Cellulose triacetate (CTA)-based hollow fiber (HF) membrane is one of the commercially successful semipermeable membranes that has had a long progress since the time the excellent semi-permeable feature of cellulose-based polymers was found in 1957. Because of the reliable and excellent performances, especially for drinking water production from seawater, CTA-HFs have been widely used as reverse osmosis (RO) membranes, especially in arid regions. In this review, recent developments and research trends on CTA-HF membranes for seawater reverse osmosis (SWRO) plants were presented. A flux analytical model, an optimization strategy for chlorine injection without losing salt rejection performance, and a module of current high performance CTA RO membranes along with its plant operation data were updated in this paper. Furthermore, a newly developed CTA-HF membrane for brine concentration (BC) application (called BC membrane) was also addressed. Finally, RO/BC hybrid operation was introduced as an effective SWRO desalination technique that enables minimizing the volume of brine disposal from the RO plant by increasing the recovery ratio and the subsequent amount of produced freshwater, without an additional energy input.

Doi and Edwards (DE) proposed that the relaxation of entangled linear polymers under large deformation occurs in two steps: the fast chain contraction (via the longitudinal Rouse mode of the chain backbone) and the slow orientational relaxation (due to reptation). The DE model assumes these relaxation processes to be independent and decoupled. However, this decoupling is invalid for a generalized convective constraint release (CCR) mechanism that releases the entanglement on every occasion of the contraction of surrounding chains. Indeed, the decoupling does not occur in the sliplink models where the entanglement is represented by the binary interaction (hooking) of chains. Thus, we conducted primitive chain network simulations based on a multichain sliplink model to investigate the chain contraction under step shear. The simulation quantitatively reproduced experimental features of the nonlinear relaxation modulus $G\left(t,\gamma \right)$ . Namely, $G\left(t,\gamma \right)$ was cast in the time-strain separable form, $G\left(t,\gamma \right)=h\left(\gamma \right)G\left(t\right)$ with $h\left(\gamma \right)=\text{damping}$ function and $G\left(t\right)=\text{linear}$ modulus, but this rigorous separability was valid only at times $t$ comparable to the terminal relaxation time, although a deviation from this form was rather small (within ±10%) at $t>{\tau }_R$ (longest Rouse relaxation time). A molecular origin of this delicate failure of time-strain separability at $t\sim {\tau }_R$ was examined for the chain contour length, subchain length, and subchain stretch. These quantities were found to relax in three steps, the fast, intermediate, and terminal steps, governed by the local force balance between the subchains, the longitudinal Rouse relaxation, and the reptation, respectively. The contributions of the terminal reptative mode to the chain length relaxation as well as the subchain length/stretch relaxation, not considered in the original DE model, emerged because the sliplinks (entanglement) were removed via the generalized CCR mechanism explained above and the reformation of the sliplinks was slow at around the chain center compared to the more rapidly fluctuating chain end. The number of monomers in the subchain were kept larger at the chain center than at the chain end because of the slow entanglement reformation at the center, thereby reducing the tension of the stretched subchain at the chain center compared to the DE prediction. This reduction of the tension at the chain center prevented completion of the length equilibration of subchains at $t\sim {\tau }_R$ (which contradicts to the DE prediction), and it forces the equilibration to complete through the reptative mode at $t⪢{\tau }_R$ . The delicate failure of time-strain separability seen for $G\left(t,\gamma \right)$ at $t\sim {\tau }_R$ reflects this retarded length equilibration.

In general, clothing pressure is measured using a sensor set on the surface of a human body or dummy, and it is not possible to measure clothing pressure without the sewing process. We have developed a numerical-analysis-based technique to simulate clothing pressure without having to sew the cloth into clothes. We presupposed that clothing made of knitted fabric was applied to a mannequin in close contact with its surface. Based on this simulation, this paper proposes a model for fabric deformation, by extension applicable to large deformation, with anisotropy and non-linearity taken into account. In this model, the fabric is separated into isotropic and anisotropic elements, and non-linearity is assigned to both the isotropic and anisotropic elements. Furthermore, to use this model, we propose a method for fitting the knitted fabric tightly to a human body model while sewing the knitted fabric model reflecting the paper pattern. To prevent excessive extension of the knitted fabric model reflecting the paper pattern during the process of fitting, we adopted the two-step fitting method involving application of the fabric to a temporary human body model (intermediary) followed by its application to a formal human body model. The clothing pressure values calculated with this method were very close to the actually measured values using a rigid mannequin.

Molecular theories for polymer rheology are based on conformational dynamics of the polymeric chain. Hence, measurements directly related to molecular conformations appear more appealing than indirect ones obtained from rheology. In this study, primitive chain network simulations are compared to experimental data of entangled DNA solutions [Teixeira et al., Macromolecules 40, 2461 (2007)]. In addition to rheological comparisons of both linear and nonlinear viscoelasticities, a molecular extension measure obtained by Teixeira et al. through fluorescent microscopy is compared to simulations, in terms of both averages and distributions. The influence of flow on conformational distributions has never been simulated for the case of entangled polymers, and how DNA molecular individualism extends to the entangled regime is not known. The linear viscoelastic response and the viscosity growth curve in the nonlinear regime are found in good agreement with data for various DNA concentrations. Conversely, the molecular extension measure shows significant departures, even under equilibrium conditions. The reason for such discrepancies remains unknown.