Shi Yan Chen

Microstructure and Property Changes of Poly ( Ethylene Terephthalate) Fiber with Moderate Tenacity during Heat Treatment under Constant-Length Conditions

In this paper, Wide Angle X-ray Diffraction (WAXD), Small Angle X-ray Scattering (SAXS), Dynamic Mechanical Analysis (DMA) and mechanical testing were employed to characterize the effect of heat treatment under constrained condition on poly(ethylene terephthalate) (PET) fiber. The microstructure and property of the PET fiber with moderate tenacity changed with the heat treatment temperature from 110 °C to 190 °C. No change happened in the crystalline phase while the micro-crystal formed in the amorphous phase from the result of crystalline parameters, which led to the increase of Tg of the fiber. The decrease of the tenacity is due to the decrease of the amorphous orientation and the decrease of the long period leads to the increase of the stability of the fiber.

Facile Preparation of Gradient Structure Bacterial Cellulose Using Potato Starch

Membranes of bacterial cellulose (BC) produced by Gluconacetobacter xylinus combines well-known cellulose properties with the outstanding features of nanoscale materials. As a remarkable benefit of BC, the property-controlling fiber network and pore system formed by self-assembly of the cellulose molecules can be modified in situ using additives during biosynthesis. The addition of potato starch (PS) caused the double-stage morphology of the BC/PS pellicles with an opaque dense upper part and a transparent porous lower part. Moreover, as the starch content went up, the double-stage morphology of BC/PS pellicle could be easily controlled. A gradient cross-section structure could be observed through the scanning electron microscopy (SEM) as potato starch addition level increased. The BC/PS nanocomposite structure was studied using X-ray diffraction and ATR-FTIR spectroscopy, and with the introduction of gelatinized starch, the crystallinity index (CrI) of BC/PS nanocomposite reduced from 82.40 % to 72.15 %. Meanwhile, tensile strength of the freeze-dried sample reached maximum as starch content was 0.5 wt%.

TEMPO-Mediated Oxidation of Bacterial Cellulose in Buffer Solution

Oxidized bacterial cellulose (BC) was prepared in Na2CO3-NaHCO3 buffer solution using NaClO as a primary oxidant with catalytic amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and NaBr at pH 10.5. Ethylenediamine was used as activators to pretreat BC in order to increase the accessibility of primary hydroxyl groups. The structures and properties of oxidized BC were characterized by attenuated total reflection infrared spectroscopy (ATR-IR), elemental analysis (EA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the reformative oxidation successfully introduces carboxyl groups into BC, and the carboxyl content was found to be 1.34mmol per gram cellulose, higher than that of BC without pretreatment (0.81 mmol/g carboxyl introduced) under the same condition. In addition, the oxidized BC maintained the original structure which could expand the application of BC.

The Effect of Bacterial Cellulose (BC) Fiber Content on the Properties of BC Fiber Reinforced Nanocomposites

Optically transparent nanocomposites were prepared by epoxy resin reinforced with bacterial cellulose nanofibers in volume fraction from 2.6 to 32.7wt%. The transparence, surface smoothness, thermal expansion and mechanic properties of the nanocomposites with different BC fiber content were characterized. It was found that the nanocomposites display high visible light transparence (84% at 600nm) even at high fiber content (32.7 wt%). The coefficient of planar thermal expansion (CTE) was reduced from 83.8 ppm/K (Epoxy resin) to 40.6 ppm/K at low fiber content (2.6 wt%). The high transparence was insensitive to the change of temperature from room temperature to 90 oC.

Effect of Relax Heat Treatment on the Performance of PET Fibers of HMLS

To characterize the performance of Poly(ethylene terephthalate) (PET) fibers of high modulus and low shrinkage (HMLS), static and dynamic mechanical test, DSC, DMA and sonic orientation experiments were carried out. The results indicated that tenacity, initial modulus, Lase-5 decreased and ultimate elongation increased with heat treatment temperature. The dimensional stability of the HMLS fiber is limited by the heat treatment especially when the temperature exceeded Tg because a larger plastic deformation happen with the relaxation of molecular chain in amorphous phase.

Preparation and Characterization Flexible Conductive PPy/BC Nanocomposite Membrane

Polypyrrole (PPy) is an intrinsically conducting polymer that has a wide variety of potential applications on electrical devices, sensors, electrode material, anticorrosion and antistatic coatings. Bacterial cellulose (BC), a natural nano-material with outstanding properties, can be used as a template material. In this study, water-wet BC was firstly used to prepare PPy/BC nanocomposite membrane by combining with PPy. The obtained nanocomposite showed excellent performances such as high conductivity, considerable mechanicl behavior and perfect flexibility. Effects of pyrrole concentration and reaction time on the electrical conductivity of the membrane were investigated. Besides, FT-IR, FE-SEM and mechanical properties were studies. The results revealed that it was possible to develop a novel PPy/BC nanocomposite with potential applications on flexible displays or sensors.

Synthesis and Characterization of Bacterial Cellulose/Calcium Silicate Composites

A novel composites material consisting of calcium silicate deposited in bacterial cellulose membrane was synthesized by immersing BC membrane in the calcium and silicate solutions by turns with different cycle times and characterized. The results indicated that the CaSiO3 particles were homogeneously dispersed on the surface of nanofibers with the effect of BC template when two cycles of soaking proceed, during which the fabrication of most CaSiO3 particles took place. The FT-IR reveals the strong interaction between the two parts of the BC/CaSiO3 composite. The XRD pattern demonstrated a crystal structure disruption of the cellulose aroused by CaSiO3 particle. BC/ CaSiO3 is considered to have a potential application in bone tissue field.

Easy Preparation of Bacterial Cellulose/Triamcinolone Acetonide Composites and their Inhibition for Fibroblasts

Wound healing is accompanied by keloids, it is important to develop a wound dressing which can inhibit keloid and relieve pain and pruritus in patients. In this paper, bacterial cellulose/triamcinolone acetonide (BC/TA) composites are prepared by easy solution impregnation method, which the structures of BC/TA composites were analyzed by fourier transform infrared spectroscopy (FTIR). The drug release and inhibition of L929 cells were also analyzed. It can be concluded that BC/TA composites have a sustained release effect on TA and can effectively inhibit proliferation of L929 in the range of 0.5-2.0 mg/cm2.

Effect of Two-Step Treatments on Interfacial and Mechanical Properties of Sugarcane Rind Fiber/Natural Latex Biodegradable Composites

Sugarcane rind fiber/natural latex biodegradable composites were prepared by compounding natural latex with sugarcane rind fiber as reinforcing filler. We selected three chemical solvents, including sodium hydroxide (NaOH), silane (KH550) and acrylic acid (AA), and used one-step or two-step treatment method to improve the interfacial adhesion between sugarcane rind fiber and natural latex matrix. Fourier Transform Infrared spectroscopy (FTIR) was used to characterize the chemical composition change at the sugarcane rind fiber surface structure by the chemical treatments. Scanning Electron Microscopy (SEM) results showed that the interfacial adhesion and dispersion of the composites based on two-step treated fiber were improved. The mechanical properties of these biodegradable composites were evaluated, which showed an increase of the tensile strength and elongation at break of the composites based on two-step treated fiber compared to those based on untreated fiber.

Preparation and Properties of BC/PPy/TiO2 Composite Membrane

Bacterial cellulose (BC) /Polypyrrole (PPy) /TiO2 composite membrane was successfully prepared by in situ chemical oxidation polymerization of pyrrole in TiO2 sol into BC membrane matrix with different concentration of TiO2. The results of the field emission scanning electron microscopy observation revealed that the TiO2 nanoparticles coated with PPy were well homogeneously dispersed in the BC matrix. The photocatalytic activity of composite membrane was measured by methyl orange reaction model. Furthermore, the chemical structure of composite membrane and the anatase-TiO2 crystal structure were characterized by FT-IR spectroscopy and XRD analysis, respectively. According to this study, the photocatalytic activity of composite membranes was improved significantly by the addition of TiO2 due to the synergistic reaction between TiO2 and PPy. Besides that, the membrane exhibited the striking flexibility and mechanical properties. This study provided a green and facile method to prepare the BC /PPy /TiO2 composite membrane which would have potential applications in wastewater treatment.