Effect of glycerol cross-linking and PDI on the shape memory effect and mechanical properties of polyurethane

A series of shape memory polyurethane (PU) copolymers synthesized from 1,4-phenyldiisocyanate (PDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD) as a chain extender, and glycerol as a cross-linking agent were tested for the mechanical properties and the shape memory effect at the temperature 20 °C above melting temperature (T _m), and were compared with other PUs synthesized from 4,4′-methylene-bis-phenyldiisocyanate (MDI), PTMG, and BD. Mechanical properties and shape memory effect were improved substantially by adopting both PDI and glycerol. Interestingly, enthalpy of melting and T _m were not affected by the glycerol content. Vibration and shock absorption ability was investigated by measuring both loss tan δ and storage modulus with dynamic mechanical analyzer (DMA).     

Photochromic fabrics with improved durability and photochromic performance

Previously, we have reported a method for producing photochromic wool fabric by applying a thin layer of hybrid silica-photochromic dye onto the wool surface. While the photochromic coating showed a very fast optical response and had little influence on the fabric handle, its durability was poor. In this study, the durability of the photochromic coating layer was improved by introducing epoxy groups into the silica matrix via co-hydrolysis and co-condensation of an alkyl trialkoxysilane compound (ATAS) and 3-glycidoxypropyltrimethoxysilane (GPTMS). The presence of epoxy groups in the silica enhanced both washing and abrasion durability or fastness. In addition, the optical response speed was slightly increased as well. Effects of the type of alkyl silane and the GPTMS/alkyl silane ratio on the coating durability, fabric handle and optical response were examined.     

Field variability and vulnerability index to identify regional precision agriculture opportunity

Innovations in precision agriculture (PA) have created opportunities to achieve a greater understanding of within-field variability. However, PA adoption has been hindered by uncertainty about field-specific performance and return on investment. Uncertainty could be better addressed by using innovative analyses that provide insights into variability among fields and across a region. The objectives of this research were to: (1) generate a within-field soil clay-content variability index (VI_c), (2) create a regional-scale growing-season precipitation variability index (VI_p), and (3) integrate the soil and weather indices with the USDA NRCS soil erosion vulnerability index (SVI) to produce a final index that incorporated both variability and vulnerability (VVI). The interpretation of the outcomes represented by each objective supports unique decisions that land managers may consider for reducing uncertainty about implementing PA. All indices were derived using publically available information for Missouri, USA. The VI_c was the ratio between the maximum and minimum clay content within fields. The VI_p was calculated as the standard deviation of the total growing-season precipitation from 2006 to 2015. Significant clustering of VI_c and VI_p were observed along the Missouri River corridor, northeast and northwest Missouri. Fields with high VVI were mostly in the claypan soil region of northeast Missouri, and along a portion of the Missouri River dominated by loess soils on steep slopes. Southeast Missouri displayed the greatest diversity in soil and weather variability, but had low vulnerability. This research could be used as a decision-support tool to aid producers and PA service and product providers in determining where PA opportunities exist.     

Crop water stress mapping for site-specific irrigation by thermal imagery and artificial reference surfaces

Variable-rate irrigation by machines or solid set systems has become technically feasible, however mapping crop water status is necessary to match irrigation quantities to site-specific crop water demands. Remote thermal sensing can provide such maps in sufficient detail and in a timely way. In a set of aerial and ground scans at the Hula Valley, Israel, digital crop water stress maps were generated using geo-referenced high-resolution thermal imagery and artificial reference surfaces. Canopy-related pixels were separated from those of the soil by upper and lower thresholds related to air temperature, and canopy temperatures were calculated from the coldest 33% of the pixel histogram. Artificial surfaces that had been wetted provided reference temperatures for the crop water stress index (CWSI) normalized to ambient conditions. Leaf water potentials of cotton were related linearly to CWSI values with R ² = 0.816. Maps of crop stress level generated from aerial scans of cotton, process tomatoes and peanut fields corresponded well with both ground-based observations by the farm operators and irrigation history. Numeric quantification of stress levels was provided to support decisions to divide fields into sections for spatially variable irrigation scheduling.     

Effects of silver content and morphology on the catalytic activity of silver-grafted titanium oxide nanostructure

As titanium oxide is a well-known photocatalyst, we investigated the effects of silver content and nanostructural morphology on the photocatalytic degradation of two dyes, methylene blue and rhodamine B. Two nano-formulations were utilized, including nanofibers and nanoparticles. Silver-grafted titanium oxide nanofibers were synthesized using the electrospinning of silver nitrate/titanium isopropoxide/poly(vinyl acetate) sol-gel. The nanoparticulate form was obtained by calcination of a ground powder prepared from the same electrospun sol-gel. The results affirmed the advantage of the silver-grafted titanium oxide nanostructures over the silver-free ones. Increasing the silver content in the nanofibers led to increases in their surface area, which is an important parameter in heterogeneous catalytic chemical reactions. Therefore, the results strongly suggest the use of silver-grafted titanium oxide in a nanofibrous form. These results further support utilizing Agloaded titanium oxide nanofibers as a photocatalyst.     

Union dyeing of the photografted PET/wool blend fabrics with dimethylaminopropyl methacrylamide

Dimethylaminopropyl methacrylamide (DMAPMA) was grafted onto PET/wool blend fabrics by continuous UV irradiation. Union dyeing of the photografted fabrics was investigated using three reactive dyes of α-bromoacrylamide reactive groups. The influence of grafting yield, DMAPMA concentration, NaCl amount, pH value, and dyeing temperature on the dyeability was evaluated. The dyeability of both PET and wool components was improved significantly by the DMAPMA photografting and successive reactive dyeing. Although the dyeability of the PET component in the blend substantially was improved with higher grafting, equal dyeability between PET and wool was difficult to achieve due to more facile grafting and higher reactivity of the wool component compared with the modified PET component. However, the color fastness of the PET/wool blend fabric was excellent for all three colors. This study may offer a way to achieve union dyeing of PET/wool blend fabrics.     

Six Edible Wild Fruits as Potential Antioxidant Additives or Nutritional Supplements

Total antioxidant activity of six non-cultivated but traditionally collected fruits from the south of Europe was assessed by measuring their ability to reduce the hydroxyl radical ( OH^· ) \left( {{\hbox{O}}{{\hbox{H}}^\bullet }} \right) and hydrogen peroxide (H₂O₂), and their Trolox equivalent antioxidant capacity (TEAC). This antioxidant activity was compared with that shown by the synthetic antioxidants BHA (E-320), BHT (E-321) and propyl gallate (E-310). Total phenolics, ascorbic acid and the carotenoid content of the fruits were also analyzed. All fruits showed a high ability to scavenge the OH^· {\hbox{O}}{{\hbox{H}}^\bullet } radical, ranging from 60.61% to 81.04% inhibition for Rosa canina and Crataegus monogyna, respectively. The H₂O₂ scavenging capacity and the TEAC value varied widely, ranging between 3.63% and 87.26% inhibition of H₂O₂ and between 0.47 and 416.64 mM trolox g⁻¹ FW for Sorbus domestica and Rosa canina, respectively. The antioxidant activity of fruits was higher than that of the synthetic additives analyzed, except in the TEAC assay. The phenolic and carotenoid content of R. canina was much higher than that of the other fruits analyzed and its ascorbic acid concentration was also high, reflecting its higher efficacy towards ABTS ^·- {\hbox{ABT}}{{\hbox{S}}^{ \bullet - }} (TEAC assay) and H₂O₂ species_. In spite of these associations, the correlation coefficients between total antioxidant activity and the antioxidant compounds analyzed were not very significant; only phenolics and carotenoids showed a marginal correlation with the TEAC assay. The results support the possible use of R. canina as natural antioxidant to replace the synthetic additives, as well as their use in the production of functional foods with a high antioxidant activity.     

Conjugating S-nitrosothiols with fluorescent nanofibers for the controlled release and real-time detection of nitric oxide

In this work, a novel hybrid fibrous vehicle was developed for the release and real-time detection of nitric oxide (NO). The vehicle consisted of poly(L-lactide)/chitosan (PLLACS), cadmium tellurium quantum dots (CdTe QDs), and conjugating S-nitrosothiols. CdTe QDs were placed on the surface of PLLACS fibers as NO fluorescent probes through coaxial electrospinning; in this method, the PLLACS was used as filament material. Water-dispersible CdTe QDs were synthesized using mercaptoacetic acid as a stabilizer. The amino groups of chitosan served as reactive sites where chitosanbased S-nitrosothiols were formed. The fibrous PLLACS-QDs-NO composite was found to release NO under UV. The released NO could be detected in real time on the basis of the fluorescence quenching mechanism of QDs. These PLLACSQDs-NO nanofibers provide insights into novel designs of biocompatible NO delivery systems.     

Mechanical behavior of composites reinforced with fibers caroa

Composites were prepared with 13, 23 30 and 40 % fiber and evaluated the mechanical performance in tensile, flexural and impact. The mechanical properties of these composites were also evaluated function of time at 110 °C thermal exposure. Caroa fibers were characterized by techniques such as thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the best mechanical properties were achieved for composites containing 23 to 30 % fiber. The incorporation of 23 % fiber caroa increased both the modulus of elasticity in the tensile test as the flexural strength and impact, the composite with 30 % fiber caroa showed higher tensile strength. The results show that the tensile and flexural strength of the composite decreased with time of thermal exposure. The thermal aging at 110 °C caused a decrease in tensile properties of the composites.     

Copper functionalization of polypropylene fabric surface in order to use in fog collectors

Polypropylene fabrics were coated with copper particles using electroless plating, screen printing and wire arc spray coating techniques. Surface morphology of the fabrics was studied using optical and scanning electron microscopes (SEM). Furthermore, tensile strength, electrical conductivity, thermal conductivity, air permeability, water contact angle and fog collection efficiency of the coated fabrics were measured and the obtained results were analyzed. SEM micrographs showed that a very thin and uniform layer of copper deposited on the surface of the electroless plated polypropylene fibers. In the printed or spray coated fabrics the copper particles filled the spaces between yarns and fibers. The polypropylene electroless copper plated fabrics showed higher tensile strength, electrical conductivity, air permeability and thermal conductivity when compared with the fabrics coated with copper screen printed and copper spray coated fabrics. Finally, the obtained results showed that copper electroless plating could increase the fog collection efficiency of polypropylene fabrics considerably. As a conclusion, the surface modified copper electroless polypropylene fabrics are good candidates for fog collection in appropriate regions which need further investigations.