Study on swelling of hydrogels (PAAm) at various temperatures by using fluorescence technique

Steady-state fluorescence (SSF) technique was employed for studying swelling of polyacrylamide (PAAm) hydrogels. Disc-shaped gels were prepared by free-radical crosslinking copolymerization of acrylamide (AAm) with N, N′- methylenebis (acrylamide) (BIS) as crosslinker in the presence of ammonium persulfate (APS) as an initiator. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of pyranine was measured during in situ swelling process at various temperatures and it was observed that fluorescence intensity values decreased as swelling is proceeded. Li–Tanaka equation was used to determine the swelling time constants, τ_c and cooperative diffusion coefficients, D _c from intensity, weight and volume variations during the swelling processes. It is observed that swelling time constants, τ_c decreased and diffusion coefficients, D _c increased as the swelling temperature is increased. The swelling activation energies, ΔE were measured from the intensity, weight and volume variations and found to be 10.7, 32.2 and 64.1 kJ mol⁻¹, respectively.     

Influence of hydroxypropyl beta-cyclodextrin on the corneal permeation of pilocarpine

The influence of hydroxypropyl β-cyclodextrin (HPβCD) on the corneal permeation of pilocarpine nitrate was investigated by an in vitro permeability study using isolated rabbit cornea. Pupillary-response pattern to pilocarpine nitrate with and without HPβCD was examined in rabbit eye. Corneal permeation of pilocarpine nitrate was found to be four times higher after adding HPβCD into the formulation. The reduction of pupil diameter (miosis) by pilocarpine nitrate was significantly increased as a result of HPβCD addition into the simple aqueous solution of the active substance. The highest miotic response was obtained with the formulation prepared in a vehicle of Carbopol® 940. It is suggested that ocular bioavailability of pilocarpine nitrate could be improved by the addition of HPβCD.     

Polynorbornene/MMT nanocomposites via surface-initiated ROMP: synthesis, characterization, and dielectric and thermal properties

Exfoliated polynorbornene (PNBN)/montmorillonite (MMT) nanocomposites were synthesized for the first time by the surface-initiated ring-opening metathesis polymerization. PNBN is one of the challenging materials in low dielectric films for packaging applications in electric–electronic industries. This is the first example of in situ polymerization of NBN within the catalyst intercalated montmorillonite layers using ROMP in different clay loading degrees. The Na–MMT clay was modified with a Quaternary ammonium salt containing ruthenium complex as a suitable catalyst and intercalant as well. Powder X-ray diffraction spectroscopy and transmission electron microscopy analysis indicated that the resultant nanocomposites exhibited exfoliated morphologies with homogeneous clay platelet distribution. Nanocomposite materials were obtained with high thermal degradation temperature and low dielectric constant when compared with pure PNBN. The dielectric constants decreased with the increase in the clay content.     

Impact and post impact behavior of layer fabric composites

In this study, the effect of impact and post impact behavior of E-glass/epoxy composite plates having different layer fabrics were investigated by considering energy profile diagram and the related load–deflection curves. Different impact energies (5 J–60 J)were subjected to the plates consisting of eight layers of plain weave (1D), double (2D) and triple (3D) layer fabrics. The impact tests were continued until complete perforation of layer fabrics. The damage modes and damage processes of layer fabrics under varied impact energies were also discussed. At the end of the impact tests, the damaged samples were mounted into a compression apparatus to determine the Compression After Impact (CAI) strength of layer fabric samples. The results of these impact and post impact tests showed that contact force occurring between the impactor and the composite specimen increased and the CAI strength reduced by increasing the impact energy. The objective of this study was to determine the perforation threshold of E-glass/epoxy composite plates having different layer fabrics as plain weave (1D), double (2D), and triple (3D) layer fabrics.     

Optimization of electrochemical treatment of industrial paint wastewater with response surface methodology

The electrochemical oxidation of water-based paint wastewater was investigated batch-wise in the presence of NaCl electrolyte with carbon electrodes for the first time in literature. The electrochemical treatment conditions were optimized using response surface methodology where potential difference, reaction temperature and electrolyte concentration were to be minimized while chemical oxygen demand (COD), color and turbidity removal percents and initial COD removal rate were maximized at 100% pollution load. The optimum conditions were satisfied at 35 g/L external electrolyte concentration, 30 degrees C reaction temperature and 8 V potential difference (64.37 mA/cm(2) current density) realizing 51.8% COD and complete color and turbidity removals, and 3010.74 mg/Lh initial COD removal rate. According to these results, the electrochemical method could be a strong alterative to conventional physicochemical methods for the treatment of water-based paint wastewater.     

Modeling of a convective-infrared kiwifruit drying process

This paper aims to evaluate the experimental performance of a convective-infrared system with heat recovery (CIRHR) at different drying temperatures (40, 45, 50 and 55 °C) and 0.5 m/s air velocity and also to discuss and predict the performance of system on energy consumption and drying kinetics of sliced kiwifruit using artificial neural networks (ANNs). The energy efficiency values were obtained between 2.85% and 32.17%. The ANN model was used to predict the energy consumption of the system and moisture content of the kiwifruit. The back-propagation learning algorithm with Levenberg–Marquardt (LM) and Fermi transfer function were used in the network. The coefficient of determination (R²), the root means square error (RMSE) and the mean absolute percentage error (MAPE) were calculated as 0.99, 0.001 and 0.34, respectively. It can be concluded that predicted values are in good agreement with experimental results.     

Effect of borax additive on the dielectric response of polypyrrole

The main aim of this study is to produce added polypyrrole (PPy) borax composites with high dielectric properties for technological applications. For this purpose, PPy–borax composites with different borax concentrations varying from 10 to 50 wt% have been prepared. To reveal their structural and morphological attributes, the composites have been characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. The real and imaginary parts of complex dielectric function, the imaginary component of complex electrical modulus and ac conductivity have been investigated at room temperature as a function of frequency in the range 100 Hz–15 MHz. It has been found that addition of borax increases the dielectric constant of pure PPy. In this respect, PPy–borax composites with the highest dielectric constant at low frequency may be utilized in charge storing devices. On the other hand, the dielectric loss is also very high in low-frequency region for the composites with high borax content. Exploiting this property, the material may also be used in decoupling capacitor applications. The relaxation mechanisms of the samples have also been determined as non-Debye type. The Nyquist curves of the samples have been analysed for calculating the grain and grain boundary resistance and capacitance values. In conclusion, borax has a promising potential to be used as a cheap and effective filler for improving the dielectric properties of PPy polymer.     

Protein fouling behavior of carbon nanotube/polyethersulfone composite membranes during water filtration

The protein fouling of membranes can be related to the hydrophobic and electrostatic interactions between proteins and the membrane material; i.e., protein fouling can be reduced by changing the membrane properties. In this study, multi-walled carbon nanotube/polyethersulfone (C/P) composite membranes were prepared via the phase inversion method in order to investigate protein fouling, with bovine serum albumin (BSA) and ovalbumin (OVA) used as the model protein for assessing the protein fouling behavior. The results show that the C/P composite membranes were fouled less compared to the bare polyethersulfone (PES) membrane at 4 h of static protein adsorption at neutral pH. Moreover, the irreversible fouling ratio of the C/P composite membranes was less than the bare PES membrane after 1 h of protein ultrafiltration, and the flux recovery ratio of the C/P composite membranes was higher than the bare PES membrane after 20 min of DI water filtration. Based on these results, C/P composite membranes were shown to have the potential to alleviate the effects of protein fouling, thereby enabling C/P composite membranes to be used for several runs of protein filtration after simple washing with water.     

Reactive red 120 and NI(II) derived poly(2‐hydroxyethyl methacrylate) nanoparticles for urease adsorption

Non‐porous poly(2‐hydroxyethyl methacrylate) [p(HEMA)] nanoparticles were prepared by surfactant free emulsion polymerization. The p(HEMA) nanoparticles was about 200 nm diameter, spherical form, and non‐porous. Reactive Red 120 (RR 120) was covalently attached to the p(HEMA) nanoparticles and Ni(II) ions were incorporated to attach dye molecules. Urease was immobilized onto RR120‐Ni(II) attached p(HEMA) nanoparticles via adsorption. The maximum urease adsorption capacity of RR120‐Ni(II) attached p(HEMA) nanoparticles was 480.01 mg g^?1 nanoparticles at pH 7.0 in phosphate buffer. It was observed that urease could be repeatedly adsorbed and desorbed without significant loss in adsorption amount. K_m values were 21.50 and 34.06 mM for the free and adsorbed enzyme. The V_max values were 4 U for the free enzyme and 3.3 U for the adsorbed enzyme. The optimum pH was 25 mM pH 7 phosphate buffer for free and adsorbed enzyme. The optimum temperature was determined at 35°C and 55°C for the free and adsorbed enzyme, respectively. These findings show considerable promise for this material as an adsorption matrix in biotechnological applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39757.