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This study presents an in vitro analysis of the bactericidal and cytotoxic properties of hybrid films containing nickel oxide (NiO) and nickel ferrite (NiFe[sub.2]O[sub.4]) nanoparticles embedded in polypropylene (PP). The solvent casting method was used to synthesize films of PP, PP@NiO, and PP@NiFe[sub.2]O[sub.4], which were characterized by different spectroscopic and microscopic techniques. The X-ray diffraction (XRD) patterns confirmed that the small crystallite sizes of NiO and NiFe[sub.2]O[sub.4] NPs were maintained even after they were incorporated into the PP matrix. From the Raman scattering spectroscopy data, it was evident that there was a significant interaction between the NPs and the PP matrix. Additionally, the Scanning Electron Microscopy (SEM) analysis revealed a homogeneous dispersion of NiO and NiFe[sub.2]O[sub.4] NPs throughout the PP matrix. The incorporation of the NPs was observed to alter the surface roughness of the films; this behavior was studied by atomic force microscopy (AFM). The antibacterial properties of all films were evaluated against Pseudomonas aeruginosa (ATCC[sup.®]: 43636™) and Staphylococcus aureus (ATCC[sup.®]: 23235™), two opportunistic and nosocomial pathogens. The PP@NiO and PP@ NiFe[sub.2]O[sub.4] films showed over 90% bacterial growth inhibition for both strains. Additionally, the effects of the films on human skin cells, such as epidermal keratinocytes and dermal fibroblasts, were evaluated for cytotoxicity. The PP, PP@NiO, and PP@NiFe[sub.2]O[sub.4] films were nontoxic to human keratinocytes. Furthermore, compared to the PP film, improved biocompatibility of the PP@NiFe[sub.2]O[sub.4] film with human fibroblasts was observed. The methodology utilized in this study allows for the production of hybrid films that can inhibit the growth of Gram-positive bacteria, such as S. aureus, and Gram-negative bacteria, such as P. aeruginosa. These films have potential as coating materials to prevent bacterial proliferation on surfaces.

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In order to evaluate the effects of human umbilical cord-derived stem cells (HUMSCs) on the biocompatibility of and tissue response to a polypropylene (PP) mesh (Gynemesh[TM] PS) implanted in rat vaginas, HUMSCs were isolated and characterized in vitro and then combined with Gynemesh[TM] PS to create a tissue-engineered mesh. This tissue-engineered mesh and pure PP mesh were implanted in the submucosae of the posterior vaginal walls of rats. Mesh/tissue complexes were harvested at 1, 4 and 12 weeks after implantation. Histological evaluations including an assessment of the inflammatory reaction, neovascularization and fibrosis around the mesh fibers were performed and real-time quantitative polymerase chain reaction (RT-PCR) was used to analyze the mRNA expression of genes involved in wound healing at the tissue-mesh interface. After being seeded onto the PP mesh scaffold, HUMSCs grew and proliferated well in vitro culture. One week after implantation, the HUMSC-seeded mesh elicited a greater inflammatory response than the pure PP mesh (3.33 ± 0.21 vs. 2.63 ± 0.18, p = 0.026), while 4 and 12 weeks after implantation, the inflammatory response in the HUMSC-seeded mesh was lower than that in the unseeded mesh (p < 0.05). At 12 weeks, the HUMSC-seeded mesh induced a lower expression of matrix metalloproteinase (MMP)-1 and a higher expression of anti-inflammatory cytokine interleukin (IL)-4. HUMSCs may decrease the inflammatory response and improve the biocompatibility of a conventional synthetic mesh and may have the potential to reduce postoperative complications such as mesh exposure or erosion.

Supercritical CO[sub.2] (scCO[sub.2]) extrusion foamed high-melt-strength (HMS) polypropylene (PP) often suffers from low cell density, large cell sizes, and poor cell structure uniformity due to the poor nucleation rates of CO[sub.2] in the PP. To remedy this, various inorganic fillers have been used as heterogeneous nucleation agents. Although their efficient nucleation effects have been demonstrated, the preparation of these fillers causes some adverse effects on the environment/human health or involves relatively expensive processes or non-eco-friendly chemicals. In this work, biomass-based lignin is studied as a sustainable, lightweight, and cost-effective nucleating agent. It is found that scCO[sub.2] could assist in situ dispersion of lignin in the PP in the foaming process, leading to significantly increased cell density, smaller cells, and improved cell uniformity. The Expansion Ratio is also simultaneously improved due to reduced diffusive gas loss. The PP/lignin foams with low lignin loadings exhibit higher compression moduli and plateau strengths than the PP foams with the same densities owing to the improved cell uniformity and probably also the reinforcing effect of the small lignin particles in cell walls. Moreover, the energy absorption capability of the PP/lignin foam with 1 wt% lignin could match the PP foam with similar compression plateau strengths; even the density of the former is 28% lower than the latter. Therefore, this work provides a promising approach to a cleaner and more sustainable production of HMS PP foams.

A number of production methods have been developed for high-performance fibers; however, most processes use toxic solvents or generate a lot of unwanted by-products. Our research resulted in the development of a new family of high-performance polypropylene (PP) fibers by utilizing a simple, ecologically friendly bath (ECOB). Various commodity polymers can be used with ECOB melt spinning system at high throughputs and performance benefits. Our treated as-spun PP fibers had a highly oriented, but not crystalline precursor morphology with [f.sub.a] up to 0.6 generating superior mechanical properties. After drawing at draw ratios of 1.49 at 120°C, highly oriented crystalline and amorphous phases were achieved for the drawn fibers with [f.sub.c] and [f.sub.a] values of 0.95 and 0.87, respectively. This fine structure for ECOB-treated fibers resulted in tenacity close to 12 g/d, initial modulus higher than 150 g/d, and ultimate elongation at break of 20 %. The polymer melting point of the new fibrillar PP fibers increased by 9°C.

Polypropylene (PP) is a versatile polymer with numerous applications that has undergone substantial changes in recent years, focusing on the demand for next-generation polymers. This article provides a comprehensive review of recent research in PP and its advanced functional applications. The chronological development and fundamentals of PP are mentioned. Notably, the incorporation of nanomaterial like graphene, MXene, nano-clay, borophane, silver nanoparticles, etc., with PP for advanced applications has been tabulated with their key features and challenges. The article also conducts a detailed analysis of advancements and research gaps within three key forms of PP: fiber, membrane, and matrix. The versatile applications of PP across sectors like biomedical, automotive, aerospace, and air/water filtration are highlighted. However, challenges such as limited UV resistance, bonding issues, and flammability are noted. The study emphasizes the promising potential of PP while addressing unresolved concerns, with the goal of guiding future research and promoting innovation in polymer applications.Graphical Abstract

Photocatalysis is widely acknowledged as an efficient technique for degrading a variety of pollutants, such as antibiotics, pesticides, herbicides, and microplastics. In this study, the micro-sized TiO.sub.2 photocatalyst with the oxidizing agents (H.sub.2O.sub.2, periodate, and oxone) was investigated for the degradation of polyethylene (PE), polypropylene (PP), and sulfathiazole (STZ). Firstly, the photocatalytic activity of synthesized TiO.sub.2 was evaluated by the decomposition of STZ ( 94% within 30 min), and then the microplastic degradation experiments were conducted. The changes before and after the experiment were characterized using SEM, FTIR, and XPS. The weight loss for PE under the different combinations of experiments was UV (0%), UV/TiO.sub.2 ( 5.7%), UV/TiO.sub.2/H.sub.2O.sub.2 ( 17%), UV/TiO.sub.2/Periodate ( 16%), and UV/TiO.sub.2/Oxone ( 13.4%). The PP globules ( 4 mm) did not have a significant impact on weight loss due to their large particle size and high rigidity. Meanwhile, PE showed improved weight loss due to a smaller particle size of 20-100 µm. SEM images confirmed the degradation of the PE was significant while only a few surface modifications can be observed for PP. FTIR analysis revealed changes in carbonyl groups of PE and PP, including ketones (1720 cm.sup.-1), acids (1718 cm.sup.-1), esters (1735 cm.sup.-1), and vinyl groups (1650 cm.sup.-1). The synergy between the oxidants and the photocatalyst unquestionably enhanced the oxidation of the microplastics.

The influence of structural water in alumina (Al[sub.2]O[sub.3]) and silica (SiO[sub.2]) coated titanium dioxide (TiO[sub.2]) pigments on the photodegradation behavior of polypropylene (PP) composites was investigated. Four commercial rutile TiO[sub.2] pigments with varying surface inorganic coatings were incorporated into PP plaques and subjected to accelerated UV weathering to simulate outdoor exposure. Photodegradation was assessed through gloss retention measurements, the carbonyl index (CI), and stress at break retention, while pigment morphology and composition were analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Surface charge and water content were determined through the zeta potential (ζ), Karl Fischer titration, thermogravimetric analysis (TGA), and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results showed that low-alumina coating alone led to the lowest photodegradation resistance, the highest CI, and the lowest stress at break retention. In contrast, increasing alumina content enhanced photostability, reaching its maximum for combined alumina–silica coatings, which mitigated electron–hole pair migration. PP composites with high alumina–silica-coated TiO[sub.2] exhibited higher gloss retention (36%) compared to low-alumina samples (21%). Furthermore, statistical analysis using ANOVA revealed significant differences in coating content and ζ potential among the pigment grades. These findings provide novel insights into oxide-water interactions and the impact of structural water on the photodegradation of polymer composites.