Property enhancement in unsaturated polyester nanocomposites by using a reactive intercalant for clay modification

Polymeric nanocomposites were synthesized from unsaturated polyester (UPE) matrix and montmorillonite (MMT) clay using an in situ free radical polymerization reaction. Organophilic MMT was obtained using a quaternary salt of coco amine as intercalant having a styryl group making it a reactive intercalant. The resultant nanocomposites were characterized via X‐ray diffraction and transmission electron microscopy. The effect of increased nanofiller loading on the thermal and mechanical properties of the nanocomposites was investigated. All the nanocomposites were found to have improved thermal and mechanical properties as compared with neat UPE matrix, resulting from the contribution of nanolayer connected intercalant‐to‐crosslinker which allows a crosslinking reaction. It was found that the partially exfoliated nanocomposite structure with an exfoliation dominant morphology was achieved when the MMT loading was 1 wt %. This nanocomposite exhibited the highest thermal stability, the best dynamic mechanical performance and the highest crosslinking density, most probably due to more homogeneous dispersion and optimum amount of styrene monomer molecules inside and outside the MMT layers at 1 wt % loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Investigation of UV and I–V characteristics of high refractive index polymer thin film for optoelectronic applications

In this study, high refractive index polymer (HRIP) [poly(pentabromobenzyl methacrylate-co-glycidyl methacrylate)] was investigated to obtain its optical and electrical performance for optoelectronic applications. UV characteristics of the polymer in solution of tetrahydrofuran were obtained and optical band gap energy of the polymer was calculated as 3.8 eV. I–V characteristics of the polymer were investigated after HRIP thin film was prepared using spin coating technique. The electrical parameters such as barrier height Φ_Bo, ideality factor n and reverse saturation current I_o were extracted from the forward biasing I–V characteristics. At the same time, series resistance R_s and Φ_Bo were determined by using a modified Norde function combined with conventional forward I–V method.     

Unethical computer using behavior scale: A study of reliability and validity on Turkish university students

This study was carried out in a Turkish university with 216 undergraduate students of computer technology as respondents. The study aimed to develop a scale (UECUBS) to determine the unethical computer use behavior. A factor analysis of the related items revealed that the factors were can be divided under five headings; intellectual property, social impact, safety and quality, net integrity and information integrity.     

Who are problematic internet users? An investigation of the correlations between problematic internet use and shyness,loneliness, narcissism,aggression and self-perception

This study investigated correlations between university students’ problematic internet use behaviors and shyness, narcissism, loneliness, aggression and self-perception. The participants were 424 students attending seven different faculties of a public university in Turkey; 215 were female and 209 male. Student’s ages ranged between 17 and 23, with a mean of 18.69. The Problematic Internet Use Scale, Shyness Scale, Narcissistic Personality Inventory, UCLA Loneliness Scale, Aggression Questionnaire, Social Comparison Scale and a Personal Data Form were used for data collection. Correlation analysis results showed positive associations between problematic internet use and shyness and aggression. No statistically significant correlation was determined between problematic internet use and narcissism, loneliness or self-perception. The results demonstrate that individuals who are problematic users are shier and more aggressive. Shyness and aggression emerged as significant antecedent variables of problematic internet use. Suggestions are made for further studies in the light of these findings.     

Computational analysis of fouling by low energy surfaces

Fouling is a cost increasing problem for a variety of industries including aerospace, chemical, petroleum, and food. There have been studies on mitigation of fouling some of which recommend use of lower surface free energy materials, manufactured by different techniques, as an alternative to conventional materials. Although modeling of fouling for a given surface has been an area of interest; there is a lack in the models about correlating the surface free energy with deposit amount computationally. In this study, computational model, including the effect of surface energy and operational parameters, was proposed and validated to estimate amount of foulants deposits and rate of deposition. Towards this purpose, four coated surfaces (Microlube/PTFE, TM117P, AMC148, and CNT) were compared with stainless steel (SS316 as control) for flow rates of 3 and 10 g/s and inlet milk temperatures of 40 and 60 °C. The percent error for the decrease in outlet milk temperatures between the experimental data and computed results was between 2% and 18% except for CNT (29.2%). The calculations of deposit amount for each test case and the surfaces tested were in good agreement with the experiments, i.e., average percent difference values between measured and calculated values were from 11.1% to 38.1% (except CNT) with overall average of 21.5%.     

Improving energy efficiency through the design of the building envelope

Buildings, their surroundings and related enterprises produce more CO₂, generate more pollution, consume more energy, and waste more natural resources than any other human enterprise or industry. Moreover, considerable parts of these environmental impacts are the results of the lodging industry [1].     

Carbon nanowalls deposited by inductively coupled plasma enhanced chemical vapor deposition using aluminum acetylacetonate as precursor

Well aligned carbon nanowalls, a few nanometers thick, were fabricated by continuous flow of aluminum acetylacetonate (Al(acac)₃) without a catalyst, and independent of substrate material. The nanowalls were grown on Si, and steel substrates using inductively coupled plasma-enhanced chemical vapor deposition. Deposition parameters like flow of argon gas and substrate temperature were correlated with the growth of carbon nanowalls. For a high flow of argon carrier gas, an increased amount of aluminum in the film and a reduced lateral size of the carbon walls were found. The aluminum is present inside the carbon nanowall matrix in the form of well crystallized nanosized Al₄C₃ precipitates.     

Characterization and charge transfer mechanism of PIN–cdse nanocomposites

This paper reports structural, thermal, and temperature‐dependent dielectric properties of polyindole–cadmium selenide (PIN–CdSe) nanocomposites. PIN and its nanocomposites were synthesized via in situ chemical oxidative polymerization method. Samples were characterized by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), scanning electron microscopy with energy dispersive X‐ray (SEM/EDX), atomic force microscope, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Dielectric properties were analyzed as a function of temperature. FT‐IR spectroscopy indicated that both N H and aromatic CC bonds were affected more by doping process. Significant structural differences were observed in XRD and SEM analyses of PIN and its nanocomposites. Both XRD and DSC measurements revealed that crystallinity of the PIN increases to a certain degree with increasing doping level. Thermogravimetric analysis showed that addition of CdSe decreased degradation temperature of the PIN. Conductivity measurements investigated by universal power law indicated that the charge transport mechanism of all the samples is consistent with correlated barrier hopping model. POLYM. COMPOS., 37:3057–3065, 2016. © 2015 Society of Plastics Engineers     

Influence of pH on recombinant human growth hormone production by Pichia pastoris

BACKGROUND: Effect of pH on recombinant human growth hormone (rhGH) production by Pichia pastoris hGH‐Mut⁺ was investigated at pH = 4.2, 5.0, 5.5, and 6.0. RESULTS: The highest cell concentration was obtained at pH = 6.0 with 53 g L^?1, while the highest rhGH concentration was attained at pH = 5.0 as 0.27 g L^?1. Total protease secretion increased with increase in pH and with the cultivation time. Oxygen uptake rate increased with increasing pH up to pH = 6.0, having the maximum value, 37 mmol m^?3 s^?1, at pH = 5.5. K_La values were similar at all the conditions, having a maximum value of 0.14 s^?1 at pH = 5.0. Taking the final rhGH concentration into account, the most favourable pH was 5.0; where AOX1 expression level showed a similar trend to AOX activity profiles, having the highest value of 9.4 × 10¹⁰ copy mg^?1 CDW at t = 15 h; in parallel to AOX1 expression profile, hGH expression level increased until t = 15 h, with the highest value of 4.0 × 10¹⁰ copy mg^?1 CDW, where a sharp increase in rhGH concentration was obtained. The expression levels of pep4, prb1 and prc1 genes, responsible from the production of proteinase A, proteinase B and, carboxypeptidase Y, were parallel to each other. CONCLUSION: Since it was shown that pH is a crucial operating parameter in fermentation processes using P. pastoris, keeping pH constant at its determined optimum value, pH = 5.0, during the bioprocess is vital in terms of recombinant protein production. Copyright © 2010 Society of Chemical Industry     

Determining the mechanical properties of epoxy resin (DGEBA) composites by ultrasonic velocity measurement

In this study, the composites of diglycidyl ether of bisphenol A (DGEBA) epoxy resin that have been formed by mixing epoxy resin with allyl glycidyl ether (AGE) and 2,3‐epoxypropyl methacrylate [glycidyl methacrylate (GMA)] were prepared in weight % ratios of 90 : 10, 80 : 20, and 70 : 30. A computer controlled analyzer with 35 MHz and a digital oscilloscope with 60 MHz were used for measuring the velocities of ultrasonic wave. The measurement of ultrasonic velocity carried out by pulse echo method at frequencies of 2.25 and 3.5 MHz at room temperature. The values of acoustic impedance (Z), Poisson ratio (μ), and coefficients of elasticity (L, G, K, E) of composites were calculated by values of densities and velocities that obtained. Thus, the effect of modificating epoxy resin (DGEBA) by AGE and GMA on mechanical properties of DGEBA was investigated using the ultrasonic method. Atomic force microscopy has been used for determining the microstructure of composites. By the results obtained from the investigation, it have been established that the longitudinal and shear ultrasonic wave velocities, and the values of all the elasticity constants of DGEBA were increased by modification with AGE and GMA. Also the most suitable combination ratio for the compound of DGEBA : AGE and DGEBA : GMA has been found as 80 : 20. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013