Cellulose Acetate Hollow Fiber Membranes from Banana Stem Fibers Coated by TiO2 for Degradation of Waste Textile Dye

Cellulose acetate hollow fiber membrane from banana stem fibers coated by TiO2 (CAHFMT) was prepared and characterized as an alternative material for degradation of waste textile dye. Its applicability was demonstrated by mechanical properties, FTIR, SEM, thermal resistance, performance, and degradation efficiency. Cellulose acetate (CA) was synthesized from banana stem fibers by swelling stage, acetylation reaction, and hydrolysis reaction. CA was modified using TiO2 of various concentrations. CAHFMT with 22 % w/v dope concentration has the optimum mechanical properties (stress, strain and Young’s modulus), as well as hydrophilic properties. The performances of CAHFMT with Congo red were determined. The SEM results showed that the membrane had rigid pores. Moreover, this research stated that CAHFMT could be a solution to overcome economical and effective problems.

Experimental and Numerical Analyses on the Poly(Lactide-Co-Glycolide) Hollow Fiber Membranes

The hollow fiber membranes (HFMs) were widely used as tissue engineering scaffold. The efficacy of the HFMs were affected by the porosity of the HFMs. In this study, the HFMs were prepared with dry-jet wet spinning method. In order to improve the performance of the HFMs, different spinning parameters were applied to systematically investigating the effects of the fabrication conditions on the porosity of the HFMs. A 1-D diffusion model was set to numerically study the volume fraction distribution along the wall thickness. The porosity of the HFMs show a significant decrease in the porosity as the dope concentration increases. The morphology analyses showed that a higher dope concentration leads to a denser porous structure which result in a lower porosity. The results were discussed based on the phase inversion process and the 1-D model was built to numerically analyze the polymer volume fraction distribution in the HFMs cross section. This study can help to better understand the effects of the different fabrication conditions on the morphology of the HFMs.

Determination of distribution of heat-conducting material concentration in protective layer of thermal protection system panel

Paper presents the problem of heating the damaged insulation of an orbiter. Changes of the insulation?s thermal properties, made by adding conductive material of high value of specific heat in a form of a dope to the protective layer, were examined. An iterative algorithm determining a variable of dope concentration in the material was developed. Insulating material LI900 was used for calculations. Determination of distribution of conductive material concentration was made for materials which, after verification, demonstrated the most beneficial effect on protective properties of the modified insulation layer. Change of properties was to enable time extension of the LI900 insulation tile heating up to the maximal temperature and, additionally, to lowering this temperature.

Effect of Molecular Weight and Concentration on Gel-Spun UHMWPE Fibers With Polybutene as a New Spin Solvent

Ultrahigh molecular weight polyethylene (UHMWPE) fibers have been investigated for years to improve performance with gel spinning process for wide applications in industry. Various spin solvents have been attempted including paraffin oil, decahydronaphthalene (decalin), kerosene etc. However, more work still needs to be done because of environmental issues or long extraction process of the aforementioned solvents. Recently, polybutene was found to be an effective spin solvent for UHMWPE fibers, which is environmentally friendly and widely available on the market. Besides producing high strength fibers, compared to paraffin oil, polybutene can form a gel with UHMWPE showing stronger phase separation behavior at room temperature. Because of this property, more extraction solvents can be saved. It was also demonstrated with experiments that the extraction efficiency is higher than that of the gel fiber formed with paraffin oil. Thus, polybutene has high potential to be used in large-scale production of UHMWPE fibers, which deserves further study. In this work, polybutene with different molecular weight was used to form spin dopes with UHMWPE. The dope concentration for each type of polybutene was also varied to check the effect of molecular weight and dope concentration on fiber properties. Viscoelastic properties of the spin dopes were obtained with parallel plate rheometry while thermodynamic properties of the dopes were characterized with differential scanning calorimetry (DSC) and thermal gravitational analysis (TGA). With optimized processing conditions, high strength fibers were collected and the crystalline structure was examined with wide angel X-ray diffraction (WAXD). DSC and TGA data also provided support for the effect of molecular weight and concentration of polybutene. It can be found that stronger fibers are obtained with lower concentration spin dopes. The viscosity of the dopes and corresponding spinning conditions are significantly affected by molecular weight of polybutene. Extraction efficiency is affected by both molecular weight and dope concentration. To obtain cost-effective superstrong UHMWPE fibers, an optimized design is needed based on the molecular weight of polybutene and the spin dope concentration.

Fabrication and Characterization of Alginate Fibers by Wet-Spinning

Alginate fibers were prepared by extruding a concentrated sodium alginate solution into calcium chloride coagulation bath. The rheological behavior of different concentrations of sodium alginate solutions were investigated to evaluate the spinnability. The effect of dope concentration on the morphologies and mechanical properties of resulting alginate fibers were examined. The results showed that sodium alginate solutions were pseudoplastic fluid and had good spinnability with concentration ranging in 1.5%-3.5%. Moreover, the morphology of obtained fibers became smoother with increasing sodium alginate concentrations. When the sodium alginate concentration was 3.5%, the tensile strength and elongation at break of alginate fibers reach to 13.6±1.2 cN/tex and 8±0.5%, respectively.

Influence of Dope Concentration on Morphology And Properties of Cellulose Hollow Fiber Membranes Prepared from Cellulose/[Amim]Cl Dope Solution

Basing on a L-S phase inversion method, cellulose hollow fiber membranes were spinned using room temperature ionic liquid 1-allyl-3-methylimidazolium chloride ([Amim]Cl) as solvent. The concentration of cellulose/[Amim]Cl solutions (dope) was varied from 6 to 9wt% by an increment of 1wt%. Effects of the dope concentration on the hollow fiber membranes structure and properties were investigated. Inner- and outer- surfaces morphology of the prepared membranes were observed using field emission scanning electron microscope (FESEM). Besides, various properties of the membranes, including apparent viscosity, pure water flux (PWF), retention rate (Rt), equilibrium water content (EWC), ultimate tensile strength (UTS) and elongation at break (Eb) were also tested. The results induced that, with the increase of dope concentration, the both surfaces showed more regular. Pure water flux and equilibrium water content of the membranes decreased with a increasing dope concentration, properties of retention rate, ultimate tensile strength and elongation at break showed a increased tendency oppositely.