Synthesis of polyvinylidene fluoride (PVDF) membranes for protein binding: Effect of casting thickness

Microporous polyvinylidene fluoride (PVDF) membranes were synthesized from PVDF/N‐methyl‐2‐pyrrolidinone (NMP) solutions using an immersion–precipitation method with a 2‐propanol/water mixture as a soft coagulant. The effects of membrane thickness on pore size distribution and surface/cross‐section morphology were studied using capillary flow porometry and scanning electron microscopy (SEM), respectively. All the synthesized membranes had a small range of pore size distribution, with the pore size decreasing with increasing casting thickness. The semicrystalline PVDF membranes demonstrated significant variations in morphology under SEM observation, with the existence of polymer agglomeration at a casting thickness of 500 μm and above. The protein binding capacity was observed to be highest at a casting thickness of 400 μm, where optimum pore morphology provided a large surface area for protein binding. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Carbon fiber-polyaniline composites: Kinetics of electrodeposition of polyaniline onto carbon fibers by cyclic voltammetry

Homogeneous and uniform coatings of polyaniline were successfully deposited on carbon fibers by an aqueous electrodeposition technique using p-toluene sulfonic acid as the electrolyte. Electrochemical deposition of aniline was carried out by cyclic voltammetry in the potential range of ?0.2 V to 1.0 V versus saturated calomel electrode (SCE). The electrochemical deposition parameters such as the number of cycles, scan rate (SR), initial monomer ([M]), and electrolyte concentration ([E]) were systematically varied. The amount of composite coatings on carbon fibers was dependent on the electrochemical deposition parameters. From a weight gain analysis, the rate of the reactions (R p ) was calculated. As the aniline concentration was increased up to 0.35 M and electrolyte concentration up to 0.5 M, the deposition rate also increased, whereas an increase in scan rate decreased the deposition rate. Kinetic analysis showed that the rate equation for the p-toluene sulfonic acid system is R p ∝SR ?1.25 [M] 0.73 [E] 0.95 . IR spectra also showed an increase in the deposition of polyaniline coatings on carbon fibers with a decrease in the scan rate and an increase in both monomer and electrolyte concentration. The ratio of two oxidation states of polyaniline obtained during electrodeposition, namely emeraldine and pernigraniline, can be varied by changing the electrochemical deposition parameters.     

Organic solvent absorbents based on linear diol

Cross‐linked poly(orthocarbonate)s were prepared by condensation of the tetraethyl orthocarbonate with different length of aliphatic diols. The synthesized polymers have been characterized by Fourier‐transform infrared spectroscopy, solid‐state ¹³C cross‐polarization magic angle spinning (CPMAS) nuclear magnetic resonance, thermal gravimetric analysis, and elemental analysis. The cross‐linked polymers were evaluated for organic solvent absorbency application. The effect of diol type on swelling properties of cross‐linked polymers was studied through the solvent absorption tests. The swelling parameters such as maximum solvent absorbency, saturation time, and retention of the solvent were evaluated for the synthesized sorbents. All of the cross‐linked polymers had moderate thermal stability and good regenerable solvent uptake abilities. POLYM. ENG. SCI., 53:2102–2108, 2013. © 2013 Society of Plastics Engineers     

Viscoelastic and Processing Effects on the Fiber-Matrix Interphase Strength. Part I. The Effects of Loading Rate,Test Temperature,Fiber Sizing and Global Strain Level

The effects of loading rate, fiber sizing, test temperature and global strain level on the adhesion strength between carbon fibers and a thermosetting epoxy (Epon 815) are studied using the single fiber fragmentation test procedure. Analytical methodology describing the viscoelastic behavior observed is also presented. The possibility of rate-temperature-interphase thickness superposition for the interfacial strength function is illustrated based on the analytical models discussed. Experimental data are discussed using Weibull statistics and also presented in the form of percent relative frequency histograms for the fiber fragments in a collective fashion. The use of histograms allows for interpretation of the skewness in the data population.     

Computational analysis on cymbal transducer

Finite Element Analysis in collaboration with experimental studies was conducted to investigate the effects of dimensional parameters on the performance of the cymbal transducer. ANSYS 5.5 FEM code was used for computational analysis. Cymbal transducers were fabricated with steel and brass endcap materials and piezoelectric ceramic, PZT-5A, as driving elements. Admittance spectrum was measured by using HP4194A Impedance/Gain phase analyzer. Displacement and generative force characteristics of the transducers were tested by using a LVDT sensor. Experimental and calculated results matched quite well. Device diameter and cavity diameter has strong effect on cymbal transducer characteristic. Adjusting the dimensional parameters can extend potential application areas of cymbal transducer.     

Mixture Design Approach in Wall Material Selection and Evaluation of Ultrasonic Emulsification in Flaxseed Oil Microencapsulation

Flaxseed oil, sensitive to oxidation, was systematically microencapsulated with six triple wall materials combinations [carbohydrate (maltodextrine and two different modified starches (N-Lok® and HiCap® 100)); protein (sodium caseinate, whey protein concentrate); and Arabic gum] for the highest microencapsulation efficiency and oxidation stability. Proportions of the triple wall materials were optimized in mixture design using the quadratic model. Effects of Ultra-Turrax and ultrasonic emulsifications on microencapsulation efficiencies were additionally characterized in the optimized wall material combinations. The microcapsules produced were investigated for particle size distribution, moisture content, water activity, bulk density, and oxidative stability. Results showed that the combination of modified starch (Hi-Cap® 100)/Arabic gum/whey protein concentrate (4/0/1, w/w/w) provided the highest efficiency in flaxseed oil microencapsulation. However, the only successful combination in preventing flaxseed oil oxidation was maltodextrine/Arabic gum/whey protein concentrate (4/0/1, w/w/w). The microcapsules produced by ultrasonic emulsification had higher microencapsulation efficiency than that of Ultra-Turrax emulsification.     

Effect of Vinyl Alcohol-Phthalic Anhydride on Properties of Low Density Polyethylene (LDPE)/Tyre Dust (TD) Composites

The effect of vinyl alcohol-phthalic anhydride as a coupling agent on the tensile properties, morphology, and thermal degradation of low density polyethylene/tyre dust (LDPE/TD) composites was studied. LDPE/TD composites with different tyre dust loading and the addition of vinyl alcohol-phthalic anhydride were prepared with Z-blade mixer at 180°C and rotor speed of 50 rpm. The result indicated that LDPE/TD_M composites with vinyl alcohol-phthalic anhydride show higher values of tensile strength, Young's modulus and mass swell, but lower elongation at break than LDPE/TD composites without vinyl alcohol-phthalic anhydride. The SEM micrographs showed that the tyre dust was more widely dispersed in the LDPE matrix with the addition of vinyl alcohol-phthalic anhydride as a coupling agent. It was also found that the addition of vinyl alcohol-phthalic anhydride offers better thermal stability in the LDPE/TD_M composites than LDPE/TD composites.     

Preparation and Properties of Ethylene Vinyl Acetate (EVA)/Organoclay/Compatibilizer Nanocomposites: Effects of Organoclay Loading and Methyl Ethyl Ketone

Ethylene vinyl acetate (EVA)/organoclay/compatibilizer nanocomposites were produced using a melt compounding technique in an internal mixer, Haake Rheometer, at 120°C and 50 rpm rotor speed. Effects of organoclay loading (from 2 to 10 phr—parts per hundred of resin and methyl ethyl ketone (MEK), used as a compatibilizer, on the processing properties, tensile properties, morphology, thermal degradation, and water absorption behavior of EVA/organoclay nanocomposites were studied. Results indicate that the presence of organoclay increase the processing torque, tensile properties, thermal degradation, and resistance to water absorption. The optimum organoclay loading was achieved at 2 phr. This was caused by the dispersion state of individual silicate layers (intercalation/exfoliation) in EVA matrix. The intercalation/exfoliation structure affects the properties of EVA/organoclay nanocomposites as evidenced from the morphology studies such as x-ray diffraction (XRD) and transmission electron microscopy (TEM) evaluation. The addition of MEK has the ability to improve the tensile properties, thermal degradation, and slightly reduces the resistance of water permeation of EVA/organoclay nanocomposites. The enhanced properties were seen as a result of the better matrix and filler interaction. The EVA/organoclay/MEK nanocomposites shows better intercalation/exfoliation of individual silicate layers in the EVA matrix as indicated by TEM. Moreover, the XRD evaluation shows that intercalation/exfoliation of the organoclay was formed in the EVA matrix.     

Influence of Electron Beam Irradiation and Coupling Agents on the Thermal Stability of Sugar Cane Bagasse Fiber-Thermoplastics Scrape Composite

The influence of blending of sugar cane bagasse with thermoplastics scrape as well as incorporation of some coupling agents has been conducted using thermogravimetric analysis (TGA). In addition, the effect of electron beam preirradiation of low density polyethylene on the properties of the bagasse-LDPE composite was also studied. Simulation of TGA data reveals that the presence of bagasse fiber accelerates the volatilization of either polypropylene or polyvinylchloride. On the other hand, polyethylene and polystyrene were stable against the heat evolved during the pyrolysis of bagasse fibers. Also, it was found that incorporation of a mixture of pentaerithrol tetraacrylate (PETA) and dicumyl peroxide (DCP) as coupling agents improve the thermal stability of low density polyethylene whereas the role of irradiation was insignificant. Moreover, pronounced enhancement in the thermal stability was detected in polypropylene followed by polystyrene and polyvinylchloride on using PETA.     

Properties of Ferrite-Filled Natural Rubber Composites

Nickel zinc ferrite (Ni-ZnFe₂O₄)-filled natural rubber (NR) composite was prepared at various loading of ferrite. The tensile properties included in this study were tensile strength, tensile modulus and elongation at break. The tensile strength and elongation at break of the composites increased up to 40 parts per hundred rubber (phr) of ferrite and then decreased at higher loading whereas the tensile modulus was increased gradually with increasing of ferrite loading. Scanning electron microscopy (SEM) was used to determine the wettability of filler in rubber matrix. From the observation, the increase of filler loading reduced the wettability of the filler. Thermal stability of the composites was conducted by using a thermogravimetry analyser (TGA). The incorporation of ferrite in NR composites enhanced the thermal stability of NR composites. The swelling test results indicate that the swelling percentage of the composites decreased by increasing of ferrite loading. The initial permeability, μ_i and quality factor, Q of magnetic properties of NR composites achieved maximum value at 60 phr of ferrite loading for frequency range between 5000–40,000 kHz. The maximum impedance, Z _max of the NR composites was at the highest value at 80 phr ferrite loading for frequency range between 200–800 MHz.