Medical applications require, in most cases, antibacterial protection. The use of silver (Ag) gives important antibacterial properties since silver is highly toxic for bacteria. In this research work, we have used silver nanoparticles (Ag NPs) with different surfactants, polyvinyl pyrrolidone (PVP) and oleic acid (OA) to facilitate dispersion. PP-Ag NPs compounds were prepared by melt mixing, and the effects of the processing conditions on nanoparticles' dispersion were investigated by transmission electron microscopy (TEM). The antibacterial efficiency of PP-Ag NPs compounds against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8379 was evaluated. Results show that good dispersion is obtained with rotating speeds in the 350-500 rpm range. TEM analysis reveals balanced dispersion and presence of some Ag NPs aggregates. Regarding antimicrobial properties, the use of PVP as surfactant leads to ' 'significant'' antimicrobial activity of 1.5 against Staphylococcus aureus and Escherichia coli; on other hand, the use of oleic acid (OA) as surfactant leads to strong protection against Staphylococcus aureus (antimicrobial activity between 2.5 and 3.3) but the overall protection against Escherichia coli is very low (lower than 1). Results show that the use of surfactants for Ag NPs has important effects on antibacterial properties of polypropylene filled with coated Ag NPs. POLYM. ENG. SCI., 51:804-811,
In this investigation, the characteristics and the rheological properties of two different nanocomposite systems were investigated. These systems consisted of a dispersion of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) in a polypropylene (PP) matrix. The mixing process was carried out by melt compounding with a twin-screw corotating extruder with different reinforcement amounts (0.2-20 wt %) from concentrated masterbatches (20 wt %) of PP/CNT and PP/CNF. The results show a remarkable increase in the viscosity for both blends as the reinforcement amount was increased. It was important to evaluate the rheological behavior to understand the effect of the nanocarbon particles on the internal structures and their processing properties of the obtained composites. CNFs were a more viable reinforcement from a processability point of view because the obtained viscosities of the PP/CNF blends were more manageable.
Sustainability in the textile industry is a challenge with an imminent need to be tackled. One approach can be focused on replacing fossil-based dyes with renewable and less polluting alternatives. In this sense, this study focuses on validating the suitability of an innovative natural-based blue dye, phycocyanin, sourced from Spirulina platensis microalgae. The laboratory-based experimental approach envisages the exhaustion dyeing of pre-mordanted cotton and bleached wool with phycocyanin-rich extract, representing the sustainable blue dye. The color characterization of naturally blue-dyed fabrics was performed via CIE Lab coordinates, depth of color by color stregth valures ( K/S), values of dye exhaustion, and colorfastness to laundering and light. The results indicate suitable dyeability with the natural blue dye, with process improvements a possibility. The main environmental character of this process was analyzed from the dyeing effluent characterization perspective. Measurements of chemical oxygen demand, biochemical oxygen demand, and metal content were performed on effluents resulting from dyeing processes with variable parameters, to analyze the influence of mordant use, process temperature, time, and pH. Findings indicate that the application of optimum dyeing process conditions results in the lowest oxygen demand values, suitable for further wastewater reuse, according to international industrial effluent limitations. The biological fungi wastewater treatment resulted in the reduction of biochemical oxygen demand and chemical oxygen demand values by around 80%, comparable with the industrial process, validating the sustainable character of using algae-based phycocyanin in the bath exhaustion dyeing process.
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