Quan Ji

THERMAL DEGRADATION AND FLAME RETARDANCY OF CALCIUM ALGINATE FIBERS

Calcium alginate fibers were prepared by wet spinning of sodium alginate into a coagulating bath containing calcium chloride. The thermal degradation and flame retardancy of calcium alginate fibers were investigated with thermal gravimetry (TG), X-ray diffraction (XRD), limiting oxygen index (LOI) and cone calorimeter (CONE). The results show that calcium alginate fibers are inherently flame retardant with a LOI value of 34, and the heat release rate (HRR), total heat release (THR), CO and CO2 concentrations during combustion are much lower compared with those of viscose fibers. Calcium carbonate and calcium oxide were formed during thermal degradation of calcium alginate fibers at different temperatures. The shape of calcium alginate fibers is well kept after LOI test. The rigid combustion residue char acts as an effective barrier to the outward diffusion of flame and heat. The combustion process and flame retardant mechanism of calcium alginate fibers are also discussed.

Improve the flame retardancy of cellulose fibers by grafting zinc ion.

Zinc ion as the only flame retardant of cellulose fibers was successfully grafted onto cellulose fibers. Grafting maleic anhydride onto cellulose fibers via homogeneous acylation reaction between N,N-dimethyl formamide (DMF) as the first step. Then, graft zinc ion onto the formed cellulose fibers was conducted with zinc carbonate. The resulting copolymers were characterized by FTIR. Flame retardancy and thermal degradation of zinc-ion-modified cellulose fibers (cellulose-Zn fibers) was investigated by limiting oxygen index (LOI), cone calorimeter (CONE), XRD, TG and SEM. Zinc ion could effectively improve flame retardancy and thermal degradation when its content increases up to 4.96 wt%.

The effect of zinc ion content on flame retardance and thermal degradation of alginate fibers

The study employs limiting oxygen index (LOI) measurements, cone calorimetry (CONE) and thermogravimetric analysis (TGA) to examine the catalytic effect of zinc ion content on the flame retardance and thermal degradation of alginate fibers. LOI results show that all zinc alginate fibers are intrinsically flame retardant, with LOI values of over 27.0, as compared with about 24.5 for alginic acid fiber. The heat release rate (HRR) and total heat release values of zinc alginate fibers (obtained from CONE) are significantly less than those of alginic acid fiber, and decrease with increasing zinc ion content. TGA indicates that char formation increases and maximum thermal weight-loss rate is reduced when zinc content in the fibers is increased. The residues of zinc alginate fibers keep their shapes better than those of the alginic acid fiber. Further discussion of the combustion process and flame retardant mechanism is presented.

Electrospinning of Sodium Alginate with Poly(ethylene oxide), Gelatin and Nanometer Silver Colloid

In this study, biocompatible polymer poly(ethylene oxide) (PEO), gelation (denatured collagen) and nanometer silver colloid was added to the electrospinnning solution of alginate sodium to get anti-bacterial nanofiber mats. The morphology and mechanical properties of the electrospun mats have been investigated. Smooth fibers with diameters around 300 nm were obtained from 4.0 % solutions of varied alginate/PEO/gelation proportion. The anti-water property of the electrospun mats has been improved by crosslink with glutaraldehyde acetone solution and aqueous calcium chloride and ethanol.

Influence of Na(+) and Ca(2+) on flame retardancy, thermal degradation, and pyrolysis behavior of cellulose fibers.

Flame-retardant cellulose-Na and cellulose-Ca fibers were successfully synthesized by grafting Na+ and Ca2+ onto cellulose fibers, and confirmed by FTIR. The combustion behavior of the fibers was assessed by the limiting oxygen index (LOI) and cone calorimeter (CONE). The maximum LOI values of cellulose-Na and cellulose-Ca fibers were 31 and 30, which are higher than that (19) of cellulose fibers. The CONE results showed that the values of heat-release rate and total heat release for cellulose-Na and cellulose-Ca fibers were significantly lower than those for cellulose fibers. The thermogravimetric analysis (TG) and differential thermogravimetric analysis (DTG) curves in the continuous and trigger modes showed that the cellulose-Na and cellulose-Ca fibers generated more residues than cellulose fibers. Thermogravimetric analysis-gas chromatography-mass spectrometry was used to detect the characteristic gases produced in the pyrolysis of cellulose-Na and cellulose-Ca fibers.

Removal of methylene blue from water by cellulose/graphene oxide fibres

ABSTRACT A novel and efficient cellulose/graphene oxide (CGO) fibre adsorbent was prepared by wet-spinning technique. The morphology and physicochemical properties of the CGO fibres were characterised by scanning electron microscope (SEM), Fourier transform infrared spectrometer, and thermo-gravimetric analysis. The equilibrium adsorption data were well fitted to the Langmuir models, and the adsorption capacity calculated from the Langmuir model reached 480.77 mg/g at 318 K. The adsorption kinetic studies revealed that pseudo-second-order model best describes the adsorption kinetic data. The thermodynamic parameters indicated that the adsorption was an endothermic and spontaneous process. Furthermore, the CGO fibre, which is very stable and easily separable, can be recycled with a dilute NaOH solution wash, retaining over 93% of the adsorption capacity after recycling three times.

Physical hydrogels constructed on a macro-cross-linking cationic polysaccharide with tunable, excellent mechanical performance

Cationic chitosan was exploited originally as a macro-cross-linker to prepare hydrogels with superb extensibility, perfect elasticity, high toughness and fatigue-resistance by one-step free-radical polymerization. The as-developed approach can be applied to a broad range of hydrophilic monomers and unsaturated Bronsted–Lowry acids, leading to hydrogels with tunable performance.

Batch Studies of Zinc(II) Ion Adsorption onto Alginic Acid Fibres

The ability of alginic acid fibres to remove Zn(II) ions from aqueous solution was investigated by batch experiments. The effect of experimental parameters including pH, agitation time, initial Zn(II) ion concentration, temperature and biosorbent dosage on the biosorption of Zn(II) ions from aqueous solution was studied. Thermodynamic studies of Zn(II) ion biosorption demonstrated the exothermic nature of the process. Kinetic studies showed that the biosorption conformed to the pseudo-second-order and intra-particle diffusion models. The Langmuir and Freundlich isotherm models provided a good fit to the experimental data. The activation energy for the biosorption process suggested that it occurred in a physical manner. Alginic acid fibres have been demonstrated to be effective marine materials for the removal of Zn(II) ions from aqueous solution.

Influence of alkaline metal ions on flame retardancy and thermal degradation of cellulose fibers

Cellulose-Na and cellulose-K fibers are obtained by alkalization and etherification of viscose fiber. Flame retardancy and thermal degradation of cellulose-Na and cellulose-K fibers are investigated using limiting oxygen index (LOI), cone calorimetry (CONE), thermal gravimetry (TG), and differential TG (DTG). The LOI values of cellulose-Na and cellulose-K fibers are 33 and 30, compared with about 20 for viscose fiber. In CONE studies, cellulose-Na and cellulose-K fibers show much lower heat release rates, total heat release and effective heats of combustion than viscose fiber does. In addition, TG and DTG studies reveal that the second initial degradation temperature, the temperature of maximum degradation rate and the maximum degradation rate for cellulose-Na and cellulose-K fibers are much lower than those of viscose fiber. Cellulose-Na and cellulose-K fibers generate much more residue or carbonaceous char than viscose fiber does. Scanning electron microscopy studies of combustion residues after LOI testing indicate that cellulose-Na and cellulose-K fibers produce massive, thick residue crusts.

Preparation and Properties of Alginate Salt Fibers: An Inherent Flame-Retardant, Biodegradable Fiber

Alginate calcium fibers were prepared through wet spinning with good tensile strength which can be used for cloth materials. The morphology, mechanical property and combustion property of alginate calcium fibers were investigated. Blending yarns and textile of alginate calcium fibers and combed cotton was fabricated with good hand feeling and strength. Alginate salt fiber was prepared with wet spinning machine designed according to viscose fiber spinning machine. The diameter of alginate calcium fibers was about 10-15µm in diameter with smooth surface. The tensile strength of alginate salt fiber was larger than 4.8 cN in the dry state. The value of Limited Oxygen Index (LOI) of alginate calcium fibers was 34%. The average heat release rates (HRR) of the alginate fiber is about 21 kW/m2 which was much lower than that of most synthetic and natural fibers analysized with Cone. Alginate calcium fibers is an inherent flame-retardant fiber.