Total Monomer Concentration Research Articles

Synthesis and Evaluation of High-Temperature Resistant Polymer Plugging Agent for Water-Based Drilling Fluids.

As the exploration and development of deep wells have emerged as a key option to extract more oil and gas resources trapped underneath, high-temperature formations impose stringent requirements on the thermal stability of plugging agents used in water-based drilling fluids. In this work, β-cyclodextrin, with its unique conical toroidal rigid stable structure and internal hydrophobic and external hydrophilic special adsorption capacity, was first grafted with maleic anhydride to prepare a silicone polymer and then copolymerized with dimethyldiallylammonium chloride (DMDAAC) in the presence of coupling agent vinyltriethoxysilane (A151) and cross-linking divinylbenzene (DVD) to finally obtain a high-temperature resistant plugging agent (AMMD). Subsequently, the molecular structure was evidenced and the performance of AMMD was examined in the polysulfonate-base fluid via a series of tests including high-temperature high-pressure filtration loss, sand tray plugging, and drilling fluid displacement, and the results were compared with the counterpart Soltex under the same conditions. The optimal synthesis conditions for the plugging agent were found as total monomer concentration of 25%, initiator mass fraction of 1% (based on the mass of monomers), monomer feed ratio of m (DVD):m(A151):m(DMDAAC):m(MD) of 15:3:2:15, pH value of 10, reaction temperature of 75 °C, and reaction time of 4 h. FT-IR spectra indicated that the monomers used to prepare AMMD were successfully involved in the reaction for the design of the plugging agent structure. TGA showed that AMMD has a total weight loss of about 35.98% in the range of 284 to 453 °C. Moreover, the addition of 3%AMMD into the base fluid produced a 4.38-fold and 3.8-fold filtration loss control over 60 min at 200 °C using 400 and 800 mD sand trays, respectively, which were comparatively higher than the commercially available Soltex (ca. 3.72-fold and 3.14-fold, respectively, using 400 and 800 mD). This then contributed to AMMD's superior plugging performance in drilling fluid based on the drilling fluid displacement experiment, implying that AMMD could find potential use as a plugging agent in polysulfonate drilling fluid under severe geothermal conditions.

Fabrication and Properties of in Situ Cross‐Linked Supramolecular Gel Based on Host‐Guest Interaction

AbstractWater‐cut control is critical to efficient reservoir development. In this investigation, a host‐guest inclusion polymer gels system with self‐assembly features was constructed stemming from the host‐guest recognition mechanism. Subsequently, the elements affecting polymer viscosity were discussed. Eventually, the injectivity and plugging performance of the host‐guest inclusion system were measured by core displacement tests. The results indicated that the optimum synthesis temperature of the host polymer and guest polymer were 30 °C and 40 °C, separately, and the optimum total monomer content should be 20 wt%. The polymer system had excellent thickening properties and shearing resistance resulting from host‐guest inclusion interaction and physical hydrophobic association. Meanwhile, it had better plugging performance than host polymer or guest polymer alone. This profile control agent system provides a novel method for settling deep profile control in oilfields.

Surfactant-Free Preparation of Conjugated Polymer Nanoparticles in Aqueous Dispersions Using Sulfate Functionalized Fluorene Monomers.

Conjugated polymer nanoparticles (CPNs) can be synthesized by a Suzuki-Miyaura cross-coupling miniemulsion polymerization to give stable dispersions with a high concentration of uniform nanoparticles. However, large amounts of added surfactants are required to stabilize the miniemulsion and prevent the aggregation of the nanoparticles. Removal of the excess surfactant is challenging, and residual surfactant in thin films deposited from these dispersions can reduce the performance of optoelectronic devices. We report a novel approach to prepare stable dispersions with no added surfactant using a fluorene monomer, 2,7-dibromo-9,9-bis(undecanesulfate)-9H-fluorene, with alkyl side chains terminated by negatively charged sulfate groups. This functionality mimics the structure of one of the most commonly used surfactants, sodium dodecyl sulfate (SDS). This charged monomer effectively stabilizes the miniemulsion through electrostatic repulsion without the use of any additional surfactant in molar ratios ranging from 2.0 to 20.0 mol % of total monomer content for the preparation of poly(9,9-dioctylfluorene) (PFO) and poly(9,9-dioctylfluorene-alt-bithiophene) (PF8T2). Incorporation of 5.0 mol % of the amphiphilic monomer gave stable dispersions with a surface potential below -40 mV and, and polymers with molar mass (Mn) above 10 kg mol-1. This method should be generally applicable to the preparation of dispersions of polyfluorenes for application in organic electronic and optoelectronic devices without the requirement for time-consuming processes to remove residual surfactant.

Solvent-induced phase separation and Hofmeister effect enhanced strong, tough, and adhesive polyion complex hydrogels

Polyion complex (PIC) hydrogels possess excellent strength and toughness due to the dynamic and synergetic energy dissipation mechanism associated with the co-existence of both strong and weak bonds, ionic and hydrogen, in their networks. On the other hand, PIC hydrogels usually exhibit poor wet adhesion properties. Furthermore, the role such dynamic energy dissipation mechanism plays in determining interfacial binding is unknown. To address these challenges, here, we report the fabrication of an adhesive PIC hydrogel, poly(sodium p-styrenesulfonate) (NaSS)/poly(acryloyloxyethyltrimethyl ammonium chloride (DAC)–co-2-vinyl-4,6-diamino-1,3,5-triazine (VDT), i.e. PNaSS/P(DAC-co-VDT), by introducing a multi-hydrogen bonding capacity functional co-monomer, VDT, and solvent-induced gel phase separation into the fabrication process. The resulting hydrogel exhibited as high as 174 kPa adhesion strength, with retained high mechanical properties, typically 1.2 MPa tensile strength, 2.12 MPa Young’s modulus, and 452% strain. The mechanical properties of PNaSS/P(DAC-co-VDT) were tunable by adjusting the content of VDT and of the total monomer concentration in hydrogel precursor solutions (Cm), as well as by taking advantage of the Hofmeister effect. The dynamic modulus spectra of PNaSS/P(DAC-co-VDT) hydrogels at different Cm’s in extended frequency windows with time–temperature superposition method (TTS) were acquired and analyzed to explore the influence of polymer entanglement on the hydrogel network structure. The microscopic structure-macroscopic mechanical property relationship of PNaSS/P(DAC-co-VDT) hydrogels at different Cm’s and immersed in different salt solutions was further studied using the Mooney-Rivlin equation and by fitting the tensile data to Creton’s viscoelastic model. This study may provide new insights into designing and constructing strong and tough PIC hydrogel-based adhesives.

Dispersion polymerization of AM-AMPS-DAM-DOH and its sand control property

Sand production in oil wells is a common challenge during the oil extraction process. Water-soluble polymers have attracted attention due to their low toxicity, cost-effectiveness, ease of direct injection, and excellent thermal stability. However, the dry polymer injection process commonly used in offshore oil fields is complex. Therefore, this paper employs acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), a dihydroxy monomer (DOH), and a functional monomer (DAM) containing ketone groups and self-crosslinking properties as monomers. A polymer latex type sand control agent was prepared through dispersion polymerization for direct application on offshore platforms. This paper utilizes flocculation time and maximum sand free flow rate as inspection indicators and utilizes both the one-factor-at-a-time method and the surface response method to optimize the synthesis conditions of the sand control agent. The optimal synthesis conditions are obtained: total monomer concentration of 9.15 wt%, DOH concentration at 10 wt% of the total monomer concentration, ammonium sulfate (AS) concentration of 27.02 wt%, dispersant concentration of 2.13 wt%, initiator concentration at 0.25 wt% of the total monomer concentration, reaction time of 12 h, and reaction temperature of 40 °C. Under the conditions of concentration ≥2000 mg/L and curing time ≥4 h, the sand control agent is suitable for sand stabilization under formation conditions of temperatures between 50 and 80 °C, pH levels ranging from 3 to 9, salinity <30000 mg/L, and sand particle size of ≥100 μm. The research results of this paper can serve as a valuable reference for the control of oilfield sand production.

Randomly cross-linked amphiphilic copolymer networks of n-butyl acrylate and N,N-dimethylacrylamide: synthesis and characterization

Abstract Five randomly cross-linked amphiphilic copolymer networks (ACPN) were prepared via the free radical cross-linking copolymerization of the hydrophobic n-butyl acrylate (BuA) and the hydrophilic N,N-dimethylacrylamide (DMAAm), in the presence of a small amount (5 mol% with respect to the sum of BuA plus DMAAm monomers) of the hydrophobic 1,6-hexanediol diacrylate (HexDA) cross-linker, initiated by 4,4ʹ-azobis(4-cyanovaleric acid) in 1,4-dioxane at a 10 % w/v total monomer concentration. The five ACPNs differed in their BuA content, fixed at 10, 30, 50, 70 and 90 mol%. The two homopolymer networks, BuA and DMAAm, were also prepared using the same polymerization method. Thus, this study involved a total of seven polymer networks, forming a homologous series with BuA contents ranging from 0 to 100 mol%. These networks were characterized in terms of their degrees of swelling in tetrahydrofuran (THF) and water, their mechanical properties in water, and their adhesion to human skin. The degrees of swelling (DS) of the networks in THF were higher than those in water because THF is a non-selective solvent, whereas water is selective for the hydrophilic DMAAm units. The DSs in THF increased with the network content in the less polar BuA units, while the opposite was true for the DSs in water which decreased with the content in the hydrophobic BuA units from 11 (0 mol% BuA) down to 1.1 (100 mol% BuA). A maximum in the elastic modulus was observed for the hydrogel with 50 mol% BuA, reflecting the opposing effects of polymer composition in soft polymer (polyBuA) content and hydrogel water content. In contrast, the tensile strain at break increased monotonically with the hydrogel BuA content, reaching a remarkable ∼900 % for the hydrogel with 90 mol% BuA. Finally, the adhesion of the ACPNs, both in their dried and hydrated states, onto human skin was explored. The adhesion of the hydrated samples onto skin was stronger than that of the dried ones. The hydrated ACPN with 30 mol% BuA exhibited the strongest adhesion onto skin, attributable to the best combination of a rather high content in polar DMAAm units (70 mol%), and a rather low aqueous DS (∼2.5), with the low DS value causing only a small dilution in the DMAAm units participating in the polar interactions with skin. The present work demonstrates that, even in this synthetically simple ACPN system, the multiple effects of ACPN composition on a certain property, in some cases opposing and in some other cooperating, lead to a rather complicated behavior. In particular, as the BuA content increases, some properties display maxima (elastic modulus, stress at break and fracture energy of hydrated ACPNs, and adhesion of hydrated ACPNs onto skin) while some other properties exhibit monotonic increases (strain at break of hydrated ACPNs, and adhesion of dried ACPNs onto skin). Thus, the optimal ACPN for a particular application will highly depend on the property best-serving the particular application, e.g., the ACPNs with 30, 50 and 90 mol% BuA for strongest wet adhesion to skin, stiffest hydrogel response, and highest hydrogel extensibility and toughness, respectively.

Synthesis of reactive polyamide porous materials and introduction of crosslinking

ABSTRACT Porous crosslinked aromatic polyamides were prepared in a single-step process by reacting a triacid chloride monomer with a diamine monomer having COOH groups via a precipitation polymerization method. The resulting materials were agglomerates of polyamide particles having COCl and COOH groups with average diameters of 30–70 nm and average pore diameters in the range of ca. 20–40 nm. The concentration of COCl groups and the porous structure were significantly affected by the monomer ratio, the total monomer concentration and the reaction solvent. These COCl groups were subsequently modified by reaction with 1,8-diaminooctane in three different solvents, and the extent of modification depended strongly on the solvent. This modification produced aromatic polyamides having two types of crosslinking, based on of the 1,8-diaminooctane and the aromatic polyamide product, which were cleaved in different temperature ranges. The COCl groups introduced were found to have high reactivity and react with NH2 groups even in water, prior to hydrolysis.

Radiation assisted hydrophobization of jute fiber

AbstractHydrophobization of hydrophilic jute fiber, is of great importance as it can expand the applications of jute fiber in many fields. This work reports the hydrophobization of jute fiber by high‐energy radiation treatment which is an easy, single‐step, economical, and environment friendly method. Surface wettability of hydrophilic jute fiber is tuned by attaching long chain hydrocarbon molecules, namely butyl methacrylate, octyl acrylate and lauryl methacrylate, using gamma radiation. Lauryl methacrylate is found to be the most suitable agent among the molecules used for generating desired extent of hydrophobicity. Important reaction parameters, namely total dose, dose rate, monomer concentration, and solvent composition are optimized to achieve the desired degree of modification, for imparting hydrophobicity. Mechanical and thermal analysis reveals that there is no considerable damage to the base structure of fibers during modification. Scanning electron microscopy (SEM) is supporting evidence of the intactness of fiber after modification. The successful grafting of jute fiber has also been evidenced by SEM. This lauryl methacrylate modified jute can separate oily toxic liquids from aqueous media. The modified jute fiber may get enhanced applications in various fields.

Dielectric barrier discharge plasma-modified chitosan flocculant and its flocculation performance

The flocculation performance of chitosan can be enhanced by grafting modification to overcome its disadvantages of poor water solubility. In this study, chitosan was modified by dielectric barrier discharge plasma and polymerized with acrylamide and aluminum chloride to synthesize a new chitosan-based flocculant, namely, chitosan–acrylamide–aluminum chloride (CA-PAC). After optimizing the synthesis conditions of CA-PAC, the best conditions were as follows: discharge time of 3 min, discharge power of 50 W, polymerization temperature of 60 °C, polymerization time of 3 h, total monomer concentration of 100 g/L, and m(AlCl3):m(CA) ratio of 2:1. Characterization was performed through SEM, XPS, FTIR, XRD, TG and 1H NMR. Results showed that the preparation of CA-PAC was successful. The influences of flocculant dosage, pH, and stirring intensity on flocculation efficiency were investigated. The removal efficiency of turbidity was 94.1 %. The investigation of the flocculation mechanism revealed that CA-PAC mainly relied on charge neutralization or the synergic action of electric neutralization, bridging, and roll–sweep under acidic and neutral conditions, but it depended on the joint action of adsorption bridging and net sweeping under alkaline conditions. This study provides new ideas for the preparation and development of modified chitosan and broadens its application in water treatment.

Synthesis and Plugging Performance of Nano-Micron Polymeric Gel Microsphere Plugging Agents for Oil-Based Drilling Fluids

As shale gas recovery progresses to deep layers, the wellbore instability during drilling in applications of oil-based drilling fluids (OBFs) becomes increasingly severe. This research developed a plugging agent of nano-micron polymeric microspheres based on inverse emulsion polymerization. Through the single-factor analysis with respect to the permeability plugging apparatus (PPA) fluid loss of drilling fluids, the optimal synthesis conditions of polymeric microspheres (AMN) were determined. Specifically, the optimal synthesis conditions are as follows: the monomer ratio of 2-acrylamido-2-methylpropanesulfonic acid (AMPS): Acrylamide (AM): N-vinylpyrrolidone (NVP) were 2:3:5; the total monomer concentration was 30%; the concentrations and HLB values of emulsifier (Span 80: Tween 60) were 10% and 5.1, respectively; the oil-water ratio of the reaction system was 1:1; the cross-linker concentration was 0.4%. The polymeric microsphere (AMN) produced via the optimal synthesis formula had the corresponding functional groups and good thermal stability. The size distribution of AMN ranged mainly from 0.5 to 10 μm. The introduction of AMND in OBFs can increase the viscosity and yield point of oil-based drilling fluids and slightly decrease the demulsification voltage but significantly reduce high temperature and high pressure (HTHP) fluid loss and permeability plugging apparatus (PPA) fluid loss. The OBFs with 3% polymeric microsphere dispersion (AMND) reduced the HTHP and PPA fluid loss by 42% and 50% at 130 °C, respectively. In addition, The AMND maintained good plugging performance at 180 °C. The AMN particles can block leakoff channels of artificial cores, effectively prevent the invasion of oil-based drilling fluids into formations and suppress pressure transfer. OBFs with 3% AMND enabled the corresponding equilibrium pressure to decrease by 69%, compared with that of the OBFs. The polymeric microspheres had a wide particle size distribution. Thus, they can well match leakage channels at various scales and form plugging layers via compression-deformation and packed accumulation, so as to prevent oil-based drilling fluid from invading formations and improve wellbore stability.

Sulfonic Cryogels as Innovative Materials for Biotechnological Applications: Synthesis, Modification, and Biological Activity.

Polymeric hydrogels based on sulfo-containing comonomers are promising materials for biotechnological application, namely, for use as a system for delivering water and minerals during seed germination in conditions of an unstable moisture zone. In this work, cryogels based on 3-sulfopropyl methacrylate and 2-hydroxyethyl methacrylate copolymers were obtained by the cryotropic gelation method. The morphology, specific surface area, and swelling behaviors of cryogels are found to depend on the total concentration of monomers in the reaction system and the content of the gel fraction in cryogels. Cryogels formed in the presence of nanodiamonds are shown to exhibit high biological activity during the germination of Lepidium sativum L. variety Ajur seeds, which manifests itself by stimulating seed germination and a significant increase in the raw weight of sprouts. These results indicate that sulfonic cryogels have a high potential to improve seed germination and plant growth, proving that such cryogels can be used as environmentally friendly materials for agricultural applications.

Functionalization of Polymer Networks to Target Trans‐Resveratrol in Winemaking Residues Supported by Statistical Design of Experiments

AbstractThe present work aims to produce functionalized polymer networks to target the bioactive molecule trans‐resveratrol found in winemaking residues, specifically at grape stems. The synergistic choice of photoinitiation, polymerization composition, and molecular imprinting approach allows the functionalization of these materials. Experimental design is applied to methodically perform the syntheses. The amount of crosslinker, the total monomer's concentration, and the ratio of trans‐resveratrol to the functional monomer 4‐vinylpyridine (4VP) are the factors selected for this experimental design. The binding capacities and the selectivity of the synthesized materials are assessed through sorption experiments in acetonitrile and hydroalcoholic media. Consequently, a multivariate linear regression analysis leads to describe the uptake of trans‐resveratrol by the materials in both media. The crosslinker content and the ratio of trans‐resveratrol to 4VP are found to be impactful parameters while designing such materials. These studies allow the identification of working conditions for sorption/desorption processes combining a high retention capability of the adsorbents with selectivity. Furthermore, four materials are selected to enrich trans‐resveratrol from grape stems extracts in a continuous process of solid‐phase extraction. The results show that the functionalized materials are able to enrich 12‐fold the content of trans‐resveratrol in some fractions demonstrating the interest of such polymers.

Fouling-resistant membranes with zwitterion-containing ultra-thin hydrogel selective layers

Zwitterions are neutrally charged molecules with an equal number of cationic and anionic groups. Their exceptional fouling resistance makes them excellent membrane materials. This study focuses on thin-film composite (TFC) ultrafiltration membranes where the selective layers consist of zwitterion-containing hydrogels. To synthesize these membranes with ultra-thin hydrogel selective layers we used a novel method, Interfacially Initiated Free Radical Polymerization (IIFRP). While previous studies focused on poly(ethylene glycol) (PEG)-based selective layers, we aimed to determine the effect of incorporating two zwitterionic monomers, sulfobetaine methacrylate (SBMA) and 2-methacryloyloxyethyl phosphorylcholine (MPC), on permeability, selectivity, and fouling resistance. Compared to a PEG-based hydrogel selective layer, all zwitterion-containing hydrogel selective layers showed increased water permeance (12.2 ± 1.8 L/m2 h bar for SBMA, 7.3 ± 1.8 L/m2 h bar for MPC). Interestingly, this permeance increase was not accompanied by a major decrease in protein rejection despite the zwitterion-containing hydrogels having lower chemical cross-link densities, with myoglobin rejections staying >90%. This was likely due to physical cross-links between zwitterionic moieties. For the same total monomer concentration, higher zwitterion concentrations led to a permeance increase of almost an order of magnitude along with only minimal decrease in protein rejection. Moreover, all hydrogel selective layer TFC membranes tested exhibited excellent oil fouling resistance.

Laponite-Doped Poly(acrylic acid-co-acrylamide) Hydrogels

Electroacoustic characterization of soft nanocomposites has provided unique insights into the microstructure of soft nanocomposites, including nanoparticle (NP)-doped hydrogels and polyelectrolyte hydrogels without NPs. An outstanding problem is how to interpret the electrokinetic sonic amplitude (ESA) of charged hydrogels bearing charged NPs because both components generate an acoustic response to the electrical forcing. To this end, we study a series of Laponite XLG-doped, neutralized poly(acrylic acid-co-acrylamide) hydrogels, drawing principally on the ESA, electrical conductivity, and linear viscoelastic rheology. The hydrogel charge density was varied by the fraction of acrylic acid monomer fAAc = 0–1 while maintaining the total monomer concentration ≈8 wt % with Laponite concentration ≈0.85 wt %. Upon comparison of data from this study to those in a recent benchmark study of charged hydrogels without NPs, Laponite doping increased the electroacoustic signal and ionic conductivity but decreased the hydrogel storage modulus. Mechanistic theoretical models predicting how the real part of the ESA (at low frequency) and ionic conductivity of polyelectrolyte hydrogels depend on fAAc were extended to Laponite-doped hydrogels, together furnishing an estimate of the partial molar volume of acrylamide (in polymer form) that is close to the value for pure acrylamide (based on its density and molecular weight). The generally lower storage modulus with Laponite doping contrasts with previous studies of Laponite-doped polyacrylamide and poly(acrylic acid) hydrogels and solutions. This seems to reflect the high degree of neutralization, which transforms an attraction between protonated carboxyl moieties and Laponite to an electrostatic repulsion. The hindering effects of polymerization and cross-linking on acrylic acid-co-acrylamide networks were also investigated by comparing the ESA and conductivity of hydrogels with their monomer solution counterparts. Systematically varying the ratio of charged to uncharged monomers, with and without chemical cross-linking, provides insights to benefit a broad range of technological applications for hydrogel nanocomposites.

Functionalized chitosan-magnetic flocculants for heavy metal and dye removal modeled by an artificial neural network

In this study, an amphoteric magnetic chitosan (CS)-based flocculant MFe3O4@CS-g-PIA was prepared from CS, Fe3O4, and itaconic acid (IA), and its apparent morphology and characteristic structure were systematically studied. The flocculation performance and mechanism of the fabricated material were also investigated in different pollution systems, and the effects of total monomer concentration, m(CS):m(IA), IA pre-neutralization degree, reaction temperature, reaction time, and initiator concentration on the synthesis of MFe3O4@CS-g-PIA were studied. Characterization results showed that MFe3O4@CS-g-PIA forms a three-dimensional network with excellent magnetic induction. The optimal removal rates of Cu(II) and Disperse Blue 56 (DB56; 90.2% and 97.0%, respectively) were obtained under the conditions of 150 mg·L−1 MFe3O4@CS-g-PIA, pH 6.0, and 300 rpm stirring speed. MFe3O4@CS-g-PIA maintained removal rates of over 80.0% for Cu(II) and DB56 after five consecutive cycles of regeneration/flocculation and demonstrated excellent acid resistance stability. Changes in the particle size distribution, fractal dimensions, and zeta potentials of the flocs indicated that the relevant flocculation mechanism involves the synergistic functions of chelation, charge neutralization, and adsorption bridging. An artificial neural network model was finally established on the basis of the experimental flocculation data to predict the removal rates of Cu(II) (R = 0.97) and DB56 (R = 0.98) accurately.

Synthesis and properties of hydrophobically associating polymer fracturing fluid

The double tailed hydrophobic monomer PMB-16 was synthesized by the reaction of phenylethylamine,1-bromohexadecane and methacryloyl chloride. The ternary hydrophobic association polymer (PADM) was synthesized by free radical copolymerization of PMB-16 with acrylamide (AM) and methacryloyloxyethyl trimethylammonium chloride (DMC). The optimum synthesis conditions were as follows, the mass ratio of m (AM):m (DMC):m (PMB-16) was 80:19.6:0.4, the total monomer concentration was 35.0 wt%, the amount of initiator (V50) was 0.1 wt% of the total mass of monomer, the reaction temperature was 55 °C, the reaction time was 6.0 h, the system pH was 7, and the amount of metal ion chelating agent (EDTA-4Na) was 0.01 wt% of the total mass of monomer. The results of performance evaluation showed that PADM aqueous solution had excellent temperature and salt resistance. Using zirconium acetylacetonate as crosslinking agent, the mass crosslinking ratio of PADM solution to zirconium acetylacetonate was 100:0.9, the crosslinking temperature was 60 °C, and the pH value was 6.0. The system presented good thickening, temperature resistance, shear stability and low residue content, so it was a low damage fracturing fluid.

Tiny yet tough: Maximizing the toughness of fiber-reinforced soft composites in the absence of a fiber-fracture mechanism

Tiny yet tough: Maximizing the toughness of fiber-reinforced soft composites in the absence of a fiber-fracture mechanism

An eco-friendly approach for blending of fast-pyrolysis bio-oil in petroleum-derived fuel by controlling ash content of loblolly pine

This paper describes the effect of the ash content in biomass on the distribution of pyrolysis products and the miscibility of bio-oil in diesel. Ash content of loblolly pine wood (0.5 wt %, 1.1 wt %, and 1.5 wt %) was systematically varied by impregnating the wood with potassium carbonate solution. Variation in the ash content did not create a significant change in the chemical composition of the impregnated biomass. However, the response to a variety of thermal treatments changed significantly. The volatile matter content decreased from 88.3% to 78.2%, while the bio-oil yield declined from 45.7% to 29.9% as the ash content increased. Although the total organic yield decreased with increased biomass ash content, the total concentration of phenolic monomers increased from 2.8 mg/g to 20.2 mg/g, and bio-oil miscibility with a commercial diesel fuel increased from 6.7% to 13.4% based on wet bio-oil. The miscibility of guaiacol and 4-methyl guaiacol in diesel was higher than that of catechol, due to the lower polar and hydrogen bonding contribution. Test in a diesel engine showed a simultaneous reduction of HC and NOx emissions using diesel extracts.

Preparation and Characterization of High-Efficiency Magnetic Heavy Metal Capture Flocculants

In this study, a high-efficiency magnetic heavy metal flocculant MF@AA was prepared based on carboxymethyl chitosan and magnetic Fe3O4. It was characterized by SEM, FTIR, XPS, XRD and VSM, and the Cu(II) removal rate was used as the evaluation basis for the preparation process. The effects of AMPS content, total monomer concentration, photoinitiator concentration and reaction time on the performance of MF@AA flocculation to remove Cu(II) were studied. The characterization results show that MF@AA has been successfully prepared and exhibits good magnetic induction characteristics. The synthesis results show that under the conditions of 10% AMPS content, 35% total monomer concentration, 0.04% photoinitiator concentration, and 1.5 h reaction time, the best yield of MF@AA is 77.69%. The best removal rate is 87.65%. In addition, the response surface optimization of the synthesis process of MF@AA was performed. The optimal synthesis ratio was finally determined as iron content 6.5%, CMFS: 29.5%, AM: 53.9%, AMPS: 10.1%. High-efficiency magnetic heavy metal flocculant MF@AA shows excellent flocculation performance in removing Cu(II). This research provides guidance and ideas for the development of efficient and low-cost flocculation technology to remove Cu(II) in wastewater.

Confined Polymers in a Poor Solvent: The Role of Bonding to the Surface

We analytically predict the concentration profile of a long polymer chain in a poor solvent, confined between two walls where some of its monomers can form strong bonds with the walls. In contrast to adsorption boundary conditions, these concentration profiles can vary nonmonotonically. Boundary conditions that lead to a decrease in the monomer concentration at the walls (at fixed, total monomer concentration) show a transition between concentration profiles in which the polymer concentration is organized peripherally (near the walls) and profiles in which the polymer concentration is the highest in the center (away from the walls). We conclude by discussing the relevance of our findings to experimental observations and simulation studies of chromatin organization in the nucleus of living cells.