Polypropylene Blends with m-EPR Copolymers: Mechanical and Rheological Properties.

The effects of two metallocene ethylene-propylene-based elastomers (m-EPR1 and m-EPR2) differing in molecular mass and viscosity on mechanical, rheological and interfacial properties were compared. The m-EPR elastomers were added to iPP in 2.5, 5, 10, 15, and 20 vol.%. Torque values, elongation at break and impact strength measured of the iPP/m-EPR1 blends were higher than the iPP/m-EPR2 blends due to higher molten viscosity of m-EPR1 than m-EPR2 copolymer. Slight differences in Young moduli as well as in tensile strength at yield and at break might indicate that tensile properties of iPP/m-EPR blends were not significantly affected by difference in viscosity or molecular mass, miscibility and spherulite size. Optimization diagrams indicated the metallocene m-EPR copolymers are efficient impact modifiers for polypropylene and showed good balancing of mechanical properties in iPP/m-EPR blends.

Tuning the photocatalytic activity of nanocrystalline titania by phase composition control and nitrogen doping, using different sources of nitrogen.

Titania nanoparticles were synthesized by employing the hydrothermal method and using TiOSO(4) as a titanium source. By varying pH between 0.5 and 1.0 and adding isopropanol to the hydrothermal reaction mixture, different mixtures of anatase, rutile, and brookite were obtained. The samples were also doped with nitrogen at different N concentrations using, respectively, urea, ammonium nitrate, and tripropylamine as nitrogen sources. The samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy, infrared spectroscopy, UV-Vis diffuse reflectance spectroscopy and according to their specific surface area. Additionally, their photocatalytic activity was measured in a gas-solid reactor system. The results show that low pH favours rutile formation, whereas a higher pH yields mixed phase titania polymorphs. Isopropanol addition also favours rutile formation, and boosted the photocatalytic activity of the resulted particles. Contrary to most data in the literature, rutile turned out to be the more active phase in the present investigation. Nitrogen doping, on the other hand, did not contribute to higher photocatalytic activity, but was rather detrimental to it.

Poly(Allylamine Hydrochloride) and ZnO Nanohybrid Coating for the Development of Hydrophobic, Antibacterial, and Biocompatible Textiles.

In healthcare facilities, infections caused by Staphylococcus aureus (S. aureus) from textile materials are a cause for concern, and nanomaterials are one of the solutions; however, their impact on safety and biocompatibility with the human body must not be neglected. This study aimed to develop a novel multilayer coating with poly(allylamine hydrochloride) (PAH) and immobilized ZnO nanoparticles (ZnO NPs) to make efficient antibacterial and biocompatible cotton, polyester, and nylon textiles. For this purpose, the coated textiles were characterized with profilometry, contact angles, and electrokinetic analyzer measurements. The ZnO NPs on the textiles were analyzed by scanning electron microscopy and inductively coupled plasma mass spectrometry. The antibacterial tests were conducted with S. aureus and biocompatibility with immortalized human keratinocyte cells. The results demonstrated successful PAH/ZnO coating formation on the textiles, demonstrating weak hydrophobic properties. Furthermore, PAH multilayers caused complete ZnO NP immobilization on the coated textiles. All coated textiles showed strong growth inhibition (2-3-log reduction) in planktonic and adhered S. aureus cells. The bacterial viability was reduced by more than 99%. Cotton, due to its better ZnO NP adherence, demonstrated a slightly higher antibacterial performance than polyester and nylon. The coating procedure enables the binding of ZnO NPs in an amount (<30 µg cm-2) that, after complete dissolution, is significantly below the concentration causing cytotoxicity (10 µg mL-1).

Degradation and Stabilization of Polymer Materials.

The growing awareness of the consequences of climate change has prompted the formulation of policies and regulations to foster sustainability [...].

Influence of Weathering on the Degradation of Cellulose Acetate Microplastics Obtained from Used Cigarette Butts.

Cellulose acetate is used in many applications, including for cigarette filters. Unfortunately, unlike cellulose, its (bio)degradability is under question, yet it often ends up uncontrolled in the natural environment. The main purpose of this study is to compare the effects of weathering on two types of cigarette filter (classic filters and newer filters that have more recently arrived on the market) following their use and disposal in nature. Microplastics were prepared from polymer parts of used (classic and heated tobacco products-HTP) cigarettes and artificially aged. TG/DTA, FTIR, and SEM analyses were performed both before and after the aging process. Newer tobacco products contain an additional film made of a poly(lactic acid) polymer which, like cellulose acetate, burdens the environment and poses a risk to the ecosystem. Numerous studies have been conducted on the disposal and recycling of cigarette butts and cigarette butt extracts, revealing alarming data that have also influenced the decisions of the EU, who addressed the disposal of tobacco products in the EU Directive (EU) 2019/904. Despite this, there is still no systematic analysis in the literature evaluating the impact of weathering (i.e., accelerated aging) on the degradation of cellulose acetate in classic cigarettes compared with that in newer tobacco products that have recently appeared on the market. This is of particular interest given that the latter have been promoted as being healthier and environmentally friendly. The results show that in cellulose acetate cigarette filters the particle size decreased after accelerated aging. Also, the thermal analysis revealed differences in the behavior of the aged samples, while the FTIR spectra showed no shifts in the position of the peaks. Organic substances break down under UV light, which can be seen by measuring the color change. The PLA film was found to be more stable than cellulose acetate under the influence of UV light.

UV Light Causes Structural Changes in Microplastics Exposed in Bio-Solids.

Bio-solids (biological sludge) from wastewater treatment plants are a significant source of the emission of microplastics (MPs) into the environment. Weakening the structure of MPs before they enter the environment may accelerate their degradation and reduce the environmental exposure time. Therefore, we studied the effect of UV-A and UV-C, applied at 70 °C, on three types of MPs, polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), that are commonly found in sewage sludge, using three shapes (fibers, lines, granules). The MPs were exposed to UV radiation in bio-solid suspensions, and to air and water as control. The structural changes in and degradation of the MPs were investigated using Attenuated Total Reflectance-Fourier Transform Infrared Spectrometry (ATR-FTIR) and surface morphology was performed with SEM analysis. UV exposure led to the emergence of carbonyl and hydroxyl groups in all of the PP samples. In PE and PET, these groups were formed only in the bio-solid suspensions. The presence of carbonyl and hydroxyl groups increased with an increasing exposure time. Overall, UV radiation had the greatest impact on the MPs in the bio-solids suspension. Due to the surface-to-volume ratio of the tested samples, which influences the degradation rate, the fibers were more degraded than the other two plastic shapes. UV-A was slightly more effective at degrading the MPs than UV-C. These findings show that ultraviolet radiation in combination with an elevated temperature affects the structure of polymers in wastewater bio-solids, which can accelerate their degradation.

Metal and Non-Metal Modified Titania: the Effect of Phase Composition and Surface Area on Photocatalytic Activity.

The application of TiO2 photocatalysis in various environmental fields has been extensively studied in the last decades due to its ability to induce the degradation of adsorbed organic pollutants. In the present work, TiO2 powders doped and co-doped with sulfur and nitrogen and modified with platinum were prepared by particulate sol-gel synthesis. PXRD measurements revealed that the replacement of HCl with H2SO4 during synthesis reduced the size of the crystallites from ~ 30 nm to ~20 nm, increasing the surface area from ~44 m2/g to ~80 m2/g. This is consistent with the photocatalytic activity of the samples and the measured photocurrent behavior of the photocatalysts. The results showed that the properties of the powders (i.e., surface area, crystallite size, photocurrent behavior) depend strongly not only on the type but also on the amount of acid and dopants used in the synthesis. Doping, co-doping and modification of TiO2 samples with nitrogen, sulfur and platinum increased their photocatalytic activity up to 6 times.

Hydrothermal Synthesis of Rare-Earth Modified Titania: Influence on Phase Composition, Optical Properties, and Photocatalytic Activity.

In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile with rare earth cations. The aim of this study was to find the influence of the modification of TiO2 with rare earths on its structural, optical, morphological, and photocatalytic properties. Titania was synthesized using TiOSO4 as the source of titanium via hydrothermal synthesis procedure at low temperature (200 °C) and modified with selected rare earth elements, namely, Ce, La, and Gd. Structural properties of samples were determined by X-ray powder diffraction (XRD), and the phase ratio was calculated using the Rietveld method. Optical properties were analyzed by ultraviolet and visible light (UV-Vis) spectroscopy. Field emission scanning electron microscope (FE-SEM) was used to determine the morphological properties of samples and to estimate the size of primary crystals. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding properties of samples. Photocatalytic activity of the prepared photocatalysts as well as the titania available on the market (P25) was measured in three different setups, assessing volatile organic compound (VOC) degradation, NOx abatement, and water purification. It was found out that modification with rare earth elements slows down the transformation of anatase and brookite to rutile. Whereas the unmodified sample was composed of only rutile, La- and Gd-modified samples contained anatase and rutile, and Ce-modified samples consisted of anatase, brookite, and rutile. Modification with rare earth metals has turned out to be detrimental to photocatalytic activity. In all cases, pure TiO2 outperformed the modified samples. Cerium-modified TiO2 was the least active sample, despite having a light absorption tail up to 585 nm wavelength. La- and Gd-modified samples did not show a significant shift in light absorption when compared to the pure TiO2 sample. The reason for the lower activity of modified samples was attributed to a greater Ti3+/Ti4+ ratio and a large amount of hydroxyl oxygen found in pure TiO2. All the modified samples had a smaller Ti3+/Ti4+ ratio and less hydroxyl oxygen.

Transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons and the influence of the transformation strategies on the photocatalytic performance.

The influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon surfaces and their optical properties was investigated. The transformations were performed (i) through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400-650 °C, (ii) through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii) through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g)/Ar(g) flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti(4+) to Ti(3+). The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the hydrothermally derived TiO2 NRs was additionally improved by a subsequent heat treatment in air.