Macromolecular Symposia最新文献

The Atlantic Forest is one of the richest regions in biodiversity in the world. Originally the biome covered around 15% of the Brazilian territory. Currently, there are approximately 12.4% of forest remnants preserved in the country. Regarding mangrove areas in the state of São Paulo, there are around 223 km² according to the Brazilian Mangrove Atlas, with around 120.5 km² located in Baixada Santista. Analysis of sediments found in the estuarine mangroves of Santos shows a high concentration of microplastics (MPs), generated by industrial processes and human activity, that constitutes today one of the main environmental problems. The MPs presented in the sediment samples are quantified using a methodology that involves drying, sieving, quantification, and identification of these MPs through FTIR and micro-Raman spectroscopy. The two techniques complement each other to identify MP filaments and fragments through common polymer spectra. Furthermore, the micro-Raman technique also identified additives flexo blue (blue ink) and neolan green 8G (dye) in MPs. All identified polymers (< 5 mm) have wide applications and demands in various sectors, including packaging, construction, automotive, electronics, and textiles.

Lignocellulosic fibers from Brewer's spent grain (BSG) represent an ecologically and economically favorable alternative that can act as reinforcing agents for starch-based polymer composites. Biodegradable composites are produced using cassava starch and BSG of the Pilsen (P) and Weiss (W) types, which are subjected to mercerization (BSM), bleaching (BSP) and a combination of those treatments (BSB). By including treated BSGs, homogeneous matrices with starch are produced, without the presence of pores and/or cracks, as evidenced by the scanning electron microscopy (SEM) images. The tensile strength of the composites is improved by up to 80% and Young's modulus by up to 50% with the addition of BSB(P) and BSB(W) fibers, indicating the role of the materials as reinforcement agents. Bleaching and mercerization treatments are efficient in the exposition of hydroxyl groups of cellulose, resulting in higher hydrophilicity and water vapor permeability (WVP) of the composites containing the BSP and BSM fibers. Biodegradable composites incorporating BSG from the brewing industry have promising properties and can be a viable alternative to non-biodegradable polymeric packaging.

AZ31 magnesium alloys stand out as a pivotal alternative for orthopedic applications owing to their inherent attributes of biocompatibility, biodegradability, favorable mechanical properties, and the facilitation of bone regeneration. The Mg AZ31 foams serve as temporary implants thanks to its bioabsorbability, offering the advantage of obviating the need for additional surgical interventions and minimizing associated ailments and discomfort. However, addressing the intrinsic corrosion rate of magnesium is imperative. To mitigate corrosion, surface activation techniques, specifically alkaline activation and hydrofluoric activation, are applied to treat the surfaces of AZ31 alloys. Subsequently, these treated alloys, configured as scaffolds, undergo coating with varying concentrations of collagen solutions (0%, 16%, and 64% w/w). The corrosion rate is then assessed through the hydrogen evolution method within a simulated physiological environment (simulated body fluid [SBF]). The analysis of results employs quantitative techniques, such as atomic absorption (AA) spectroscopy and qualitative methods, including electron microscopy with atomic analysis. The outcomes reveal the successful consolidation of the collagen coating, identification of corrosion byproducts, a notable reduction in corrosion rate, and additional indicators providing evidence of potential bone tissue regeneration.

The air is a fundamental element for the life on Earth. Rapid urbanization and industrialization release large amounts of pollutants (harmful gases, microorganisms, and particulate matter, among others) into the atmosphere, leading to health hazards. Air filtration is still the most used and promising technique for protecting air against pollutants. The quality and efficiency of filtering process are dependent of the material used for the filter and other filter's properties. Several methods can be used for manufacturing filters, one of them uses fibrous membranes obtained mainly through electrospinning from polymeric solutions. Electrospinning is a technique that combines the application of an electrostatic field to a polymer solution that induces the fluid to move and, due to the solvent evaporation, results in the fibers formation. Electrospun membranes are constituted by fibers that the sizes spread on submicro and or nanometric scales. This review focuses on fiber membranes obtained by electrospinning for filtration of particulate matter. It is addressed the effect of solution, processing, and ambient parameters on the morphology and dimensional characteristics of fiber membranes. The basic principles of air filtration, test, and characterization of filter performance are also presented. The research progress on electrospun nanofibers as air filters in recent years is summarized and discussed. Finally, conclusion and future perspectives in electrospun fibers for air filtration are provided and discussed.

Cover:

This issue of Macromolecular Symposia contains selected papers presented at the 17th Brazilian Polymer Conference (17th CBPol), held in presential mode and taken place at the EXPOVILLE Convention and Exhibition Center) in Joinville, Santa Catarina, Brazil from October 29 to November 02, 2023. The cover shows a figure provided from the manuscript 2400070 by Carla Dalmolin and co-authors.

The immobilization of enzymes increases their stability and allows their reuse, and bacterial cellulose (BC) is a material that can be used in this technique. This work aims to produce an enzymatic product to degrade oils and fats using BC as a matrix. Komagataeibacter hansenii bacteria produce BC membranes, and lipase is immobilized on the membranes by ex situ method. Then, the surface of the membranes is modified with zein, a hydrophobic corn protein. The membranes are characterized by TGA, FTIR, scanning electron microscopy (SEM) analysis and oil degradation test. TGA demonstrates higher stability for the membranes with lipase and zein. The FTIR spectrum of pure BC membrane and zein-modified membrane are very similar because of the high zein coating. SEM analysis shows that zein-modified membranes with lipase present smaller amounts of pores. Finally, using soy oil, lipase degrades oil even after immobilization during the degradation test.

Electromechanical sensors obtained by electrospun mats have a high surface area and porosity, allowing superior flexibility and sensitivity of response to the sensor. Based on this context, in this work, electrospun mats based on thermoplastic polyurethane (TPU) and multi-wall carbon nanotubes (MWCNTs) are produced by electrospinning. The electrical resistivity under different compressive stress levels is evaluated in recurring loading and unloading cycles. Incorporating MWCNT increases the elastic modulus and thermal stability but does not significantly increase the electrical conductivity. However, the electrospun mats with different concentrations of MWCNT show variation in electrical resistivity under compressive stress. The response is stable with a compressive stress of 0.25 MPa and five cycles of compression and decompression, with a variation in the relative resistivity of approximately −0.8 for all MWCNT concentrations. A similar response is observed with the increasing of the compressive stress to 0.5 MPa.

This study explores the potential of using a composite material made of polylactic acid (PLA), polybutylene adipate-co-terephthalate (PBAT), and rice husk (RH) as an alternative for food containers. Two blends with 10 wt%–20 wt% of PBAT and four composites with 10 wt%–20 wt% of RH reinforcement are evaluated. The composite is created using an internal mixer and is analyzed using torque vs time mixing curves, melt flow index (MFI), thermogravimetric analysis, and differential scanning calorimetry (DSC). The blends exhibit higher crystallinity and superior mechanical properties compared to composites. Adding RH improves sustainability and decreases costs by utilizing agricultural waste but reduces flexural strength. However, the addition of PBAT increases flexibility, making it suitable for pliable material applications. The composite CO4 with 20 wt% of PBAT and RH demonstrates balanced performance in terms of lower MFI, thermal stability, and flexural strength, making it suitable for food tray applications. Further studies are needed to optimize the mechanical and barrier properties of these composites for specific applications.

Petrochemical polymers provide most packaging materials in the food industry and cause environmental problems due to their non-biodegradability. Developing biodegradable polymers with additives is a strategy, and bacterial cellulose (BC) presents favorable properties for this application. This work aims to evaluate the effect of essential oils (EOs) of clove, cinnamon, basil, and oregano as additives in BC matrix for application in food packaging. BC membranes are synthesized by the bacteria Komagataeibacter hansenii and incorporated into EOs using ethanol as a solvent. The membranes are characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), antibacterial activity, and soil biodegradation. Furthermore, the samples are also tested for their antifungal potential on the surface of bread slices. FTIR analyses confirm the incorporation of EOs into BC membranes. TGA analysis indicates a slight increase in thermal stability for the incorporated samples. All samples show antibacterial potential, except BC, incorporated with the essential basil oil. The fungal analysis is performed by visually evaluating the appearance of filamentous fungi on the surface of the bread pieces. Soil biodegradation tests demonstrate mass loss for all membranes.