Development of dual purpose,industrially important PLA–PEG based coated abrasives and packaging materials

Fabrication of industrially valuable PLA based coated abrasive and packaging products are made using bio-polymeric blends of PLA–PEG without involving the use of hazardous halogen based solvents, such as, chloroform and dichloromethane. Accordingly, an attempt has been made in our study to substitute a relatively less harmful ethyl acetate (EA) solvent in place of the toxic halogenated solvents to dissolve both PLA and PEG polymer blends to produce an environmentally safe PLA–PEG coating and film formulation in EA. This attempt in turn eliminates and replaces the use of non-degradable polymer coatings, (such as, acrylates, PVC, and synthetic latex) on Kraft paper thereby contributing to sustainability and environmental safety besides reduction in waste disposal to realize a cleaner environment. PLA is a hard and brittle polymer, which restricts its unexplored industrial user applications. On the other hand, PEG toughens the brittle PLA due to its plasticizing action. Hence, PLA–PEG polymer blends were prepared using increasing percentage of PEG content systematically from 5% to 25% and the % of PEG in PLA was optimized to 10% to get the maximum toughening effect in PLA–PEG formulation, which is ascertained by differential scanning calorimetry analysis. FTIR analysis confirmed the possible interaction that occurred between PLA and PEG, due to which a shift in vibration frequency of the PLA carbonyl group is observed. The other important test results from mechanical properties, contact angle, surface roughness, Cobb values, WVTR, and SEM analysis support to reveal that PLA–PEG (10%) blend is the best coating and film forming material on Kraft paper for the fabrication of industrially valuable both coated abrasive and packaging products to demonstrate its dual purpose applications.     

The influence of forming surface on the vacuum pressure in hydroentangling process

Hydroentangling is a process that uses waterjet curtains issued from a series of parallel jet-heads (manifolds) for entangling and interloping fibres in a loose fibre web carried on a belt or perforated surface. The efficient removal of the stagnant water remaining from each waterjet curtain is crucial for the success of fibre entanglement when the web reaches the next jet-head. In this article, we discuss different methodologies that can be used to calculate the minimum vacuum pressure required for extracting the hydroentangling water from non-woven fabrics. A distinction has been made between hydroentangling on tightly and openly woven screens and different modelling strategies are recommended for each. In particular, it is demonstrated that a one-dimensional flow pattern coupled with available analytical permeability expressions can be used to predict the required vacuum pressure in the case of tightly woven screens. In the case of open woven screens where the flow pattern becomes three-dimensional, numerical simulation is needed for calculating the vacuum pressure required for complete removal of hydroentangling water. We also demonstrated that the vacuum pressure increases by decreasing the fibre diameter or increasing the fabrics' solid volume fractions.     

Improvement of passivity of Fe–<Emphasis Type=Italic>x</Emphasis>Cr Alloys (<Emphasis Type=Italic>x</Emphasis> < 10%) by cycling through the reactivation potential

Classically, 13% Cr is required for stable passivity of a Fe–Cr alloy in acidic and neutral solutions not containing inhibitors. Some authors (Mansfeld, Fujimoto) have published potential cycling procedures that generate thick Cr-rich films. In this work, a similar technique, but with a far smaller potential cycle, was used to enrich a surface layer in chromium, thereby increasing corrosion-resistance in otherwise non-passivating steels. This was achieved by potential stepping across the iron reactivation potential, firstly forming passive iron(III) oxide, then reducing it to soluble iron(II) ions, while ensuring the passivity of chromium. The use of potential stepping was found to result in a more robust film than that formed through a single continuous passivation step.     

Preparation of NiCo2O4 microspheres employing hydrothermal approach

In this study, nickel cobalt oxide (NiCo₂O₄) microspheres were prepared by using facile hydrothermal route. The structural confirmation of bimetal oxide formation was acquired by X-ray powder diffraction and Raman studies. The formation of microspheres combined via irregular nanosheets was confirmed by scanning electron microscopy. Highly oriented NiCo₂O₄ microspheres yielded a high current density (258 mA/g) at 10 mV/s and low overpotential (224 V). The highly active electrode showed efficient electron transportation towards oxygen evolution reaction. Long-term stability over 16 h was achieved by the fabricated high-performance NiCo₂O₄ electrode. It is recommended that NiCo₂O₄ microspheres obtained from 3:1 stoichiometry ratio of Ni and Co would lead to new electrocatalysts that give best performance than expensive catalysts used currently in the water oxidation process.     

Advanced nanofibrous textile-based dressing material for treating chronic wounds

In the present work, an electrospun nanofibrous textile composed of polyurethane (PU), sodium bicarbonate (\(\hbox {NaHCO}_{3}\)) and pantothenic acid (PA) is developed for treating chronic wounds. Wounds are a common health problem and in particular, the chronic wounds such as vascular ulcers, diabetic ulcers and pressure ulcers cause a large number of morbidity and mortality. The main problems of the chronic wounds are prolonged inflammation phase and presence of acidic environment. These events deactivate the operation of growth factors and also the progression of natural healing mechanism. Hence, various types of advanced textile-based dressings are developed to address the clinical complications associated with chronic wound management. The prepared electrospun scaffolds were characterized to study their physicochemical and haemocompatible properties. The scanning electron microscopy micrographs depicted continuous, smooth-interconnected nanofibrous morphology of PU–NaHCO\(_{3}\)–PA scaffolds. The Fourier transform infrared spectroscopy spectra indicated the addition of NaHCO\(_{3}\) and PA-based hydrophilic chemical groups, which significantly enhanced the wettability of the composites. Further, the PU–NaHCO\(_{3}\)–PA composite membrane inferred to have a highly porous structure with the mean porosity of 79.4 ± 4.8%, which may provide a conducive environment for adherence and proliferation of skin cells. The composite scaffold also offers a highly haemocompatible surface by delaying coagulation of blood through contact activation pathways and by limiting red blood cells damage. Therefore, the excellent physicochemical properties, blood compatibility and the delivery of PA are anticipated to speed up the impaired healing process of chronic wounds.