Search

Boron nitride (hBN) serves as an outstanding high‐performance polymer organic filler. However, its hexagonal crystal structure renders it chemically inert, thus limiting its applications. This study proposes the modification of hBN using economical amine and anhydride curing agents to reduce aggregation and enhance the heat conduction of epoxy resin. Specifically, the DETA curing agent and methyl tetrahydrophthalic anhydride (MTHPA) curing agent were grafted onto the hBN surface via ball milling and eco‐friendly water scrubbing processes. Subsequently, the modified functionalized BNNS were uniformly dispersed in epoxy resin via a wet process to form composite materials. Results indicate that both modified fillers maintain good dispersion at the epoxy interface. Compared to epoxy resin, the heat conduction of the EP/MTHPA‐BNNS composite material with 10 vol% loading increased by 212%. The EP/DETA‐BNNS composite exhibited a relative thermal conductivity enhancement of 191%. Moreover, both of materials demonstrated significantly improved thermal stability, with slightly reduced breakdown strength. Mechanical property testing revealed a maximum increase of 187.5% in fracture elongation. Highlights: Comprehensive study on curing agent modified hBNHigh dispersion of BNNS after wet ball millingModified BNNS improves composite interface propertiesThe thermal conductivity increases twice under 10 wt% BNNS loadingComposite materials with outstanding electrical insulation and high fracture elongation [ABSTRACT FROM AUTHOR]

This research study focused on the effect of adding boric acid to epoxy resin in order to obtain a composite material with improved properties and performance. To this end, a fine powder of boric acid (H3BO3) was introduced into epoxy resin in different amounts, i.e., 0.5 g, 1.0 g, and 1.5 g. As the matrix of the epoxy composites, styrene-modified epoxy resin based on bisphenol A (BPA) (Epidian 53) was used. It was cross-linked with two types of curing agents, i.e., an amine (ET) and a polyamide (PAC). The mechanical properties of the obtained epoxy composites (in terms of compressive strength, compressive modulus, and compressive strain) were determined at room temperature in order to assess the effect of the addition of boron acid and of the type of curing agent employed to cure the epoxy on these characteristics. Calorimetric measurements were made to highlight any changes in the glass transition temperature (Tg) as a result of the addition of boric acid to epoxy resin. Finally, flammability tests were performed on both Epidian 53/PAC and Epidian 53/ET epoxy composites to analyze their fire behavior and consequently establish the effectiveness of the selected additive as a flame retardant. [ABSTRACT FROM AUTHOR]

Although research shows that waterborne epoxy resin emulsified asphalt (WER-EA) is an environmental protection material with potential high resistance to multiple types of pavement distress, its performance is rather complicated and much affected by the curing agent and epoxy resin value. This paper serves as a follow-up study to the preliminary published research on evaluating the impact of the epoxy value and common curing agents on the performance of asphalt mixtures. Four groups of emulsified asphalt were filtered out to prepare mixture samples, and laboratory tests on mixture performance under high and low temperatures were conducted. Specifically, Marshall and rutting tests were conducted for evaluating mixture resistance to rutting under high temperatures, and indirect tensile tests were conducted to indicate resistance to cracking at low temperatures. Water stability performance was also assessed by comparing the mixture properties before and after water absorption. The results showed that the mixture with an epoxy value of 20 and curing agents using triethylenetetramine (TETA) had the best overall performance among the investigated mixtures, with the highest resistance to high-temperature deformation and water damage. However, more research should be conducted to improve the low-temperature resistance to cracking for WER-EA mixtures. [ABSTRACT FROM AUTHOR]

During meat processing, lactic acid bacteria (LAB) have to competitively adapt to the hostile environment produced by curing additives (CA). The objective of this study was to investigate the ability of Latilactobacillus curvatus CRL 705, a bioprotective strain of meat origin, to adapt to CA. A physiological and proteomic approach was performed. CRL 705 was grown in a chemically defined medium (CDM) containing specific concentrations of CA (NaCl, nitrite, sucrose, and ascorbic acid). The results showed minor differences in growth kinetics in the presence of CA. Glucose consumption, present in the CDM, and production of lactic acid and bacteriocins were not significantly affected. Proteomic analyses indicated that most of the identified proteins (36 out of 39) mainly related to carbohydrate metabolism (18%), posttranslational modifications (15.6%), energy production and conversion (11.1%), translation (11.1%), and nucleotide metabolism (8.9%) were underexpressed. In response to the studied CA, CRL 705 slowed down its general metabolism, achieving slight changes in physiological and proteomic parameters. The observed performance is another characteristic that extends the well-known competitive profile of CRL 705 as a meat starter and bioprotective culture. This is the first report dealing with the impact of CA on LAB proteomics.

During meat processing, lactic acid bacteria (LAB) have to competitively adapt to the hostile environment produced by curing additives (CA). The objective of this study was to investigate the ability of Latilactobacillus curvatus CRL 705, a bioprotective strain of meat origin, to adapt to CA. A physiological and proteomic approach was performed. CRL 705 was grown in a chemically defined medium (CDM) containing specific concentrations of CA (NaCl, nitrite, sucrose, and ascorbic acid). The results showed minor differences in growth kinetics in the presence of CA. Glucose consumption, present in the CDM, and production of lactic acid and bacteriocins were not significantly affected. Proteomic analyses indicated that most of the identified proteins (36 out of 39) mainly related to carbohydrate metabolism (18%), posttranslational modifications (15.6%), energy production and conversion (11.1%), translation (11.1%), and nucleotide metabolism (8.9%) were underexpressed. In response to the studied CA, CRL 705 slowed down its general metabolism, achieving slight changes in physiological and proteomic parameters. The observed performance is another characteristic that extends the well-known competitive profile of CRL 705 as a meat starter and bioprotective culture. This is the first report dealing with the impact of CA on LAB proteomics. [ABSTRACT FROM AUTHOR]

The continuous development of the industry of composite materials and epoxy resins requires the development of components that modify these systems. It is extremely beneficial to modify functionality by using one or two substances instead of modifying only one system parameter. Typically, this end-use will determine the key parameters of the resin system that should be modified and the modification systems designed as such. In this study, we introduce novel systems utilizing ionic liquids, strategically designed to concurrently alter multiple system parameters, including: (i) flexibility, (ii) crosslinking density, and (iii) fire resistance. The following techniques were used in the research: (i) Differential Scanning Calorimetry (DSC), (ii) Thermogravimetric Analysis (TGA), (iii) Dynamic Mechanical Analysis (DMA) and (iv) fire performance tests (UL-94, Limiting Oxygen Index and Mass loss type cone calorimetry (MLC)) to show as much dependence of material parameters on the type of modifying additive as possible. Both the cured resin and the curing process as well as a single-layer composite reinforced with carbon fiber were tested. The results show that properly designed ionic liquids are able to perform many functions in the composite material and simultaneously affect several parameters, both by lowering and increasing them. In addition, they can exhibit activity in the field of flame-retardant composites. [ABSTRACT FROM AUTHOR]

One of the urgent scientific and technical objectives in the technologies of plywood and wood boards is the search for ways to reduce of hot pressing time without increasing the formaldehyde emission from finished products. To solve this problem was developed the new modifier-curing agent MC-4SF, is mainly a product of interaction of citric acid with urea and ammonia. Compared to traditional ammonium salts, the modifier-curing agent combines the properties of both direct and latent catalysts. Determination of the composition of residual methylol groups in the aqueous extracts obtained by treating the resin cured at 100 °C showed that the modifier-curing agent provides relatively high hydrolytic stability of the UF-polymer during extraction. Spectra of solid-state 13C NMR showed that in resins cured with MC-4SF increased the compound of methylene bridges compared to resins cured with standard catalysts. It is possible that the amino groups of urea (or its derivatives) included in the modifier-curing agent, react with the methylol groups of UF oligomers, fitting urea into the structure of the resulting polymer. Thus explains the increased hydrolytic stability and reduced toxicity of the cured resin. Manufacturing tests of nine-layer plywood made with a modifier-curing agent showed that replacing ammonium sulfate with MC-4SF allows a significant reduction in pressing time at 110 °C without loss of quality of the finished product. With the same pressing time, it was possible to increase the line shear strength by 14% and to reduce formaldehyde emission by 45%. [ABSTRACT FROM AUTHOR]

Although research shows that waterborne epoxy resin emulsified asphalt (WER-EA) is an environmental protection material with potential high resistance to multiple types of pavement distress, its performance is rather complicated and much affected by the curing agent and epoxy resin value. This paper serves as a follow-up study to the preliminary published research on evaluating the impact of the epoxy value and common curing agents on the performance of asphalt mixtures. Four groups of emulsified asphalt were filtered out to prepare mixture samples, and laboratory tests on mixture performance under high and low temperatures were conducted. Specifically, Marshall and rutting tests were conducted for evaluating mixture resistance to rutting under high temperatures, and indirect tensile tests were conducted to indicate resistance to cracking at low temperatures. Water stability performance was also assessed by comparing the mixture properties before and after water absorption. The results showed that the mixture with an epoxy value of 20 and curing agents using triethylenetetramine (TETA) had the best overall performance among the investigated mixtures, with the highest resistance to high-temperature deformation and water damage. However, more research should be conducted to improve the low-temperature resistance to cracking for WER-EA mixtures.

A high-pressure resin transfer molding injector has a limitation in that it can use only one type of curing agent—an amine or an acid anhydride species—owing to a chemical reaction occurring between the two curing agents when an epoxy composition is employed. This study compares the changes in the physical properties of carbon fiber-reinforced plastics (CFRPs) prepared using different types of curing agents to guide the selection of appropriate epoxy-curing compositions based on applications. Two epoxy compositions—polyamine and acid anhydride mixtures—were prepared, and their reaction behavior, such as curing kinetics, conversion rate at curing temperature, and glass transition temperature, were investigated. The physical properties of the CFRPs synthesized by impregnating and curing with both resins were tested and compared. Furthermore, weathering tests were performed to provide a detailed understanding of each composition for the final application. The experimental data showed that the epoxy–polyamine composition has higher tensile and impact strengths, whereas the epoxy-acid anhydride mixture has higher thermal stability and weathering resistance. [ABSTRACT FROM AUTHOR]

The continuous development of the industry of composite materials and epoxy resins requires the development of components that modify these systems. It is extremely beneficial to modify functionality by using one or two substances instead of modifying only one system parameter. Typically, this end-use will determine the key parameters of the resin system that should be modified and the modification systems designed as such. In this study, we introduce novel systems utilizing ionic liquids, strategically designed to concurrently alter multiple system parameters, including: (i) flexibility, (ii) crosslinking density, and (iii) fire resistance. The following techniques were used in the research: (i) Differential Scanning Calorimetry (DSC), (ii) Thermogravimetric Analysis (TGA), (iii) Dynamic Mechanical Analysis (DMA) and (iv) fire performance tests (UL-94, Limiting Oxygen Index and Mass loss type cone calorimetry (MLC)) to show as much dependence of material parameters on the type of modifying additive as possible. Both the cured resin and the curing process as well as a single-layer composite reinforced with carbon fiber were tested. The results show that properly designed ionic liquids are able to perform many functions in the composite material and simultaneously affect several parameters, both by lowering and increasing them. In addition, they can exhibit activity in the field of flame-retardant composites.

This review presents various types of epoxy resins and curing agents commonly used as composite matrices. A brief review of cross-linking formation and the process of degradation or decomposition of epoxy resins by pyrolysis and solvolysis is also discussed. Mechanical engineers are given a brief overview of the types of epoxy resin, which are often applied as composite matrices considering that they currently play a large role in the research, design, manufacturing, and recycling of these materials.

Powder coatings are the fastest growing variety of coatings due to their high compliance with the standards of 5E. Particularly, epoxy powder coatings with bisphenol A diglycidyl ether (BADGE) as the resin matrix are widely used in building materials, ship pipelines, electronic devices and automotive furniture decoration materials, attributed to their excellent mechanical properties, corrosion resistance, electrical insulation and good appearance. The properties of the cured products of epoxy powder coatings are dominated by the curing systems. This review discusses the types, reaction principles, characteristics of curing agents and accelerators that participate in the curing reaction with different epoxy resins. Particularly, curing agents (amines, anhydrides, phenols, polyester resins, acrylic resin, polycarboxylic acid and its derivatives), curing accelerators (tertiary amines, imidazole and its derivatives, substituted urea, metal coordination compound and Lewis acid) and reaction mechanisms in curing systems based on BADGE for epoxy powder coatings are compared. Different from the previous reviews of powder coatings focusing on the formulation optimization and performance improvement, this review interprets curing reactions of epoxy powder coatings from the perspectives of chemical mechanism and selection strategy. [Display omitted] • Compositions and processing of epoxy powder coatings are described. • Types and characteristics of epoxy resins for powder coatings are summarized. • Chemical mechanisms and curing conditions for epoxy powder coatings are discussed. • Accelerators matched curing agents for epoxy powder coatings are classified. [ABSTRACT FROM AUTHOR]

Absorbed Glass Mat (AGM) waste filaments are waste staple fibers from the production of AGM functional paper. Incorporation of AGM waste filaments into solid waste based curing agents, the experimental results showed that the maximum increase in compressive strength and flexural strength of the cured specimens was achieved when 5% mass fraction AGM waste filament was added with compressive strengths of 9.87 MPa and 10.96 MPa at 7 d and 28 d, respectively, representing an increase of 15.57% and 17.34% compared to the unadulterated one. The flexural strength was increased by 53.55% and 49.71% compared with that of the unadulterated AGM waste filament. The strength enhancement effect of mixing different shapes of AGM waste filaments is higher than that of mixing each shape alone, which proves that AGM waste filaments have a mixed enhancement effect. [ABSTRACT FROM AUTHOR]

The urgent need to replace fossil resource-based products is considerably increasing in the past few years, resulting in the search for more sustainable materials, with the aim of reducing the wastes from polymer pollution, solving economic and environmental issues. This is even more relevant in industrial fields, where toxic compounds are the basis of their polymeric formulations. Herein is reported the most relevant advances of epoxy resins (ERs) in the past decade, with great emphasis on the replacement of bisphenol A (BPA), leading to the production of renewable-based ERs with good properties. The synthesis of ERs based on renewable sources, such as vegetable oils, phenolic compounds, sugars and the outcome in the material's structure is explored within this review. Emphasis is also given to the use of new biobased curing agents and biofillers to enhance the biocharacter of the ERs. [ABSTRACT FROM AUTHOR]

We have developed the curing agents that have good storage stability for cyanate ester resins. It should be noted that these agents can be given rapid and efficient curing at low temperatures around 100°C. Even though the nucleophilicity was reduced by a phenol‐amine salts consisting of basic aliphatic amines and weakly acidic phenols, the curing reaction with the cyanate ester occurred immediately. It means that the control of the curing reaction with cyanate esters is not easy due to the equilibrium between phenol and amine. In order to overcome this difficultly cyanate esters reactivity, the molecular motions suppression by polymer was applied in addition to the phenol‐amine salts. The effect of the suppression for hardeners was studied in terms of the storage stability and reactivity to cyanate esters. It has been found out that PSM‐EPEDA composed of ethylenediamine‐epoxy adducts and novolac phenolic resin exhibits a large storage stability against cyanate esters by its effective suppression of molecular motions accompanied with efficient and rapid curing around 100°C. [ABSTRACT FROM AUTHOR]

Self-cured concrete is a type of cement-based material that has the unique ability to mitigate the loss rate of water and increase the capacity of concrete to retain water compared to conventional concrete. The technique allows a water-filled internal curing agent to be added to the concrete mixture and then slowly releases water during the hydration process. Many researchers have studied the composition of self-curing concrete using different materials such as artificial lightweight aggregate (LWA), porous superfine powders, superabsorbent polymers (SAP), polyethylene glycol (PEG), natural fibers, and artificial normal-weight aggregate (ANWA) as curing agents. Likewise, physical, mechanical, and microstructure properties, including the mechanisms of curing agents toward self-curing cement-based, were discussed. It was suggested that adopting self-curing agents in concrete has a beneficial effect on hydration, improving the mechanical properties, durability, cracking susceptibility behavior, and mitigating autogenous and drying shrinkage. The interfacial transition zone (ITZ) between the curing agent and the cement paste matrix also improved, and the permeability is reduced.

This article presents an experimental study on the surface properties of epoxy resin nanocomposites (EPNCs) manufactured with a thermosetting epoxy resin (EP)–bisphenol A diglycidyl ether (BADGE)–2-[[4-[2-[4-(Oxiran-2-ylmethoxy)phenyl]propan-2-yl]phenoxy]methyl]oxirane) and filled with alumina nanoparticles (NPs). The NPs consist of pretreated (with a silane agent) alpha alumina with irregular shapes and a 100 nm maximum size. Three weight fractions of NPs were studied: 1, 3, and 5 wt. (%). Two different epoxy (EP) resins were manufactured, one cured and postcured with bis (4-aminophenyl) methane (DDM); and another one cured with 3-dodec-2-enyloxolane-2,5-dione (DDSA) + 8-methyl-3a,4,7,7a-tetrahydro-4,7-methano-2-benzofuran-1,3-dione (MNA). The wettability and the surface roughness of the obtained EPNCs were studied through the measurement of contact angles and topographic images obtained with atomic force microscopy (AFM), respectively. Significant influence of both the loading of NPs and used curing agents was observed. EPNCs cured with DDM were shown to be hydrophobic for 0, 1, and 3 wt. (%) and hydrophilic for 5 wt. (%). Maximum surface roughness was observed for 5 wt. (%). EPNCs cured with DDSA+MNA were shown to be hydrophilic for 0 and 1 wt. (%) and hydrophobic for 3 and 5 wt. (%). The surface roughness decreased as the weight fraction of NPs increased until 3 wt. (%), and then increased for 5 wt. (%). [ABSTRACT FROM AUTHOR]

Heme and nitrosyl-heme have been pointed out as responsible for the association between processed meats and cancer. The objective of this study was to obtain reliable data on the current proximate composition, total iron, total heme, zinc-protoporphyrin, and nitrosyl-heme content in 40 meat derivatives consumed in Spain. The determination of heme and nitrosyl-heme was achieved using the classical spectrophotometric determination of the acetone extracts and compared with the chromatographic determination of these extracts which enables the separation of other porphyrins. Results revealed a high variability of heme and nitrosyl-heme contents in meat derivatives which may reflect differences in meat derivatives ingredients and formulations, manufacturing processes, storage, and cooking conditions. In addition, certain derivatives contain considerable amounts of nitrosyl-heme despite the fact there was no addition of nitrite or nitrate. Although the comparison of both methodologies for heme and nitrosyl-heme determination were in good agreement, the chromatographic method is advisable as some interfering compounds may lead to an overestimation when using the classical spectrophotometric determination. In the Spanish adult population and based on the obtained data the estimated total iron, nitrosyl-heme, and total heme intakes resulting from meat derivatives consumption, were 14.6 mg/day, 528.6 µg/day, and 1676.2 µg/day, respectively. [Display omitted] • The contents of heme and nitrosyl-heme in Spanish meat derivatives are variable. • Formulation, processing and storage conditions may contribute to this variability. • Nitrosyl-heme can be present in meat derivatives without adding nitrite sources. • For intake assessment, determination of heme and nitrosyl-heme by HPLC is advised. [ABSTRACT FROM AUTHOR]

The aim of this work was to examine the influence of new curing agents proposed for brominated butyl rubber (BIIR) on the cross-linking process of rubber compounds and the thermal behavior of the vulcanizates. Rubber blends that were filled with carbon black and contained acetylacetonates of different transition metals in the presence of triethanolamine (TEOA) as new cross-linking agents were prepared. The performed studies showed that metal acetylacetonates (Me(acac)) are effective cross-linking agents for BIIR, which was confirmed by high values of the torque increment (∆M) and significant cross-linking degree of the vulcanizates (α(T)). The most active curing agent seems to be iron acetylacetonate (Fe(acac)). Its application results in a shorter optimal vulcanization time, lower onset vulcanization temperature and similar vulcanization enthalpy compared to the BIIR cured with a sulfur curing system. The BIIR vulcanizates cured with Me(acac) reveal good mechanical properties with tensile strengths in the range of 9–14 MPa and better damping properties comparing to the sulfur-cured rubber. The proposed curing agents do not significantly affect the thermal stability of the BIIR vulcanizates. [ABSTRACT FROM AUTHOR]

Electret properties of polymeric materials based on DER-331 epoxy oligomer and amine curing agents, produced in the course of synthesis of the polymer in a constant electric field, were examined. It was shown that the presence of certain polar functional groups and fragments in the structure of the curing agent can both raise the electret characteristics of polymers (by making larger the number of polar groups capable of orientation) and diminish these characteristics (due to steric factors). To obtain polymeric epoxy materials possessing good electret characteristics, it is preferable to use diethylenetriamine as the amine curing agent. The hardness of epoxy polymers is determined by parameters of the network of chemical bonds and by their structural organization. Using N-aminoethylpiperazine in manufacturing polymeric materials based on the epoxy oligomer makes it possible to obtain 3D structures providing a higher hardness owing to the presence of a heterocyclic fragment in the structure of the curing agent. Converting the network polymeric structures to the polarized state results in hardness increases. This is due to the orientation of polar groups, which gives rise to a denser network of physical bonds. [ABSTRACT FROM AUTHOR]

In our study, zeolite, sepiolite, vermiculite and biochar were added to high-concentration lead-contaminated soils, respectively, and the metal fractions, toxicity leaching amount and leaching characteristics of lead (Pb) in soils were studied after 30 d. Besides, the feasibility of chemical immobilization to reduce Pb was investigated. In the soil immobilization experiments, compared with the control, the toxicity leaching amount of soils added zeolite, sepiolite, vermiculite and biochar decreased. The decreasing ratios were 40.12%, 41.28%, 25.50%, and 16.04%, respectively. It is clear that the treatment of zeolite showed the best effect. And the group matching curing agents (GMCAs) with a mass ratio of 2:1 for zeolite and sepiolite was the best, of which the Pb content in soil leaching solutions decreased by 41.4%. Meanwhile, through soil column leaching experiment, compared with the control, the pH of leachates generally increased, and the electrical conductivity (EC) of leachates presented a falling trend. The Pb content of accumulated leachates from treatments decreased, and the best effect treatment was at a mass ratio of 1:2 for zeolite andsepiolite with the highest decrease rate at 93.35%. And the immobilization effect was further verified. Therefore, the addition of curing agents could decrease the bioavailability and migration of Pb. [ABSTRACT FROM AUTHOR]

• Several novel silicon-containing imidazole and thiazole derivative curing agents were designed and successfully synthesized through a facile and cost-effective approach and utilized as a modifier for epoxy resins. • The thermal stability and possible curing mechanism were proposed and discussed. • The dissipative particle dynamics (DPD) method was further used to get insight into the mechanism of the thermal stability and predict the mechanical properties. A trifunctional epoxy resin (TGPAP) with excellent thermal stability was cured by several novel curing agents through a facile and cost-effective approach. The temperature of maximum weight loss rate (T peak) of cured TGPAP were up to 370 °C and 330 °C under N 2 and air atmospheres, which attributed to the synergistic effects between curing agents and TGPAP. The dissipative particle dynamics simulations also reveal that the curing agents with more functional groups and higher reactivity induce the higher cross-linking density, leading to better mechanical properties. The simulations well reproduced the experimental results and also predicted the effect of the curing agents on mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract The epoxy resin coating is a fundamental species with epoxy resins used as main components to form the final film. Unexpectedly, bulky CO 2 bubbles that occasionally appeared during the curing process of epoxy resin coatings might destroy the final film properties. With an attempt to thoroughly understand the formation mechanism of CO 2 bubbles and further propose countermeasures to control them, Density Function Theory (DFT) in this paper was employed to calculate the absorption process, the curing reaction and the formation mechanism of CO 2 bubbles. The gas phase basicity (GB) values and pK a values of common amine curing agents were calculated. The total Gibbs free energies difference of the curing reactions between polluted curing agents and epoxy resins were calculated according to a thermodynamic cycle. Whether in gas phase or resin phase, the energetically negative ΔG solv indicated that the curing reactions might occur spontaneously and CO 2 molecules would be separated and released from amine molecules. The total Gibbs free energy calculations also revealed that the re-absorption of CO 2 by the curing system was energetically unfavorable. Thus, the formation mechanism of CO 2 bubbles of epoxy resin coatings could be summarize in three steps: (1) Carbon dioxide pollutes accidentally the curing agents. (2) CO 2 molecules are gradually released as the curing process occurs. (3) CO 2 molecules are collected to form big bubbles which can lead to seriously surface and/or internal defects. Finally, based on practical experiences three tips were proposed to control CO 2 bubbles. The present results not only evidenced the nature of the unexpected bubbles of epoxy resin coatings, but also additionally paved to the way to full utilization of the formation mechanism to improve the epoxy coatings' properties. Graphical abstract Image 1 Highlights • GB & pK a and ΔG solv were calculated. • Formation mechanism of CO 2 bubbles was proposed. • Tips to control CO 2 bubbles were provided. [ABSTRACT FROM AUTHOR]

This article presents an experimental study on the surface properties of epoxy resin nanocomposites (EPNCs) manufactured with a thermosetting epoxy resin (EP)−bisphenol A diglycidyl ether (BADGE)−2-[[4-[2-[4-(Oxiran-2-ylmethoxy)phenyl]propan-2-yl]phenoxy]methyl]oxirane) and filled with alumina nanoparticles (NPs). The NPs consist of pretreated (with a silane agent) alpha alumina with irregular shapes and a 100 nm maximum size. Three weight fractions of NPs were studied: 1, 3, and 5 wt. (%). Two different epoxy (EP) resins were manufactured, one cured and postcured with bis (4-aminophenyl) methane (DDM); and another one cured with 3-dodec-2-enyloxolane-2,5-dione (DDSA) + 8-methyl-3a,4,7,7a-tetrahydro-4,7-methano-2-benzofuran-1,3-dione (MNA). The wettability and the surface roughness of the obtained EPNCs were studied through the measurement of contact angles and topographic images obtained with atomic force microscopy (AFM), respectively. Significant influence of both the loading of NPs and used curing agents was observed. EPNCs cured with DDM were shown to be hydrophobic for 0, 1, and 3 wt. (%) and hydrophilic for 5 wt. (%). Maximum surface roughness was observed for 5 wt. (%). EPNCs cured with DDSA+MNA were shown to be hydrophilic for 0 and 1 wt. (%) and hydrophobic for 3 and 5 wt. (%). The surface roughness decreased as the weight fraction of NPs increased until 3 wt. (%), and then increased for 5 wt. (%).

The viability and competitiveness of Staphylococcus xylosus in meat mostly depend on the ability to adapt itself to rapid oxygen and nutrients depletion during meat fermentation. The utilization of nitrite instead of oxygen becomes a successful strategy for this strain to improve its performance in anaerobiosis; however, metabolic pathways of this strain underlying this adaptation, are partially known. The aim of this study was to provide an overview on proteomic changes of S. xylosus DSM 20266T cultured under anaerobiosis and nitrite exposure. Thus, two different cultures of this strain, supplemented or not with nitrite, were in vitro incubated in aerobiosis and anaerobiosis monitoring cell viability, pH, oxidation reduction potential and nitrite content. Protein extracts, obtained from cells, collected as nitrite content was depleted, were analyzed by 2DE/MALDI-TOF/TOF-MS. Results showed that DSM 20266T growth was significantly sustained by nitrite in anaerobiosis, whereas no differences were found in aerobiosis. Accordingly, nitrite content was depleted after 13 h only in anaerobiosis. At this time of sampling, a comparative proteomic analysis showed 45 differentially expressed proteins. Most differences were found between aerobic and anaerobic cultures without nitrite; the induction of glycolytic enzymes and glyoxylate cycle, the reduction of TCA enzymes, and acetate fermentation were found in anaerobiosis to produce ATP and maintain the cell redox balance. In anaerobic cultures the nitrite supplementation partially restored TCA cycle, and reduced the amount of glycolytic enzymes. These results were confirmed by phenotypic microarray that, for the first time, was carried out on cell previously adapted at the different growth conditions. Overall, metabolic changes were similar between aerobiosis and anaerobiosis NO2-adapted cells, whilst cells grown under anaerobiosis showed different assimilation profiles by confirming proteomic data; indeed, these latter extensively assimilated substrates addressed at both supplying glucose for glycolysis or fueling alternative pathways to TCA cycle. In conclusion, metabolic pathways underlying the ability of S. xylosus to adapt itself to oxygen starvation were revealed; the addition of nitrite allowed S. xylosus to take advantage of nitrite to this condition, restoring some metabolic pathway underlying aerobic behavior of the strain.

The viability and competitiveness of Staphylococcus xylosus in meat mostly depend on the ability to adapt itself to rapid oxygen and nutrients depletion during meat fermentation. The utilization of nitrite instead of oxygen becomes a successful strategy for this strain to improve its performance in anaerobiosis; however, metabolic pathways of this strain underlying this adaptation, are partially known. The aim of this study was to provide an overview on proteomic changes of S. xylosus DSM 20266T cultured under anaerobiosis and nitrite exposure. Thus, two different cultures of this strain, supplemented or not with nitrite, were in vitro incubated in aerobiosis and anaerobiosis monitoring cell viability, pH, oxidation reduction potential and nitrite content. Protein extracts, obtained from cells, collected as nitrite content was depleted, were analyzed by 2DE/MALDI-TOF/TOF-MS. Results showed that DSM 20266T growth was significantly sustained by nitrite in anaerobiosis, whereas no differences were found in aerobiosis. Accordingly, nitrite content was depleted after 13 h only in anaerobiosis. At this time of sampling, a comparative proteomic analysis showed 45 differentially expressed proteins. Most differences were found between aerobic and anaerobic cultures without nitrite; the induction of glycolytic enzymes and glyoxylate cycle, the reduction of TCA enzymes, and acetate fermentation were found in anaerobiosis to produce ATP and maintain the cell redox balance. In anaerobic cultures the nitrite supplementation partially restored TCA cycle, and reduced the amount of glycolytic enzymes. These results were confirmed by phenotypic microarray that, for the first time, was carried out on cell previously adapted at the different growth conditions. Overall, metabolic changes were similar between aerobiosis and anaerobiosis NO2-adapted cells, whilst cells grown under anaerobiosis showed different assimilation profiles by confirming proteomic data; indeed, these latter extensively assimilated substrates addressed at both supplying glucose for glycolysis or fueling alternative pathways to TCA cycle. In conclusion, metabolic pathways underlying the ability of S. xylosus to adapt itself to oxygen starvation were revealed; the addition of nitrite allowed S. xylosus to take advantage of nitrite to this condition, restoring some metabolic pathway underlying aerobic behavior of the strain. [ABSTRACT FROM AUTHOR]

Organic electronic devices require dielectric layers made from materials with high dielectric constant (ε′) and good dielectric strength, which allow reducing the threshold voltage and decreasing the power consumption of electronic circuitry. Poly(vinylalcohol-co-vinylcyanoethoxy) (CEPVA) has high ε′ (≈ 15) and low conductivity (σ′), which are exactly the characteristics needed for dielectrics. Its Tg close to room temperature limits, however, its applicability in electronics and improvements of its stability and mechanical properties are necessary. Here, we report on curing of this polymer, exploiting the residual hydroxyl groups present in the polymers after reaction of the parent poly(vinylalcohol) with acrylonitrile. Different curing agents were tested and showed a strong influence on the relaxation phenomena of the crosslinked polymer. The reduced mobility of backbone and side groups of the polymer decreased ε′ but improved the mechanical stability at high temperature and decreased σ′, especially at low frequencies, where ionic conductivity and interface polarization usually occur. At the same time, the hydrophilicity of the polymer was reduced. [ABSTRACT FROM AUTHOR]

About 90% gelatine is coming from porcine. Indonesia has largest muslim community worldwide, and muslim is prohibited to consume any products containing porcine gelatin. This study explores buffalo's skin gelatine and characterizes it based on physico-chemical properties. Gelatin from buffalo skin was extracted using different curing agents, namely alkaline of sodium hydroxide (NaOH) and neutral agent (the mixture of NaOH and citrate acid) with different molarity. The yield of gelatin using NaOH generally is higher than that of using the mixture of NaOH and citrate acid. FTIR spectra of gelatines revealed functional groups supporting the polypeptides chains. Amino acid profiles of gelatines extracted using different curing agents of NaOH 0.25 M; 0.50 M and 0.75 M have the similar profiles in terms of type and composition. Gelatin from buffalo's skin is potential to be developed as substitute of porcine gelatin. [ABSTRACT FROM AUTHOR]

Previously 12 Lactobacillus plantarum strains were isolated from fermented olives. Among these, only L. plantarum OL15 produced bacteriocin (plantaricin OL15). In this study, the 12 strains were examined for plasmid DNA content. Of these, 9 strains have shown one to three plasmid bands ranging in size from 5.4 to 12.2 kb. L. plantarum OL15 exhibited one plasmid (9.6 kb) which was named pOL15. After curing with novobiocin and ethidium bromide, the plasmid profile analysis of non producing derivatives, showed that the 9.6 kb plasmid pOL15 harbored by the parental strain had been lost in all cases and none of them regained the ability to produce plantaricin OL15 suggesting that the production of plantaricin OL15 is plasmid linked. Plantaricin OL15 was not inactived by amylase and lipase suggesting that plantaricin OL15 activity was not dependent on the presence of either a carbohydrate or lipid moiety. Plantaricin OL15 showed activity against lactic acid bacteria of different species and also against olive spoilage and phytopathogenic bacteria, including Pseudomonas and Erwinia.

A series of DOPO-based curing agents with similar structures were prepared through Mannich-type reaction and characterized. The curing agents with weak electron-donating methylene groups, strong electron-withdrawing sulfonyl groups and strong electron-donating ether groups were then incorporated into epoxy resins, and the structure-property relationships of the curing agents on the fire safety of epoxy resins were investigated. Thermal and flame-retardant properties of the resins were investigated by thermogravimetric analysis, cone calorimeter, microscale combustion colorimeter, UL-94 and limiting oxygen index. The results showed that the curing agents with proper structure could impart epoxy resins with high thermal stabilities and low flammability. The curing agents containing ether groups exhibited better flame-retardant efficiency compared with other curing agents. In order to further investigate the mechanism, the char residues of the resins were studied by scanning electron microscopy, Fourier transform infrared and Raman spectroscopy. Char residues of the resins containing ether groups exhibited a condense char morphology, associated with a high degree of graphitization. This work not only provides novel epoxy resins with good thermal stability, but also will trigger more scientific interest in the development and investigation of the structure-property relationships of the DOPO-based flame retardants. [ABSTRACT FROM AUTHOR]

Samples of epoxy resin (EP) based on the diglycidyl ether of bisphenol A (DGEBA), cured with nadic methyl anhydride (NMA) and mercaptan (CAPCURE 3-800), or amine-phenol (CAPCURE EH-30), respectively, SE 4 and SE 5, were prepared in the stoichiometric ratio determined by the supplier. The curing behaviour of the epoxy systems SE 4 and SE 5 was followed by DSC (Differential Scanning Calorimetry). These SE and their ingredients were analyzed using FTIR transmission techniques (KBr pellets, pyrolysis without control and controlled pyrolysis-FT-IR, the CONTROLPIR/FT-IR) for characterizing the curing agents (CA). The temperature range used for samples pyrolysis was found from TG (thermogravimetry). Thus, the FT-IR bands of liquid pyrolysate obtained by CONTROLPIR/FT-IR were evaluated, in comparison to the reference spectrum of CA. The characterization of CA was also possible, by the analysis of such SE with the TG/FT-IR technique.

Self compacted concrete (SCC) describes concrete with the ability to compact itself only by means of its own weight without the requirement of vibration. It fills all recesses reinforcement spaces and voids even its highly reinforced concrete members and flows free of segregation nearly to a level balance. This research aims to assess the fresh and hardened properties of SCC using saturated porcelinite as curing agents for the internal curing of SCC. Five mixes with different percentages of replacement of saturated porcelinite ranging from (0, 12, 16, 20, 24) % of the fine aggregate volume of the same grading, were prepared, each mix tested in a fresh state with a slump test. Then 120 concrete cubes of (100*100*100)mm for different mixes were tested for, density and compressive strength, at (7,28,60, and 90) days of water and air curing. Results show that the slump decreases as saturated porcelinite content increases, density, and compressive strength increase with increasing saturated porcelinite for all age’s . The rate of increase is (10.1-30.0) % and (8.2-25.7) % for compressive strength of cubes cured in water and air respectively. The optimum percentage of saturated porcelinite which gave higher density and compressive strength was 20%.

The role played by curing agents (nitrite, ascorbate) on protein oxidation and Strecker aldehyde formation is studied. To fulfill this objective, increasing concentrations of nitrite (0, 75 and 150 ppm) and ascorbate (0, 250 and 500 ppm) were added to sausages subjected to a 54 day drying process. The concurrence of intense proteolysis, protein carbonylation and formation of Strecker aldehydes during processing of sausages suggests that α-aminoadipic semialdehyde (AAS) and γ-glutamic semialdehyde (GGS) may be implicated in the formation of Strecker aldehydes. The fact that nitrite (150 ppm, ingoing amount) significantly promoted the formation of protein carbonyls at early stages of processing and the subsequent formation of Strecker aldehydes provides strength to this hypothesis. Ascorbate (125 and 250 ppm) controlled the overall extent of protein carbonylation in sausages without declining the formation of Strecker aldehydes. These results may contribute to understanding the chemistry fundamentals of the positive influence of nitrite on the flavor and overall acceptability of cured muscle foods. [ABSTRACT FROM AUTHOR]

Severe capsular contracture around silicone expander breast implants leading to pain and failure is a major clinical problem. Even though earlier studies have implicated the immunogenicity of silicone, the role of physical and chemical properties of the silicone material in excessive collagen deposition and fibrosis has been less addressed. The present study investigates whether there is any correlation between the type of curing systems i.e. addition and free radical curing and the fibrosis around silicone elastomer. The experiment carried out uses commercially available silicone ventriculo-peritoneal shunt material elastomer cured by platinum and the results are compared with results obtained in a similar study carried out by the authors using commercially available silicone tissue expander material cured by peroxide. Ultra-high molecular weight poly-ethylene (UHMWPE), the standard reference for biocompatibility evaluation, was used as the control material. The materials were implanted in rat skeletal muscle for 30 and 90 days. Inflammatory cells, myofibroblasts, cytokines, and collagen deposition at the material-tissue interface were identified by haematoxylin-eosin and Masson's Trichrome stains and semi-quantitated based on immunohistochemical studies. Results indicate that even though the cellular response in the initial phase of wound healing was similar in both platinum and peroxide-cured materials, the collagen deposition in the proliferative phase was more around peroxide-cured material in comparison to the platinum-cured silicone elastomer. There is a need to look into the molecular mechanisms of this interaction and the possibility of using curing systems other than free radical peroxide in the manufacture of silicone elastomer expanders for breast prosthesis. [ABSTRACT FROM AUTHOR]