Band 16, Heft 2

An appropriate approach has been used for the preparation of silica/P(MMA- co -St) hybrid nanoparticles through converting previously prepared inverse miniemulsions into a direct miniemulsion and consequently, using the droplet nucleation polymerization technique. In the early stage of the procedure, silica particles were synthesized from TEOS in the presence of NH 4 OH or HCl as a catalyst through a base or acid-catalyzed sol-gel process. TEOS, ethanol and tirmethoxyvinylsilan were mixed in MMA:St (50:50) to create the inverse miniemulsion I, similarly CTAB, NH 4 OH/HCl and distilled water were dispersed into MMA:St (50:50) and called inverse miniemulsion II. Then, the two mentioned inverse miniemulsions were emulsified in water to achieve direct miniemulsion. The nature of the catalyst and TEOS concentration varied, for the aims of investigation, their effect on the morphology and size of hybrid nanoparticles. This route provided a unique process for silica/polymer hybrid nanoparticles production, avoiding organic solvents. Transmission electron microscopy micrographs revealed that, the morphology of the hybrid nanoparticles can be controlled by the nature of the catalyst.

Novel chitosan/diatomite (CS/DM) membranes were prepared by phase inversion technique to remove anionic azo dyes from wastewater. The fabricated composite membranes exhibited the combined advantages of inorganic substances, diatomites, and polysaccharides. These composite membranes were characterized through Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analysis. The mechanical properties of the membranes were also evaluated. Adsorption experiments were conducted under varied initial dye concentration, solution pH values, contact time, and adsorbent dosage. The results indicate that pH 3 is the optimal pH value for Orange G adsorption. The CS/DM membranes exhibit the highest adsorption capacity of 588 mg g -1 and removal rate of 94% under an initial dye concentration of 200 mg l -1 , contact time of 6 h, and membrane dosage of 8 mg. Langmuir, Freundlich and Redlich-Peterson adsorption models were applied to describe the equilibrium isotherms at different dye concentrations. The equilibrium data was found to be fitted well to the Redlich-Peterson isotherm. Pseudo-first-order and pseudo-second-order kinetics models were used to describe the adsorption of membranes. The adsorption data were well explained by pseudo-second-order models, and also followed by the Elovich model. In addition, these membranes display high adsorption capacity and mechanical performance even after reused for seven times.

The effect of electron beam (EB) irradiation on polytetrafluoroethylene (PTFE) film was studied in air at room temperature. The structural changes of the PTFE film irradiated by EB were determined by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). The morphological changes on the film surface were described using scanning electron microscopy (SEM). The surface hydrophilicity of the modified film was characterized through water contact angle measurement. The results show that scission of the chain on the surface of PTFE film was induced by EB irradiation. The atomic ratio of F/C decreased and the atomic ratio of O/C increased. The surface roughness of the irradiated sample increased. In the case of irradiation in the presence of residual air, carboxylic acid fluoride groups appear and can hydrolyze to carboxylic groups in the surface-near regions. These polar groups significantly reduced the hydrophobicity and oleophobicity of the PTFE film and consequently cause the decline of the water contact angle of the film surface. XRD analysis reveals an increase of the crystallite size of PTFE along with the increasing time of the irradiate.

[Ru(NH 3 ) 6 ] 3+ /Nafion modified indium tin oxide (ITO) electrodes were fabricated via the drop coating technique and were used for the simultaneous determination of lead (Pb 2+ ), cadmium (Cd 2+ ), and zinc (Zn 2+ ) in trace amounts using anodic stripping voltammetry (ASV). The amount of [Ru(NH 3 ) 6 ] 3+ in the coating solution was varied at 5 mg, 10 mg, and 15 mg. The fabricated electrodes were used to detect varying concentrations of Pb, Cd and Zn. ASV results showed that as the amount of [Ru(NH 3 ) 6 ] 3+ was increased, the reduction current of the heavy metals increased as well. The Pearson correlation values obtained for Pb and Cd were close to 1.0, indicating a strong positive linear relationship between the variables. The minimum heavy metal concentration that can be simultaneously detected by the fabricated electrodes is 0.5 ppm.

In this work, polyvinyl alcohol/nylon6 hybrid nanofiber yarns were produced to achieve good properties of each component. The influence of the twist level in the range of 3000–14,666 tpm and take-up speed in the range of 2.5–8.5 cm/min of yarns on the tensile properties was investigated. The highest strength and elongation at break of yarns were achieved in twist level and take-up speed of about 11,000 tpm (8.13±0.72 cN/tex and 72.44±7.64%) and 6.5 cm/min (6.20±0.57 cN/tex and 70.23±7.95%), respectively. Excessive values over these amounts caused a drastic decrement in tensile properties. This could be due to the loss nanofiber arrangement in the yarn structure that was confirmed by the study of orientation of the nanofibers in the yarns by the SEM images. These yarns have the potential to be used in medical applications such as a non-absorbable suture due to the drug loading ability and bio-compatibility properties of PVA nanofibers.

Lignin is one of the most abundant macromolecules on Earth. Lignins are obtained as by-products from the paper industry and used mostly as fuel. Their diverse composition has limited the development of high added-value applications: however, because of their abundance and sustainable origin, there is a growing interest in using lignins as a raw material and as a replacement for oil derivatives. In order to use lignins in bio-refineries, several processes must be studied and standardized. Lignin fractionation using solvents is a promising process. In this study, lignin from sugar cane bagasse (L1) was fractionated with solvents, and the fractions were characterized to evaluate structural aspects relevant for the production of fibers. L1 was extracted into four fractions with toluene (E1), ethanol (E2), methanol (E3), and dimethyl sulfoxide (DMSO, E4). Fractions E2, E3, and E4, showed only slightly different molar masses and molar mass distribution, but have relevant differences in their structural characteristics and processability. The ethanol extract (E2) provided lignins with a more flexible structure, and electro-spinning resulted in the production of nanofibers with diameters between 60 and 120 nm; the methanol fraction (E3) produced nanospheres with diameters between 90 and 350 nm; the DMSO fraction (E4) covered only a surface with electro-spray. These results show the possibility of developing high added-value applications using fractions of lignin from distinct biomasses or from their combination.

Isotactic polypropylene/ultrahigh-molecular-weight polyethylene blends (iPP/UHMWPE) and iPP/carbon nanotubes composites (iPP/CNTs) were prepared by a coagulation method followed by compression molding. The percolation thresholds for melts of iPP/UHMWPE blends and iPP/CNTs composites determined by rheometer, were beyond 5.0 wt% and close to 4.0 wt%, respectively. The creep and creep-recovery behavior of iPP/UHMWPE and iPP/CNTs melts were systematically investigated by rheological measurements. The results indicated that UHMWPE and CNTs played similar roles in the material’s elastic recovery, the addition of 2.0 wt% UHMWPE or 0.2 wt% CNTs increased the elastic recovery about 10 fold in comparison with neat iPP.

The slow release urea fertilizer was prepared by the boric acid crosslinked starch/polyvinyl alcohol (SPB) matrix as biodegradable carrier material. Using a two level factorial design of experiment, a comprehensive understanding of the concentration of boric acid, reaction time and heating temperature in the preparation of SPB matrix was obtained. The swelling ratio, release profile of urea in water, and crushing strength were selected as the response. The interaction between the variables and response was analyzed using the ANOVA model. The system was confirmed using the constant determination, R 2 with values above 0.99. The high concentration of boric acid with a prolonged reaction time at high temperature gave relative good results of swelling ratio, dissolution rate of urea and crushing strength. In the 28-day soil incubation experiment, the retention of exchangeable ammonium ion (NH4+)${\rm{(NH}}_4^ + )$ was significant higher in SPB urea as compared to pure urea. There was a potential for SPB matrix to improve nitrogen efficiency by increasing the accumulation of exchangeable NH4+${\rm{NH}}_4^ + $ and decreasing the dissolution rate of urea in the flooded condition.

The urea-crosslinked starch (UcS) film has a major drawback of very rapid biodegradability when applied as slow release fertilizer in soil. Lignin reinforcement of the UcS was used to prepare composite films, aimed to reduce the starch biodegradability and slow the release of nitrogen in aerobic soil condition. Study results revealed that mineralization of the composite films was delayed from 6.40 to 13.58% more than UcS film. Inhibition of composite films mixing with soil, the Michaelis-Menten reaction rates for α -amylase were inhibited ~1.72–2.03 times whereas the Michaelis-Menten reaction rates for manganese peroxidase were increased ~1.07–1.41 times compared to UcS film. Saccharides–glucose, maltose and maltotriose demonstrated that their rates of formation (zero-order reaction) and depletion (first-order reaction); both were slowed more in aerobic soil which received the composite films. Increasing of lignin in composite films, the acid to aldehyde ratios of vanillyl and syringyl phenols of the lignin declined from 1.18 to 1.17 (~0.76%) and 1.59–1.56 (~1.78%), respectively. The diffusivity of nitrogen was effectively slowed 0.66–0.94 times by the lignin in composite films and showed a “Fickian diffusion” mechanism (release exponent n =0.095–0.143).

Fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are both perfluorinated polymer, thus endowing FEP fibers excellent chemical stability. Compared with the difficult processing of PTFE, FEP fibers can be fabricated by melt spinning. The FEP fibers were treated by H 2 SO 4 and NaOH. After treatment, FEP fibers have a slight swelling observed by optical microscope (OM). Meanwhile, the strength of treated FEP fibers decreases slightly, while tensile modulus and elongation at break increases because of the infiltration of H 2 SO 4 and NaOH. Differential scanning calorimeter (DSC) results show that the crystallinity of FEP fibers decreases, due to the regularity of macromolecules destroyed by H 2 SO 4 and NaOH, which enter into crystalline region. This is consistent with WAXD results, indicating crystal size and crystal plane space decreases, owing to the infiltration of H 2 SO 4 and NaOH. However, chemical bonds of FEP fibers are unaffected, which is confirmed by FTIR spectra. Therefore, FEP fibers possess excellent chemical stability.