Acetone Method Research Articles

A blue fluorescent waterborne polyurethane-based Zn(ii) complex with antibacterial activity

Abstract Polymer-based transition metal complexes have attracted much attention in many fields of application. In this article, a fluorescent polymer-based transition metal complex was prepared by bonding the transition metal complex with the polymer. First, Schiff base salicylaldehyde ethanolamine (HL) as a ligand was prepared by the reaction of salicylaldehyde with ethanolamine. Then, salicylaldehyde glycolamine Zn(ii) transition metal complexes (ZnL2) were synthesized with HL and Zn2+ as the central ion. Finally, a blue fluorescent waterborne-based polyurethane Zn(ii) complex (ZnL2-WPU) with an antibacterial function was prepared with ZnL2 as a chain extender by modified acetone method. The characteristics of fluorescence, heat stability, and bacteriostasis were characterized. Compared with ZnL2, the UV–vis absorption peak of ZnL2-WPU shows a blue shift of about 20 nm. ZnL2-WPU has a strong blue fluorescence emission at 450 nm, and the intensity increases significantly with ZnL2 content. Surprisingly, the fluorescence lifetime of ZnL2-WPU is obviously increased, reaching more than one time that of ZnL2. Interestingly, the antibacterial efficiency of ZnL2-WPU against E. coli reached an incredible 99%. More importantly, ZnL2-WPU uses water as the dispersing medium, which is more environmentally friendly.

Mechanism of aqueous extract of Strychni Semen in improving pain in rats with rheumatoid arthritis based on TLR4/TNF-α/MMP-9 signaling pathway

This study aims to explore the mechanism of aqueous extract of Strychni Semen(SA) in relieving pain in the rat model of rheumatoid arthritis(RA) via Toll-like receptor 4(TLR4)/tumor necrosis factor-α(TNF-α)/matrix metalloproteinase-9(MMP-9) signaling pathway. Firstly, the main chemical components of Strychni Semen were searched against TCMSP, TCMID, ETCM, and related literature, and the main targets of the chemical components were retrieved from TargetNet and SwissTargetPrediction. The main targets of RA and pain were searched against GeneCards, Online Mendelian Inheritance in Man(OMIM), and Therapeutic Target Database(TTD). Venny 2.1.0 was used to obtain the common targets shared by Strychni Semen, RA, and pain, and STRING and Cytoscape 3.6.1 were used to build the protein-protein interaction network. Then, molecular docking was carried out in AutoDock Vina. Finally, the rat model of type Ⅱ collagen-induced arthritis(CIA) was established. The up-down method and acetone method were employed to examine the mechanical pain threshold and cold pain threshold of rats, and the pain-relieving effect of SA on CIA rats was evaluated comprehensively. Hematoxylin-eosin(HE) staining was employed to evaluate the histopathological changes of joints in CIA rats. The expression levels of key target proteins was determined by immunohistochemistry and Western blot, and the mRNA levels of key targets were determined by real-time fluorescence quantitative polymerase chain reaction(real-time PCR). The results of network prediction showed that Strychni Semen may act on the TLR4/TNF-α/MMP-9 signaling pathway to exert the pain-relieving effect. The results of molecular docking showed that brucine, the main active component of SA, had strong binding ability to TLR4, TNF-α, and MMP-9. The results of animal experiments showed that SA improved the mechanical and cold pain sensitivity(P<0.05, P<0.01) and reduced the joint histopathological score of CIA rats(P<0.01). In addition, medium and high doses of SA down-regulated the protein and mRNA levels of TNF-α, TLR4, and MMP-9(P<0.05,P<0.01). In conclusion, SA alleviated the mechanical pain sensitivity, cold pain sensitivity, and joint histopathological changes in CIA rats by inhibiting the over activation of TLR4/TNF-α/MMP-9 signaling pathway.

PLANKTON ABUNDANCE AND PRIMARY PRODUCTIVITY IN AN INDUSTRIAL SCALE IN POND RACEWAY SYSTEM

An in-pond raceway system (IPRS) is an efficacious aquaculture approach confining a limited land resources with flowing water system. Several studies have been conducted on IPRS culture systems in various parts of the world. This study was executed to evaluate the plankton abundance and primary productivity in an industrial scale in pond raceway system. The quantitative enumeration of plankton was carried out with the use of a Sedgwick-Rafter (S-R) counting cell, and the identification of distinct kinds of plankton were done using a range of bibliographic references, with the help of books and journals. 90% acetone method with spectrophotometric analysis was performed to determine the concentrations of chlorophyll-a in the microalgae as a means of primary productivity. One-way analysis of variance was conducted to determine the variation of plankton abundance as well as primary productivity among the study sites. Relationship between plankton availability and primary productivity was assessed by Pearson correlation

The Effect of Dietary Supplementation with Haematococcus pluvialis for Enhanced Pigmentation in Amphiprion ocellaris

Among the minority seawater species in the ornamental fish market, clownfish (Amphiprion ocellaris) have a high market value due to their vibrant appearance. Astaxanthin, a promising coloring agent, is applied in diets as a food additive to enhance the physical appearance of clownfish. However, as the retail price of astaxanthin has been inflating, the industry is eager to find more affordable astaxanthin products. The present study evaluated the nutrients and pigmentation performance of the algae-extracted astaxanthin diets of clownfish, followed by a comparative feeding trial evaluating the graded levels of either Haematococcus pluvialis powder or extracted astaxanthin supplements in the experimental diets. The study included three stages: assessing the utilization of H. pluvialis powder as an astaxanthin source, investigating the optimal practical extraction method, and revisiting the effects of crude extracted astaxanthin on clownfish based on the identified preparation processes. In the first stage, H. pluvialis powder was applied as the feed additive for a feeding trial, resulting in a low-utilization rate of astaxanthin in clownfish. This indicated that a suitable extraction method was essential for clownfish. Two chemical-based methods for astaxanthin extraction were investigated to obtain the optimal extraction yields; results showed that the HCl–acetone method had an astaxanthin yield of 21.99 ± 0.52 mg/g cell, which was significantly higher than the yield from the acetic acid-DMSO method. Finally, the effects of HCl–acetone-extracted astaxanthin was compared with the effects of synthesized astaxanthin. The pigmentation performance study was performed using a digital image acquisition and processing technique. A significant increase in the red color signal was observed at week six after fed with 400 and 200 mg/kg of the extracted astaxanthin, compared to the control 0 mg/kg. In conclusion, H. pluvialis-extracted astaxanthin following the HCl–acetone method can significantly improve the pigmentation performance of A. ocellaris after 42 days of oral administration.

Synthesis of waterborne polyurethane aerogels-like materials via freeze-drying: an innovative approach

Waterborne polyurethane (WBPUR) aerogels using acetone method and freeze-drying procedure have been successfully synthesized. The morphology, chemical structure, and thermal and mechanical properties of obtained aerogels were analysed by means of scanning electron microscopy, Fourier-transform infrared spectroscopy, contact angle, thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis. In addition, the influence of the solids content in the hydrogel (2–15 wt.%), obtained by varying the amount of water added in the suspension, on the density and thermal conductivity was evaluated. Obtained results demonstrated that the properties of aerogels strongly depend on the solids content assayed in the parent solution. As the solids content in the WBPUR aerogels increases, the density and thermal conductivity for materials with 2.5 and 10% solids content follow an upward trend, while their elasticity decreases. Materials with solids content below 2.5% and above 10% have not demonstrated adequate processability due to their high deformity and hardness, respectively. The drying methodology (freeze-drying) can be profitably used to prepare aerogels-like materials in a cost-effective way.Graphical abstractIllustration of the alternative preparation process of WBPUR aerogels and its potential industrial application.

Optimization of Targeted Plant Proteomics Using Liquid Chromatography with Tandem Mass Spectrometry (LC-MS/MS).

This study was conducted to optimize a targeted plant proteomics approach from signature peptide selection and liquid chromatography with tandem mass spectrometry (LC-MS/MS) analytical method development and optimization to sample preparation method optimization. Three typical protein extraction and precipitation methods, including trichloroacetic acid (TCA)/acetone method, phenol method, and TCA/acetone/phenol method, and two digestion methods, including trypsin digestion and LysC/trypsin digestion, were evaluated for selected proteins related to the impact of engineered nanomaterials (ENMs) on wheat (Triticum aestivum) plant growth. In addition, we compared two plant tissue homogenization methods: grinding freeze-dried tissue and fresh tissue into a fine powder using a mortar and pestle aided with liquid nitrogen. Wheat plants were grown under a 16 h photoperiod (light intensity 150 μmol·m-2·s-1) for 4 weeks at 22 °C with a relative humidity of 60% and were watered daily to maintain a 70-90% water content in the soil. Processed samples were analyzed with an optimized LC-MS/MS method. The concentration of selected signature peptides for the wheat proteins of interest indicated that the phenol extraction method using fresh plant tissue, coupled with trypsin digestion, was the best sample preparation method for the targeted proteomics study. Overall, the optimized approach yielded the highest total peptide concentration (68,831 ng/g, 2.4 times the lowest concentration) as well as higher signature peptide concentrations for most peptides (19 out of 28). In addition, three of the signature peptides could only be detected using the optimized approach. This study provides a workflow for optimizing targeted proteomics studies.

Antifriction and anti-wear performances of bionic lubricating fluid containing gelatin nanoparticles for artificial joint materials

The antifriction and antiwear effects of gelatin nanoparticles (GLN-NP) on artificial joint materials in bionic joint lubricant were investigated to provide a theoretical basis for the development of new bionic joint lubricant. GLN-NP was prepared by cross-linking collagen acid (type A) gelatin with glutaraldehyde by acetone method, and the particle size and stability of GLN-NP were characterized. The biomimetic joint lubricants with different concentrations were prepared by mixing 5, 15, and 30 mg/mL GLN-NP with 15 and 30 mg/mL hyaluronic acid (HA), respectively. The friction reduction and antiwear effects of the biomimetic joint lubricants on zirconia ceramics were investigated on a tribometer. The cytotoxicity of each component of bionic joint lubricant on RAW264.7 mouse macrophages was evaluated by MTT assay. The particle size of GLN-NP was about 139 nm, and the particle size distribution index was 0.17, showing a single peak, indicating that the particle size of GLN-NP was uniform. In complete culture medium, pH7.4 PBS, and deionized water at simulated body temperature, the particle size of GLN-NP did not change more than 10 nm with time, indicating that GLN-NP had good dispersion stability and did not aggregate. Compared with 15 mg/mL HA, 30 mg/mL HA, and normal saline, the friction coefficient, wear scar depth, width, and wear volume were significantly reduced by adding different concentrations of GLN-NP ( P<0.05); there was no significant difference between different concentrations of GLN-NP ( P>0.05). Biocompatibility test showed that the cell survival rate of GLN-NP, HA, and HA+GLN-NP solution decreased slightly with the increase of concentration, but the cell survival rate was more than 90%, and there was no significant difference between groups ( P>0.05). The bionic joint fluid containing GLN-NP has good antifriction and antiwear effect. Among them, GLN-NP saline solution without HA has the best antifriction and antiwear effect.

Quantification of Gypsum in Soils: Methodological Proposal

Gypsum is widely found in soils under arid and semi-arid climates due to its semi-soluble nature. In spite of that, they are less known than other soils, and this has generated some misunderstandings in some initial pedological concepts and in soil classification systems. In addition, the quantification of gypsum, and in particular of its secondary accumulations is affected by the sampling procedures and sample handling in the lab; besides by the methods used for the determination of gypsum themselves, since they differ on the accuracy, cost, and expertise needed. The objective of our research is to improve some laboratory procedures in order to determine and quantify gypsum in the soil, especially secondary accumulations. We applied several methods of sample handling and gypsum analysis to a loess profile in the Ebro Valley (NE Iberia), consisting of 10 horizons containing gypsum in varying amounts (0 to about 50%); of different sizes and morphologies. We propose a protocol considering procedures (sieving or not), qualitative determinations and two methods (turbidimetry and dehydration of crystallization water) for an optimal determination of gypsum depending on the characteristics of the sample and compared them with the acetone method (US Salinity Laboratory Staff, Agric. Handb., 1954, 60, 175; Nelson, 1978, 181), as it is the reference method in the main Classification Systems. The results obtained after applying the different methods for the analysis of gypsum in bulk samples have allowed us to propose a decision tree procedure for the determination of gypsum in soil materials. This procedure includes, determination of gypsum in all fractions, coarse and fine, the estimated amount of gypsum in the field (as a major or minor component) and the presence of other components that may interfere with the results. The most accurate results are obtained with those methods based on the loss of gypsum water upon heating when gypsum content is &amp;gt;4%, and with the turbidimetric method in case of lower amounts of gypsum. Finally, we discuss the implications of these analyses when a soil is classified according to the main soil classification systems (WRB 2014; Soil Survey Staff, SSS- NRCS, 2014).

Evaluation of Poly-3-Hydroxybutyrate (P3HB) Scaffolds Used for Epidermal Cells Growth as Potential Biomatrix.

Advances in tissue engineering have made possible the construction of organs and tissues with the use of biomaterials and cells. Three important elements are considered: a specific cell culture, an adequate environment, and a scaffold. The present study aimed to develop P3HB scaffolds by 3D printing and evaluate their biocompatibility with HaCaT epidermal cells, as a potential model that allows the formation of functional tissue. By using a method of extraction and purification with ethanol and acetone, a biopolymer having suitable properties for use as a tissue support was obtained. This polymer exhibited a higher molecular weight (1500 kDa) and lower contact angle (less than 90°) compared to the material obtained using the conventional method. The biocompatibility analysis reveals that the scaffold obtained using the ethanol–acetone method and produced by 3D printing without pores was not cytotoxic, did not self-degrade, and allowed high homogenous cell proliferation of HaCaT cells. In summary, it is possible to conclude that the P3HB scaffold obtained by 3D printing and a simplified extraction method is a suitable support for the homogeneous development of HaCaT keratinocyte cell lineage, which would allow the evaluation of this material to be used as a biomatrix for tissue engineering.

A waterborne polyurethane‐based hybrid fluorescent silicon quantum dot

AbstractAn amino‐hydroxy‐functionalized strongly fluorescent hybrid silicon quantum dots (znoSiQDs) were prepared by a green and simple method. Waterborne polyurethane‐based hybrid fluorescent silicon Quantum dots (znoSiQDs‐WPU) was prepared by a modified acetone method using znoSiQDs as chain extender. The structure and properties were also investigated by Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analyzer (TGA), fluorescence spectroscopy (FL), and so on. ZnoSiQDs was successfully connected to the polyurethane backbone by covalent bonding. ZnoSiQDs‐WPU can effectively shield UV in the range of 300–400 nm. Compared with WPU, the UV shielding range of znoSiQDs‐WPU is significantly larger, attributed to the direct band gap transition Γ → Γ. The fluorescence intensity of znoSiQDs‐WPU was dramatically enhanced compared with that of znoSiQDs. Compared with znoSiQDs, the maximum emission peak of znoSiQDs‐WPU is blue shifted at about 18 nm, which was related to the increased polarity of the imidazole chromophore. The luminous life of znoSiQDs‐WPU is up to 6.58 ns. The thermal stability of znoSiQDs‐WPU is improved by bonding znoSiQDs to the main chains of WPU. Furthermore, it is water as a solvent, especially suitable for safety, green, environment amity of materials.

A long-life green fluorescent waterborne polyurethane-based Tb(III) ternary complex with UV shielding

A green fluorescent complex [Tb(PABA)3Phen] with fluorescence lifetime up to 0.837 ms was synthesized in ethanol by using p-aminobenzoic acid as the first ligand, o-phenanthroline as the second ligand and Tb3+ as the central ion. A long-life green fluorescent waterborne polyurethane-base Tb(III) ternary complex (Tb-WPU) with UV shielding was prepared by a modified acetone method using Tb(PABA)3Phen as chain extender. The structure and properties were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA), fluorescence spectroscopy (FL), etc. The absolute value of Zeta potential increases with the increase of Tb(PABA)3Phen content, and all of them are greater than 40. Tb-WPU can effectively shield UV in the range of 200 nm–315 nm. With the increase of Tb(PABA)3Phen content, the fluorescence intensity of Tb-WPU increased gradually and the luminous life is up to an astonishing 1.375 ms. The initial thermal decomposition temperature of Tb-WPU is above 220 °C. In addition，Tb-WPU uses water as the dispersed phase and is suitable for environmental protection.

Structure and adhesion properties of waterborne poly(urethane urea)s containing small amounts of different graphene derivatives

Waterborne poly(urethane urea)s (PUDs) containing graphene derivatives with different morphologies and surface polarities were synthesized via in situ polymerization by using the acetone method. Small amounts (0.04–0.30 wt.%) of graphene oxide (GO), graphite nanoplatelets (GP) or milled graphite (MG) were mixed with polyadipate of 1,4-butanediol polyol and added during synthesis of the PUDs. The addition of graphene derivatives changed differently the degree of micro-phase separation of the poly(urethane urea)s (PUs) depending on the balance between the extent of covalent interactions between the surface functional groups on the graphene sheets and the isocyanate groups, and the number of stacked graphene sheets. Whereas MG mainly intercalated between the soft segments showing a typical behavior of nanofiller, GP and, particularly, GO showed different degrees of micro-phase separation due to more net covalent interactions with the poly(urethane urea) chains which caused higher crystallinity. The addition of graphene derivative decreased the glass transition temperature of the hard segments and increased the percentages of associated by hydrogen bond urethane and urea groups, more noticeably by adding GP and MG. Lower temperatures of decomposition and higher amounts of urethane and urea hard domains, and soft domains were found in PU + GO and PU + MG, and they showed an additional structural relaxation at 11–16 °C. PU and PU + GP had higher thermal stabilities than PU + GO and PU + MG and the addition of GP and, more markedly, GO imparted toughening to the poly(urethane urea). The T-peel strength values were higher in the joints made with PUD + GO due to the more net covalent interactions between the surface functional groups on the GO sheets and the poly(urethane urea) chains. On the other hand, the lap-shear strength of the joints made with PUD + MG and, in less extent, with PUD + GP noticeably increased.

Synthesis of isopropyl acetate by acetone method and its reaction mechanism

Isopropenyl acetate, an important chemical raw material intermediate, has an extremely wide range of applications in chemicals, materials and medicine. In this paper, acetone and ketene are used as raw materials to synthesize isopropenyl acetate under acidic conditions. The process conditions were studied through experiments with one variable, and the effects of the catalyst activity and dosage, the reaction time and the reaction temperature on the yield of isopropenyl acetate were investigated. The optimal reaction conditions were obtained, and macroscopic kinetic equations of esterification reaction was obtained by fitting the experimental data. The mechanism of the reaction was studied by quantum chemistry. The results of experimental and theoretical research can provide theoretical guidance for further expanding experiment and industrial quantitative production.

Relationship between betahydroxybutyrate (BHB) and acetone concentrations in postmortem blood and cause of death

Unexpected death caused by diabetic or alcoholic ketoacidosis is easily overlooked due to the non-specific symptoms. Although the acid betahydroxybutyrate (BHB) is the most abundant ketone body formed in conditions with ketoacidosis, routine analysis in postmortem investigations often only includes the neutral ketone body acetone. This study aims to evaluate the usefulness of implementing routine BHB analysis in postmortem cases, by investigating the relationship between BHB and acetone concentrations in postmortem blood and the main cause of death. From our database of forensic autopsy cases examined from 2012 to 2015, there were 376 cases with BHB and/or acetone detected in postmortem blood that could be paired with data from the Norwegian Cause of Death Registry. Cases were categorized into three groups based on cause of death: “Diabetes-related” (n = 38), “Alcohol-related” (n = 35) and “Other” (n = 303). Analysis of BHB in blood was performed using UHPLC-MS/MS (limit of quantification (LOQ) 52 mg/L) and of acetone using HS-GC-FID (LOQ 87 mg/L). For the purpose of the study, the acetone method was also validated for a LOQ of 23 mg/L. The median BHB concentration was significantly higher in the group of diabetes-related deaths (671 mg/L, range 68–1311 mg/L) compared to the group of alcohol-related (304 mg/L, range 65–1555 mg/L, p <0.001) and other causes of deaths (113 mg/L, range 0–1402 mg/L, p <0.001). In seven deaths (1.9%), the BHB blood concentration was above the suggested pathological threshold of 250 mg/L, without detection of acetone in blood above 23 mg/L. In 15% of deaths by other causes than diabetes or alcohol, a pathologically significant BHB blood concentration was detected. Our results indicate that BHB is a more reliable marker of pathologically significant ketoacidosis than acetone, and we suggest that BHB should be routinely analyzed in postmortem investigations.

Secondary structural analysis of non-mulberry silk fibroin nanoparticles synthesized by using microwave and acetone method

The 3D structure analysis for Muga silk protein was predicted through homology modeling and Ramachandran plot with the determination of quality index for Stereo/packing and 3D quality index. Silk Nanoparticles were synthesized using conventional desolvation and microwave-assisted radiolysis method from Muga silk fibroin. The secondary structure evolution due to two different synthesis methods was investigated using FTIR and Circular Dichroism (CD) spectroscopy. The microwave synthesized nanoparticles showed enhanced β-sheet content than desolvation synthesized nanoparticles. The conformational changes of Muga silk fibroin protein to nanoparticle followed an ordered transition from random coil to α-helix then from α-helix to β-turn and from β-turn to β-sheets where α-helix and β-turn are the intermediate forms before getting stabilized to the metastable β-sheets structure. The thermodynamics involved in secondary structure evolution was studied from CD analysis and activation energy involved in the formation of the secondary structure was determined. Communicated by Ramaswamy H. Sarma

Mechanically strong waterborne poly(urethane‐urea) films and nanocomposite films

AbstractA series of transparent waterborne poly(urethane‐urea) (PUU) films and nanocomposite films were prepared using isocyanate excess (5–50 mol% excess relative to the hydroxyl groups) and omitting the common chain‐extension step in the acetone method of the preparation. The surplus isocyanate groups were converted into urea and eventually biuret linkages via the reaction with water during the last phase inversion step. Nanocomposites were prepared by the direct mixing of the PUU nanoparticles in water with aqueous nanosilica or montmorillonite powder followed by slow water evaporation. Variable urea/biuret content is responsible for substantially different tensile properties; the neat organic films show elongation‐at‐break values of 100%–1120%, tensile strength values of 0.07–22.1 MPa, and energy‐to‐break of 0.1–85 mJ × mm−3. All of the materials can be potentially used as soft‐to‐hard topcoats, depending on the specific demands. The most promising materials are films prepared at 30 and particularly 40 mol% isocyanate excess.

Addition of small amounts of graphene oxide in the polyol during the synthesis of waterborne polyurethane urea adhesives for improving their adhesion properties

Mixtures of polyadipate of 1,4-butanediol polyol and different small amounts (0.01–0.10 wt%) of graphene oxide (GO) were added during the synthesis of waterborne polyurethane urea dispersions (PUDs) carried out with the acetone method. The addition of 0.02–0.04 wt% GO increased the T-peel strength of plasticized poly (vinyl chloride)/PUD/plasticized poly (vinyl chloride) joints whereas the addition of 0.05–0.10 wt% GO increased the single lap-shear strength of stainless steel/PUD/stainless steel joints. The improved adhesion of the PUDs containing GO was ascribed to the creation of covalent interactions between the surface groups on the GO surface and the NCO groups of the isocyanate during prepolymer formation, creating new urethane groups; during the phase inversion, the covalently bonded GO sheets were embedded between the polyurethane urea chains inside the PUD particles, this changed the degree of phase separation between the hard and the soft segments. When more than 0.04 wt% GO was added, some GO particles cannot be covalently bonded to the prepolymer during the PUD synthesis but they agglomerated and physically “trapped” between the polyurethane urea chains. As a consequence, the adhesion properties of the PU + GO films were different in the PU films containing 0.01–0.04 wt% GO and the ones containing 0.05–0.10 wt% GO.

Synthesis and Application of Aliphatic Superplasticizer by Two-stage Acetone Process

Aliphatic superplasticizer is a kind of admixture that is widely used in concrete. This article propose a two-stage acetone method is based on existing raw materials and technology. An aliphatic superplasticizer with higher water reduction rate and slump retention performance. It has been verified by experiments that compared with the aliphatic superplasticizer collected in the market, it has obvious advantages in the initial water reduction rate and slump retention performance.

Addition of Graphene Oxide in Different Stages of the Synthesis of Waterborne Polyurethane-Urea Adhesives and Its Influence On Their Structure, Thermal, Viscoelastic and Adhesion Properties.

In this study, 0.04 wt % graphene oxide (GO) was added in different stages (before and after prepolymer formation, and during water addition) of the synthesis of waterborne polyurethane-urea dispersions (PUDs) prepared by using the acetone method. The structural, thermal, mechanical, viscoelastic, surface and adhesion properties of the polyurethane-ureas (PUUs) containing 0.04 wt % GO were studied. The addition of GO before and after prepolymer formation produced covalent bonds between the GO sheets and the NCO groups of the isocyanate, whereas the GO sheets were trapped between the polyurethane chains when added during water addition step. As a consequence, depending on the stage of the PUD synthesis in which GO was added, the degree of micro-phase separation between the hard and soft segments changed differently. The addition of GO before prepolymer formation changed more efficiently the polyurethane-urea structure, i.e., the covalently bonded GO sheets disturbed the interactions between the hard segments causing lower percentage of free urethane groups, higher crystallinity, lower storage modulus, higher yield stress and T-peel strength. The interactions between the GO sheets and the polymeric chains have been evidenced by plate-plate rheology, thermal gravimetric analysis and spectroscopy. On the other hand, physical interactions between GO and the polyurethane-urea chains were produced when GO was added in water during the synthesis, i.e., GO was acting as a nanofiller, which justified the improved mechanical properties and high lap-shear strength, but poor T-peel strength.

Analysis of Samples Cleaning Methods Prior to Hydrogen Content Determination in Steel

There are multiple references to sample cleaning methods prior to hydrogen content determination, or hydrogen spectroscopy analysis, but there is still no unified criteria; different authors use their own “know-how” to perform this task. The aim of this paper is to solve, or at least clarify, this issue. In this work, the most commonly used sample cleaning methods are compared. Then, five different methodologies are applied on certified hydrogen content calibration pins and on high strength steel concrete-prestressing strands and the three main situations regarding hydrogen content in the microstructural net (non-charged, charged, and charged and uncharged) are studied. It was concluded that the HCl solution C-3.5 cleaning method recommended by ASTM G1 introduces large amounts of hydrogen in the samples; but can be useful for eliminating superficial oxides if necessary. The rest of the methods had similar results; but the more complete ones that involve ultrasounds and last longer than 8 min are not appropriated when important diffusion may occur on the samples during their application. Simple methods that involve acetone or trichloroethylene and last around 1 min are preferable for almost all situations as these are faster, easier, and cheaper. As a final recommendation, as trichloroethylene is toxic, the simple acetone method is, in general, the most convenient one for regular hydrogen content analysis.