Investigation of twisted monofilament cord properties made of nylon 6.6 and polyester

A tire is a composite of rubber and reinforcing materials. Polymeric materials used as reinforcing components are usually synthetic yarns. These synthetic yarns have high tenacity, they are made of continuous multifilaments. The yarns are converted in the cord form to provide desired mechanical, thermal and adhesion properties by a series of conversion processes. Besides of multifilament synthetic cords, there are some specific areas in which single ply monofilament cords have been utilized as a reinforcing element. In this study, new cord structures have been developed by using monofilament yarns and by imitating multifilament cords. New cord structures exhibited some very interesting cord properties compared to both single ply monofilament cord and multifilament cords. Monofilament yarns having diameter between 0.23 and 0.50 mm have been twisted together from 3 to 6 plies based on mixed Taguchi model to form cords. Nylon 6.6 and Polyester monofilament yarns have been selected because of common application of their multifilament counterpart yarns in tire carcass and capply. The twisted monofilament cords have been adhesive treated to produce cords ready to adhere rubber. The mechanical properties, thermal stability, adhesion with rubber, fatigue properties under dynamic conditions, retention of properties after curing and microscopic analysis of the cords have been analyzed. The cords have been found to possess some benefits for tire carcass, breaker, belt and belt protective layer applications with their superior fatigue performance, cut resistance, stiffness, ligth weigth etc.     

The influence of thermal stabilization stage on the molecular structure of polyacrylonitrile fibers prior to the carbonization stage

Structural transformation from a linear chain structure to crosslinked chain structure, occuring during the thermal stabilization stage of carbon fiber manufacture, was followed through the use of infrared spectroscopy, differential scanning calorimetry (DSC), elemental analysis and gel-fraction measurements. The results obtained from the analysis of IR spectroscopy showed the gradual and continuous loss of intensity of the nitrile (C≡N) vibration at 2242 cm⁻¹ closely associated with the cyclization reactions whereas the intensity loss of the methylene (CH₂) groups vibration around 2920–2939 cm⁻¹ has been attributed to the loss of hydrogen atoms as part of the dehydrogenation reactions. The dehydrogenation index, evaluated using the absorbance ratio of A₁₄₅₂/A₁₃₆₈, also indicated the gradual loss of hydrogens in agreement with decreasing hydrogen content with progressing stabilization process. IR spectroscopy also showed the emergence of new absorption bands attributed to the formation of crosslinked ladder-like structure in the 1590–1600 cm⁻¹ region. The amount of newly formed crosslinked structure was characterized using DSC conversion index, IR conversion index and gel-fraction measurements. The results are compared and discussed in detail.     

A study on structural characterization of thermal stabilization stage of polyacrylonitrile fibers prior to carbonization

Structural transformations taking place during the thermal stabilization of polyacrylonitrile (PAN) fiber used for the production of carbon fiber were characterized using a combination of polarized infrared spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and density measurements. Direct relationship between the increasing oxygen content and the density values was confirmed with increasing stabilization time. Linear density values were found to be directly influenced by the stabilization time. Thermal stability of stabilized precursor fibers was evaluated in terms of weight loss and residual weight fraction. The results showed that a residual weight fraction of 65 % at 1000 °C can be obtained but longer stabilization time resulted in a loss of residual weight fraction due to excessive thermal degradation. SEM was used for the observation of surface morphological features of stabilized precursor fibers. Polarized infrared spectroscopy showed the loss of molecular orientation of methylene (CH₂), nitrile (Ct=N), and carbonyl (C=O) groups in direct response to the effects of cyclization, dehydrogenation, and amorphization (i.e. decrystallization) processes taking place during the stabilization stage.     

A REVIEW OF PRODUCTION FRONTIER RESEARCH IN AQUACULTURE (2001–2011)

Most research works on the production frontier in aquaculture focus on efficiency measurement using either Stochastic Production Frontier (SPF) or Data Envelopment Analysis (DEA). The studies on productivity growth in aquaculture were limited, perhaps due to lack of time-series data. Nevertheless, total factor productivity analysis (TFP) in fish farms has started gaining popularity in recent years. In addition, the majority of the efficiency studies have centered on technical efficiency analysis but substantial increases in the output levels can be fully realized through improving overall economic efficiency. Therefore, this review suggests that future research should estimate all three efficiency indices (i.e., technical, allocative and economic efficiencies).     

Effect of log seasonality on reproductive potential ofMonochamus galloprovincialis reared in scots pine logs under laboratory conditions

Insect reproduction may be affected by a number of factors including seasonal changes in larval or adult nutrition. The effect of season on the reproductive potential ofMonochamus galloprovincialis (Olivier) females reared inPinus sylvestris L. (Scots pine) logs was investigated by constructing fertility tables for each log that differed only in the season they were cut. Population parameters were compared among three seasonal cohorts. The intrinsic rate of increase and most of the associated population parameters of beetles that emerged from logs cut during spring were higher than for beetles emerged from summer and autumn logs. Slight differences were found between summer and autumn cohorts. We suggest that seasonal differences in the nutritional quality of logs caused differences inM. galloprovincialis survival and reproductive potential. http://www.phytoparasitica.org posting March 16, 2008.     

Visible-Light-Driven Photocatalytic N-Doped TiO<Subscript>2</Subscript> for Degradation of Bisphenol A (BPA) and Reactive Black 5 (RB5) Dye

Bisphenol A (BPA) and reactive black 5 (RB5) dye are among the most persistent and non-biodegradable contaminants in water which require an urgent need for the development of effective removal method. The ubiquitous existence of both contaminants could interfere with the human health and aquatic environmental balance. Photocatalytic process as one of advanced oxidation processes (AOPs) has shown high performance for degradation of organic compounds to the harmless materials under sensible condition. Therefore, this study aims to develop a visible-light-driven photocatalyst that can efficiently degrade BPA and RB5 present in household water. N-doped TiO₂ were successfully synthesized via simple and direct sol–gel method. The prepared TiO₂ nanoparticles were characterized by field emission scanning microscope (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Brunauere Emmette Teller (BET) analysis. The incorporation of nitrogen in TiO₂ lattice exhibited excellent optical responses to visible region as revealed by UV–Vis–NIR spectroscopy absorption capability at 400–600 nm. The photocatalytic activity of the N-doped TiO₂ nanoparticles was measured by photocatalytic degradation of BPA and RB5 in an aqueous solution under visible-light irradiations. Degradation of BPA and RB5 was 91.3% and 89.1%, respectively after 360 min illumination. The degradation of BPA and RB5 by N-doped TiO₂ was increased up to 89.8% and 88.4%, respectively under visible-light irradiation as compared to commercial TiO₂ P25. This finding clearly shows that N-doped TiO₂ exhibits excellent photocatalytic degradation of BPA and RB5 under visible irradiation, hence have a promising potential in removing various recalcitrant contaminants for water treatment to fulfill the public need to consume clean water.

Open image in new window

Graphical Abstract ?

     

Low-Cost Synthesis of Organic–Inorganic Hybrid MSU-3 from Gold Mine Waste for CO<Subscript>2</Subscript> Adsorption

Amine-grafted MSU-3 mesoporous silica samples were synthesized from pure and waste silica sources and their CO₂ adsorption performances were evaluated. The obtained samples were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), N₂ adsorption–desorption isotherm analysis, Fourier transform infrared (FTIR), and transmission electron microscopy (TEM). CO₂ adsorption capacities of the samples at different temperatures were determined by TGA. The amine-modified MSU-3 synthesized from waste exhibited the highest CO₂ adsorption capacity of 1.32 mmol/g at 25 °C and 1 bar, depending essentially on the porous texture and the amine content of the material. The CO₂ adsorption isotherms of the synthesized samples were measured by a static volumetric method. Adsorption isotherm indicated that the amine-modified samples presented significantly higher CO₂ adsorption capacity than the pure samples. The Avrami kinetic model fitted the experimental data well and suggested that complex reaction mechanism or the appearance of multiple reaction pathway occurred in the CO₂ adsorption.

Open image in new window

Graphical Abstract CO₂ uptake capacities and TEM images of the amine modified samples

     

Genetic variation and environmental stability of grain mineral nutrient concentrations in <Emphasis Type="Italic">Triticum dicoccoides</Emphasis> under five environments

Nineteen wild emmer wheat [Triticum turgidum ssp. dicoccoides (Körn.) Thell.] genotypes were evaluated for the grain concentrations of phosphorous (P), potassium (K), sulfur (S), magnesium (Mg), calcium (Ca), zinc (Zn), manganese (Mn), iron (Fe) and cooper (Cu) under five different environments in Turkey and Israel. Each mineral nutrient has been investigated for the (1) genotype by environment (G × E) interactions, (2) genotype stability, (3) correlation among minerals and (4) mineral stability. Among the macronutrients analyzed, grain concentrations of Ca (range 338–2,034 mg kg^?1) and S (range 0.18–0.43%) showed the largest variation. In the case of micronutrients, the largest variation was observed in the grain Mn concentration (range 13–87 mg kg^?1). Grain concentrations of Fe and Zn also showed important variation (range 27–86 and 39–115 mg kg^?1, respectively). Accessions with higher nutrient concentrations (especially Zn and Fe) had also greater grain weight, suggesting that higher grain Zn and Fe concentrations are not necessarily related to small grain size or weight. Analysis of variance showed that environment was the most important source of variation for K, S, Ca, Fe, Mn and Zn, explaining between 44 and 78% of the total variation and G × E explained between 20 and 40% of the total variation in all the minerals, except for S and Zn where its effect accounted for less than 16%. Genotype was the most important source of variation for Cu (explaining 38% of the total variation). However, genotype effect was also important for Mg, Mn, Zn and S. Sulfur and Zn showed the largest heritability values (77 and 72%, respectively). Iron exhibited low heritability and high ratio value between the G × E and genotype variance components \( \left( {\sigma_{\text{GE}}^{2} /\sigma_{G}^{2} } \right) \), suggesting that specific adaptation for this mineral could be positively exploited. The wild emmer germplasm tested in the current study revealed some outstanding accessions (such as MM 5/4 and 24-39) in terms of grain Zn and Fe concentrations and environmental stability that can be used as potential donors to enhance grain micronutrient concentrations in wheats.