Modification Agent Research Articles

STUDY OF THE INFLUENCE OF THE CROSSLINKING METHODS ON THE PROPERTIES OF POLYETHYLENE

Polyethylene (PE) is considered one of the most versatile thermoplastics available today. However, it exhibits several limitations related to its low melting point, low heat resistance, tendency to crack propagation, and its low resistance to rupture under stress. In order to overcome these deficiencies, several processes for crosslinking PE chains were developed, which makes this material more stable to temperature changes. In this work, methods based on peroxide (PEX-A) and silane (PEX-B) as chemical modification agents for PE chain crosslinking were analyzed, aiming to apply PE in pipes for conduction water. The materials were characterized by infrared spectroscopy (FTIR), gel content, and thermal analysis (TGA and DSC) to achieve those objectives. Also, some mechanical properties such as tensile strength and hardness and the determination of the heat deflection temperature (HDT) were evaluated. Spectra demonstrated the presence of the functional groups characteristic of PE and the incorporation of siloxane groups in PEX-B. Gel content values obtained were above 60% and indicated the formation of crosslinked chains between the molecules of the polymers. The thermal analysis suggests a greater efficiency in forming a chain network by the silane crosslinking process compared to the peroxide process. As for the mechanical tests, they also showed improvement in the mechanical properties of the crosslinked polymer when compared to the respective original PE. Thus, the silane method provided sufficient results to conclude that the properties evaluated are superior compared to the peroxide crosslinking method.

Characteristics of aluminium AC4B reinforced with nano -SiC composites through stir casting methods

Aluminium with a composition of 7-10% Silicon (Si), 2-4% Copper (Cu) is a matrix used by adding Nano SiC reinforcement particles with variations of 0.25; 0.3; 0.4%Vf with the purpose of making bullet-proof materials that have high toughness, impact resistance, and good strength. In this study, fabricated composites used a stir casting process to produce superior mechanical properties which was caused by the bond between an effective matrix and reinforcement particles. Besides, the addition of Nano SiC reinforcement particles, it was also followed by adding 5%wt Magnesium (Mg) as a wetting agent, 0.04%wt Strontium (Sr) as modifier agent, and 0.15%wt Al-5Ti-1B as a grain refining agent. Fabricated composite specimens will be carried out several tests to determine mechanical properties such as density, porosity, hardness, tensile strength, impact resistance, and ballistic test. The result of the test will be compared to the results of that without the addition of reinforcement particles. Then, using the Optical Microscope (OM), Scanning Electron Microscope (SEM), Dispersive X-Ray Spectroscopy (EDX), and X-Ray Diffraction (XRD) to analyse the dispersion of reinforcement particles in the selected alloy matrix.

Functional Materials Based on Active Carbon and Titanium Dioxide in Fog Seal.

Due to its ability to degrade nitrogen oxides under ultraviolet, titanium dioxide has been applied in asphalt concrete to degrade automobile exhaust in recent years. To highlight the protection of road traffic environmental quality and mitigate automobile exhaust on human health, this study proposes combining titanium dioxide and active carbon into Sand-fog seal to form a pavement coating material with a photocatalytic function. It uses active carbon to reinforce the material’s function, and the coupling agent for modification makes it well dispersed in the Sand-fog seal. The indoor experiments were carried out at 30 °C and relative humidity of 30%. It tested the composite material’s degradation efficiency on nitrogen dioxide in relation to component proportions, coupling agents, and dosages. The study concluded that the optimal photocatalytic efficiency could be achieved when the ratio of active carbon to titanium dioxide is 0.6. After being modified by the titanate coupling agent and through Scanning Electron Microscope tests, it can be seen that materials can be well dispersed into the Sand-fog seal. When the composite material accounts for 10% of the fog seal, it can achieve the optimal photocatalytic efficiency of about 23.9%. The British pendulum tests show it has good skid resistance performance. Half a kilometer of concrete roadway was sprayed with the material coating in Tianjin, China. The photocatalytic experimental road degrades nitrogen oxides better than the original road. The method is feasible for practical implementation.

Physicochemical Analysis and Heavy Metals Remediation of Pharmaceutical Industry Effluent Using Bentonite Clay Modified by H2SO4 and HCl

Environmental pollution by industrial effluent has become an important issue partly because of the detection of heavy metals in them which need to be mitigated. Adsorbents were produced from Bentonite clay using 2 M H2SO4 and HCl as modifying agents in ratio 1:2 by wet impregnation method. Physicochemical properties of the pharmaceutical effluents such as pH, temperature, turbidity, conductivity, Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD) and heavy metals were determined. High concentration of Fe(III) and Zn(II)were observed in the effluents when compared with standards. Optimal value of pH for Fe(III) and Zn(II) were 8 and 7 respectively and dose of 0.1 g was found to be optimal value for all the adsorption system. The adsorption was best fit to Langmuir isotherm and the pseudo second order kinetic model. The results obtained in this study showed that the produced adsorbents could be used to supplement the commercial adsorbents in the specific application. Furthermore, acid modification was helped to increase the sorption capacity of the clay to the heavy metals studied with H2SO4 being the better modification agent.

Synthesis of Bamboo-like Multiwall Carbon Nanotube-Poly(Acrylic Acid-co-Itaconic Acid)/NaOH Composite Hydrogel and its Potential Application for Electrochemical Detection of Cadmium(II).

A poly(acrylic acid-co-itaconic acid) (PAA-co-IA)/NaOH hydrogel containing bamboo-type multiwall carbon nanotubes (B-MWCNTs) doped with nitrogen (PAA-co-IA/NaOH/B-MWCNTs) was synthesized and characterized by SEM, absorption of water, point of zero charges, infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The possible use of the PAA-co-IA/NaOH/B-MWCNT hydrogel as an electrode modifier and pre-concentrator agent for Cd(II) sensing purposes was then evaluated using carbon paste electrodes via differential pulse voltammetry. The presence of the B-MWCNTs in the hydrogel matrix decreased its degree of swelling, stabilized the structure of the swollen gel, and favored the detection of 3 ppb Cd(II), which is comparable to the World Health Organization’s allowable maximum value in drinking water. A calibration curve was obtained in the concentration range of 2.67 × 10−8 to 6.23 × 10−7 M (i.e., 3 and 70 ppb) to determine a limit of detection (LOD) of 19.24 μgL−1 and a sensitivity of 0.15 μC ppb−1. Also, the Zn(II), Hg(II), Pb(II) and Cu(II) ions interfered moderately on the determination of Cd(II).

The Influence of Strontium on Microstructural and Rheological Behavior of the Semi-solid A380 Aluminum Alloy

This article aims to correct the lack of information regarding the combined effect of grain refinement and strontium modification on the microstructure and rheological behavior of semi-solid slurries. The A380 aluminum alloy was studied in the semi-solid state in three different conditions: as received, grain refined and grain refined/modified with Sr. To determine the semi-solid temperature, a DSC analysis and Thermo-calc® simulations were used. SEM, optical and polarized light microscopy analyses were performed to analyze the microstructural changes caused by the refiner and modifier agents as well as to evaluate the morphological evolution of the alloys in the semi-solid state. The rheological behavior was studied with a hot compression test between parallel plates. The main results show that the addition of Sr, besides its influence on the Si and Fe-β particles, also leads to a better globularization of α-Al phase particles in the semi-solid state. Furthermore, the rheological analysis of stress vs strain and apparent viscosity vs average shear rate also point to a better behavior of the alloy in the semi-solid state after Sr modification, thus indicating that Sr addition could improve the performance of the A380 alloy as a semi-solid feedstock.

The Mechanical Properties of Organic Modified Epoxy Resin

Epoxy resins have been presenting a lot of scientific and technical interests and organic modified epoxy resins have recently receiving a great deal of attention. For obtaining the composite materials with good mechanical proprieties, a large variety of organic modification agents were used. For this study gluten and gelatin had been used as modifying agents thinking that their dispersion inside the polymer could increase the polymer biocompatibility. Equal amounts of the proteins were milled together and the obtained compound was used to form 1 to 5% weight ratios organic agents modified epoxy materials. To highlight the effect of these proteins in epoxy matrix mechanical tests as three-point bending and compression were performed.

Fabrication of superhydrophobic polyethersulfone-ZnO rods composite membrane

The development of superhydrophobic membrane has gained more attention. The current methods for superhydrophobic surface mostly involve fluorosilanes as surface modification agent which is expensive and harmful to the environment. We herein report, simple and cost effective, fabrication of novel superhydrophobic polyethersulfone-composite membranes. The superhydrophobicity of the membrane surface was achieved by growing ZnO rods ex-situ followed by modification with stearic acid. SEM results showed the presence of ZnO rods with the length ranging from 1 µm to 11 µm on the membrane surface while AFM results revealed high surface roughness. The as-prepared membrane exhibited high water repellent with contact angle of ~163° and excellent superoleophilicity. The PES-ZnO rod-SA modified membrane could be an excellent candidate for oil-water separation.

Characterization of surface properties of dry-coated anhydrous borax powders

Dry particle coating of anhydrous borax (ANB) powders with hydrophobic stearic acid (SA) in the planetary ball mill was investigated. Two process parameters, the amounts of modifier agent and the processing periods, were selected to investigate their effects on solubility, wettability, dispersibility, and hydration properties of ANB powders. Each of the process parameters, i.e., SA amounts (0.5, 1, and 2 wt.%), and coating periods (30, 60, and 120 min), was set at three different levels. Structural changes in the dry-coated powders were characterised using X-ray diffraction (XRD) and photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and Differential thermal and thermogravimetric analysis (DTA-TG). A discrete coating at an efficiency of 68% was acquired with SA amount of 1 wt.% at a coating period of 60 min, and, thus, resulted in a 31.4% decrease (from 40% to 8.6%) in water solubility of ANB. Moreover, this discrete SA coating made ANB more hydrophobic (99o) and prevented its further hydration. Furthermore, FT-IR and XPS results indicated that SA is coated over the surface of ANB via physical adsorption rather than chemical bonding. Thus, the effective dry coating could be applied to obtain surface-coated ANB, which offers controlled solubility in water-based suspensions.

Influence of Ca2+ on phosphate removal from water using a non-core-shell Fe3O4@ZIF-67 composites

Excessive phosphate in surface water can spur the growth of organism, which put a threat on the bio-safety of drinking water. Different from previous study, sodium acetate (NaAc) was used as modification agent of Fe3O4, then the magnetic Fe3O4@ZIF-67 composites with a non-core-shell sturture were synthesized. According to ZIF-67 loading and phosphate adsorption of synthesized Fe3O4@ZIF-67, the Fe3O4@ZIF-67 composites with a Co2+/Fe3O4 molar ratio of 1:2 was taken into further evaluation. Fe3O4@ZIF-67 composites exhibited satisfactory adsorption performance and easy magnetic recovery, and the sorption capacity reached 116.59 mg P/g within 180 min (C0 = 20 mg P/L, 298 K). The maximum adsorption capacity of phosphate was obtained at the neutral pH, and not significantly interfered with ions of K+, Mg2+, NO3− and SO42-. Remarkably, Fe3O4@ZIF-67 described enhanced phosphate adsorption ability in the presence of Ca2+. To investigate the role of Ca2+, two modes (preloading and addition) of Ca2+ dosing were examined and the improved adsorptive performance could be owing to the synergistic eff ;ect of adsorption and Ca-P micro-precipitation on the surface of Fe3O4@ZIF-67. During the regeneration process, the performance of desorbent was evaluated by phosphate releasing and secondary adsorption, and the absence or presence of Ca2+ would have a significant impact on the selection of desorption solution.

Hydrophobic Modification of Cellulose Nanocrystals from Bamboo Shoots Using Rarasaponins.

Because of their hydrophilic tendencies, the modification of cellulose nanocrystals (CNCs) is needed for applying them as a hydrophobic drug carrier. Previous studies have investigated several modification agents, such as cetyltrimethylammonium bromide. Natural surfactants, such as rarasaponins (RSs), are suitable to avoid human health and environmental issues. In this work, RSs were attached onto CNCs from bamboo shoots to enhance their hydrophobicity. The initial RS concentration and the operating temperature were studied to obtain the best conditions for the modification process, which had significances (p-value < 5%) toward the amount of RSs linked on the CNCs (q) as the response. A q as high as 203.81 ± 0.98 mg/g was obtained at an initial RS concentration of 2000 mg/L and an operating temperature of 30 °C. The curcumin uptake on CNCs-RSs reached 12.40 ± 0.24%, while it was slowly released until approximately 78% in 3 days.

Surface Passivation of All‐Inorganic CsPbI2Br with a Fluorinated Organic Ammonium Salt for Perovskite Solar Cells with Efficiencies over 16%

Surface modification is demonstrated as an efficient strategy to enhance the efficiency and stability of perovskite solar cells (PVSCs). Fluorinated organic ammonium salts featuring a strong hydrophobic nature are seldom used as passivation agents for the surface modification of CsPbI2Br perovskites. Herein, a fluorinated organic ammonium halide salt, 4‐trifluoromethyl phenethylammonium iodide (CFPEAI), is incorporated into the surface of CsPbI2Br perovskite for the first time. After the CFPEAI modification, the defects of CsPbI2Br perovskite are significantly passivated with reduced trap densities. The best‐performance PVSC with CFPEAI modification shows an excellent power conversion efficiency (PCE) of 16.07% with a high fill factor (FF) of 84.65%, a short‐circuit current density (JSC) of 15.45 mA cm−2, and an open‐circuit voltage (VOC) of 1.23 V. In contrast, the control PVSCs without the surface modification exhibit a lower PCE of 14.50% with a FF of 80.56%, a JSC of 15.05 mA cm−2, and a VOC of 1.20 V. With CFPEAI passivation, the CsPbI2Br perovskite film exhibits enhanced hydrophobicity, thereby leading to improved stability for the corresponding PVSC in comparison with the control PVSC without any surface modification.

Hybridization of superparamagnetic Fe3O4 nanoparticles with MWCNTs and effect of surface modification on electromagnetic heating process efficiency: A microfluidics enhanced oil recovery study

This study investigated the effect of different surface modifications on the microwave absorption performance of new synthesized MWCNT-Fe3O4 nanohybrid. MWCNT-Fe3O4 nanohybrids were synthesized via a co-precipitation method. For the dispersion of these nanomaterials into the water (as the injected fluid), the surfaces of them were modified. For this purpose, three different materials included 3-AminoPropylTriEthoxySilane (APTES), citric acid (CA), and polyethylene glycol (PEG 6000) were used as the surface modification agents. The nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray crystallography (XRD), vibrating sample magnetometer (VSM), and field emission scanning electron microscopy (FESEM). Stability of the coated nanomaterials in distilled water studied by zeta potential analysis and qualitative deposition of particles over time. Microwave absorption of coated nanomaterials investigated by determining the temperature rises of solution (oil and water) containing nanoparticles. The results showed that modification of nanohybrid particles by citric acid had a significant impact on the no sediment condition of them in distilled water in comparison with APTES and PEG 6000. All of the coated nanoparticles were superparamagnetic and citric acid, APTES and PEG had minimum effects on the magnetic properties of uncoated nanoparticles, respectively. Also, by adding only 0.1 wt% of MWCNT-Fe3O4 nanohybrid modified with citric acid, the solution temperature rises significantly. Therefore, after 180 s of microwave radiation, the water-based solution temperature would increase about 11° C more than the deionized water. Finally, it was found that, by using 400 W microwave radiation, the microfluidic oil recovery increased 24.9%, 30.3%, and 43.9% in comparison with water, Fe3O4 @ CA, and Fe3O4-MWCNT @ CA injection without microwave radiation, respectively.

Application of Multiplex Microfluidic Electrochemical Sensors in Monitoring Hematological Tumor Biomarkers.

Rapid yet accurate detection of disease-related biomarkers is key for point of care testing, where there is an increasing demand for multi-index analysis. Here, we present a versatile device for multianalyte quantification based on the microfluidic technique and electrochemical sensor array. The analytes were shunted through inner-built channels to screen-printed electrodes installed at different positions of the chip. These electrodes were modified with different nanomaterials and sensing agents to afford specific responses to the corresponding indicators. To prove the applicability of the platform for multifunction, we chose leukemia as the model disease and determined four relevant markers: methotrexate (MTX), lactate dehydrogenase (LDH), uric acid (UA), and urea. They are indicative as/for the therapeutic drug (MTX), prognosis (LDH), and side effect (UA and urea). The sensing chip exhibited low detection limits of 35 nM, 25 U/L, 450 nM, and 20 μM toward the four analytes, which are much lower than their minimum contents in human serum. Furthermore, practical application of the chip was demonstrated by simultaneous detection of the four analytes in the blood plasma of rabbit. By simply replacing the modification agents, the sensing platform is expected to serve the detection of a wide range of chem/biosubstances in various fields.

Preparation of nano-micron vanadium adsorbent for VO3− adsorption

With Miyi diatomite as the carrier and ferric nitrate as the modification agent, nano-micron vanadium adsorbent was prepared in the study. Then the adsorption properties of the prepared adsorbent were characterized by XRD, XRF, SEM, and ICP-OES analysis. The effects of adsorption time, initial pH value and initial vanadium concentration on VO3− adsorption performance were studied and the adsorption mechanism was discussed. The adsorption of VO3− on Miyi diatomite was significantly improved by the modification with ferric nitrate. The adsorption process of VO3− on nano-micron vanadium adsorbent was in accordance with Langmuir isothermal equation and quasi-second-order kinetic model. The saturated adsorption capacity was 43.38 mg/g. The adsorption capacity was higher in the weak acid environment and peaked at pH = 4.

In situ synthesizing silver nanoparticels by bio-derived gallic acid to enhance antimicrobial performance of PVDF membrane

Modifying membranes with nanoparticles is a promising approach to mitigate biofouling in membrane preparation processes. However, high costs of the modification agents limit the practical applications of this approach. In this work, we developed a cost-effective and ecofriendly method to provide polyvinylidene fluoride membrane with a strong antimicrobial activity by loading silver nanoparticles (AgNPs). In this approach, gallic acid (GA) was used as a capturing and reducing agent to in situ synthesize AgNPs on membrane surface. The resulting AgNPs-functionalized membrane exhibited a 3.5-fold higher pure water flux and enhanced antifouling capacity compared to the control membrane. Specifically, AgNPs endowed the membrane a compelling antimicrobial activity on both Gram-positive and Gram-negative bacteria, evidenced by diffusion inhibition zone and bacterial proliferation test results. More importantly, pomegranate peel extracts rich in GA was effectively used in such a membrane functionalization approach. Taken together, this work demonstrates the robust in situ fabrication of antimicrobial AgNPs-functionalized membranes through bio-derived GA and provides a promising alternative for their potential practical applications.

High thermal stability multilayered electrolyte complexes via layer-by-layer for long-life lithium-sulfur battery

In this work, polyacrylonitrile/sulfonated poly(ether ether ketone) (PAN/SPEEK) composite fiber membrane as separator for lithium-sulfur battery was first prepared by electrospinning. In order to reduce the shuttle effect, multilayered polyelectrolyte complexes (CS/CNTs)n as surface modification agents were prepared by alternating deposition of oppositely charged hydroxylated multi-walled carbon nanotubes (MWCNTs-COOH) and chitosan (CS) via the layer-by-layer method. The as-prepared fiber multilayered complex separator (FMCS) was finally treated by heating at 120 °C to form cross-linked network for better thermal stability. FMCS possessed much higher porosity than that of the commercial PP separator (44%). As expected, the assembled membranes remained intact even at 150 °C, while PP separator shrunk severely. Compared with PP, PAN/SPEEK/(CS/MWNTs-COOH)10 showed the discharge capacity of 956.9 mAh/g at 0.1 C and maintained 463 mAh/g after 100 cycles with the capacity retention rate of 48.4% which is higher than that of the commercial PP separator. Thus, this work can provide a simple method for modifying separator for long-life lithium-sulfur battery.

Efficacy of more intensive lipid-lowering therapy on cardiovascular diseases: a systematic review and meta-analysis

BackgroundCardiovascular disease is the leading cause of morbidity and mortality with incidence rates of 5–10 per 1000 person-years, according to primary prevention studies. To control hyperlipidemia—a major risk factor of cardiovascular disease—initiation of lipid-lowering therapy with therapeutic lifestyle modification or lipid-lowering agent is recommended. Few systematic reviews and meta-analyses are available on lipid-lowering therapy for the primary prevention of cardiovascular diseases. In addition, the operational definitions of intensive lipid-lowering therapies are heterogeneous. The aim of our study was to investigate whether intensive lipid-lowering therapies reduce greater cardiovascular disease risks in primary prevention settings.MethodsMEDLINE, EMBASE, and Cochrane Library databases were searched from inception to March 2019 for randomized controlled trials. We used random effects model for overall pooled risk ratio (RR) estimation with cardiovascular events of interest and all-cause mortality rate for the intensive lipid-lowering group using the standard lipid-lowering group as the reference. The Cochrane Risk of Bias Tool was used for quality assessment.ResultsA total of 18 randomized controlled trials were included. The risk reductions in cardiovascular outcomes and all-cause mortality associated with more intensive vs. standard lipid-lowering therapy across all trials were 24 and 10%, respectively (RR 0.76, 95% confidence interval 0.68–0.85; RR 0.90, 95% confidence interval 0.83–0.97); however, the risk reduction varied by baseline LDL-C level in the trial. A greater risk reduction was noted with higher LDL-C level. Intensive lipid-lowering for coronary heart disease protection was more pronounced in the non-diabetic populations than in the diabetic populations.ConclusionsMore intensive LDL-C lowering was associated with a greater reduction in risk of total and cardiovascular mortality in trials of patients with higher baseline LDL-C levels than less intensive LDL-C lowering. Intensive lipid-lowering was associated with a significant risk reduction of coronary heart disease and must be considered even in the non-diabetic populations.

Chemically Modified Electrodes in Electrochemical Drug Analysis

Electrode modification is a technique performed with different chemical and physical methods using various materials, such as polymers, nanomaterials and biological agents in order to enhance sensitivity, selectivity, stability and response of sensors. Modification provides the detection of small amounts of analyte in a complex media with very low limit of detection values. Electrochemical methods are well suited for drug analysis, and they are all-purpose techniques widely used in environmental studies, industrial fields, and pharmaceutical and biomedical analyses. In this review, chemically modified electrodes are discussed in terms of modification techniques and agents, and recent studies related to chemically modified electrodes in electrochemical drug analysis are summarized.

Corn derivative mesoporous carbon microspheres supported hydrophilic polydopamine for development of new membrane: Water treatment containing bovine serum albumin

A new mixed matrix membrane (MMM) was prepared by incorporating biological mesoporous carbon microspheres (mCMSs) from corn starch polysaccharide-supported hydrophilic polydopamine (PDA), as a mesoporous and large-surface area filler, selective modifier, and pore-forming agent, into polyvinylidene fluoride (PVDF) matrix in presence of polyethylene glycol (PEG) as a hydrophilic agent. The structural parameters of the prepared membranes were characterized via FE-SEM, BET/BJH, XRD, FT-IR, and AFM analyses, sorption experiments, water permeability assessments, porosimetry tests, flux recovery ratio (FRR) evaluations, and contact angle measurements, with the so-called central composite design (CCD) been successfully applied for optimization and investigation of the effects of the operational parameters. The results were then applied to treat double-distilled water containing bovine serum albumin (BSA) utilizing a cross-module set-up. Based on the findings, the content of the mCMS-PDA in the PVDF matrix significantly affected the contact angle, pure water flux (PWF), FRR, and BSA removal. In this respect, the PWF of the PVDF-PEG-mCMS-PDA increased from 10.25 to 27.78 L/m2 h with increasing the mCMS-PDA content, with the peak FRR (93.84%) of the PVDF-PEG-mCMS-PDA seen at maximum surface hydrophilicity of the membrane.