Search

Propylene glycol methyl ether acetate (PGMEA) serves as a crucial solvent in semiconductor and display material processes, demanding high purity and low acidity. Despite its significance, its conventional synthesis method using homogeneous catalysts requires extensive purification. Our study explores the use of Amberlyst-15, a stable solid catalyst, to streamline this process. Through batch reactions with a 1:1 reactant ratio at various temperatures and modeling using an integrated reaction rate equation, we obtained kinetic parameters. These parameters were used to predict the kinetics under different reactant ratios and different catalyst amounts, and the predictions match well with experimental results, especially when we used the catalyst amount scaled by the amount of the limiting reactant (PGME) rather than the total amount of the reactants. This highlights the importance of reporting kinetic parameters with proper scaling for catalyst used. Furthermore, we integrated these parameters into process simulations to determine the length of a plug flow reactor (PFR), constructed a PFR system, and confirmed that the simulation results matched well with experimental data obtained from the PFR system. Our findings suggest Amberlyst-15's potential in simplifying PGMEA synthesis, promising advancements in industrial applications. [ABSTRACT FROM AUTHOR]

Various commercial zeolites, including FER, MOR, ZSM‐5, BEA, and FAU frameworks, were treated with NH4F aqueous solutions to study the effects of fluoride etching on different zeolite frameworks. NH4F‐treated small‐medium pore FER, MOR, and ZSM‐5 samples showed much higher mesoporosities than the untreated ones without alteration of the structural compositions and acidic properties. On the other hand, the 12‐membered ring zeolites BEA and FAU showed severe dissolution of the framework aluminosilicate structure after NH4F etching due to the high accessibility of fluoride species into the framework structures. The effect of NH4F concentration on the fluoride treatment of H‐ZSM‐5 zeolite was specifically studied. From the results, we observed that structural etching with 20 wt % NH4F was optimal for fabricating open‐pore H‐ZSM‐5 zeolite and resulted in a high mesoporosity with comparable relative crystallinity and acidity with respect to the untreated H‐ZSM‐5. The catalytic activities of the open‐pore H‐ZSM‐5 were evaluated with acid‐catalyzed methanol and bioethanol conversions. Remarkably, the hierarchical open‐pore H‐ZSM‐5 zeolite fabricated via fluoride etching exhibited an enhanced catalytic performance in bioethanol conversion with >85 % conversion over 34 h TOS and a higher catalytic stability in methanol conversion than the parent H‐ZSM‐5 (~50 % of bioethanol conversion at 34 h TOS). [ABSTRACT FROM AUTHOR]

Plastic pollution and food waste are two pressing global challenges that require immediate attention and innovative solutions. In this study, we address these challenges by upcycling brewers' spent grain (BSG) into biodegradable composite films. BSG, a by-product of the beer brewing process, is commonly discarded in landfills or used as animal feed. By utilizing BSG as a raw material for biodegradable films, we simultaneously reduce waste and decrease plastic pollution. To create the composite films, we employed poly(vinyl alcohol) (PVA) and glycerol as binder materials, along with hexamethoxymethylmelamine (HMMM) as a water-repelling agent. By varying the ratios of these components, we investigated the effects on film properties. Our characterization included assessing moisture uptake and tensile properties. The results revealed that the practical BSG content in the films was 20–60 wt%. Films with this composition exhibited a balance between moisture absorption and mechanical strength. The addition of glycerol improved the flexibility and toughness of the films, while HMMM reduced moisture absorption, enhancing their water resistance. This study contributes to the development of sustainable materials by showcasing the potential of upcycling BSG into valuable biodegradable films. By transforming food waste into useful applications, we reduce environmental burdens and promote a circular economy. Further research is warranted to explore the potential applications and optimize the properties of BSG-based composites. [ABSTRACT FROM AUTHOR]

Plastic pollution has become a global concern, demanding urgent attention and concerted efforts to mitigate its environmental impacts. Biodegradable plastics have emerged as a potential solution, offering the prospect of reduced harm through degradation over time. However, the lower mechanical strength and slower degradation process of biodegradable plastics have hindered their widespread adoption. In this study, we investigate the incorporation of New Zealand (NZ) jade (pounamu) particles into poly(lactic acid) (PLA) to enhance the performance of the resulting composite. We aim to improve mechanical strength, flame retardation, and degradability. The material properties and compatibility with 3D printing technology were examined through a series of characterization techniques, including X-ray diffraction, dispersive X-ray fluorescence spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, 3D printing, compression molding, pycnometry, rheometry, tensile tests, three-point bending, and flammability testing. Our findings demonstrate that the addition of NZ jade particles significantly affects the density, thermal stability, and mechanical properties of the composites. Compounding NZ jade shows two different changes in thermal stability. It reduces flammability suggesting potential flame-retardant properties, and it accelerates the thermal degradation process as observed from the thermogravimetric analysis and the inferred decrease in molecular weight through rheometry. Thus, the presence of jade particles can also have the potential to enhance biodegradation, although further research is needed to assess its impact. The mechanical properties differ between compression-molded and 3D-printed samples, with compression-molded composites exhibiting higher strength and stiffness. Increasing jade content in composites further enhances their mechanical performance. Th results of this study contribute to the development of sustainable solutions for plastic pollution, paving the way for innovative applications and a cleaner environment. [ABSTRACT FROM AUTHOR]

Biodegradable plastics are thought to be the possible directions in managing plastic pollutions. Unfortunately, they are not recycled in most countries since they are designed to decompose even though recycling is a more pragmatic method than landfill or incineration. Thus, it is more constructive to develop methods to recycle biodegradable plastics or to develop biodegradable yet recyclable plastics. In this study, we used cutlery with a composite of poly(lactic acid) (PLA) and talc. The possibility to recycle it to make foams was studied even though it will have lowered mechanical strength from the recycling process as it is less significant for this product. Tensile properties of solid PLA and foams showed no significant decrease in the strength up to three processes of compression molding and foaming. We performed shear rheometry to determine the thermal stability and dependences of the complex viscosity on frequency and temperature. The magnitude of the complex viscosity dramatically increased with decreasing frequency and such an upturn increased with temperature, but time-temperature superposition was valid at high temperatures. The extensional rheometry showed no strain hardening, but physical foaming using supercritical carbon dioxide (CO2) could still occur, and the operating conditions to obtain various foamed structures were determined. We also compared the effects of one-directional against three-dimensional expansion. Overall, the concentration of CO2 in PLA and crystallinity of the foams are the two key variables to describe the bulkiness of foams. Surprisingly, the lower the CO2 concentration, the bulkier the foams at any sorption temperature and pressure. [ABSTRACT FROM AUTHOR]

Hydrogels with or without chemical cross-linking have been studied and used for biomedical applications, such as tissue repair, surgical sealants, and three dimensional biofabrication. These materials often undergo a physical sol–gel or gel–sol transition between room and body temperatures and can also be chemically cross-linked at these temperatures to give dimensional stability. However, few studies have clearly shown the effect of heating/cooling rates on such transitions. Moreover, only a little is known about the effect of cross-linking temperature or the state on the modulus after cross-linking. We have established rheological methods to study these effects, an approach to determine transition temperatures, and a method to prevent sample drying during measurements. All the rheological measurements were performed minimizing the normal stress build-up to compensate for the shrinking and expansion due to temperature and phase changes. We chemically modified gelatin to give gelatin methacryloyl and determined the degree of methacryloylation by proton nuclear magnetic resonance. Using the gelatin methacryloyl as an example, we have found that the gel state or lower temperature can give more rigid gelatin-based polymers by cross-linking under visible light than the sol state or higher temperature. These methods and results can guide researchers to perform appropriate studies on material design and map applications, such as the optimal operating temperature of hydrogels for biomedical applications. We have also found that gelation temperatures strongly depend on the cooling rate, while solation temperatures are independent of the heating rate. [ABSTRACT FROM AUTHOR]

Allogeneic lung transplant is limited both by the shortage of available donor lungs and by the lack of suitable long-term lung assist devices to bridge patients to lung transplantation. Avian lungs have different structure and mechanics resulting in more efficient gas exchange than mammalian lungs. Decellularized avian lungs, recellularized with human lung cells, could therefore provide a powerful novel gas exchange unit for potential use in pulmonary therapeutics. To initially assess this in both small and large avian lung models, chicken (Gallus gallus domesticus) and emu (Dromaius novaehollandiae) lungs were decellularized using modifications of a detergent-based protocol, previously utilized with mammalian lungs. Light and electron microscopy, vascular and airway resistance, quantitation and gel analyses of residual DNA, and immunohistochemical and mass spectrometric analyses of remaining extracellular matrix (ECM) proteins demonstrated maintenance of lung structure, minimal residual DNA, and retention of major ECM proteins in the decellularized scaffolds. Seeding with human bronchial epithelial cells, human pulmonary vascular endothelial cells, human mesenchymal stromal cells, and human lung fibroblasts demonstrated initial cell attachment on decellularized avian lungs and growth over a 7-day period. These initial studies demonstrate that decellularized avian lungs may be a feasible approach for generating functional lung tissue for clinical therapeutics. [ABSTRACT FROM AUTHOR]

It is a concern that microplastics have been discovered in the food sources and water that we consume. This research was to evaluate the methods to isolate microplastics from organisms and how much of the environment of New Zealand (NZ), which is one of the least polluted countries, is contaminated by microplastics. New Zealand green-lipped mussels (Perna canaliculus) are considered to be an important product in the NZ food industry. For this reason, the existence of microplastics in these were investigated. Tarakihi fish (Nemadactylusmacropterus) consume food near the bottom of ocean, so this fish can be an indicator of the contamination of microplastics denser than water. In addition, bottled water, tap water and sea salt samples were also investigated. To isolate solid particles in an animal body, its tissues were chemically digested. It was found that 10% (w/w) potassium hydroxide (KOH) was a practical digestive protocol on biological tissues since polymers such as polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) are relatively resistant to KOH. Thus, treating tissues with KOH can be considered a viable method to remove tissues and isolate microplastics. Nile red was used to stain the plastic particles from the samples for visual inspection. Fourier-transform infrared spectrometry (FTIR) was performed to identify the particles. It was evaluated that all those samples had traces of microplastics. [ABSTRACT FROM AUTHOR]

Two tube-based molecular models, the hierarchical 3.0 model and the branch-on-branch model were evaluated for their abilities to predict the behavior of a series of polydisperse, H-shaped, 1,4-polybutadienes. The samples had been synthesized using a novel technique designed to suppress the generation of high molar mass by-products. While size exclusion chromatography data indicated that the samples were monodisperse, low molar mass by-products were later revealed by temperature gradient interaction chromatography. Viscoelastic data were obtained at temperatures ranging from -75 °C to 25 °C, and the samples were found to be thermorheologically simple. Sensitivity and uncertainty analyses revealed that among the model parameters, the value of plateau modulus has the strongest effect on model predictions. As molecular models improve, it will become ever more essential to evaluate them using accurate data on materials whose microstructures have been reliably established. This is especially important for materials that are structurally polydisperse. [ABSTRACT FROM AUTHOR]

We studied polymer-polymer interfacial slip in bilayer films of highly immiscible (interaction parameter, χ≅0.1) polyethylene and fluoropolymer from medium to higher shear stresses (10-200 kPa) using both visualization and stress reduction. We found good agreement between results from the two methods as well as with previous studies using multilayers by Lee et al. [J. Rheol. 53, 893-915 (2009)] and visualization of flow in a transparent capillary by Migler et al. [J. Rheol. 45, 565-581 (2001)]. We observed two power-law regions: Vslip∝τ6.2 with a transition to Vslip∝τ1.8 at 50 kPa. This is in contrast to the theory of Brochard-Wyart and de Gennes [C. R. Acad. Sci., Ser. II: Mec., Phys., Chim., Sci. Terre Univers 317, 13-17 (1993)], which predicts a transition from infinite slope to a slope of one at a critical stress. [ABSTRACT FROM AUTHOR]

Publisher's Note: "Recycling and rheology of poly(lactic acid) (PLA) to make foams using supercritical fluid" [Phys. Comparison of the top view of the cell structure after cutting samples in the direction that is parallel to the bottom surface [Fig. This article was originally published online on 29 June 2021 with an error in the captions for Figs. [Extracted from the article]

Strain hardening has important roles in understanding material structures and polymer processing methods, such as foaming, film forming, and fiber extruding. A common method to improve strain hardening behavior is to chemically branch polymer structures, which is costly, thus preventing users from controlling the degree of behavior. A smart microfiber blending technology, however, would allow cost-efficient tuning of the degree of strain hardening. In this study, we investigated the effects of compounding polymers with microfibers for both shear and extensional rheological behaviors and characteristics and thus for the final foam morphologies formed by batch physical foaming with carbon dioxide. Extensional rheometry showed that compounding of in situ shrinking microfibers significantly enhanced strain hardening compared to compounding of nonshrinking microfibers. Shear rheometry with linear viscoelastic data showed a greater increase in both the loss and storage modulus in composites with shrinking microfibers than in those with nonshrinking microfibers at low frequencies. The batch physical foaming results demonstrated a greater increase in the cell population density and expansion ratio with in situ shrinking microfibers than with nonshrinking microfibers. The enhancement due to the shrinkage of compounded microfibers decreasing with temperature implies that the strain hardening can be tailored by changing processing conditions. [ABSTRACT FROM AUTHOR]