-RPP we may be able to improve its mechanical properties and durability so that they are almost the same as those of VPP.

Single-Point Intrinsic Viscosity: Intrinsic Viscosity in the SEC-Viscometry

Many workers proposed an equation for a single point determination of intrinsic viscosity [η]. In these methods Solomon-Cuitas and Solomon Gotesmans equations were suitable with concentration of polymer c up to specific viscosity ηSp<0.6, and Fikentschers with concentration c nearly equal to ηSp=1.5. In SEC-Viscometry, ηSp/c was equal to Solomon-Cuitas and Solomon Gotesmans. Significant data were ηSp and c.

Self‐diffusion of micelles and viscoelasticity of aqueous detergent solutions (abstract)

The viscoelasticity and self‐diffusion were investigated for aqueous solutions of cetyltrimethylammonium bromide (CTAB) containing sodium salicylate (NaSal). The concentration of CTAB, CD, was equal to that of NaSal, CS. This system contains thread‐like micelles and exhibits pronounced viscoelastic behavior. The storage modulus G’ and loss modulus G ‘ could be fitted with the Maxwell model of one relaxation time when CD<0.5 M. The plateau modulus GN was proportional to CD2; over a wide range of CD. This property is similar to that of concentrated polymer solutions. The relaxation time τ was evaluated from the frequency at which G ‘ takes maximum. The self‐diffusion coefficient D was measured by forced Rayleigh scattering measurement. The quantities D and τ−1 varied in a similar manner as a function of CD; when CD<0.2 M, they increased with CD and when CD<0.2 M, they decreased with CD. This behavior is remarkably different from polymer solutions. The rate of diffusion may be controlled by the rate of the p...