Chemical Degradation Research Articles

Assessment of chemical degradation of epoxy resin binder used in the service of the Qin terracotta warriors

Since the Qin terracotta warriors were unearthed, polyamide 650 cross-linked E-44 epoxy resin binder has been employed to bond and restore them. In this paper, the chemical aging of the binders service in indoor natural environment during the past 30 years in the terracotta warriors was studied by means of infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The results indicated that the binders did not emerge the characteristic peak of carbonyl stretching vibration at 1700 cm−1 in the IR spectra of all determined binders, and their thermal decomposition curves did not emerge any abnormal changes, and the thermal decomposition mainly occurred above 300 °C. There are evident ceramic grains attached to the surface of the binders being peeled off for sampling. These results that the binders service in the Qin terracotta warriors did not exhibit an observable chemical aging and still has strong adhesion. Generally, discrepancies were observed between natural aging and accelerated artificial aging due to the ineffectiveness of the latter to reproduce the effects of complex weather conditions. Compared to artificially accelerated aging, the evaluation results in a long-term natural aging of the binder which is used for restoration of the life-size Qin terracotta warriors, providing in the present investigation, are more reliable in terms of predicting the safety of restored terracotta warriors.

Application of ultrasonic radiation for the development of polypropylene/multi-walled carbon nanotubes nanocomposites and its effect on the PP chemical degradation

Application of ultrasonic radiation for the development of polypropylene/multi-walled carbon nanotubes nanocomposites and its effect on the PP chemical degradation

Chemical Degradation of the Ternary Al2O3–YAG–ZrO2 Eutectic Ceramic by Molten CMAS

Chemical Degradation of the Ternary Al2O3–YAG–ZrO2 Eutectic Ceramic by Molten CMAS

STEM Investigation of Structural and Chemical Degradation Mechanisms in Na-Based Batteries

STEM Investigation of Structural and Chemical Degradation Mechanisms in Na-Based Batteries

The two-faced functionality of birch glucuronoxylan in an emulsion-based carrier of vitamin D3

Emulsions are commonly used to fortify beverages with oil-soluble nutrients. Such emulsions must be physically stable, prevent the cargo nutrient from chemical degradation, and release the nutrient at the right time during digestion. Wood hemicelluloses, with their proven capability in producing nanoemulsions and preventing oil oxidation, have the potential to facilitate such a fortification method. These hemicelluloses are unique, as the presence of residual lignin was proven essential in their functionality. However, the structural interplay between the residual lignin and the polysaccharide fraction at the oil-water interface is unknown, including their effects on the storage stability and digestibility of a loaded bioactive compound. We studied the performance of emulsions stabilized by two grades of birch glucuronoxylans (GX) as vessels for vitamin D3. Both GXs showed similar protective performance to methylcellulose regardless of the lignin content during storage and the gastric phase of digestion. The unrefined GX, which contained larger lignin moieties, delayed the release of vitamin D3 during intestinal digestion. We concluded that the interface is primarily built of a polysaccharide layer with the lignin moieties facing towards the oil phase. We have thus highlighted the potential of GX-stabilized emulsions as carriers of vitamin D3. Additionally, these results advance the understanding of lignin-polysaccharide interplay towards a rationalized strategy in biorefining of wood hemicelluloses, for which the ratio of lignin-to-polysaccharide can be adjusted during extraction and post-extraction treatments to obtain a tailor-made emulsifier for various emulsion-based products.

Rapid repair and degradation: A study of high-performance recyclable vitrimer epoxy resin based on disulfide bonds

Petroleum-based epoxy resin is commonly used in electrical equipment due to its outstanding performance and affordability. However, its non-melting characteristics present challenges for recycling, leading to significant resource waste and environmental pollution. To address this issue, this study prepared and synthesized a kind of vitrimer epoxy resin polymer material based on disulfide bonds with 2,2′-Diaminodiphenyl disulphide as the curing agent. The research investigated the impact of the curing agent ratio on the resin's structure and properties. The resin was mechanically recovered through hot pressing at high temperature and pressure, and its chemical degradation and recovery were achieved via the reduction reaction of the thiol and disulfide bond. The findings revealed that a curing agent to epoxy group material ratio of 0.75 improved the resin system's electrothermal properties. The electrical insulation property retention rate after hot pressing recovery reached 95 %, with a mechanical property retention rate of 85 %. The disulfide bonds can be reoxidized and crosslinked to realize the recovery and reuse of vitrimer resin degradation solution. Vitrimer epoxy resin based on disulfide bonds is a significant way to realize the environmental protection of epoxy electrical equipment.

Environmental impact of the variations in solar reflectance index values of some selected dimension stones due to cyclic thermal shock

Natural stones are widely used environmentally appropriate building materials as dimension stone both for exterior cladding and floor coverings in urban areas. Depending on their solar reflectivity, these materials may absorb more solar radiation, especially with noontime summer sunlight exposure, which may cause both increasing cooling costs in commercial buildings and overheating of a city with the formation of urban heat islands. Solar reflectance index (SRI) is defined as the ability of a surface to reject solar heat which tends to change with physical, chemical and biological degradation processes by varying solar reflectance (SR) and thermal emissivity (TE) values. Weakening of the stone matrix structure by physical degradation mechanism, such as thermal shock (T-S) cycles mostly have significant impact on SRI. Within the scope of this study, SRI values were calculated before and after cyclic T-S by measuring the optical properties such as SR and TE values of 30 selected sedimentary and metamorphic originated carbonate-based natural stone types. The changes in surface properties such as color, roughness, and gloss, that may have an impact on the SRI values were also analyzed. In addition, a multivariate regression analysis was established to predict SRI value from such properties with a high degree of accuracy. Finally, it was found that, initial SRI values of 9 natural stone types (mostly metamorphic originated) have been increased considerably by cyclic T-S and tend to increase their ability to reduce urban temperatures by higher SRI values, one of the most important selection criteria in energy consumption for natural stones.

Study of liquid photopolymer 3D printing resins exposed to accelerated aging for cultural heritage purposes

PurposeThis paper aims to study the suitability of a selection of 3D printing liquid photopolymer resins for their application in the cultural heritage context.Design/methodology/approachThe main concerns regarding the conservation and restoration of cultural assets are the chemical composition and long-term behavior of the new materials that will be in contact with the original object. Because of this, four different LED curing resins were exposed to an accelerated aging procedure and tested to identify the materials which demonstrated a better result. Some specific properties of the material (color, glossiness, pH and volatile organic compound emissions) were measured before and after the exposure.FindingsSome of the properties measured reported good results demonstrating a decent stability against the selected aging conditions. The main changes were produced in the colorimetric aspect, probably indicating other chemical reactions in the material. Likewise, a case study could be also executed to demonstrate the usefulness of these materials in the cultural field.Research limitations/implicationsIt is necessary to study in more detail the long-lasting behavior of the materials employed with these technologies. Further analysis should be carried out highlighting the chemical composition and degradation process of the materials proposed.Originality/valueThis paper contributes to the introduction of curing 3D printing resins in the restoration methodologies of cultural assets. For this, the study of a selection of properties represents the first stage to suggest or reject their use.

A chemo-enzymatic method for preparation of saturated oligosaccharides from alginate and other uronic acid-containing polysaccharides

Oligosaccharides from uronic acid-containing polysaccharides can be produced either by chemical or enzymatic degradation. The benefit of using enzymes, called lyases, is their high specificity for various glycosidic linkages. Lyases cleave the polysaccharide chain by an β-elimination reaction, yielding oligosaccharides with an unsaturated sugar (4-deoxy-l-erythro-hex-4-enepyranosyluronate) at the non-reducing end. In this work we have systematically studied acid degradation of unsaturated uronic acid oligosaccharides. Based on these findings, a method for preparing saturated oligosaccharides by enzymatic degradation of uronic acid-containing polysaccharides was developed. This results in oligosaccharides with a pre-defined distribution and proportion of sugar residues compared to the products of chemical degradation, while maintaining the chemical structure of the non-reducing end. The described method was demonstrated for generating saturated oligosaccharides of alginate, heparin and polygalacturonic acid. In the case of alginate, the ratio of hydrolysis rate of Δ-G and Δ-M linkages to that of G-G and M-M linkages, respectively, was found to be approximately 65 and 43, at pH* 3.4, 90 °C. Finally, this method has been demonstrated to be superior in the production of α-l-guluronate oligosaccharides with a lower content of β-d-mannuronate residues compared to what can be achieved using chemical depolymerization alone.

Boosting the anti-tumor activity of natural killer cells by caripe 8 – A Carapichea ipecacuanha isolated cyclotide

Cyclotides are head-to-tail cyclized peptides with a unique cystine-knot motif. Their structure provides exceptional resistance against enzymatic, chemical, or thermal degradation compared to other peptides. Peptide-based therapeutics promise high specificity, selectivity and lower immunogenicity, making them safer alternatives to small molecules or large biologicals. Cyclotides were researched due to their anti-cancer properties by inducing apoptosis in tumor cells in the past, but the impact of cyclotides on cytotoxic immune cells was poorly studied. Natural Killer (NK) cells are cytotoxic innate lymphoid cells and play an important role in the defense against infected, stressed and transformed cells. NK cells do not need prior sensitization and act in an antigen independent manner, holding promising potential in the field of immunotherapy. To investigate the effect of immunomodulatory cyclotides on NK cells, we evaluated several peptide-enriched plant extracts on NK cell mediated cytotoxicity. We observed that the extract samples derived from Carapichea ipecacuanha (Brot.) L. Andersson augments the killing potential of mouse NK cells against different tumor targets in vitro. Subsequent isolation of cyclotides from C. ipecacuanha extracts led to the identification of a primary candidate that enhances cytotoxicity of both mouse and human NK cells. The augmented killing is facilitated by the increased degranulation capacity of NK cells. In addition, we noted a direct toxic effect of caripe 8 on tumor cells, suggesting a dual therapeutic potential in cancer treatment. This study offers novel insights how natural peptides can influence NK cell cytotoxicity. These pre-clinical findings hold significant promise for advancing current immunotherapeutic approaches.

Environmental Assessment of Narmada River Tributary I. E Ganjal River Water and its Photo Chemical Degradation using TiO2 Nanocatalyst

Environmental Assessment of Narmada River Tributary I. E Ganjal River Water and its Photo Chemical Degradation using TiO2 Nanocatalyst

Comprehensive aging model coupling chemical and mechanical degradation mechanisms for NCM/C6-Si lithium-ion batteries

The aging of lithium-ion batteries (LIBs) is synergistically influenced by multiple chemical/mechanical degradation mechanisms. Therefore, conventional models that incorporate only partial mechanisms exhibit limited predictive accuracy and applicability, failing to fully reflect the effects of chemical/mechanical degradation under complex operating conditions. Here, we propose an aging model for NCM/C6-Si LIBs coupled with comprehensive chemical/mechanical degradation mechanisms. The model includes chemical mechanisms at the C6-Si anode solid electrolyte interface (SEI), Li plating, and NCM cathode electrolyte interface (CEI), as well as mechanical mechanisms of loss of active material (LAM) for C6, Si, and NCM. Based on this model, we comprehensively investigate the effect of capacity loss by (dis)charge rates and ambient temperatures, obtaining the aging characteristics and the contribution of each mechanism to loss under different variables. Furthermore, we quantitatively analyze the sensitivity and response characteristics of the degradation sub-mechanism to (dis)charge rate and temperature. This study introduces an advanced aging analysis model for NCM/C6-Si LIBs, which can effectively decouple the operational characteristics of the degradation mechanism and provide guidance for developing next-generation high-energy LIBs.

SHG behavior of the solid isomorphic compounds Ni- and Cu-5,10,15,20- tetraphenylporphyrinate. An experimental and theoretical study

We prepared and investigated the SHG behavior in the solid state of the two isomorphic Nickel and Copper 5,10,15,20-tetraphenylporphyrinate, that crystallize in the same acentric I4¯2d space group. The compounds were synthesized and characterized, and the Second Harmonic Generation (SHG) response of powdered samples was measured employing a 1.907 μm pulsed laser radiation. During laser irradiation, for both compounds, a gradual increase of the intensity of the SH signal was observed until, after a few minutes, it reached a plateau of about fifty times (for the Ni-TPP) or ten times (for the Cu-TPP) the initial value. We attempted to understand the origin of this phenomenon both through experimental analysis and theoretical calculations. Absorption and vibrational spectroscopies, in solution and solid state, combined with powder X-ray diffraction, both before and after irradiation, do not evidence any chemical degradation, phase transition or amorphization process. Theoretical calculations on little fragments of the Ni/Cu-TPP structure simulate appropriately the structural features of the complexes and their initial experimental SHG response. Magnetic balance measurement in the solid state before and after irradiation, in conjunction with DFT/B3LYP optimization of excited spin states and TDDFT calculations, highlight a change in the electronic and/or spin state due to the irradiation of the complexes.

Selective electrochemical degradation of bottlebrush elastomers

AbstractWe introduce a simple synthetic strategy to selectively degrade bottlebrush networks derived from well‐defined poly(4‐methylcaprolactone) (P4MCL) bottlebrush polymers. Functionalization of the hydroxyl groups present at the terminal ends of P4MCL side chains with α‐lipoic acid resulted in bottlebrush polymers having a range of molecular weights (Mn = 45–2200 kg mol−1) and a tunable number of reactive dithiolane chain ends. These functionalized chain ends act as efficient crosslinkers due to radical ring‐opening of the dithiolane rings under UV light. The resulting redox‐active disulfide crosslinks enable mild electrochemical or chemical degradation of the SS crosslinks to regenerate the starting bottlebrush polymer. P4MCL side chains and the disulfides can be degraded simultaneously using harsher reducing conditions. This combination of bottlebrush architecture with facile disulfide crosslinking presents a versatile platform for preparing highly tunable elastomers that undergo controlled degradation under mild conditions.

Fabrication of pristine 2D heterostructures for scanning probe microscopy

Material-by-design has been a long-standing aspiration that has recently become a reality. Such designer materials have been repeatedly demonstrated using the top-down approach of mechanical exfoliation and stacking, leading to a variety of artificial 2D heterostructures with new properties that are otherwise unattainable. Consequently, tremendous research frontiers in physics, chemistry, engineering, and life science have been created. While thousands of layered crystals exist in nature, only a few dozen of them with manageable chemical-stability have been made into heterostructures using this method. Moreover, experimental investigations of materials that have received limited exploration in the 2D realm, such as cuprates, halides, and perovskites, along with their heterostructures, have been fundamentally hindered by their rapid chemical degradation. Another critical challenge imposed by exfoliating and stacking 2D layers in ambient environment is the absorption of itinerant gas molecules that further contaminate sensitive 2D interfaces in the heterostructures. Such contamination and compromised material properties significantly hinder surface-sensitive local probes—scanning probe microscopy (SPM)—that often require nanometer to atomic scale surface cleanliness. In this article, we aim to provide a technical review of recent development toward 2D materials and heterostructure fabrication in more controlled environments that are suitable for SPM characterizations. These include the development of more efficient mechanical exfoliation and dry-transfer techniques, as well as the incorporation of 2D material exfoliation and transfer in inert gas, low vacuum, and, eventually, ultra-high vacuum environments. Finally, we provide an outlook on the remaining challenges and opportunities in ultra-clean 2D material fabrication techniques.

Theoretical Studies on the Chemical Degradation and Proton Dissociation Property of PBI used in High-Temperature Polymer Electrolyte Membrane Fuel Cells.

High-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are gaining more and more attention due to their higher efficiency than low-temperature ones. Polybenzimidazole (PBI) membranes are the most popular membranes used in HT-PEMFCs. However, their chemical stability and chemical degradation mechanisms, which directly affect the lifetime of fuel cells, have been hardly reported. We applied the density functional theory and used ABPBI as an example membrane to investigate the chemical degradation mechanisms of PBI membranes. The possible degradation mechanisms that occurred on eight sites have been proposed, where sites 2 and 3 located on the phenyl ring are determined as two weak sites toward OH radical and oxygen molecule attack. When the terminal is the H atom at site 7, it is also weak under OH radical attack. Regarding these, the substituent effect on the chemical stability of polymers has been studied. By introducing four -C2F5 or -CN groups, the barrier heights of the corresponding degradation reactions are increased; thus, the chemical stabilities of related membranes are improved. The selection of terminal atoms was also explored for alleviating the chemical degradation of the membrane. The investigated proton transfer properties of nine model compounds revealed that introducing four -C2F5 or -CN groups improves the proton dissociation properties occurring at the cathode. The increase of phosphoric acid concentration is helpful for the proton transfer at both the membrane and the cathode. This work may hopefully help the design and synthesis of HT-PEMFCs with good stability and high efficiency.

Digital Twin‐Assisted Degradation Diagnosis and Quantification of NMC Battery Aging Effects During Fast Charging

AbstractA comprehensive understanding of aging mechanisms and degradation diagnosis under fast charging in battery electric vehicles is needed. However, there is a lack of tools to capture both macroscopic and microscopic parameters, still focusing on experiment results analysis. To get a comprehensive degradation insight for improved service life, this study explores aging mechanisms in LiNi0.5Co0.2Mn0.3O2 graphite batteries under different fast charging conditions (0.6C to 2C) for up to 1000 equivalent full cycles (EFCs). An improved digital twin is used to quantify aging effects and identify aging modes, combining electrochemical techniques with post‐mortem analysis for assessing chemical and structural degradation. After 1000 EFCs, the dominant aging modes are loss of active material (LAM) in the negative electrode and loss of lithium inventory (LLI), surpassing LAM in the positive electrode. Compared to constant current charging, multistep fast charging effectively mitigates Li plating effects and graphite cracking, resulting in a 13% reduction in LAM. Additionally, optimizing the depth of discharge leads to at least 4% reductions in LLI and 16% in LAMpos. This study proves the electrochemical digital twin's potential for quantifying aging effects and serves as a basis for future physics‐informed machine learning to predict aging behavior and modes.

Stability of Protein Pharmaceuticals: Recent Advances.

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Geministatins: new depside antibiotics from the fungus Austroacremonium gemini

Two new depside antibiotics, geministatins A (1) and B (2), were isolated from the fungus Austroacremonium gemini MST-FP2131 (Sordariomycetes, Ascomycota), which was recovered from rotting wood in the wet tropics of northern Australia. The structures of the geministatins were elucidated by detailed spectroscopic analysis, chemical degradation and comparison with literature values. Chemical degradation of 1 and 2 yielded three new analogues, geministatins C–E (3–5), as well as a previously reported compound dehydromerulinic acid A (6). Compounds 1, 2 and 6 exhibited antibacterial activity against the Gram-positive bacteria Bacillus subtilis (MIC 0.2–1.6 µg mL−1) and Staphylococcus aureus (MIC 0.78–6.3 µg mL−1), including methicillin-resistant S. aureus (MRSA), while 4 exhibited antifungal activity against the yeast Saccharomyces cerevisiae (MIC 13 µg mL−1).

Review of Sulfate Removal in Low Concentration Brine Solutions

Sulfate is a common ion present in natural water bodies at low concentrations and as effluent in different metallurgical processes. The discharge of sulfate in rivers and waterbodies can cause direct and indirect damage to the environment. Regulatory agencies have been increasing the constraints in sulfate content limit for discharge focused on human equity and environmental protection. A common practice is the precipitation of sulfate with lime, but the remaining solution still has ca. 1,500 mg L-1 of sulfate, which is not acceptable for disposal or reuse. This work describes the main routes for sulfate removal such as chemical precipitation, biological degradation, ion exchange, and separation through membranes and discusses the main advantages and issues of each approach. One of the main challenges is to scale up the tests and show the performances at the industrial level. The subject must be the focus of constant study to obtain relevant results so that usual technologies are replaced by more innovative, cheap and efficient methods.