Synthesis and properties of a phosphate ester as curing agent in an epoxy resin system

Phosphate ester compounds display good flame retardancy effect in epoxy resin systems. In this paper, several novel phosphate esters, used as curing agents for epoxy resins, were synthesized based on P₂O₅, phosphoric acid, and different types of alcohol. The structures of phosphate esters were characterized by ³¹P nuclear magnetic resonance (³¹P NMR). Then, a series of flame retardant epoxy composites were prepared by curing the epoxy resins (E-44) with the phosphate esters. The flame retardancy and thermal degradation behaviors of flame retardant epoxy composites were investigated by cone calorimeter test (CCT) and thermogravimetric analysis (TGA), respectively. The results of CCT indicated that phosphate esters can significantly decrease heat release rate, total heat release (THR), and smoke production rate. The sample cured by butyl phosphate ester from phosphorus pentoxide, phosphoric acid and butanol showed the best flame retardant performance among all samples. The TGA results showed that phosphate esters could enhance char residues of flame retardant epoxy composites when compared with those of a composite using T31 as a curing agent at high temperature. It may be concluded that good flame retardant properties of flame retardant epoxy composites are related to the formation of a protective phosphorus-rich char layer. These phosphate esters have a good future on flame retardant epoxy composites.     

Microwave induced synthesis of thieno[2,3-b]quinoline-2-carboxylic acids and alkyl esters and their antibacterial activity

A series of thieno[2,3-b]quinoline-2-carboxylic acids and alkyl esters, (3a–i) have been synthesized by the condensation of 2-chloro-3-formyl quinolines (1a–c) with thioglycolic acid/alkyl esters under microwave irradiation using anhydrous potassium carbonate. These compounds were characterized by elemental analysis, IR, ¹H NMR, and mass spectral studies. Their antibacterial activity was also evaluated.     

4-hydroxy-3-methoxycinnamate esters of milkweed oil: Synthesis and characterization

The common milkweed (Asclepias syriaca L.) is a new industrial crop. Its seed oil (TAG) is highly polyunsaturated. In the search for novel applications for milkweed seed oil, the olefinic groups in the TAG were oxidized to polyhydroxy TAG via epoxidation and subsequent epoxy ring-opening reactions. These polyhydroxy TAG exhibit unique industrially desirable emulsoid properties in water. Esterification of the secondary polyhydroxy functionalities of the TAG derivatives of the oil with trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid) has resulted in the development of novel cinnamate esters of milkweed oil. These cinnamates are also obtainable via direct ring-opening of the epoxy TAG intermediate with ferulic acid. Among the interesting characteristics of the ester derivatives is their UV radiation-absorbing property.     

Plasticizing properties of esters of monohydric alcohols and tall oil fatty acids

Tall oil fatty acid esters prepared as intermediates in an epoxy ester plasticizer program were similarly evaluated as low-temp plasticizers in polyvinyl chloride resins. Performance characteristics as primary and secondary plasticizers in polyvinyl sheeting and extruded tapes were determined on esters from methyl to heptadecyl tallate. Results indicate that these materials impart low-temp properties which would make them of value as low-cost plasticizers in extruded and molded products where light and heat stability are not primary factors.     

A novel reaction of epoxy resins with polyfunctional active esters

Addition reactions of commercial epoxy resins such as bisphenol-A diglycidylether (BADGE), ethylene glycol diglycidylether (EGGE), and N,N-diglycidylaniline (GAN) with various active esters such as di[S-(benzothizolyl)] thioadipate (BTAD), di(4-nitrophenyl) adipate (NPAD), di(S-phenyl) thioadipate (PTAD), and 4-nitrobenzoyl esters of polyfunctional phenols were carried out in neat using quaternary salts or crown ether-salts complexes as a catalyst at 50–130°C. The rate of addition reaction of BTAD was faster than that with other esters under the same reaction conditions. Furthermore, it was found that the rate of addition reaction of the epoxy resins with some active esters was strongly affected by the kind of epoxy resin, the structural formula of carboxylic acid, and the kind of catalyst. The reaction of epoxy resins with polyfunctional active esters proceeded quantitatively at the elevated temperatures. However, some of the mixtures of epoxy resin, polyfunctional active ester and the catalyst showed excellent storage stability at 30°C.     

Improving energy dissipation and damage resistance of CFRP laminates using alumina nanoparticles

ABSTRACT

In this paper, the effect of a toughened epoxy matrix on the damage evolution, energy dissipation, and permanent indentation of composite laminates under out-of-plane (transverse) loading is presented experimentally. The epoxy matrix was toughened by 3% alumina nanoparticles with sizes less than 200?nm. A quasi-static indentation test was exploited to characterise the damage modes and evaluate the dissipation of energy of the composite laminate. The dissipated energy was evaluated as the enclosed area between the loading and unloading curves, while the damage resistance was expressed as the number of delaminations and their size. The results showed that epoxy toughened by alumina nanoparticles, showed an improvement in the damage threshold load by 27.3% and higher ultimate load under indentation. Regarding the damage resistance, the toughened laminates showed lower number of delaminated interfaces and lower projected delamination area than untoughened laminates. This is due to the localised damage under the indenter, the matrix cracks at low indentation energy and fibre breakages occur at high indentation energy.     

Investigation on the anticorrosion,adhesion and mechanical performance of epoxy nanocomposite coatings containing epoxy-silane treated nano-MoO3 on mild steel

Abstract

The effect of introducing MoO₃ (Molybdenum oxide) nanoparticle in the epoxy coating was analyzed by EIS and SECM methods in natural seawater. The aminopropyl triethoxy silane (APTES) was treated with the nanoparticle for the proper dispersion and chemical interaction of nanoparticle with the epoxy resin. The introduction of MoO₃ nanoparticle in the epoxy coating enhances the charge transfer resistance (R_ct) as well as the film resistance (R_f). The observation of iron dissolution and oxygen consumption was carried out by applying the appropriate SECM tip potential in the MoO₃ modified nanocomposite coated steel. The epoxy and epoxy-MoO₃ nanocomposite-coated samples were used to study the mechanical, adhesion and anticorrosion properties. The analysis using SEM/EDX displayed that the enriched Mo was detected in the nanocomposite coated steel. The presence of the nano level corrosion product containing Mo was confirmed by FIB-TEM analysis. The high corrosion protection properties of the epoxy based nanocomposite coating was due to the complex nanoscale layer formed and chemical interactions of epoxy resin with surface-modified nanoparticle in nanocomposites.     

Reactions of conjugated fatty acids. V. Preparation and properties of diels-alder adducts and their esters fromtrans,trans-conjugated fatty acids derived from soybean oil

Summary Soybean fatty acids were conjugated with alkali, and the contained, conjugated dienoic acids were isomerized with iodine to thetrans,trans configuration. Adducts were prepared from thesetrans,trans-conjugated acids by condensation with maleic anhydride and acrylic acid. The adducts were isolated, purified, and converted to esters by using a variety of alcohols, including methyl, ethyl,n-propyl,n-butyl, and allyl alcohols. Esters made from saturated alcohols were converted into the corresponding epoxy derivatives. All of the esters (except allyl) and all of the epoxy esters were compatible with an equal weight of polyvinyl chloride and appeared to be primary plasticizers for this plastic. The epoxy esters were effective in inhibiting heat deterioration of polyvinyl chloride. Presented at fall meeting. American Oil Chemists' Society, September 23–26, 1956, Chicago, Ill.     

Simultaneous determination by GC-MS of epoxy and hydroxy FA as their methoxy derivatives

We report on a capillary GC-MS method for the quantitative analysis of hydroxy and epoxy FA. Catalytic hydrogenation of lipid extracts produces stable saturated lipids. Saponification followed by methylation with boron trifluoride in the presence of methanol converts FA to methyl esters and epoxy groups to methoxy-hydroxy groups. These compounds are purified from nonoxidized methyl esters using solid phase extraction. Derivatization of the hydroxy group using tetramethylammonium hydroxide forms methoxy and vicinal dimethoxy FAME. When subjected to El-MS, fragmentation gives two characteristic ion fragments for each epoxy and hydroxy positional isomer. Quantitative measurements were achieved using uniformly labeled hydroxy and epoxy ¹³C FA as internal standards. Epoxy and hydroxy FA were identified in both plasma and adipose tissue of men, and the levels of hydroxy and epoxy in these tissues were related. The levels of hydroxy isomers were typical of oxidation of linoleic acid, whereas epoxy isomers were characteristic of oxidation of oleic acid.     

Functionalization of soy fatty acid alkyl esters as bioplasticizers

The combination of various functional groups, such as epoxy, acetoxy, methoxy, thiirane, and aziridine, on the fatty acyl chain of soy fatty acid alkyl esters have been synthesized and evaluated as plasticizers in poly(vinyl chloride) (PVC) applications. Numerous synthetic procedures, such as epoxidation, methoxylation, acetylation, thiiration, and aziridination, were used for synthesizing multifunctional soy fatty acid alkyl esters. Epoxidized soybean oil fatty acid alkyl ester served as the key intermediate for functionalization. Partial or complete ring opening of the epoxide by reacting with methanol and the subsequent etherification or acetylation of the hydroxyl function produced epoxy, alkoxy, and acetoxy derivatives. The nucleophilic substitution of epoxide with sulfur by reacting with ammonium thiocyanate produced thiirane and epoxy thiiranes. Although the aziridine derivatives were synthesized by reacting unsaturated fatty acid alkyl esters with chloramine‐T, the compounds were fully characterized and their physical and analytical properties were determined. The high viscosity and darker color of aziridine and thiirane derivatives limit their usefulness, whereas the physical properties of the other derivatives were acceptable. The plasticizer evaluation of methoxy and acetoxy soy fatty acid esters (methyl and n‐butyl) demonstrated good compatibility with PVC, high efficiency (Shore hardness), and gelling properties were comparable to commercial plasticizer, di‐isoonyl phthalate. The abundant availability and cost‐effectiveness of starting materials and the readily adoptable chemical processes make the fatty acid ester derivatives viable bioplasticizers to replace the fossil fuel‐derived phthalates. J. VINYL ADDIT. TECHNOL., 23:93–105, 2017. © 2015 Society of Plastics Engineers     

A study of fatty acid methyl esters with epoxy or alkyne functionalities

Described are the physical and chemical properties of the methyl esters of two uncommon fatty acids: vernolic acid, containing an epoxy group, and crepenynic acid, containing a triple bond. The incorporation of an epoxy or alkyne group into the fatty acid structure is shown to greatly affect the properties compared to conventional unsaturated fatty acids. The methyl esters have been characterized and compared with ordinary fatty acid methyl esters (i.e., methyl oleate and linoleate) with respect to spectroscopic characterization [¹H nuclear magnetic resonance (NMR)], ¹³C NMR, and Fourier transform infrared), rheological properties, and oxidative reactivity (using chemiluminescence). Both methyl vernoleate and methyl crepenynate could successfully be produced by transesterification under basic conditions without reaction of the epoxy or alkyne groups. Rheological measurements showed that the methyl esters had a significantly lower viscosity compared to their triglyceride analogs. Smaller differences were seen when comparing the different methyl esters where methyl vernoleate had the highest viscosity due to the presence of the more polar oxirane group. Very large differences were found with respect to the oxidation rate of the different methyl esters. Methyl crepenynate was shown to oxidize extremely rapidly, whereas methyl vernoleate was very stable toward oxidation.     

Comparative Study on Improvement in Mechanical and Flame Retarding Properties of Epoxy-CaCO3 Nano and Commercial Composites

ABSTRACT

Commercial and nano calcium carbonate (CaCO₃) filled epoxy composites were processed at 2 to 10 wt% compositions. Nano size CaCO₃ was synthesized using in-situ deposition technique. Its nanosize and mixing with epoxy were confirmed by X-ray diffraction (XRD) method. X-ray diffractograms show that complete exfoliation occurs in the case of nanosize particles while micron size particles do not exfoliate. The effect of nanosize and commercial CaCO₃ was studied on mechanical and flame retarding properties. The impact strength of composite increased up to 6 wt% loading of nano filler and further decreased. Young's modulus was observed at 1400 Mpa and 1100 Mpa for nano and commercial CaCO₃, respectively at their 10 wt% loading, while pure epoxy showed 1000 Mpa; likewise, flame retarding properties improved six to four times on loading of nano and commercial CaCO₃, respectively in comparison to pure epoxy resin. The improvement is due to exfoliation of nano in epoxy matrix, which is observed by X-ray diffractograms.     

The Fischer-Tropsch Synthesis in the Liquid Phase

Abstract

The hydrogenation of carbon monoxide by the Fischer-Tropsch (F-T) process [1] forms saturated and unsaturated compounds of the homologous hydrocarbon series. It permits the synthesis of hydrocarbons ranging from methane to high-melting paraffins with molecular weights above 20,000, depending on the catalyst, temperature, and type of process employed. By-products such as alcohols, aldehydes, ketones, acids, and esters are formed on a smaller scale. Small amounts of aromatic compounds are formed at high temperatures by secondary dehydrocyclization reactions from the primary hydrocarbons formed.     

Hybridizing MWCNT with nano metal oxides and TiO2 in epoxy composites: Influence on mechanical and thermal performances

In this study, the effects of multi‐walled carbon nanotubes (MWCNT), and its hybrids with iron oxide (Fe₂O₃) and copper oxide (CuO) nanoparticles on mechanical characteristics and thermal properties of epoxy binder was evaluated. Furthermore, simultaneous effects of using MWCNT with TiO₂ as pigment and CaCO₃ as filler for epoxy composites were determined. To investigate effects of nano‐ and micro‐particles on epoxy matrix, the samples were evaluated by TGA and DTA. It was found that the hybrid of MWCNT with nano metal oxides caused considerable increment in the tensile and flexural properties of epoxy samples in comparison to the single MWCNT containing samples at the same filler contents. Significant improvement in the thermal conductivity of epoxy samples was obtained by using TiO₂ pigment along with MWCNT. The TiO₂ pigment also caused considerable improvement in mechanical properties of the epoxy matrix and the MWCNT containing nanocomposite. The best mechanical and thermal properties of epoxy nanocomposites were obtained at 1.5 wt % of MWCNT and 7 wt % of TiO₂ that it should be attributed to particle network forming of the particles which cause better nano/micro dispersion and properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43834.     

Experimental investigation on the enhancement of Mode I fracture toughness of adhesive bonded joints by electrospun nanofibers

ABSTRACT

The use of an electrospun nylon nanofibrous mat at the interface between adjacent plies of a composite laminate is a promising mean to improve the delamination strength, as the nanomat acts a reinforcing web enabling a ply-to-ply bridging. This kind of reinforcement can be potentially used in other applications, such as adhesive bonding, where it may also work as adhesive carrier. The present work is therefore aimed at analysing the potential of an electrospun polymeric nanomat as adhesive carrier and reinforcing web in adhesive bonding. The adhesive is used to pre-impregnate a nylon nanofibrous mat that is then placed at the interface between two metal pieces and cured. The effectiveness of this procedure is evaluated by comparing of the mode-I fracture toughness measured 2024-T3 aluminum alloy DCB (Double Cantilever Beam) specimen bonded using a two-part epoxy resin with and without the nanomat.     

Novel lipidic enaminones from a C18 keto-allenic ester

Primary amines (ammonia, methyl, propyl, octyl, octadecyl, phenyl, benzyl, phenethyl) including methyl esters of amino acids (glycine, dl-alanine, l-valine, l-leucine, L-tyrosine, and l-methionine), and secondary amines (dimethyl, diethyl, dipropyl, diisopropyl, dioctyl, and diphenyl) attack regiospecifically the central carbon atom of the allene system of methyl 12-keto-9,10-octadecadienoate (1) to give the corresponding lipidic enaminone derivatives (2–21) with an average yield of 77%. The E- and Z-configuration of the enaminone system of these novel lipid derivatives was confirmed by infrared and nuclear magnetic resonance spectroscopic techniques. Primary amines furnished Z-enaminones, while secondary amines gave E-enaminones.     

Gas chromatography-mass spectrometry of methyl esters of unsaturated oxygenated fatty acids

Silylation of hydroxyl groups in methyl esters of unsaturated hydroxy acids provides compounds that give mass spectra which can be readily interpreted, whereas spectra of underivatized esters are extremely difficult to evaluate. The relationship of the double bond(s) to the trimethylsiloxy (TMS) group results in specific mass spectral patterns. In esters that have the TMS group separated from the double bond by one methylene group, the ions caused byα-cleavage at the TMS group on the side closest to the olefinic group are much more abundant than those produced fromα-cleavage on the other side of the TMS group. In esters that have the TMS group and the double bond separated by two methylene groups,α-cleavage ions are approximately equal. When the TMS group and the double bond are allylic, no fragmentation results between them. Cleavage does occur on either side of this system, and those ions resulting from cleavage alpha to the TMS group are in greatest abundance. Silylation of esters that have a conjugated diene or ene-yne system adjacent to a hydroxyl group also gives derivatives amenable to gas chromatographymass spectrometry. In these esters, large peaks are observed that arise fromα-cleavage at the TMS group and at the other end of the olefinic system. No fragmentation between the TMS group and the sites of unsaturation occurs. Unsaturated epoxy methyl esters produce spectra difficult to interpret. When the epoxide is converted to methoxy-hydroxy derivatives by BF₃-methanol, the spectrum locates the position of the epoxide group. Silylation of the hydroxyl group produces a compound that gives a less complicated spectrum which also locates the original epoxy group. Mass spectrometry of a series of unsaturated keto-esters, without derivatization, provides spectra that are easily interpretable. Presented at the AOCS Meeting, Los Angeles, April 1972. N. Market. Nutr. Res. Div., ARS, USDA.     

Vernolic acid esters as plasticizers for polyvinyl chloride

The methyl, propyl, butyl, isobutyl, hexyl, cyclohexyl, octyl, and 2-ethylhexyl esters of vernolic (epoxyoleic) acid, a naturally-occurring epoxy acid, were prepared and evaluated as plasticizers of polyvinyl chloride. All the esters showed good compatibility. The data indicated that they are excellent low temperature plasticizers having T_f temperatures below −50C. They also have the added advantage of greatly increasing the heat stability of the polyvinyl chloride and improving the light stability. The results are compared with DOP and other epoxy-containing plasticizers now being used commercially. These esters should not only be useful as primary plasticizers but also in combination with other plasticizers as plasticizer-stabilizers. Presented at the AOCS Meeting. Cineinnati, October 1965 E. Utiliz. Res. Dev. Div., ARS, USDA.     

Structure‐Property Correlation for Optically Transparent Epoxy/Montmorillonite Hybrids. I. Synthesis and Optical/Thermal Properties

Abstract

A new type of transparent epoxy‐based nanohybrides has been prepared by the reaction of alkylammonium exchanged montmorillonite (AMT) with diglycidyl ether of bisphenol A (DGEBA) and triethylamine as the curing agent. The light transmittance and the coefficient of thermal expansion (CTE) have been studied in detail. Results demonstrate that the light transmittance of hybrids decreases with increasing the concentration of AMT, whereas the CTE shows an opposite tendency. When the AMT concentration is below 3 phr (3 g AMT/100 g epoxy resin), the light transmittances in near IR region of hybrids are more than 80% of that of the pristine epoxy, and the CTE values of hybrids decrease from 0% to 20% of that of pure epoxy, indicating that epoxy/AMT hybrids could be used as packaging materials for optoelectric. The dependence of light transmittance of the hybrids depends on the concentration of AMT and the wavelength at which it is measured, and an empirical equation was developed to describe their relationship.     

Tensile Properties of Arenga pinnata Fiber-Reinforced Epoxy Composites

The aim of this study is to determine the tensile properties of Arenga pinnata fiber as a natural fiber and epoxy resin as a matrix. The Arenga pinnata fibers were mixed with epoxy resin at the various fiber weight percentages of 10%, 15%, and 20% Arenga pinnata fiber and with different fiber orientations such as long random, chopped random, and woven roving. Hand lay-up processes in this experiments were to produce specimen test with the curing time for the composite plates is in the room temperature (25–30°C). Results from the tensile tests of Arenga pinnata fiber reinforced epoxy composite are that the 10 wt.% woven roving Arenga pinnata fiber showed the highest value for maximum tensile properties. The tensile strength and Young's modulus values for 10 wt.% of woven roving Arenga pinnata fiber composite are 51.725 MPa and 1255.825 MPa, respectively. The results above indicate that the woven roving Arenga pinnata fiber has a better bonding between its fiber and matrix compared to long random Arenga pinnata fiber and chopped random Arenga pinnata fiber. Scanning electron microscopy (SEM) tests were carried out after tensile tests to observe the interface of fiber and matrix adhesion.