Improvement of corrosion resistance, antimicrobial activity, mechanical and chemical properties of epoxy coating by loading chitosan as a natural renewable resource

The efficient chitosan-polythiophene-graphene oxide bionanocomposite with enhanced antibacterial activity, dye adsorption ability, mechanical and thermal properties

Water pollution is the most serious environmental issues due to toxic impurity such as dye and pathogenic microorganisms. The main goal of the present study is to produce a novel ternary chitosan-polythiophene-graphene oxide (CS-PTh-GO) bionanocomposites using the intercalation of GO into CS through solution mixing process followed by the in-situ polymerization of thiophene for removal of dye and killing microorganisms from an aqueous solution. The fabricated CS-PTh-GOs were characteristically examined via FTIR, XRD, SEM, TEM, TGA, tensile analysis and subsequently applied for adsorption of cationic dyes such as methylene blue (MB) in the dark or under light and killing the growth of Gram-positive and Gram-negative microorganisms. The data revealed that presence of PTh-GO enhanced the surface roughness, tensile strength, thermal stability, adsorption characteristics and antibacterial activity. The CS-PTh-GO showed 97% dye removal of MB in 50 min. Ultimately, the CS-PTh-GO bionanocomposites analysis against the growth of Staphylococcus aureus, and Escherichia coli manifesting a minimum inhibitory concentration (MIC) of 5 µg/mL, respectively. Thus, the CS-PTh-GO bionanocomposite has the potential to use as an efficient adaptable antimicrobial and dye absorbent of organic dyes in industrial wastewater.

Titanate-polyurethane-chitosan ternary nanocomposite as an efficient coating for steel against corrosion

In this study, a titanate-polyurethane-chitosan ternary nanocomposite was prepared by physical mixing. Sodium titanate nanotubes (Na-TNTs) were prepared by the hydrothermal method, and chitosan was extracted from shrimp shell. Na-TNTs were mixed with polyurethane (PU) of different ratios by weight, and chitosan was added after optimization. All of the nanocomposite samples were characterized by field-emission scanning electron microscopy (FESEM), and the mechanical properties were investigated by abrasion, adhesion pull-off, impact resistance, and T-bending tests. The anticorrosion ability was tested by the salt spray method. The obtained results revealed that the binary composite of PU and 1.5% Na-TNTs exhibited remarkable anticorrosion activity among all the binary composites where the disbonded area 5% compared to blank PU 19% and adhesion 5.1 MPa compared to blank 3.5 MPa, while the ternary composite containing 4% chitosan exhibited the best anticorrosion activity where the disbonded area 2% and also exhibit better adhesion 7.9 MPa.

Gas barrier coating based on cellulose nanocrystals and its preservation effects on mango

Mango is the "king of tropical fruits" because of its attractive appearance, delicious taste, rich aroma, and high nutritional value. However, mango keeps fast metabolizing after harvest, leading to water loss, starch conversion into sugar, texture softening, and decay. Here, a gas barrier coating based on cellulose nanocrystals (CNCs) is proposed to control the post-harvest metabolism of mango. The results of gas barrier permeability show that CNCs enhance the barrier ability of the chitosan (CS) membrane on mango by 202 % and 63 % for oxygen and water vapor, respectively. The gas-barrier coating reduces the climb in pH and the decrease in firmness by 84.9 % and 45.8 %, respectively, decelerating the conversion process from starch to sugar. Besides, introducing clove essential oil (CEO), the CEO mainly adsorbs and crystalizes on the hydrophobic facets of CNCs, presenting high compatibility, increases the antibacterial rate to nearly 100 %. As a consequence, the preservation period of the mango coated by the CNC-based membrane is at least 7-day longer than the control group. Such a gas-barrier coating based on eco-friendly composites must have excellent potential in the preservation of mango, and even for other tropical fruits.

Simultaneous Enhancement of Flame Resistance and Antimicrobial Activity in Epoxy Nanocomposites Containing Phosphorus and Silver-Based Additives

The design and manufacture of innovative multifunctional materials possessing superior characteristics, quality and standards, rigorously required for future development of existing or emerging advanced technologies, is of great importance. These materials should have a very low degree of influence (or none) on the environmental and human health. Adjusting the properties of epoxy resins with organophosphorus compounds and silver-containing additives is key to the simultaneous improvement of the flame-resistant and antimicrobial properties of advanced epoxy-based materials. These environmentally friendly epoxy resin nanocomposites were manufactured using two additives, a reactive phosphorus-containing bisphenol derived from vanillin, namely, (4-(((4-hidroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)-2-methoxyphenyl) phenylphosphonate (BPH), designed as both cross-linking agent and a flame-retardant additive for epoxy resin; and additional silver-loaded zeolite L nanoparticles (Ze-Ag NPs) used as a doping additive to impart antimicrobial activity. The effect of BPH and Ze-Ag NPs content on the structural, morphological, thermal, flame resistance and antimicrobial characteristics of thermosetting epoxy nanocomposites was investigated. The structure and morphology of epoxy nanocomposites were investigated via FTIR spectroscopy and scanning electron microscopy (SEM). In general, the nanocomposites had a glassy and homogeneous morphology. The samples showed a single glass transition temperature in the range of 166-194 °C and an initiation decomposition temperature in the range of 332-399 °C. The introduction of Ze-Ag NPs in a concentration of 7-15 wt% provided antimicrobial activity to epoxy thermosets.

Biodegradable chitosan-graphene oxide as an affective green filler for improving of properties in epoxy nanocomposites

In this work, we investigated the effect of biodegradable Chitosan-encapsulated Graphene Oxide (CGO) on the morphology and properties of epoxy composites prepared using solution mixing with different filler loadings. The microstructures and properties of chitosan-GO and composites were studied using FTIR, XRD, SEM, TEM, tensile, impact, bending analysis, DMTA and TG tests. Microstructural observations confirmed that the CGO composition and its content in the matrix affected the distribution of fillers in the epoxy matrix. Mechanical and thermal tests indicated that the loading level of CGO and the ratio of chitosan to GO were the main factors that changed the strength of epoxy/CGOs composites. The tensile analysis confirmed that nanocomposites containing CGO exhibited a 65 % increase in elastic modulus due to the improved load transfer as a result of interfacial interactions between CGO and the matrix. DMTA analysis showed that the presence of CGO in the epoxy matrix increased T_g of the composite by ~30 °C. In the TGA test, although the introduction of CGO caused higher decomposition temperature of the CGO filled resins. CGO enhanced the final properties of epoxy-based nanocomposites as a result of the synergistic effect of chitosan and GO and the formation of 3-D CGO structures in the epoxy matrix.

Preparation and Characterization of Multilayer pH-Responsive Hydrogel Loaded Ganoderma lucidum Peptides

To develop a safe, targeted, and efficient assembly of a stable polypeptide delivery system, in this work, chitosan, sodium alginate, and sodium tripolyphosphate were used as materials for the preparation of hydrogels. M-SCT hydrogels were prepared by ionic gelation and the layer-by-layer (LBL) method. The composite hydrogels exhibited excellent pH sensitivity and Ganoderma lucidum peptides (GLP) loading capacity. The prepared hydrogels were characterized and evaluated. The internal three-dimensional network structure of the hydrogel was observed by scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy confirmed the electrostatic interactions among the components. X-ray diffraction (XRD) was used to observe the crystal structure of the hydrogel. The maximum peptide encapsulation efficiency was determined to be 81.73%. The digestion stability and thermal stability of M-SCT hydrogels loaded GLP were demonstrated to be improved. The amount of peptides released from the GLP/M-SCT-0.75 hydrogels in simulated gastric fluid was lower than 30%. In addition, the ABTS assays showed that the free radical scavenging ability of the GLP/M-SCT-0.75 hydrogels confirmed the efficacy of the hydrogels in retaining the antioxidant activity of GLP. The study suggested the M-SCT-0.75 hydrogels had a great deal of potential as a peptide carrier for oral delivery.

Current Downhole Corrosion Control Solutions and Trends in the Oil and Gas Industry: A Review

In the oil and gas industry, the presence of aggressive fluids and gases can cause serious corrosion problems. Multiple solutions have been introduced to the industry to minimize corrosion occurrence probability in recent years. They include cathodic protection, utilization of advanced metallic grades, injection of corrosion inhibitors, replacement of the metal parts with composite solutions, and deposition of protective coatings. This paper will review the advances and developments in the design of corrosion protection solutions. The publication highlights crucial challenges in the oil and gas industry to be solved upon the development of corrosion protection methods. According to the stated challenges, existing protective systems are summarized with emphasis on the features that are essential for oil and gas production. Qualification of corrosion protection performance based on international industrial standards will be depicted in detail for each type of corrosion protection system. Forthcoming challenges for the engineering of next-generation materials for corrosion mitigation are discussed to highlight the trends and forecasts of emerging technology development. We will also discuss the advances in nanomaterial and smart material development, enhanced ecological regulations, and applications of complex multifunctional solutions for corrosion mitigation which have become of great importance in recent decades.

Chitosan-bodipy macromolecular fluorescent probes prepared by click reactions for highly sensitive and selective recognition of 2,4-dinitrophenylhydrazine

Chitosan-based probes were prepared and they could identify 2,4-dinitrophenylhydrazine (DNH). CC bonds formed in a click reaction act as recognizing sites for DNH.

Cellulose nanofibril as a crosslinker to reinforce the sodium alginate/chitosan hydrogels

Hydrogels derived from natural polymers have received great attention, but their practical applications are severely hindered by the relatively poor mechanical properties. In this work, cellulose nanofibril (CNF) was used as a crosslinker to reinforce the sodium alginate (SA)/chitosan (CS) hydrogels for drug sustained release. The CNF was prepared via a combined process of ball milling and deep eutectic solvents (DESs) pretreatment and characterized using SEM, FT-IR, and XRD. Furthermore, the microstructure, mechanical/biological properties and swelling performance of SA/CS/CNF hydrogels were investigated. Results showed that 1.0 wt% CNF addition led to the increases of 23.6% in storage modulus and 54.4% in loss modulus for the SA/CS/CNF hydrogels, indicating that CNF addition was effective in reinforcing the three-dimensional entangled networks of the hydrogels. Moreover, the presence of CNF was found to weaken the swelling performance of SA/CS/CNF hydrogels. When the synthesized SA/CS/CNF hydrogel with 1.0 wt% CNF was applied as a carrier for drug release, 50.8% reduction in the release rate in simulated gastric juice was achieved, demonstrating its outstanding sustained release properties. This work suggested that CNF might be conducive to enhancing the properties of SA/CS hydrogels, which can serve as an ideal polymeric carrier for drug release.

Microwave Technology Using Low Energy Concentrated Beam for Processing of Solid Waste Materials from Rapana thomasiana Seashells

The solid waste of Rapana thomasiana seashells both from domestic activities and natural waste on seashore can be used to obtain viable products for medical applications. However, conventional technologies applied for sintering the materials require massive energy consumption due to the resistance heating. Microwave heating represents an advanced technology for sintering, but the stability of the process, in terms of thermal runaway and microwave plasma arc discharge, jeopardizes the quality of the sintered products. This paper aims to present the results of research focused on viable heating technology and the mechanical properties of the final products. A comparative analysis, in terms of energy efficiency vs. mechanical properties, has been performed for three different heating technologies: direct microwave heating, hybrid microwave heating and resistance heating. The results obtained concluded that the hybrid microwave heating led to final products from Rapana thomasiana solid waste with similar mechanical properties compared with resistance heating. In terms of energy efficiency, the hybrid microwave heating was 20 times better than resistance heating.

Improving the Antimicrobial and Mechanical Properties of Epoxy Resins via Nanomodification: An Overview

The main purpose of this work is to provide a comprehensive overview on the preparation of multifunctional epoxies, with improved antimicrobial activity and enhanced mechanical properties through nanomodification. In the first section, we focus on the approaches to achieve antimicrobial activity, as well as on the methods used to evaluate their efficacy against bacteria and fungi. Relevant application examples are also discussed, with particular reference to antifouling and anticorrosion coatings for marine environments, dental applications, antimicrobial fibers and fabrics, and others. Subsequently, we discuss the mechanical behaviors of nanomodified epoxies with improved antimicrobial properties, analyzing the typical damage mechanisms leading to the significant toughening effect of nanomodification. Some examples of mechanical properties of nanomodified polymers are provided. Eventually, the possibility of achieving, at the same time, antimicrobial and mechanical improvement capabilities by nanomodification with nanoclay is discussed, with reference to both nanomodified epoxies and glass/epoxy composite laminates. According to the literature, a nanomodified epoxy can successfully exhibit antibacterial properties, while increasing its fracture toughness, even though its tensile strength may decrease. As for laminates-obtaining antibacterial properties is not followed by improved interlaminar properties.

Imidazole-modified C6 -chitosan derivatives used to extract β-sitosterol from edible oil samples with a microwave-assisted solid phase extraction method

β-Sitosterol is a major bioactive constituent in plants with potent anticancer effects against many human cancer cells, but its bioavailability and therapeutic efficacy are limited by its poor solubility in water. In this study, C₆ -imidazole chitosan, C₆ -1-methylimidazole chitosan, C₆ -1-ethylimidazole chitosan, C₆ -1-vinylimidazole chitosan, C₆ -1-allylimidazole chitosan, and C₆ -1-butylimidazole chitosan were prepared to extract β-sitosterol from edible oil samples via ultrasonic-assisted solid liquid extraction. The structures and properties of the newly synthesized products were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and elemental analysis. The extraction abilities of the derivatives were tested in the experiment with high-performance liquid chromatography (limit of detection 0.21 μg/g and limit of quantification 0.67 μg/g), and the % relative standard deviation (<3.25%) and recovery values of the prepared chitosan derivatives toward β-sitosterol (average: 100.20%) were acceptable. The spiked interday and intraday recoveries of β-sitosterol were 102.60 ± 2.78 and 103.90 ± 3.04%, respectively. The actual amounts of β-sitosterol extracted from three real samples using C₆ -imidazole chitosan according to the solid phase extraction method were 3302.40, 901.70, and 2045.60 mg/kg for corn oil, olive oil, and pea oil, respectively.

Modified Epoxy with Chitosan Triazine Dihydrazide Derivatives for Mechanical and Corrosion Protection of Steel

Modification of the curing exothermic reaction of epoxy resin with polyamine (PA) hardeners by new chemically bonded fillers to improve the mechanical properties and anticorrosion performances of the epoxy coatings is the main goal for wide applications of epoxy coatings. In this work, the chemical structure of chitosan was modified with triazine hydrazide moiety that contains primary, secondary, and tertiary amine groups to act as activator and dangling chain linkers during the curing of epoxy/PA system. Different molecular masses of chitosan were modified with triazine dihydrazide moiety (Ch-TH2), and their chemical structures and surface morphologies were identified. Their thermal stabilities were investigated, and the grafting percentages with triazine hydrazide were determined from thermal analysis. Different weight percentages of Ch-TH2 ranged from 1 to 10 Wt. % were added to the epoxy/PA system, and their curing characteristics, such as heat enthalpy and glass transition temperature, were determined from non-isothermal dynamic scanning calorimetric thermograms. The effects of molecular masses, triazine dihydrazide %, and Ch-TH2 Wt. % on the mechanical, adhesion and anticorrosive properties of the cured epoxy/PA coatings for steel were investigated. The optimum Ch-TH2 Wt. % was selected from 3 to 6 Wt. % to improve the mechanical, adhesion, and anticorrosive properties of the cured epoxy/PA coatings.

Antibacterial epoxy composites with addition of natural Artemisia annua waste

Antibacterial epoxy resins (EP) have great potential in medical and electronic fields. During the process of extracting artemisinin from Artemisia annua, artemisia naphtha (AN) is generated as waste. The components of AN show antibacterial activity, and hence, it is introduced as a novel antibacterial agent in the epoxy matrix. In this study, the properties of epoxy resins with various AN loading were investigated. The results showed that AN/EP composites presented strong antibacterial activity against Escherichia coli and Staphylococcus aureus at the sterilization ratio of 100% against E. coli and 99.96% against S. aureus, respectively. Meanwhile, the thermal properties (curing temperature and glass transition temperature) of AN/EP composites remained well, and the mechanical property was even improved. Especially, the flexural strength of AN/EP composites could be reinforced by 62.9% when the content of AN was up to 5 wt%. For comparison, Artemisia annua powder (AAP), which was directly smashed from natural A. annua, was also mixed with epoxy resins as an antibacterial agent and showed excellent antibacterial property. Therefore, antibacterial epoxy composites containing A. annua waste as a natural resource with the enhanced mechanical property may have enormous potential in future biological and healthcare fields.