Polyester condensation adducts as novel photo stabilizers for polystyrene

Polycondensation adducts formed by the reaction of maleic anhydride with some Polyalcohols, namely, phloroglucinol, glycerol, and ethylene glycol, were prepared, characterized, and investigated as photostabilizers for polystyrene. Their Photostabilizing effectiveness was evaluated by measuring the extent of weight loss (%), the amount of gel formed as well as the viscosity average molecular weight of the soluble fractions of the degraded polymer. The results indicated better stabilizing effects of these stabilizers compared with that of the UV absorber, phenyl salicylate. A synergistic effect was achieved when the investigated photostabilizers were mixed with phenyl salicylate in a weight ratio of 1 : 1, and a radical mechanism is proposed to account for the action of the polycondensation adducts as photostabilizers. J. VINYL ADDIT. TECHNOL., 19:293–301, 2013. © 2013 Society of Plastics Engineers     

Characterization and Electrical Properties of Some Hydrochloric Acid-Doped Aniline and 2-Amino-Pyridine Homopolymers and Copolymers

The synthesis of (group I) hydrochloric acid-doped poly(aniline-co-toluidine), poly(aniline-co-thiophene), poly(aniline-co-o-phenylenediamine), and poly(aniline-co-2-aminopyridine) as well as their hydrochloric acid-doped homopolymers of polyaniline, poly-m-toluidine, poly-o-phenylene diamine, and poly-2-aminopyridine and the synthesis of (group II) hydrochloric acid-doped poly (2-aminopyridine-co-o-phenylene diamine) and its hydrochloric acid-doped homopolymers of poly 2-amino pyridine and poly-o-phenylene diamine have been carried out via a chemical oxidation process using ammonium and potassium persulphate as chemical initiators. The synthesized homo- and copolymers were characterized by ultraviolet-visible spectroscopy (UV-VIS), infrared spectroscopy (IR), and thermal analysis. The variation of the electrical conductivity (σ, S cm^?1) with the reciprocal of the absolute temperature (1000/T, K) at different frequencies (1–1000 kHz) for hydrochloric acid homopolymers and copolymers is illustrated.     

Catalytic Effect of Various Kaolinite Forms on the Emulsion Polymerization of Vinylacetate Using Acetone Sodium Bisulfite as Initiator

Kaolinite was intercalated with N-methylformamide (NMF) and dimethylsulphoxide (DMSO), separately. The intercalation of these species expanded the basal space of kaolinite from 0.72 to 1.08 and 1.13 nm, respectively as shown by the X-ray diffraction (XRD). Emulsion polymerization of vinylacetate (VAc) was carried out at different temperatures (60–80°C) using acetone sodium bisulfite as initiator in the absence and presence of untreated as well as the modified forrms of kaolinite (K-NMF, K-DMSO). The results revealed that the presence of kaolinite decreased the rate of polymerization (Rp) by factor of 4 at 60 and 70°C and 7 at 80°C and also the activation energy of polymerization (E _a ) was decreased from 43.35 × 10⁴ to 10.32 × 10⁴ J mole^?1 if compared with the polymerization of VAc in absence of kaolinite. Using the modified forms of kaolinite (K-NMF, K-DMSO) enhanced the Rp and reduced effectively the E _a to ? 27.92 and ? 55.78, respectively. Conversely to untreated kaolinite, the Rp was declining with increasing the temperature in these cases. In all cases, Rp was the highest in the absence of any kaolinite form but in the same time the E _a was also the highest. These results were discussed and explained on the basis of the catalytic activity of the different forms, radical scavenging nature of the kaolinite, and chain transfer.     

Exfoliation of Kaolinite Nanolayers in Poly(methylmethacrylate) Using Redox Initiator System Involving Intercalating Component

Injection molding is one of the most widely employed methods for the fabri- cating of polymer articles, being characterized by high production rates and accurately dimensioned products. The process includes the flow of polymer melt through a runner system and gates followed by injection into a cold mold, packing under high pressure, and subsequent cooling to solidification. Accordingly, during the injection-molding process the polymer undergoes simultaneous mechanical and therma! influences while in fluid, rubbery, and glassy states. Such effects introduce residual stresses and strains into the final product [1,2], resulting in highly anisotropic mechanical behavior [3–9] and warpage and shrinkage [10–13]. Thus, understanding the factors governing the residual-stress development during molding is of great importance.     

UNSTEADY FLUID AND HEAT FLOW INDUCED BY A STRETCHING SHEET WITH MASS TRANSFER AND CHEMICAL REACTION

The effect of chemical reaction on the flow, heat, and mass transfer within a viscous fluid on an unsteady stretching sheet is examined. The stretching rate, temperature and concentration of the sheet, and the chemical reaction rate are assumed to vary with time. The time-dependent boundary layer equations governing the flow are reduced through a convenient similarity transformation to a set of ordinary differential equations, which are numerically solved by applying the fourth-order Runge-Kutta-Fehlberg scheme with the shooting technique. Results for the velocity, temperature, and concentration distributions as well as the wall temperature and concentration gradients are presented graphically for various values of the unsteadiness parameter A, Prandtl number Pr, Schmidt number Sc, and chemical reaction parameter γ.     

The Anti-Fasciolasis Properties of Silver Nanoparticles Produced by Trichoderma harzianum and Their Improvement of the Anti-Fasciolasis Drug Triclabendazole

Recently, new strains of Fasciola demonstrated drug resistance, which increased the need for new drugs or improvement of the present drugs. Nanotechnology is expected to open some new opportunities to fight and prevent diseases using an atomic scale tailoring of materials. The ability to uncover the structure and function of biosystems at the nanoscale, stimulates research leading to improvement in biology, biotechnology, medicine and healthcare. The size of nanomaterials is similar to that of most biological molecules and structures; therefore, nanomaterials can be useful for both in vivo and in vitro biomedical research and applications. Therefore, this work aimed to isolate fungal strains from Taif soil samples, which have the ability to synthesize silver nanoparticles. The fungus Trichoderma harzianum, when challenged with silver nitrate solution, accumulated silver nanoparticles (AgNBs) on the surface of its cell wall in 72 h. These nanoparticles, dislodged by ultrasonication, showed an absorption peak at 420 nm in a UV-visible spectrum, corresponding to the plasmon resonance of silver nanoparticles. The transmission electron micrographs of dislodged nanoparticles in aqueous solution showed the production of reasonably monodisperse silver nanoparticles (average particle size: 4.66 nm) by the fungus. The percentage of non hatching eggs treated with the Triclabendazole drug was 69.67%, while this percentage increased to 89.67% in combination with drug and AgNPs.     

Impact of hydrogen concentrations on the impedance spectroscopic behavior of Pd-sensitized ZnO nanorods

ZnO nanorods were synthesized using a low-cost sol-gel spin coating technique. The synthesized nanorods were consisted of hexagonal phase having c-axis orientation. SEM images reflected perpendicular ZnO nanorods forming bridging network in some areas. The impact of different hydrogen concentrations on the Pd-sensitized ZnO nanorods was investigated using an impedance spectroscopy (IS). The grain boundary resistance (R_gb) significantly contributed to the sensing properties of hydrogen gas. The boundary resistance was decreased from 11.95 to 3.765 kΩ when the hydrogen concentration was increased from 40 to 360 ppm. IS gain curve showed a gain of 6.5 for 360 ppm of hydrogen at room temperature. Nyquist plot showed reduction in real part of impedance at low frequencies on exposure to different concentrations of hydrogen. Circuit equivalency was investigated by placing capacitors and resistors to identify the conduction mechanism according to complex impedance Nyquist plot. Variations in nanorod resistance and capacitance in response to the introduction of various concentrations of hydrogen gas were obtained from the alternating current impedance spectra.     

Relaxation phenomenon of poly(vinyl alcohol)/sodium carboxy methyl cellulose blend by thermally stimulated depolarization currents and thermal sample technique

The dipolar relaxation in poly(vinyl alcohol) (PVA), sodium carboxy methyl cellulose (NaCMC_s), and their blends were studied using a thermally stimulated depolarization current (TSDC) technique. The mutual effects of polarization conditions such as heating rate, poling temperature, time, and field on the properties of TSDC were investigated. Quantitative analysis of the experimental data is given in terms of dipolar and space charge polarization. A thermal sampling (TS) technique was applied to decompose the complex relaxations in individual polymers and their blend of 0.5/0.5 wt/wt into its normal distribution components. The activation energy of TS‐formed electrets was determined by fitting the experimental curve to Bucci and Fieschi equations. Peak parameters such as activation energy and preexponential factor τ₀ were obtained. A linear relationship between the activation energy and logarithm of the preexponential factor was found, thus confirming operation of the compensation law. In addition, by using the Eyring equation of the rate theory, the activation enthalpy ΔH^≠ and the activation entropy ΔS^≠ were calculated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1342–1353, 2005     

Electrocopolymerization kinetics of a binary mixture of 3‐chloroaniline 2‐amino‐4‐phenylthiazole and characterization of the obtained block copolymer films

Electrocopolymerization of a binary mixture of 3‐chloroaniline and 2‐amino‐4‐phenylthiazole on platinum electrode in acid medium was carried out under different reaction conditions such as temperature, current density, hydrochloric acid, and monomer concentrations with duration time. The initial rate of the electrocopolymerization reaction on platinum electrode is small and the rate law is R_p = K₂ [D]^1.29[HCl]^0.97[M]^1.94. The apparent activation energy is found to be 38.87 kJ/mol. The obtained copolymer film is characterized by ¹H‐NMR, elemental analysis, GPC IR, UV‐visible, and cyclic voltammetry and compared with those of the two homopolymers. The mechanism of the electrocopolymerization reaction is also discussed and the monomer reactivity ratio (r₁and r₂) is calculated. The thermogravimetric analysis (TGA) is used to confirm the proposed structure and determination of the number of water molecules in the polymeric chain unit. X‐ray and scanning electron microscopic analysis are used to investigate the surface morphology. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2076–2087, 2005