Chang Fa Xiao

Preparation of Hydrophilic and Antifouling PVC/PAN Hollow fiber Membrane

Poly (vinyl chloride) /poly (acrylonitrile) (PVC/PAN) hollow fiber membrane was prepared by phase inversion method and it was hydrolyzed in different NaOH solution concentration. After hydrolysis modified, the change of surface characteristic of the PVC/PAN hollow fiber membrane was described by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and water contact angle. Morphological structures of membranes were observed by field-emission scanning electron microscope (FESEM). Protein filtration was employed to evaluate the antifouling performance of the membrane. All these results demonstrated that PVC/PAN hollow fiber membrane modified by hydrolysis showed high permeation flux, good hydrophilicity and antifouling.

Formation Mechanism and Properties of Polyvinylidene Fluoride (PVDF)/Nano-Silica Hybrid Membranes

By means of the wet phase inversion process, the PVDF/silica (SiO2) hybrid membranes with different content of nano-silica (nano-SiO2) were prepared. It was investigated that the pure water flux and retention based on egg albumin solution for different PVDF hybrid membrane samples. The pure water flux and porosity of PVDF/SiO2 hybrid membranes are enhanced simultaneously with increasing SiO2 content in PVDF composite system. When SiO2 content is around 7.5%, the phase separation rate of casting solution increases to peak value, meanwhile, the retention of hybrid membrane achieves the best effect. The SEM micrographs show that the quantity of finger-like pores of PVDF/SiO2 hybrid membranes decreases and the micropores becomes fine compared to PVDF membrane. The results of DSC indicate that there are almost no effects on the melting point, but enhancement the fusion enthalpy and the crystallinity of PVDF along with increasing the SiO2 content.

Preparation and Electrospinning of Acidified-Oxidized Potato Starch

This paper investigates the preparation and electrospinning of acidified-oxidized potato starch. In this article, acidified-oxidized potato starch was prepared by adding ammonium persulfate as an oxidizing agent and hydrochloric acid as a catalyst. The effect of reaction time, temperature, the concentration of hydrochloric acid and the content of ammonium persulfate on the viscosity and content of carboxyl were discussed. The optimum reaction conditions were as follows: 1.5 hours ,50°C, 0.5mol/l HCl, 2.5% (NH4)2S2O8. And then, the acidified-oxidized potato starch prepared at the optimum condition was dissolved in dimethyl sulfoxide (DMSO) to be electrospinned by contrast to native starch. Electrospinning of 5wt%-21wt% of modified starch in DMSO produced beads, beaded fibers, and smooth fibers, depending on the concentration range. Smooth fibers were observed until the concentration reached 19wt%, while native starch was 5wt%.

Preparation of Aligned Polysulfonamide Nanofibers by Magnetic Electrospinning

Preparation of uniaxially aligned nanofibers by electrospinning has been a new research hot spot in recent years. Well-aligned polysulfonamide (PSA) nanofibers with the diameter of 200nm were successfully prepared by magnetic electrospinning with the distance between the two magnets of 8cm. The key to the success of this method was the use of a collector composed of two permanent magnets to suffer an applied magnetic field. And the mechanism of magnetic electrospinning was also discussed in detail.

Non-Isothermal Crystallization Behavior of Poly(Ethylene Terephthalate)/Carbon Black Composite

Poly(Ethylene Terephthalate)(PET)/carbon black(CB) composite was prepared by melt blending using a separate feeding technique. The non-isothermal crystallization process of virgin PET and PET/CB composite were investigated by differential scanning calorimetry (DSC) and the different methods such as Jeziorny modified Avrami equation, Ozawa equation and the method developed by Mo were employed to analyze the non-isothermal kinetics of virgin PET and PET/CB composite. The results show that the CB particles dispersed in PET matrix act as heterogeneous nucleating agents, while CB particles hinder the movement of molecular chains of PET, meanwhile, the crystallization activation energy(⊿E) of PET/CB composite is much greater than that of virgin PET according to Kissinger formula, which is opposite to the low CB content condition. This indicates that CB particles reduce the rate of crystal growth. Whereas, the results obtained from the mentioned three methods simultaneously demonstrate the addition of CB greatly increases crystallization temperature and crystallinity and accelerates crystallization rate. Taking the two seemingly contradictory results, crystal growth has little effect on the crystallization rate and crystal nucleation dominate the crystallization process of PET/CB composite with very high CB content. According to Jeziorny method, the constant of crystallization rate (Zc) increases with the increment of cooling rate and Avrami index (n) doesn’t change significantly, but the Zc and n of PET/CB composite are greater than that of PET. Based on Ozawa method, lg[-ln(1-Xt)] and lgR don’t show a good linear relationship. The parameter F(T) increases significantly with the increasing of relative crystallinity and n is almost unchanged. Besides, the F(T) of PET/CB composite is less than that of PET, while a is greater than that of PET. Comparing with Ozawa and Avrami equation, Mo method can better describe the non-isothermal crystallization of PET and PET/CB composite.

Research on Preparation and Semi-IPN Structure of Absorptive Copolymethacrylate Fiber

By adding potential crosslinking agent--hydroethyl methacrylate (HEMA), the oil-absorptive fiber with semi-IPN structure CPMAF were prepared using heat crosslinking technology after spinning. The crosslinking structure of the fiber was researched. The results showed that the oil absorbency of fiber with semi-IPN structure was higher than the chemical crosslinked copolymethacrylate particle.

Study on the Preparation of Polytetrafluoroethylene Hollow Fiber Membranes and the Properties

In the present study, Polytetrafluoroethylene (PTFE) porous hollow fiber membranes were prepared by PTFE concentrated suspension with the mixture of Poly(vinyl alcohol) (PVA) and Sodium alginate as the fiber-forming carrier. Factors affecting PTFE membrane pore structure and mechanical properties were investigated. Results showed that, (1) the permeation and mechanical properties of the PTFE membrane were influenced significantly by the sintering condition, (2) Morphologies of membranes were observed by scanning electronic microscopy (SEM), fixed sintering state was aided to form the pore structure which was much different from the node-fibril network obtained by PTFE biaxial-stretching process.

Preparation of Polyacrylamide Nanofibers by Electrospinning

Polyacrylamide (PAM) nanofibers was spun by electrospinning. In order to increase the molecular weight of the PAM, It has been cross linked by Glutaraldehyde solution. By means of scanning electron microscopy (SEM), the effect of electrospun technological parameters on the fibers’ morphology were researched. The parameters include the concentration of PAM spinning solution, the applied voltage and tip-collector distance (TCD). The PAM nanofibers of uniform thickness with the fibers’ diameter distribution of 80 ~ 160nm were got under the conditions as followers: the concentration of 16 wt.%, applied voltage of 23 kV, the TCD of 13cm.

Poly(vinylidene fluoride) (PVDF) Membrane Preparation with an Ionic Liquid via Thermally Induced Phase Separation Melt Technology

Poly(vinylidene fluoride) (PVDF)/1-butyl-2,3-dimethylimidazolium Tetrafluoroborate ([BMMIm][BF4]) flat sheet membranes were made via thermally induced phase separation (TIPS) melt technology, and [BMMIm][BF4]) was used as a diluent. The prepared membranes were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) and etc. Furthermore, [BMMIm][BF4] as a liquid-diluent was effectively recovered by vacuum distillation. In conclusion, this work may provide a green and sustainable preparation method to produce PVDF membranes via TIPS.

Preparation and Properties of Two-Dimensional Braid Heterogeneous-Reinforced Polyvinylidene Fluoride Hollow Fiber Membrane

The two-dimensional braid heterogeneous-reinforced (BHR) polyvinylidene fluoride (PVDF) hollow fiber membranes which include PVDF polymer solutions (coating layer) and the two-dimensional braid as a reinforcement were prepared through the dry-wet spinning process. The influence of PVDF concentration in polymer solutions on performance of BHR hollow fiber membranes were investigated by terms of pure water flux, protein rejection, a mechanical strength test, and morphology observations by a scanning electron microscope (SEM). The results of this study indicated that the tensile strength of the BHR PVDF hollow fiber membranes was nearly 75 MPa and the hollow fiber membranes were endowed with better flexibility performance. The BHR PVDF hollow fiber membranes had a favorable interfacial bonding between the coating layer and the two-dimensional braid. The pure water flux decreased, while the rejection ratio increased with the increase of polymer concentration.