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In this paper, the effects of sepiolite as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene (PP/IFR) were studied using the limiting oxygen index (LOI), the UL-94 test, thermogravimetric analysis (TGA), laser Raman spectroscopy (LRS), cone calorimeter test (CCT) and scanning electron microscopy (SEM), and the IFR system mainly consisted of the ammonium polyphosphate modified with γ-aminopropyltriethoxysilane coupling agent, melamine and dipentaerythritol. The results from the LOI and UL 94 tests show that sepiolite added to the PP/IFR system has a synergistic flame retardant effects with the IFR system. The TGA results reveal that sepiolite enhances the thermal stability of the PP/IFR composite and increases the char residue formation. The cone calorimeter results indicate that the heat release rate, mass loss rate, total heat release and average specific extinction area of the PP/IFR/sepiolite composite decrease in comparison with the PP/IFR composite. The LRS measurements provide useful information on the carbonaceous microstructures. The morphological structures observed by SEM have demonstrated that sepiolite promote the formation of the reinforced and homogeneous char barrier on the surface of the composites. Simultaneously, the Young’s modulus and flexural modulus of the PP/IFR composites are also much better improved with the increase of sepiolite added.
This paper reports the wettability transition of plasma-treated polystyrene (PS) micro/nano pillars-aligned patterns. The micro/nano pillars were prepared using hot embossing on silicon microporous template and alumina nanoporous template, which were fabricated by ultraviolet (UV) lithography and inductive coupled plasma (ICP) etching, and two-step anodic oxidation, respectively. The results indicate that the combination of micro/nano patterning and plasma irradiation can easily regulate wettabilities of PS surfaces, i.e. from hydrophilicity to hydrophobicity, or from hydrophobicity to superhydrophilicity. During the wettability transition from hydrophobicity to hydrophilicity there is only mild hydrophilicity loss. After plasma irradiation, moreover, the wettability of PS micro/nano pillars-aligned patterns is more stable than that of flat PS surfaces. The observed wettability transition and wettability stability of PS micro/nano pillars-aligned patterns are new phenomena, which may have potential in creating programmable functional polymer surfaces.
Electrostatic spinning (Electrospinning, ES) was applied to prepare Donepezil HCl loaded nanofibers as a potential orally dissolving dosage form. Electrospinning of water solutions of different polymers were performed in order to fabricate a consistent and removable web on the collector with ultra-fast dissolution in water based media. Poly(vinyl-alcohol) of low molecular weight was found to be the most appropriate for this purpose. Morphology of the prepared nanofibers was characterized by scanning electron microscope as a function of viscosity and drug content. Diameters of the fibers were between 100 and 300 nm with narrow distribution. In vitro drug release of the webs was immediate (less than 30 s) after immersion independently of their drug content owing to the formed huge surface area, while cast films with the same compositions and commercial tablets needed 30 min or more for complete dissolution. The developed technology for the preparation of orally dissolving web (ODW) formulations is a promising way for producing effective and acceptable dosage forms for children, older people and patients with dysphagia.
In this study, a novel pH/temperature sensitive hydrogel bead with core-shelled structure, composed of calcium alginate (Ca-alginate) and poly((N-acryloylglycine) (PAG), was prepared using as a drug delivery system. The equilibrium swelling has indicated the distinct sensitivities of the beads to pH value and temperature. In pH = 7.4 phosphate buffer solution (PBS), the cumulative release amount of indomethacin loaded in the core of the beads was about 83.5% within 650 min, whereas this value only reached 16.6% in pH = 2.1 PBS. In addition, the release rate of indomethacin was much faster at 37°C than that at 24°C. The experimental results have showed that the Ca-alginate/PAG beads have a potential application for the pH/temperature-controlled drug release carrier in the biomedical field.
In the present study biodegradable microparticles of silk fibroin (SF)/starch blends were prepared by a simple water-in-oil emulsion solvent diffusion technique. SF/starch blended solution and ethyl acetate were used as water and oil phases, respectively. The influence of SF/starch ratios on characteristics of the blended microparticles was investigated. The SF conformation of microparticle matrices from FTIR analysis was changed from random coil to β-sheet form by blending with starch. The blended microparticles had lower dissolution in water than those of SF and starch microparticles. The 1/3 (w/w) SF/starch blended microparticles exhibited the lowest dissolution. The SF and starch microparticles showed irregular and deflated shapes, respectively. The blended microparticles were nearly spherical in shapes and smaller sizes. Thermal stability of the blended microparticles slightly increased with the starch blended ratio. The results suggested that SF conformational transition, thermal stability, morphology and dissolution of the blended microparticles can be adjusted by varying the blended ratio.
In recent years a great interest in the study of the association of magnetic with biological material for bioapplications has been observed in the literature. This work analyses the development of new magnetic biocomposite films from a magnetic ferrite and a biopolymer. Magnetic and dielectric properties of Y3Fe5O12 (YIG)/collagen composite films were studied as a function of the YIG concentration. This biocomposite was also characterized by Infrared Spectroscopy (IR), Thermal Analysis (DSC and TG) and scanning electron microspcopic (SEM) methods. The magnetization and dielectric measurements were performed at room temperature. The results demonstrated that ferrimagnetic garnet (YIG) and collagen (Col) can be used to obtain a homogeneous composite. All the composite films showed a ferromagnetic behavior and they were characterized as a soft magnet material. These results show that Col-YIG biocomposites are biological films with magnetic properties that can be employed as a versatile performance materials, due to their flexible dielectric and magnetic features. They could be used as electronic devices in biological applications.
The influence of sizing constituent distribution on the properties of sized glass fibres (GFs) and corresponding polypropylene (PP) composites was studied by two-stage sizing application, i.e. applying silane coupling agent and polymeric film former at separate stages and with different sequences, in comparison with one-stage sizing application usually used. Surface properties of sized GFs and transverse tensile strength of unidirectional GF reinforced composites were studied using various surface and interface analysis methods and tensile testing, respectively. Two-stage technology achieved sized GFs with lower loss-on-ignition (LOI) and resulted in poor fibre-matrix adhesion strength. However, applying silane coupling agent at the first sizing stage with an increased roller speed achieved sized GFs with lower LOI but composites with mechanical properties quite close to those of composites based on one-stage technology. Moreover, the difference in surface properties of sized GFs is discussed in terms of the wetting ability difference of sizing constituents and the interactions between sizing components.