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4CHEMICAL SCIENCES
WAYS TO REGULATE THE PROPERTIES OF THE EPOXY OLIGOMER
Musayeva A. Yu.
Associate Professor of the Department of "Technology Organic Substances and High-Molecular Compounds ",
PhD in Chemistry, Azerbaijan State University Oil and industry
Azerbaijan, Baku
Abstract
The most effective way to regulate the properties of epoxide oligomer is their modification. For this purpose, finding wide-ranging modifiers is one of the actual problems. Investigating specific properties of modifying additives and their purposeful use can lead to high technology, physico-mechanical and optical properties. It is also important to find modifiable additions easily. In the study of epoxide oligomer modification, amide-containing compound was used. As a result of the modification, epoxide oligomer with high physical and mechanical properties has been obtained.
Keywords: acetamide, modification, physical-mechanical properties, butadieneacrylnitrile rubber, starch, composition
This research demonstrates, epoxy resin modified with carbonyl-terminated butadiene acrylonitrile cCo-polymer liquid rubber.
One of the successful methods used to toughen EPs is the incorporation of the rubber phase into the brittle epoxy matrix, which may be achieved by the use of reactive liquid rubber or preformed rubber particles [1]. The rubbers are initially miscible with the epoxy, but during the polymerization the rubber, phase separates due to slightly immiscibility with the matrix. At the proper concentration of rubber, the dispersed rubber phase can improve the toughness without a significant decrease in other properties of the epoxies [2]. The improvement in the toughness mechanisms: crazing, shear banding, and elastic deformation of the rubber particles. These mechanisms can act either alone or together to produce the toughening effect [3-5].
An attempt to toughen the EP using a polyurethane (PU) prepolymer as a modifier via an interpenetrating network (IPN) grafting has been reported by HARANI et al [6]. For this purpose, a PU prepolymer has been synthesized based on hydroxyl-terminated polyester resins and used as a modifier for the EP at different concentrations. Ratna and Banthia showed that carboxyl terminated poly (2-ethylhexylacrylate) liquid rubber can be used as an impact modifier for the EP cured with an ambient temperature hardener [7]. However, carboxyl terminated oligomers can only be synthesized by bulk polymerization, which is difficult to control. QIan et al. studied the synthesis and application of core-shell rubber particles as toughening agents for epoxies [8]. The effect of the epoxidised natural rubber, ENR (50 mole %) on the curing behaviors and adhesive strengths of an epoxy (DGEB-A) and dicyandiamide/2-methyl imidazole system was studied by Hong and Chan [9]. Many works in toughening of the EP have been reported. The following information shows the result of experiment related to compatibility between CTBN and the EP, and to investigate the thermal, mechanical, and morphological properties of the modified Ep.
CTBN is qualified for the toughening of the EPs because it has good reactivity and acceptable compatibility with the EP matrix, which is supported by the reduction in the glass transition temperature of the EP with increasing rubber content. The tensile energy and tensile strain at the break was clearly improved with CTBN additives without significant sacrifices in other tensile and flexural properties of the modified EP.SEM analysis indicated that the dispersed rubber particles act as stress concentrators during the fracture and this might explain the observed increase in the fracture toughness of the modified EP compared to be unmodified EP. The toughening effect becomes more apparent at high testing speeds.
In this study, the technological properties of modified epoxy composites have been studied. One of the main tasks in the choice of compositions of polymeric materials is to improve the plastic viscous properties of polymer binders by various modification methods. This problem is even more important for epoxy composites with a higher degree of filling, since the epoxy resin is a low Newtonian liquid with a dynamic viscosity value of 12-25% with a temperature of 200 ° C. The dynamic viscosity of a binder with a high degree of filling creates certain difficulties in the preparation and formation of mixtures. An attempt was made to modify the epoxy resin with silica-organic KO-922. The resulting heat-resistant varnish is used for thermal insulation of connecting wires in high-temperature environments [10,11].
Analysis of experimental data showed that KO-922 renders plasticizing effect upon polymer composite material. The dependencies are clearly pronounced. The decrease in the dynamic viscosity of the formulations at maximum concentration of the additive ranges from 48 to 61 %. Epoxy polymers have a static coil-shaped conformation with a strong intertwining of chains at the molecular level. When a small amount of KO-922 is added to the resin, the frictional forces between congregations and certain molecules of the epoxy oligomer are decreased, which in turn leads to a
sharp decrease in dynamic viscosity. With a further increase in concentration of KO-922, aggregates are formed from epoxy oligomers and additives. At the same time, the plasticity of the epoxy resin slows down. Further increase in the concentration of additive content in the binder leads to viscosity of the system. It should be noted that, given the equality of the degree of filling for all compositions ( in this case ration is equal to Polymer/Filler =1/10),the specific surface of the filler has a determining effect on the mobility of the mixture, which is: FFCI-4.39 m2/kg, for FWCI-10.31 m2/kg for serpentinite-7.62 m2/kg).
> The workability of mixtures and forming of products based on a modified polymer binder is facilitated using plasticizers in the form of silica-organic fluids.
> The nature of the dependence of dynamic viscosity of mixtures on the concentration of the silica-organic plasticizer is established. The optimum content determined in the range of 2.5 to 3 % by mass.
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> The optimum values of the content of the silica-organic plasticizer are determined, at which the wetting of the filler by the binder has the greatest impact on the technological properties of the material. The most effective concentration is the content of the plas-ticizer in the range of 0.1-3 % by mass.
Numerous studies have been carried out in our department to improve the properties of the epoxide oli-gomer [12, 13].
The modification of the epoxide oligomer was used in the study of the amide-containing compound. As a result of the modification, epoxide oligomer with high physical and mechanical properties has been obtained.
Infrared spectra of the modified epoxidian oligomer are plotted. Figure 1 shows the spectrum of the unmodified epoxide oligomer, and Figure 2 shows the modified epoxide oligomer.
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Fig.1. Infrared spectrum of epoxy oligomer
It is clear from this spectrum that the strips characteristic of amide-containing compounds in the range of 3500 to 3200 cm-1 will almost disappear. This is caused by a chemical reaction between epoxide
oligomerization and the resulting epoxide amide derivative. This is clearly visible in the range 31002800 cm-1 .
Fig. 2. Infrared spectrum of modified epoxy oligomer
Thus, the investigation of the infrared spectrum of the epoxide oligomer with the amide-containing compound enables the identification of the nature of the interaction between the components, which functional groups participate in these reactions.
It has been determined that, due to the combination of amide-containing compound and epoxy oligomer, the characteristic strips belonging to the imine group disappear. The construction of the modified modifier compound into the oligomer is accompanied by the formation of C-N communication.
Conventional epoxy resin (DGEBA), in varying proportion, was used to modify epoxidized soybean oil
(ESO) based systems, crosslinked by phthalic anhydride. The properties of DGEBA modified ESO systems were investigated by dynamic mechanical analysis, impact testing, tensile and flexural testing, scanning electron microscopy, and thermogravimetric analysis [14].
In this study, bio-based compositions were prepared by ESO and diglycidylether of bisphenol-A (DGEBA). The modified system shows the properties corresponding to the amount of modifier (DGEBA). At lower concentration of modifier, properties characteristic to ESO, which is soft and flexible with higher impact property, were obtained. At higher concentration of
modifier, system obey property characteristic to DGEBA, which is inherently brittle [15].
in another practice a novel biobased resin-epox-idized soybean oil modified cyanate ester.
Cyanate ester (CE) resin was modified with renewable resource, i.e. epoxidized soybean oil (ESO), and the effects of ESO content on the curing co-reaction, morphologies, water absorption behaviors, thermal and mechanical properties of CE/ESO blends were studied. Differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA) were employed to characterize the ESO-modi- fied CE polymer networks. Homogeneous structures were observed for low-content of ESO modified CE systems by SEM, while ESO-rich particles were observed in the modified systems with ESO above 15 wt. %. The blend of the CE and ESO resulted in an excellent combination as a new biobased thermoset material having relatively high mechanical properties with 15 and 20 wt. % ESO as replacement of CE. Enhanced elongations at break were observed for the modified systems while the tensile strengths kept about the same level at the same time. The storage moduli and glass transition temperatures of the modi- fied systems in the glassy state and rubber plateau were observed to be lower than those of neat CE with the increase of ESO weight percent [16].
The morphologies of the CE/ESO blends changed from homogeneous below 10 wt. % of ESO content to separated particles of ESO when its content was above 15 wt. %, especially, the uniformly separated ESO-rich particles with diameter of about 0.7-1.2 lm were observed in the modified systems with 20 wt. % and 30 wt. % of ESO. The co-reaction of ESO and CE resin increased the curing conversion and curing rate of the modified systems. Enhanced elongations at break were observed for the modified systems with increase of ESO content, while the tensile strengths keep about the same level at the same time. The glass transition temperatures and storage moduli of the networks in the glassy state and rubber plateau were observed to be lower than those of neat CE with the increase of ESO weight percent. At low ESO content, the water absorption of blends would drop down compared to that of neat cyanate ester resin. From the results and discussion, the novel biobased resin-epoxidized soybean oil would be an expecting replacer at suitable content and modifier for cyanate ester resin.
Examples include: synthesis and modification of epoxy resins using recycled polyethylene terephthalate [17].
The glycolic fluid was split into a long chain alkyl chain. The contribution and structure of the products were determined by the use of GPX and spectroscopic methods. PET products were expelled from the product of polychromoxic reagents for synthesis of epoxy resins with epichlorhydrin. Bis (2-hydroxyalkyl)-tereph-thalate has been used in the modeling conjugation. Products were applied using low molecular weight epoxidase supplements on the basis of bisfenol A. It was discovered that the news had been announced that
the news had been announced that it had been announced that it had been announced as it had been announced, as it had been announced, that the news had been announced, what had been announced, that it would be used in pesticidal. The best results for products with more long alkyl moieties are obtained. The addition of alkylether chains to glycolysis PET does not only increase the water absorption of modified chemicals, but also increases their chemical stability to 10% HNO3, 75% H2SO4 and ethyl acetate.
Products of the waste PET glycolysis can be used as polyhydroxyl compounds in the reaction with epichlorohydrin giving new epoxy materials suitable for the modification of lowmolecular-weight epoxy resins. Mechanical properties and thermal and chemical stability of the compositions with epoxy resins based on glycolyzed PET wastes depend on the glycol type and contents of the oligomers in the degradation products. Long oligomers fragments built into the structure of cured epoxy compositions provide better properties of cured materials than the modification only with the resin based on pure BHET monomer or resins based on waste PET glycolyzed with short chains glycols.
Modification of epoxy by a liquid elastomer and solid rubber particles is another example for our work. This work covers studies on epoxy resin systems modified with two different rubber phases. The first modification was the use of recycled car tire rubber particles; while in the second one a silicon based liquid elastomer was mixed with the epoxy resin matrix. In the third method epoxy resin was modified with both solid rubber particles and liquid elastomer together. Mechanical tests showed that these modifications resulted in no significant improvements in the mechanical performance of the epoxy resin system. Fractographic studies indicated that poor interfacial adhesion was occurred between the epoxy matrix and the solid rubber particles, while liquid elastomer resulted in formation of round rubbery domains and some plastic deformation lines in the epoxy matrix. For better improvements interfacial phenomenon will be explored.
When epoxy was modified with solid rubber particles there were no iinproveineiits in the mechanical performance of the samples due to mainly very poor interfacial adhesion between the rubber particles and epoxy matrix. When epoxy was modified with liquid elastomer, slight increases were observed in the mechanical behaviour of the samples which should be mainly due to the forination of round rubber domains and plastic deformation linec. When epoxy was modified with both solid rubber particles and liquid elastomer, no significant synergistic effect was observed in the mechanical perfoi inance of the s amp 1 e s . a Therefore, it may concluded that in order to use car tyre rubber particles as filler or toughening agent, better interfacial adhesion should be achieved for instance by using certain surface treatment techniques on the surfaces of rubber particles.
The cellulose nanofibers (CNFs) were made from the wood powder with the chemical and the mechanical treatment. The image of the scanning electron microscopy (SEM) could help to analysis the morphology of the obtained CNFs combined with the photographs of
dispersions of the CNFs' suspensions. It was found the fibers distribute uniformly, and the high aspect ratio was be calculated through the SEM images. Then the obtained CNFs were used as the fiber-reinforced material in the epoxy composite because of their structure of the network and the high aspect ratio [18].
The mechanical properties of the epoxy nanocom-posite were evaluated by tensile test, and the increase in Young's modulus was observed at different fiber contents. The mechanism of action was analyzed combined the tensile test and the SEM images of fracture surface that the CNFs restricted the free movement of thermoset polymer chains by crack tip pinning.
In order to fabricate epoxy-based glass fiber composites with superior mechanical and thermal properties, starch was chemically modified by E-51 epoxy resin, as a sizing for glass fibers. The hydrophilicity of starch was enhanced after modification as the surface tension decreased from 64.98 to 47.99 mN m-1, and the contact angle between the starch suspension and slide glass decreased from 50.26° to 33.53°. Besides, the interfacial adhesion between glass fiber and epoxy resin was obviously improved with the help of the modified starch, which can be clearly observed from SEM images. Consequently, significant increases of tensile strength from about 36 MPa to over 54 MPa, bending strength from about 60 MPa to over 82 MPa, and impact strength from about 5 KJ m-2 to over 18 KJ m-2 were obtained. Moreover, with the improvement of interfacial adhesion between the modified-starch sized glass fiber and epoxy resin, the thermo-stability of the composite was also improved as demonstrated by DSC. This study suggested a simple but effective chemical modification technique using a modifier to enhance interfacial adhesion in fabricating epoxy-based glass fiber composites with superior properties.
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