Polyamine Hardener Research Articles

Сравнительная оценка полиаминных отвердителей эпоксидных композиций

Сравнительная оценка полиаминных отвердителей эпоксидных композиций

Avaliação das características da resina epóxi com diferentes aditivos desaerantes

Este trabalho tem por objetivo a busca por técnicas alternativas para diminuir a incidência de vazios em resinas poliméricas e, por consequência, em materiais compósitos. Foram produzidas formulações diferentes utilizando resina epóxi à base de éter diglicidílico do Bisfenol A, endurecedor de poliamina alifática com e sem a adição de diferentes aditivos desaerantes a base de éteres e ésteres modificados. As formulações produzidas foram submetidas a condições extremas de agitação e processamento, sendo posteriormente avaliadas quanto a incidência de bolhas e vazios, densidade, propriedades mecânicas, morfológicas e térmicas. Os resultados foram bastante positivos quanto à diminuição da quantidade e do tamanho de poros pela utilização de técnicas de desgaseificação a vácuo e pelo uso de aditivos desaerantes.

SiAlON nanoparticles effect on the corrosion and chemical resistance of epoxy coating

Effect of incorporating SiAlON nanoparticles at different loading levels (0–12 wt%) on chemical resistance of epoxy coating was investigated by immersion in basic (Na2CO3, pH = 11) and salty (NaCl 3.5 wt%) (environments at 85 °C for 60 days. Epoxy resin chemical resistant coating grade based on bisphenol A was used with polyamine hardener as a curing agent. In these testes, surface morphology changes of the samples were studied and compared owing to initiation and propagation of cracks. Results indicate an enhancement in the epoxy nanocomposite chemical resistance due to the addition of small fraction of SiAlON nanoparticles. Samples containing 3 and 5 wt% of SiAlON nanopowders were considered as optimum samples compared to all the other samples, because they showed more resistances to initiation and propagation of cracks and lower permeability in chemical environment in comparison with neat resin and other samples. Also, epoxy coatings containing SiAlON nanoparticles were successfully coated on steel substrates and corrosion electrochemical behavior of these nanocomposite coatings were characterized by electrochemical impedance spectroscopy (EIS). The electrochemical monitoring of the coated steel over 35 days of immersion in 3.5 wt% NaCl solution at room temperature suggested the positive role of nanoparticles in improving the corrosion resistance of the coated steel.

SiAlON nanoparticles effect on the behaviour of epoxy coating

In this work, the influence of SiAlON nanoparticles loading level (0–12 wt%) was investigated on the mechanical and chemical properties of epoxy resin-based nanocomposites coatings. The samples were characterized by fracture toughness, chemical, pull off, hardness and abrasion tests, followed by scanning electron microscopy of the fracture surfaces and sample surface after performing a chemical test. Nanoparticles were also characterized by transmission electron microscopy and linear light scattering analysis techniques. Epoxy resin coating based on bisphenol A was treated with polyamine hardener as a curing agent. Fracture toughness measurements were carried out using a single edge notched bend specimens within a three-point bending test at room temperature. Effect of SiAlON nanoparticles on the chemical resistance of epoxy resin was investigated by immersion of samples in 3.5 wt% NaCl solution at 85 °C for 60 days. Results indicated the enhancements in the mechanical properties and chemical resistance of epoxy nanocomposite due to the addition of small parts of SiAlON nanoparticles. The contents of samples with 3 and 5 wt% of SiAlON nanopowders have been considered as optimum contents compared to the other samples. They showed improvement in the crack propagation resistance in chemical solution and fracture toughness tests, both. Enhancment in abrasion resistance was found at either of 3 and 5 wt% SiAlON epoxy nanocomposite samples where they showed 59 and 34% abrasion resistance more than that of the neat resin, respectively.

Epoxy resins modified with reactive low molecular weight siloxanes

A typical composition consisting of a low-molecular commercial epoxy resin based on bisphenol A and aliphatic polyamine hardener: triethylenetetramine was modified by replacing a part of the composition with up to 15 wt.% of low molecular weight bis(glycidylpropyl)- or bis(aminopropyl)-tetramethyldisiloxane. The reactivity of the compositions and basic properties of the resulting epoxy polymers, including glass transition temperature, storage modulus, thermal stability, impact and bending strengths, Brinell hardness, and flammability (limiting oxygen index) were evaluated.

Nonisothermal reaction, thermal stability and dynamic mechanical properties of epoxy system with novel nonlinear multifunctional polyamine hardener

N,N,N′,N′-tetra(3-aminopropyl)-1,6-diaminohexane (TADH), a nonlinear multifunctional polyamine, was prepared and employed as a novel hardener for diglycidyl ether of bisphenol A (DGEBA). Nonisothermal reactions of DGEBA/TADH were systematically investigated with differential scanning calorimetry (DSC). According to the Málek method, the two-parameter Šesták–Berggren model was selected to simulate the reaction rate with a good match achieved, and a correlation of effective activation energies E α with fractional conversion α was determined with the mode-free isoconversional Vyazovkin method. As α rose, E α reduced quickly from ∼65 to 57 kJ/mol up to α ≈ 15%, then decreased slowly to ∼50 kJ/mol till α ≈ 75%, and finally dropped to ∼30 kJ/mol at full conversion. In addition, analysis of thermal stability of the cured DGEBA/TADH with thermogravimetric analysis (TGA) revealed that it possessed quite good thermal stability and increased residual char content at 600 °C in nitrogen. Furthermore, dynamic mechanical analysis (DMA) of the DGEBA/TADH network showed its relaxations were characterized by localized motions of hydroxyl ether segments ( β relaxation) and cooperative motions of whole network chains (glass relaxation) at different temperature regions.

Protective epoxy dispersion coating materials modified a posteriori with organophilized montmorillonites

Two types of paints (primer and topcoat) and coatings based on epoxy resin dispersions, water solution of polyamine hardener and a posteriori introduced four types of organophilized montmorillonite (mMMT) nanofillers: two commercial Nanofil-type (used as powders) and two pilot plant NanoBent-type products (in a powder and water-slurry form) were formulated and investigated. Pulverized organoclays were preliminarily incorporated (in various doses: 1, 2.5 and 5 wt.%) into the epoxy resin dispersions, filled mainly with iron oxides (primer) or the TiO 2/white filler (topcoat) using either a pearl-mill or a dissolver. Water-slurry of semihydrophilic modified montmorillonite was mixed with epoxy resin dispersions in the dissolver. The paints were applied on steel substrate and cured at room temperature. An influence of the method of introduction, handling form and type of mMMT on properties of epoxy dispersion paints and coatings has been investigated. In most cases coatings with semihydrophilic NanoBent-type nanofillers exhibited better properties than those with hydrophobic mMMT. Differences of barrier and mechanical features for primer, topcoat and primer/topcoat (multilayer) coatings based on results of water uptake, relative impedance, adhesion to steel, hardness and abrasion resistance tests, are discussed.

Effects of stress ratio on fatigue crack growth of thermoset epoxy resin

The influences of stress ratio ( R) on fatigue crack growth (FCG) of thermoset epoxy resin with polyamine hardener were investigated. The FCG growth rates (d a/d N) have been correlated by the linear-elastic fracture mechanics parameters (Δ K and K max), and nonlinear-elastic fracture mechanics parameter (Δ J). The effects of R on FCG were observed when the Δ K and Δ J were used as fracture mechanics parameters for FCG. However, the K max successfully characterized FCG under cyclic-dependent condition (FCGs at R = 0.1 and 0.4); but it failed to characterize the FCG under time-dependent condition (FCG at R = 0.7). As a time-dependent fracture mechanics parameter, C* was applied to correlate the time-dependent FCG rate (d a/d t). A reasonable agreement was obtained between time-dependent FCG ( R = 0.7) and creep crack growth (CCG) results.

Polyurea based aerogel for a high performance thermal insulation material

Less fragile lightweight nanostructured polyurea based organic aerogels were prepared via a simple sol–gel processing and supercritical drying method. The uniform polyurea wet gels were first prepared at room temperature and atmospheric pressure by reacting different isocyanates with polyamines using a tertiary amine (triethylamine) catalyst. Gelation kinetics, uniformity of wet gel, and properties of aerogel products were significantly affected by both target density (i.e., solid content) and equivalent weight (EW) ratio of the isocyanate resin and polyamine hardener. A supercritical carbon dioxide (CO2) drying method was used to extract solvent from wet polyurea gels to afford nanoporous aerogels. The thermal conductivity values of polyurea based aerogel were measured at pressures from ambient to 0.075 torr and at temperatures from room temperature to −120 °C under a pressure of 8 torr. The polyurea based aerogel samples demonstrated high porosities, low thermal conductivity values, hydrophobicity properties, relatively high thermal decomposition temperature (~270 °C) and low degassing property and were less dusty than silica aerogels. We found that the low thermal conductivities of polyurea based aerogels were associated with their small pore sizes. These polyurea based aerogels are very promising candidates for cryogenic insulation applications and as a thermal insulation component of spacesuits.

Gel-casting of β-TCP using epoxy resin as a gelling agent

A water-soluble epoxy resin combined with a polyamine hardener is applied for gel-casting of β-tricalcium phosphate (TCP) ceramics. The influence of dispersant and the solids loading on the rheological behavior of β-TCP slurries are investigated. When the concentration of the slurries increases from 40 vol.% to 55 vol.%, the compressive strength of the dried pieces increases in the range from 36.4 ± 2.1 MPa to 65.8 ± 2.3 MPa, and flexural strength increases from 30.4 ± 1.4 MPa to 36.4 ± 1.7 MPa. The mechanical properties of the sintered pieces are satisfying, with compressive strength, flexural strength, elasticity modulus and the fracture toughness 319 ± 18 MPa, 97.4 ± 6.0 MPa, 90 ± 2 GPa and 1.00 ± 0.07 MPa m 1/2, respectively. The structures of green body and sintered ceramics are homogeneous, and large defects are not observed.

Effects of loading rate and thickness on mixed‐mode I/II fracture toughness of thermoset epoxy resin

AbstractThe influences of loading rate and thickness on fracture behavior and mechanism of thermoset epoxy resin with polyamine hardener under mixed‐mode (mode I/II) loading have been studied at low thickness and low loading rate (LTLL), as well as high thickness and high loading rate (HTHL). Under the variation of mixed‐mode loading from mode I to mode II, fracture toughness of HTHL specimens were under plane‐strain condition. For LTLL specimens, the fracture toughness at dominated mode I loading was under plane‐stress condition, whereas those at dominated mode II loading were under plane‐strain condition. The stretched zone due to the principal stress in the normal direction to the crack plane as well as shear lips due to the Poisson contraction in the thickness direction were the main characteristic of the fracture surface of LTLL specimen tested at pure mode I loading. On the other hand, the mirror‐like fracture surface was observed for the HTHL specimen tested at pure mode I loading. Under pure mode II loading, the aligned stretched zone due to the maximum shear stress was the main characteristic of the fracture surface of LTLL specimen, whereas irregular appearance of the stretched zone was observed for the HTHL specimen. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Synthesis and Characterization of Cardanol-Based Epoxy Systems

The use of cardanol, a renewable natural resource, in place of a phenol or diphenol, in the synthesis of two different epoxy systems has been studied in this work. Cardanol, prepared by the distillation of cashew nut shell liquid (CNSL), was epoxidised using epichlorohydrin in presence of caustic soda catalyst at different reaction intervals and the products were characterized by spectroscopy, gel-permeation chromatography and by determining the epoxide equivalent. The epoxide equivalent increased sharply with time of epoxidation and reached almost a limiting value around 9 h. Cardanol, being less reactive, undergoes epoxidation to a smaller extent than phenol or bisphenol. Although these epoxy compounds do not form cross-linked networks due to being mono-functional, they are found to be effective in producing relatively flexible systems when reactive blended with commercial DGEBA. Co-epoxides containing bisphenol A and cardanol in varying molar compositions were also synthesised and characterised. Introduction of 20 mol% cardanol into bisphenol A resulted in a resin having reduced tensile, impact and compressive strengths upon curing by a polyamine hardener. However, the resin showed considerable improvement in elongation-at-break without much decrease in energy absorption.

Gelcasting of alumina foams consolidated by epoxy resin

A water-soluble epoxy resin combined with a polyamine hardener was developed to consolidate foamed suspensions to manufacture alumina foams. This gelling system could be carried out in air atmosphere, thus more convenient than those based on acrylamide derivatives. The influence of solid loading on the viscosity of suspensions as well as on the relative density of sintered foams was evaluated. The resulting alumina foams, with relative densities between 17% and 38%, comprised microstructures of spherical cells. Both the flexural strength and the compressive strength of the foams had a power law relation against the relative density. The permeability of sintered foams decreased exponentially with the relative density.

New hyperbranched polyether containing cyclic carbonate groups as a toughening agent for epoxy resin

Hyperbranched polyglycerol containing terminal five-membered cyclic carbonate groups has been obtained by anionic polymerization of glycidol and then in the reaction of its terminal vicinal hydroxyl groups with dimethyl carbonate in the presence of potassium carbonate. The remaining OH groups of the polymer were protected in the reaction with acetic anhydride to reduce polymer hydrophilicity and increase miscibility with the epoxy resin. A strong decrease in viscosity was observed after esterification, from 73 to 3.6Pas. The product (HBPG 3) was used for modification of the bisphenol A based epoxy resin. The epoxide–cyclic carbonate compositions were cured using a polyamine hardener (TETA) in a one-step procedure. Thermal and mechanical properties of the cured compositions were characterized and compared with the parent epoxy resin. The optimal mechanical properties were obtained for the compositions containing HBPG 3 when phase separation takes place. The mechanical properties are discussed in terms of the morphology observed by SEM.

Gelcasting of Alumina Using Epoxy Resin as a Gelling Agent

A water‐soluble epoxy resin and hardener system for gelcasting of ceramics was developed. Polymerization of the system is a nucleophilic addition reaction, and not affected by oxygen. Therefore, this gelcasting system can be carried out in an air atmosphere. The ceramic slurries were prepared by mixing the aqueous premix solution of epoxy resin with alumina powder and dispersant. For cross‐linking, a polyamine hardener was added. Both the rheological properties of the slurries and the gelling behaviors of the aqueous premix solutions were evaluated. The slurry with a solid loading of 80 wt% is optimized for gelcasting. The flexural strength of the sintered ceramics is 335±47 MPa with 98% of theoretical density.

Epoxy resin modified with soybean oil containing cyclic carbonate groups

AbstractCarbonated soybean oil (CSO) containing five‐membered cyclic carbonate groups has been obtained in the reaction of epoxidized soybean oil with carbon dioxide in the presence of KI activated by 18‐crown‐6 under 6 MPa CO2 pressure at 130°C. The CSO was used for modification of bisphenol‐A based epoxy resin. The composition epoxide‐cyclic carbonate was cured using polyamine hardeners by one‐step and two‐step procedures. All cured compositions were characterized for their thermal and mechanical properties and compared with the parent epoxy network. The optimal properties were obtained for compositions containing CSO and cured by one‐step method when phase separation takes place. The mechanical properties were discussed in terms of morphology observed by SEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2904‐2914, 2006

A study of the effects of pigments and fillers on the properties of anticorrosive paints

PurposeTo investigate the properties of coatings containing various types of fillers from the point of view of their physical‐mechanical properties and anticorrosive properties.Design/methodology/approachResearch used fillers of different types varying in morphology and/or chemical composition; these were then compared with selected pigments and zinc phosphate, an anticorrosive pigment. The following parameters were observed for all of the fillers and pigments: oil absorption, CPVC value, density, extract pH, specific surface, particle size, and water‐soluble substances. The morphology of particles was observed by means of an electron‐scanning microscope. The coatings of these fillers and pigments were formulated on an epoxy resin binder basis cured with a polyamine hardener. The coatings prepared were subjected to the measurement of physical‐mechanical properties such as hardness and deepening resistance, flex resistance, adhesion to steel, and the gloss of the coatings. The coatings containing the fillers and pigments studied underwent corrosion tests in a condenser chamber and in a salt‐spray cabinet.FindingsThe results obtained through the tests allowed the selection of the optimum filler for an epoxy coating with barrier anticorrosive properties. As per respective findings, some fillers in these coatings of significant thickness can be comparable to their zinc phosphate counterparts.Research limitations/implicationsThe anticorrosive properties of the coatings studied can also be tested in paints by means of atmospheric exposure, for instance, with the aid of a Florida test.Practical implicationsThe findings are helpful towards applications in the formulations of anticorrosive coatings of significant thickness that offer an effective barrier mechanism.Originality/valueThe research presents the results of the properties of a whole range of industrially employed fillers and pigments contained in paints. Based on this study, the formulation of steel protecting coatings can be optimised.

Effects of loading rate on fracture behavior and mechanism of thermoset epoxy resin

Effects of loading rate on fracture behavior and mechanism of thermoset epoxy resin with polyamine hardener have been studied at various loading rates (10 −1–10 3 mm/min). The displacement to fracture continuously decreased with increasing loading rate, and became stable at high loading rates. The maximum load, critical stress intensity factor ( K IQ), and critical strain energy release rate ( G IQ) were high and stable at low loading rates, and became low and stable at high loading rates with the transition of loading rate at approximately 10 mm/min. The formation of shear lips, stretched zone, crazes, and crack blunting, i.e. localized plastic deformation processes, were dominating mechanisms and resulted in the plane stress-dominated condition for specimens tested at low loading rates, while brittle fracture and the condition of plane strain were dominating mechanisms for specimens tested at loading rate of 10 mm/min or higher.

Determination of the cross-linking degree of unmodified epoxy resin by cycloaliphatic polyamine and polyamidamin hardeners by ftir spectroscopy

Unmodified epoxy resin GY250 was crosslinked by the cycloaliphatic polyamino hardener HY847 and polyamidamine hardener HY848 in the different mass ratios. The degree of crosslinking of the epoxy resin and the quantity of unreacted epoxy groups were determined by a spectroscopic FTIR method. The optimal time of complete crosslinking, as a criterion of the degree, was determined by measuring the film hardness indirectly (JUS H.C8.055). The optimal stoichiometric ratio of 100:18:32 (GY250:HY847:HY848) was defined by correlating parameters which directly depend on the degree of crosslinking and the period of application of the epoxy resins, as a prerequisite for forming 2-component epoxy systems which are comparatively more elastic adhesive and waterproof.

Epoxy resin particles, 2. An efficient synthetic method of epoxy resin particles in organic solvent by the aid of modified polyolefins as dispersant

Epoxy resin particles were efficiently prepared by addition of Bisphenol A diglycidyl ether to a solution of polyamine hardener in organic solvents containing polyolefin dispersants modified with maleic anhydride and maleimide. Aliphatic hydrocarbons and their mixtures with aromatic hydrocarbons were used as the reaction solvents. The size and size distribution of the particles could be controlled by modulating the difference in solubility parameter between the solvent and the polymer and by changing the reaction temperature. Smaller particles were formed when combined with more highly reactive amine hardeners. The particles prepared by this method showed a rough surface probably because of the polymer deposition on the finally formed particles in the final reprecipitation process. The present synthesis can afford an efficient method for manufacturing the epoxy resin particles in large scale.