Number Of Epoxy Groups Research Articles

Study of Surface Chemistry, Temperature and Strain Rate on the Tensile Properties of Monolayer Graphene Oxide

The mechanical properties of graphene oxide (GO) during tensile fracture were studied using molecular dynamics methods, and the influence of hydroxyl and epoxy groups on the mechanical properties of GO was explored. In addition, the changes in mechanical properties of GO under different temperatures and strain rates were studied to gain a deeper understanding of its mechanical behavior. The results indicate that hydroxyl and epoxy groups have a significant influence on the elastic modulus, ultimate stress, and ultimate strain of GO. The presence of hydroxyl and epoxy groups can alter the molecular structure of GO, thereby affecting its ultimate stress and strain. When the number of hydroxyl groups is 16 and the number of epoxy groups is 20, the ultimate stress decreases by about 31% and the elastic modulus decreases by about 20%. The variation of elastic modulus, ultimate stress, and ultimate strain of GO with temperature was studied at three temperatures: 300[Formula: see text]K, 500[Formula: see text]K, and 800[Formula: see text]K. As the temperature increases, the amplitude of atomic vibration increases and internal defects and cracks in GO continue to form and expand. At the same time, its coefficient of thermal expansion also increases, causing deformation and loosening of the crystal structure, resulting in a decrease of about 10% in the ultimate stress of GO, and a slight decrease in the ultimate strain and elastic modulus. Finally, the influence of different strain rates on the mechanical properties of GO was studied. As the strain rate increases, the intermolecular interactions within GO are rapidly altered, and the previously loose structure gradually becomes tightly ordered, resulting in an increasing trend in the elastic modulus, ultimate stress, and ultimate strain of GO.

Multifunctional Block Copolymers, Acting as Recycling Aids, by Atom Transfer Radical Polymerization.

Block copolymers utilizing oligomeric poly(pentylene-co-hexylene carbonate)diol modified with 2,4-diisocyanatotoluene and further with 2-bromo-N-(3-hydroxypropyl)-2-methylpropanamide were synthesized and utilized as Activators ReGenerated by Electron Transfer Atom Transfer Radical Polymerization macroinitiators to obtain a first generation of multifunctional recycling additives with poly(glycidyl methacrylate-co-butyl methacrylate-co-methyl methacrylate) side chains, which could act as chain extenders. Then, chosen additive was reacted with a radical scavenger, 3,5-ditertbutyl-4-hydroxybenzoic acid (DHBA), to obtain a second generation of reactive additives. Those copolymers had different numbers of epoxy groups per polymer chain, and different number of epoxides opened with DHBA, hence showed a range of properties, and were utilized as reactive modifiers for polylactide (PLA) extrusion melting. The first-generation modifiers caused an increase in PLA's blends relative melt viscosity, stabilized material properties, and enhanced impact strength, while the second-generation modifiers with more than 8 % of epoxide ring opened showed worse properties. However, they managed to suppress the UV degradation of PLA blend plates.

SYNTHESIS AND STUDY OF THE PROPERTIES OF EPOXYCYCLOCARBONATES BASED ON ACRYLATE-VINYL COPOLYMERS

A method of synthesis of acrylate-vinyl copolymers based on glycidyl methacrylate and styrene at different molar ratios and epoxy cyclocarbonates based on them was developed. Synthesis of styrene-glycidyl methacrylate (СP GMA/St) copolymers was carried out by the method of thermally initiated radical polymerization in steel reactors in the presence of 1% azo-bis-isobutyronitrile initiator at a temperature of 65 °C for 10 hours. The number of epoxy groups in the synthesized СP GMA/St, determined by the potentiometric titration method, naturally decreases with a decrease in the molar ratio of GMA/styrene. The synthesis of СP GMA/St epoxycyclocarbonates was carried out in a high-pressure autoclave by passing CO2 through the reaction mixture of a solution of KP in toluene with a catalyst (tetrabutylammonium bromide 5%) with stirring at a temperature of 110–120 °C, a pressure of (4-5) atm. The structure of СP and ECC was confirmed by IR spectroscopy. No bands of double bonds are observed in the IR spectra of СP GMA/St, there are vibration bands characteristic of oligostyrene and vibration bands of C=O, C–O–C and epoxy groups. During the formation of ECC, new vibration bands of cyclocarbonate groups with a maximum of 1802 cm-1 appear, changes are observed in the absorption region of C–O–C groups (1100–1300) cm-1, and the vibration bands of epoxy groups with a maximum of 843 cm-1 decrease. The study of relaxation transitions in acrylate-vinyl copolymers GMA/St and epoxy cyclocarbonates based on them using the DSC method showed that all samples are amorphous single-phase polymers. After changing the background, the excessive enthalpy observed during the first heating disappears, and the glass transition temperature shifts towards higher temperatures, which indicates the formation of a denser and thermodynamically balanced structure. The thermostability of the synthesized GMA/St copolymers and epoxy cyclocarbons was investigated by the method of thermogravimetry. It was established that all the obtained substances have one stage of weight loss and are heat resistant, since weight loss begins at a temperature above 240 °C. In the future, the obtained epoxycyclocarbonates will be used for the synthesis of polyurethanes by the non-isocyanate method.

Plasticizing and thermal stabilizing effect of bio‐based epoxidized cardanol esters on PVC

AbstractPoly(vinyl chloride) (PVC) is a widely used plastics in different industries. It is an intrinsically hard and brittle polymer and requires the use of plasticizers to improve the processability. Commonly used phthalate‐based plasticizers have serious toxicity issues and we present alternatives based on epoxidized soybean oil (ESO) and epoxidized cardanol esters (ECEs). ECEs are synthesized from cardanol and three fatty acids (oleic, ricinoleic, and myristic) using 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC) as a coupling agent. Their structure and purity are confirmed by Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance. Moreover, plasticized PVC films are prepared using a solvent‐free method. The replacement of 10 phr of ESO with 5 phr of ECE improves the plasticizing power due to the co‐solvency effect. Mechanical properties and thermal stability of plasticized PVC films are correlated with the chain length and the number of epoxy groups in ECE. The best plasticizing effect is observed for epoxidized cardanol‐myristate (ECD‐MA). ECD‐MA as a shorter‐chain secondary plasticizer is more compatible with ESO and allows higher conformational mobility of PVC chains. PVC/30ESO/5ECD‐MA polymer exhibits an exceptionally high initial thermal decomposition temperature (314.4°C) while preserving moderate ductility and tensile strength (263.4% and 23.3 MPa). Overall, this study highlights the potential applicability of ECD‐MA in combination with ESO as a sustainable, bio‐based plasticizer and heat stabilizer for flexible PVC products.

Recycled Poly(Ethylene Terephthalate) from Waste Textiles with Improved Thermal and Rheological Properties by Chain Extension.

Annual production of textile fibers is continuing to rise and the substantial discharge of undegradable waste polyester fibers can cause serious environmental and even health problems. Thus, the recycling and reuse of recycled poly(ethylene terephthalate) from waste textiles (rPET-F) is highly desirable but still challenging. Here, five chain extenders with a different number of epoxy groups per molecules were used to blend with discarded PET fibers and improve its viscosity and quality loss in the recycling process. The molecule weight, thermal properties, rheological properties and macromolecular architecture of modified r-PET were investigated. It was found that all modified rPET-F samples show higher viscosities and better thermal properties. rPET-F modified by difunctional EXOP molecules show linear structure and improved rheological properties. rPET-F modified by polyfunctional commercial ADR and synthesized copolymers exhibit a long chain branched structure and better crystallization. This study reveals a deeper understanding of the chain extension and opens an avenue for the recycling of PET textiles.

СОСТАВ И НЕКОТОРЫЕ СВОЙСТВА ЭПОКСИДНЫХ ОЛИГОМЕРОВ НА ОСНОВЕ ГЕКСАХЛОРЦИКЛОТРИФОСФАЗЕНА И ДИФЕНИЛОЛПРОПАНА

Phosphazene-containing oligomers (FEO) were synthesized by the one-pot method by reacting hexachlorocyclotriphosphazene, diphenylolpropane, and epichlorohydrin at 80 °C in the presence of solid KOH. In contrast to analogous oligomers previously obtained at a lower temperature, according to MALDI-TOF spectrometry data, they contain about 10% of compounds with two or three phosphazene rings linked by one or two oxyaryleneoxy radicals, while the total number of epoxy groups in the molecules of these compounds is from 4 to 8. FEO are cured with polyamine hardeners to form compositions with increased fire resistance, retaining at the same time the basic properties of conventional epoxy materials.

Electronic Properties of Oxidized Graphene: Effects of Strain and an Electric Field on Flat Bands and the Energy Gap.

A multiscale modeling and simulation approach, including first-principles calculations, ab initio molecular dynamics simulations, and a tight binding approach, is employed to study band flattening of the electronic band structure of oxidized monolayer graphene. The width of flat bands can be tuned by strain, the external electric field, and the density of functional groups and their distribution. A transition to a conducting state is found for monolayer graphene with impurities when it is subjected to an electric field of ∼1.0 V/Å. Several parallel impurity-induced flat bands appear in the low-energy spectrum of monolayer graphene when the number of epoxy groups is changed. The width of the flat band decreases with an increase in tensile strain but is independent of the electric field strength. Here an alternative and easy route for obtaining band flattening in thermodynamically stable functionalized monolayer graphene is introduced. Our work discloses a new avenue for research on band flattening in monolayer graphene.

Polybutadiene Vitrimers with Tunable Epoxy Ratios: Preparation and Properties.

Traditional crosslinked diene rubber has excellent thermal–mechanical properties and solvent resistance, yet it is incapable of being recycled via universal molding or injecting. Vitrimers, a new class of covalently crosslinked polymer networks, can be topologically rearranged with the associative exchange mechanism, endowing them with thermoplasticity. Introducing the concept of vitrimers into crosslinked networks for the recycling of rubbers is currently an attractive research topic. However, designing tailored rubber vitrimers still remains a challenge. Herein, polybutadiene (PB) vitrimers with different structures were prepared via partial epoxidation of double bonds and ring-opening esterification reactions. Their mechanical and relaxation properties were investigated. It was found that the increasing crosslinking density can increase tensile strength and activation energy for altering the network topology. The influence of side-group effects on their relaxation properties shows that an increase in the number of epoxy groups on the polybutadiene chain can increase the chance of an effective exchange of disulfide units. This work provides a simple network design which can tune vitrimer properties via altering the crosslinking density and side-group effects.

Aqueous dispersions of epoxy oligomers: Stability and rheological properties

In this study, the stability of the aqueous dispersions of epoxy oligomers was investigated. The following epoxy oligomers with various numbers of epoxy groups were used for the characterization: NPEL 127, NPEL 128, NPEL 134, NPPN 631, EPOXY 520 and DEG-1. A non-ionic surfactant Emulsogen LCN-287 based on alkyl polyethylene glycol ether was used as an emulsifier. The dispersions of epoxy resins were fabricated by changing the content of a non-ionic surfactant (emulsifier) in a range from 2 to 6 wt.%. It was demonstrated that the stability of aqueous emulsions depends not only on the type of resin, but also on the content of the oil phase and the concentration of the emulsifier. The rheological properties of the aqueous dispersions of epoxy oligomers were investigated as well.

Synthesis and Thermal Decomposition Kinetics of Epoxy Poly Glycidyl Nitrate as an Energetic Binder

An energetic binder epoxy poly glycidyl nitrate (e-PGN) with a molecular weight of about 1244 gr/mol was synthesised via end modified poly glycidyl nitrate (PGN) is presented in the paper. This structure was characterised by the number of epoxy groups, infrared spectroscopy, and nuclear magnetic resonance. The thermal degradation behavior of e-PGN was studied by thermo gravimetric analysis (TG) and differential scanning calorimetry (DSC) under nitrogen atmosphere at different heating rates. The glass transition temperature (Tg) was measured to determine the compatibility of energetic plasticizer with the binder in the mixture of plasticizer/binder and compared with the results of e-PGN, and initial decomposition temperature in e-PGN was studied using the DSC method. The DSC results showed that the glass transition temperature of a mixture of 20 % Bu-NENA/e-PGN mixture (Tg = −56 °C) was lower than e-PGN (Tg = −37.78 °C) that shows the most compatible plasticizer is Bu-NENA. The activation energy of degradation e-PGN and e-PGN-20% Bu-NENA were calculated with DSC by the model-free methods and compared with the results of AKTS software in version 3.51(2013-07-10). The activation energy of exothermic decomposition of the e-PGN and e-PGN-20% Bu-NENA were calculated by the Kissinger, Flynn–Wall–Ozawa, Starink, and AAdvanced kinetics and technology solutions (Friedman) methods. Finally, the half-life prediction of the e-PGN and e-PGN-20% Bu-NENA were investigated.

The Potential Use of Epoxy‐POSS as a Reactive Hybrid Compatibilizers for PLA/PBAT Blends: “Effect of PBAT Molecular Weight and POSS Type”

This article focuses on the effect of molecular weight of poly(butylene adipate‐co‐terephthalate) (PBAT) on the immiscible poly(lactic acid) (PLA)/PBAT blends compatibilized with epoxidized polyhedral oligomeric silsesquioxanes (Epoxy‐POSSs) having different numbers of epoxy groups per molecule. Mechanical, thermomechanical, thermal, rheological, and morphological properties of the blends were investigated as a function of PBAT molecular weight and epoxy‐POSS type. Mechanical tests revealed that all epoxy‐POSS types significantly improved the performance of the blends containing low‐molecular‐weight PBAT. On the other hand, epoxy‐POSS with three epoxy functional groups (TriEpPOSS) and Epoxy‐POSS with multiple‐epoxy functional groups (MuEpPOSS) only slightly improved the performance of blends with high‐molecular‐weight PBAT. Thermomechanical and thermal test results supported that the compatibilization effects of the epoxy‐POSSs were more prominent in the PLA/PBAT blends with low‐molecular‐weight PBAT due to the observation of the shifts in the glass transition temperatures of the PLA phase. According to the rheological results, the addition of epoxy‐POSSs increased the interactions between the PLA and PBAT phases much more effectively in the PLA/PBAT with low‐molecular‐weight PBAT. The dispersed phase size of the PBAT further decreased in the low‐molecular‐weight PLA/PBAT blend system due to the enhanced compatibility much better. POLYM. ENG. SCI., 60: 398–413, 2019. © 2019 Society of Plastics Engineers

Epoxy oligomers modified with epoxyphosphazenes

Phosphazene-containing epoxy oligomers are obtained through a one-stage method via the interaction of hexachlorocyclotriphosphazene with an excess of diphenylolpropane in the medium of epichlorohydrin in the presence of a solid alkali. With the use of 31Р NMR and MALDI mass spectrometry, it is shown that the main components of the phosphazene fraction are penta- and tetra-aryloxysubstituted cyclotriphosphazene compounds with the corresponding numbers of epoxy groups. The maximum content of the phosphazene fraction in phosphazene-containing epoxy oligomers (~40 wt %) is attained at a hexachlorocyclotriphosphazene-to-diphenylolpropane molar ratio of 1: 8. Phosphazene-containing epoxy oligomers cured with isomethyltetrahydrophthalic anhydride have oxygen indexes of 26–28 and are self-extinguishing.

Microencapsulation of 1-methylimidazole using solid epoxy resin: study on microcapsule residence time and properties of the system

In this study for the first time 1-methylimidazole was microencapsulated successfully by solid epoxy resin using solvent evaporation method. Fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric and differential scanning calorimetry were used for characterization of microcapsule and epoxy resin/microcapsule systems. The results revealed that although the solid epoxy shell was in contact with imidazole curing agent for a long time, it still remained as a thermoplastic. The chain length of the solid epoxy resin was grown in anionic polymerization process which led to an increase in the melting temperature from 64 to 78 °C. On the other hand, all epoxy functional groups of the shell did not participate in the curing reaction of resin with core curing agent of the microcapsule. The results showed that by increasing the residence time of the microcapsules, the number of epoxy groups of liquid epoxy decreased slightly but the rate of complex viscosity increase or the rate of curing reaction was increased and the cured epoxy system exhibited a single-phase morphology. On the other hand, in the presence of microcapsules the curing reaction of epoxy resin was successfully carried out and the curing temperature and the onset of viscosity increase or gel time at 120 °C were not more or less affected by sufficiently long contact time of epoxy and microcapsule.

An efficient method for the immobilization of inulinase using new types of polymers containing epoxy groups.

New glycidyl methacrylate copolymers containing different numbers of epoxy groups were synthesized and used to develop effective procedures for inulinase immobilization. The beneficial characteristics of the carriers included a high degree of crosslinking, stability at ambient temperature, an appropriate surface, and the presence of reactive epoxy groups. Some factors affecting the efficiency of immobilization of crude inulinase, including the kind and amount of carrier, the number of epoxy groups, as well as buffer pH and buffer concentration were examined. The yield of immobilization of this enzyme on the investigated type of microspheres was higher than on the commercial carrier, Eupergit® C. After immobilization, the optimum temperature for inulinase activity shifted from 55 to 45 °C, whereas the optimum pH = 5 remained unchanged. The basic parameters of inulin hydrolysis were examined, and the possibility of applying the obtained biocatalyst in continuous conditions was tested. Inulin at a concentration of 0.5 % (w/v) was almost completely hydrolyzed to fructose (in a yield of 98 %) at a flow rate of 0.1 mL/min. A tenfold increase in the speed of flow resulted in an increase in the yield of oligosaccharides (DP2-DP6) up to ~41 % in the overall hydrolysate, as analysed by HPLC-RID and LC-ESI/MS. These results indicate that two forms of inulinase, an exo- and an endo-acting enzyme, were immobilized on our carrier. The enzyme showed good operational stability in a packed column over 28 days. There were no significant decreases in the efficiency of continuous hydrolysis during this time (about 17.4 % in comparison to its initial value).

Elastic polyesters improved by ATRP as reactive epoxy-modifiers of PLA

Block copolymers comprising poly(1,4-butylene adipate) or poly(1,4-butylene adipate-co-terephthalate) middle elastic segment and poly(glycidyl methacrylate-co-n-butyl methacrylate) side chains were obtained using the ARGET ATRP method. These copolymers were characterized by various average molar masses, compositions, numbers of epoxy groups per chain and epoxy equivalent weights and were utilized as reactive modifiers of polylactide (PLA) in extrusion type melt processing at 175 or 190 °C. Contrary to neat PLA processing, when modifiers of lower molar masses were applied then an increase in relative melt viscosity was observed in systems throughout the test run due to reactions of PLA-COOH with epoxy side groups in modifiers. The high molar mass modifiers were not as effective in compensation of the PLA degradation effect. Tensile strength properties of all the obtained compositions extruded in the form of thin strands were measured. Most of the obtained modifiers were able to enhance PLA in elasticity or/and strength. An aliphatic modifier acted as a reactive-internal plasticizer, therefore just slightly worsened the tensile strength but improved the elastic modulus and boosted elongation at break (it was up to 120 times higher than that of PLA). Although aliphatic-aromatic modifiers did not change elongation at break significantly, one of them reinforced and elasticized the PLA based system at once.

Effect of the surface parameters on the interaction of epoxy polymer supports with a lipase enzyme

Four porous polymeric supports prepared from epoxy monomers have been analyzed with respect to their catalytic behavior and characterized by means of infrared spectroscopy (FTIR-ATR), nitrogen adsorption and Inverse Gas Chromatography at Infinite Dilution (IGC-ID). The Pseudomonas stutzeri lipase has been used to determine the adsorption and desorption rates on each support. It has been found that the specific surface area increases with the number of epoxy groups and the pore volume increases as well. The surface energies are also related with the number of epoxy groups in the monomer and show a decrease in the dispersive component of the surface energy, γ S d , from 104.87 to 71.12 mJ m−2, but an increase in the polar or acid–base characteristics. Regarding the adsorption–desorption rates of the enzyme lipase, it occurs in two stages being the short-time processes controlled by the dispersive surface energy of the polymer, but the desorption rate is opposite to the base-to-acid surface energy ratio of the polymer indicating that for long-time processes the enzyme is attached to the polymer surface mainly by acid–base interactions.

Investigation of moisture diffusion in cross-linked epoxy moulding compound by molecular dynamics simulation

Molecular dynamics (MD) simulation was carried out to study the moisture diffusion in cross-linked epoxy resin, with the influence of temperature, water concentration and polymer conversion taken into account. The simulation results showed that the moisture diffusion coefficients increased with the increase in temperature. And generally, with the increased moisture concentration or decreased polymer conversion, the moisture diffusion coefficients reduced. However, the moisture diffusion was strongly inhibited when the number of epoxy groups in completely reacted epoxy resins was equal to the number of water molecules.

Microporous hydrogels of cellulose ether cross-linked with di- or polyfunctional glycidyl ether made for the delivery of bioactive substances

Hydrogels were prepared by the cross-linking reactions of carboxymethyl cellulose with di- or polyfunctional glycidyl ether to investigate the effects of different cross-linker’s chain length and the number of epoxy groups on the properties of the gels. Fourier transform infrared spectra showed a new peak at ν = 1,740 cm−1 assigned to the absorption of carbonyl groups in the new ester structure formed by the cross-linking of –COONa with the epoxy compounds. The interior morphology data indicated microporous network structures which correlated with the swelling of hydrogels. The swelling data in water, urea, sucrose, urine and aspartame showed increases in swelling with an increase in chain length of the cross-linker but decreased with the number of epoxy groups on the cross-linker. Collectively, the gels were ionic strength sensitive. The rheology experiments showed that gel point (tgel) increased with the chain length of the cross-linker but reduced with increase in number of epoxy groups on the cross-linker. Dynamic oscillatory measurements indicated stronger material functions in gels prepared with polyfunctional epoxy cross-linkers. The hydrogels prepared with difunctional epoxy groups had higher loading capacity and faster release of bovine serum albumin compared with hydrogels based on polyfunctional epoxy group cross-linkers.

Phase separation in epoxy resin‐reactive dendritic hyperbranched polymer blends

AbstractEquilibrium phase diagrams in composition‐conversion space have been calculated for stoichiometric blends of an epoxy resin with a diamine hardener and dendritic hyperbranched polymers, to which various numbers of epoxy groups have been grafted. An attempt has been made to incorporate both the effects of the polydispersity of the resin and the reactivity of the functionalized hyperbranched polymers for any given value of the interaction parameter. However, if the reactivities of all the epoxy groups are comparable, the presence of a highly functionalized modifier is expected to lead to a reduction of the gel point conversion and a narrowing of the composition‐conversion window available for cure induced phase separation. The experimental cloud point data are consistent with the model, although they sugget that the functionalized hyperbranched polymers may be significantly less reactive than the resin. Moreover, in the present system, the influence of functionalization on the phase behavior is also strongly linked to the accompanying changes in the interaction parameter.

Core-shell particles to toughen epoxy resins. I. Preparation and characterization of core-shell particles

A two-stage, multistep soapless emulsion polymerization was employed to prepare various sizes of reactive core–shell particles (CSPs) with butyl acrylate (BA) as the core and methyl methacrylate (MMA) copolymerizing with various concentrations of glycidyl methacrylate (GMA) as the shell. Ethylene glycol dimethacrylate (EGDMA) was used to crosslink either the core or shell. The number of epoxy groups in a particle of the prepared CSP measured by chemical titration was close to the calculated value based on the assumption that the added GMA participated in the entire polymerization unless it was higher than 29 mol %. Similar results were also found for their solid-state 13C-NMR spectroscopy. The MMA/GMA copolymerized and EGDMA-crosslinked shell of the CSP had a maximum glass transition temperature (Tg) of 140°C, which was decreased with the content of GMA at a rate of −1°C/mol %. However, the shell without crosslinking had a maximum Tg of 127°C, which decreased at a rate of −0.83°C/mol %. The Tg of the interphasial region between the core and shell was 65°C, which was invariant with the design variables. The Tg of the BA core was −43°C, but it could be increased to −35°C by crosslinking with EGDMA. The Tg values of the core and shell were also invariant with the size of the CSP. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2069–2078, 1998