Curing characteristics of carboxyl functionalized glucose resin and epoxy resin

The curing characteristics of carboxylic functionalized glucose resin (glucose maleic acid ester vinyl resin: GMAEV) and epoxy resin have been studied using DSC and FTIR methods. Exothermic reactions attributed to esterification and etherification reactions of the hydroxyl and carboxyl functionalities of GMAEV with the epoxy groups were identified. Exothermic reactions showed very different patterns according to the degree of carboxyl group substituent of GMAEV. The results showed that esterification reaction occurs in the early stage of cure and then etherification followed after completion of the esterification. A cured matrix containing epoxy resin and 50 wt.% of GMAEV was prepared and characterized. The cured matrix showed thermal stability up to 300 °C. The average glass transition temperature and storage modulus of the matrix were as high as 95 °C and 2700 MPa, respectively. The cured matrix of epoxy resin and GMAEV with higher degree of carboxyl group was found to have a lower density due to the formation of bulky groups in the crosslinks.     

Preparation and properties of high performance epoxy–silsesquioxane hybrid resins prepared using a maleimide–alkoxysilane compound as a modifier

An alkoxysilane compound possessing maleimide moiety (MSM) was prepared from N‐(4‐hydroxyphenyl)maleimide and 3‐glycidoxypropyltrimethoxysilane and was used as a modifier of epoxy resins. In situ curing epoxy resins with MSM resulted in epoxy resins with good homogeneity. Just 5–10 wt % of MSM is sufficient to yield high glass transition temperature (165 °C), good thermal stability above 360 °C, and high flame retardancy (LOI = 30) to bisphenol‐A‐based epoxy resins. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5787–5798, 2005     

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 (t _gel) 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.     

NMR investigations of the possible cross reactions between cyanate and epoxy resins

The possible cross reactions indicated by solid-state NMR between cyanate functionalized resin and epoxy functionalized resin have been investigated by using both natural abundance and labeled monofunctional model compounds. These soluble products were isolated and purified by silica gel adsorption chromatography and gel permeation chromatography. They were fully characterized by high resolution ¹H-, ¹³C-, ¹⁵N-NMR spectroscopy and by mass spectrometry. The major cross-reaction product is a racemic mixture of enantiomers, which contain an oxazolidinone ring formed by one cyanate molecule and two epoxy molecules. However, epoxy consumption lags cyanate consumption in the overall reaction as triazine formation from the cyanate is much faster than the two competing reactions, the cross reaction between cyanate and epoxy, and the self-polymerization of epoxy, under the conditions investigated. The cross reaction between cyanate and epoxy is limited. Approximately 12% of cross reaction between cyanate and epoxy was found in the overall reaction. In addition to the cross reactions of epoxy and cyanate, the reactions of epoxy and the carbamate, which is the major side product for the curing reaction of cyanate resin in solution, have also been investigated, and the mechanism of these reactions discussed. From the reactions of epoxy and carbamate, several products related to cross reaction between epoxy and cyanate have been isolated and identified. It is suggested that the reaction of epoxy and carbamate is one of the pathways in the overall cross reaction between epoxy and cranate resins. Finally, the mechanism of the overall cross-curing reaction between the diepoxy and dicyanate mixed resins is discussed. © 1994 John Wiley & Sons, Inc.     

Effect of flocculated structure on rheology of poly(butylene terephthalate)/clay nanocomposites

The microstructure and rheological property of poly(butylene terephthalate) (PBT)/epoxy/montmorillonite nanocomposites (PCNs) were investigated. For the study, PCNs were prepared by melt intercalation in clay content of 4 wt % and, epoxy loadings were varied from 2 to 4 wt %. The intercalated PCNs are characterized by different techniques such as transmission electron microscopy, Fourier transform infrared and rheology. It is interesting that the percolated tactoids network in the ternary hybrids becomes insensitive to the shear deformation with the addition of epoxy in contrast to that in the sample without epoxy, which can be attributed to the formation of a flocculated structure of clay tactoids because of the chain‐extension reactions between PBT matrix and epoxy and possible hydrogen bonding. The flocculated structure has influence on the rheological behavior of the hybrids remarkably, strengthening the percolated strong‐associated‐tactoids network and reducing the percolation threshold, while not changing the strain‐scaling. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2807–2818, 2005     

Synthesis and photochemical properties of novel multifunctional photopolymers with both pendant epoxy groups and phenacyl ester groups

Novel multifunctional photopolymers with both pendant epoxy groups and phenacyl ester groups were synthesized by the one‐pot method for the reaction of poly(methacrylic acid) with epibromohydrin; this was followed by a reaction with phenacylbromide with 1,8‐diazabicyclo‐[5.4.0]undecene‐7 as a condensation reagent. These esterification reactions proceeded smoothly and quantitatively under mild conditions. Moreover, the photochemical reactions of the resulting polymers were evaluated by UV and IR spectroscopy. The pendant phenacyl ester groups were photocleaved to give corresponding carboxyl groups, and then the produced carboxyl groups reacted with pendant epoxy groups. Furthermore, the baking process promoted a crosslinking reaction because of the addition reaction of epoxy groups with carboxyl groups after irradiation. It was also proven that the photochemical reactivity of the resulting polymers was affected by the structure of the phenacyl ester group. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 530–538, 2001     

Synthesis of Phosphate Epoxy Hardener-Flame Retardant and Rheokinetics of Curing of Epoxy Composites with Its Use

The effect of phosphate hardener obtained from phosphoric acid and acetic anhydride on the rheokinetics of extended epoxy composite is studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 860–864.Original Russian Text Copyright © 2005 by Nikolaev, Nikolaeva.     

Reactions in aminosilane–epoxy prepolymer systems I. Kinetics of epoxy–amine reactions

The reactions of an epoxy prepolymer based on bisphenol A diglycidylether (DGEBA) with γ-aminopropyltriethoxysilane (γ-APS) are studied. The results of different techniques are compared: size exclusion chromatography, differential scanning calorimetry, chemical titration, and Fourier Transform Infrared absorption. Epoxy amine reactions are shown to be faster than the crosslinking reactions between alkoxysilane and hydroxy groups, and thus, can be studied seprately. The reactivity of the epoxy group in DGEBA is compared with that of phenylglycidylether (PGE). And the reactivity of the amine group of γ-APS is compared with that of hexylamine. The kinetic constants are calculated with a mechanism which takes into account both the catalytic and noncatalytic reactions. The ratio r = k₂/k₁ of the reactivity of the secondary to the primary amino-hydrogens was also determined. The values of r are 1.4 for hexylamine and 1.2 for γ-APS. The reactivity of the epoxy groups are the same for both PGE and DGEBA.     

Dual‐curable fluorinated poly(methacrylate) copolymers for optical adhesives

In pursuit of photo‐curable adhesive for optical communication, dual‐curable acrylic oligomers (AOs) having alkoxy silane group, fluorine atoms and vinyl group as a pendent group were synthesized by two‐stage reactions. The isocyanate group containing oligomers were firstly synthesized via radical polymerization of acrylic monomers, and followed by urethane reaction with 2‐hydroxy ethyl methacrylate. The dual curing behaviors, e.g. thermal and photo‐cure, were studied by using photo‐differential scanning calorimetry (DSC) and real‐time IR. An optimum adhesive formulation, based on AO (15 g), epoxy acrylate (80 g), isobonyl methacrylate (17 g) and photo‐initiator (3 g), was obtained. As the content of AO was increased in the optical adhesive formulation, refractive index decreased but transmittance increased due to the increase in fluorine content. The optical transmittance at the range of 1.3 to 1.55 μm was higher than 90%. The addition of colloidal silica with the earlier mentioned formulation was helpful in decreasing crosslinking volume shrinkage and the increasing of glass fiber adhesion. The required properties for the optical adhesive, including chemical resistance and thermal resistance, dimension stability, etc. were also investigated. Copyright © 2005 John Wiley & Sons, Ltd.     

Alkylation of C-Phosphorylated Acetimidates Containing an Activated Methylene Group

N-substituted dialkoxyphosphorylacetimidates, the methylene group located between the phosphoryl and imide groups exhibits substantial CH acidity. One methylene hydrogen atom is replaced in the reactions of these imidates with sodium metal or sodium alcoholates. The sodium derivatives react with alkyl halides to form the corresponding homologs of N-substituted dialkoxyphosphorylacetimidates.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 3, 2005, pp. 411–414.Original Russian Text Copyright © 2005 by Shishkin, Mednikov, Anishchenko.     

Syntheses,structure, reactivity,and thermal properties of new cyclic phosphine oxide epoxy resins cured by diamines

A new type of epoxy resin which contained cyclic phosphine oxide group in the main chain was synthesized. The structure of the new type of epoxy resin was confirmed by elemental analyses (EA), infrared spectroscopy (IR), and ¹H-NMR and ¹³C-NMR spectroscopies. In addition, compositions of the new synthesized cyclic phosphine oxide epoxy resin (EPCAO) with three curing agents, e.g., bis(3-aminophenyl)methylphosphine oxide (BAMP), 4,4′-diamino-diphenylmethane (DDM), and 4,4′-diaminodiphenylsulfone (DDS), were used for making a comparison of its curing reactivity, heat, and flame retardancy with that of Epon828 and DEN438. The reactivities were measured by differential scanning calorimetry (DSC). Through the evaluation of thermal gravimetric analysis (TGA), those polymers which were obtained through the curing reactions between the new epoxy resin and three curing agents (BAMP, DDM, DDS) also demonstrated excellent thermal properties as well as a high char yield. © 1996 John Wiley & Sons, Inc.     

Synthesis of Epoxy Methacrylate Resin and Coatings Preparation by Cationic and Radical Photocrosslinking

This work involves the synthesis of hybrid oligomers based on the epoxy methacrylate resin. The EA resin was obtained by the modification of industrial-grade bisphenol A-based epoxy resin and methacrylic acid has been synthesized in order to develop multifunctional resins comprising both epoxide group and reactive, terminal unsaturation. Owing to the presence of both epoxy and double carbon–carbon pendant groups, the reaction product exhibits photocrosslinking via two distinct mechanisms: (i) cationic ring-opening polymerization and (ii) free radical polymerization. Monitoring of EA synthesis reactions over time using PAVs, MAAC and NV parameters, and the FT-IR method reveals that esterification reactions proceed faster at the start, exhibiting over 40% of conversion within the initial 60 min, which can be associated with a relatively high concentration of reactive sites and low viscosity of the reaction mixture at the initial reaction stage. With the further increase in the reaction time, the reaction rate tends to decrease. The control of the EA synthesis process can guide how to adjust reactions to obtain EAs with desired characteristics. Based on obtained values, one can state that the optimum synthesis time of about 4–5 h should be adopted to prepare EAs having both epoxy groups and unsaturated double bonds. The structure of the obtained EA was confirmed by FT-IR and NMR methods, as well as the determination of partial acid value and epoxy equivalent. Samples at various stages of synthesis were cured with UV radiation in order to study the kinetics of the process according to cationic and radical polymerization determined via photo-differential scanning calorimetry (photo-DSC) and real-time infrared spectroscopy (RT-IR) and then the properties of the cured coatings were tested. It turned out that the cationic polymerization was slower with a lower conversion of the photoreactive groups, as compared to the radical polymerization. All the obtained EA coatings were characterized by good properties of cured coatings and can be successfully used in the coating-forming sector.     

Cyanoethylation of Aromatic Aldehyde Imines Containing a Hydroxy Group in the β- or γ-Position. Synthesis of 3-Cyanoethyl-1,3-oxazacycloalkanes

Acrylonitrile reacts with aromatic aldehyde imines containing a hydroxy group in the β- or γ-position to give 70–85% of the corresponding 2-aryl-3-cyanoethyltetrahydro-1,3-oxazines or 2-aryl-3-cyanoethyl-1,3-oxazolidines, respectively. The results of these reactions are rationalized in terms of ring-chain isomerism of the initial imines.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1064–1066.Original Russian Text Copyright © 2005 by Kon’kova, Abovyan, Khachatryan, Badasyan, Panosyan, Sargsyan.     

A flame‐retardant phosphate and cyclotriphosphazene‐containing epoxy resin: Synthesis and properties

A novel flame‐retardant epoxy resin, (4‐diethoxyphosphoryloxyphenoxy)(4‐glycidoxyphenoxy)cyclotriphosphazene (PPCTP), was prepared by the reaction of epichlorohydrin with (4‐diethoxyphosphoryloxyphenoxy)(4‐hydroxyphenoxy)cyclotriphosphazene and was characterized by Fourier transform infrared, ³¹P NMR, and ¹H NMR analyses. The epoxy resin was further cured with diamine curing agents, 4,4′‐diaminodiphenylmethane (DDM), 4,4′‐diaminodiphenylsulfone (DDS), dicyanodiamide (DICY), and 3,4′‐oxydianiline (ODA), to obtain the corresponding epoxy polymers. The curing reactions of the PPCTP resin with the diamines were studied by differential scanning calorimetry. The reactivities of the four curing agents toward PPCTP were in the following order: DDM > ODA > DICY > DDS. In addition, the thermal properties of the cured epoxy polymers were studied by thermogravimetric analysis, and the flame retardancies were estimated by measurement of the limiting oxygen index (LOI). Compared to a corresponding Epon 828‐based epoxy polymer, the PPCTP‐based epoxy polymers showed lower weight‐loss temperatures, higher char yields, and higher LOI values, indicating that the epoxy resin prepared could be useful as a flame retardant. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 972–981, 2000     

A Highly Stereoselective Synthesis of Glycidic Amides Based on a New Class of Chiral Sulfonium Salts: Applications in Asymmetric Synthesis

A new type of chiral sulfonium salts that are characterized by a bicyclic system has been designed and synthesized from α‐amino acids. Their corresponding ylides, which were prepared by basic treatment of the sulfonium salts, reacted smoothly with a broad array of simple and chiral aldehydes to provide trans‐epoxy amides in reasonable to very good yields and excellent stereoselectivities (>98 %). The obtained epoxy amides were found to be useful as synthetic building blocks. Thus, they were reduced into their corresponding epoxy alcohols and subjected to oxirane‐ring‐opening reactions with different types of nucleophiles.     

Nonaqueous synthesis of nanosilica in epoxy resin matrix and thermal properties of their cured nanocomposites

Nonaqueous synthesis of nanosilica in diglycidyl ether of bisphenol‐A epoxy (DGEBA) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly with DGEBA epoxy matrix, at 80 °C for 4 h under the catalysis of boron trifluoride monoethylamine (BF₃MEA). BF₃MEA was proved to be an effective catalyst for the formation of nanosilica in DGEBA epoxy under thermal heating process. FTIR and ²⁹Si NMR spectra have been used to characterize the structures of nanosilica obtained from this direct thermal synthetic process. The morphology of the nanosilica synthesized in epoxy matrix has also been analyzed by TEM and SEM studies. The effects of both the concentration of BF₃MEA catalyst and amount of TEOS on the diameters of nanosilica in the DGEBA epoxy resin have been discussed in this study. From the DSC analysis, it was found that the nanosilica containing epoxy exhibited the same curing profile as pure epoxy resin, during the curing reaction with 4,4′‐diaminodiphenysulfone (DDS). The thermal‐cured epoxy–nanosilica composites from 40% of TEOS exhibited high glass transition temperature of 221 °C, which was almost 50 °C higher than that of pure DGEBA–DDS–BF₃MEA‐cured resin network. Almost 60 °C increase in thermal degradation temperature has been observed during the TGA of the DDS‐cured epoxy–nanosilica composites containing 40% of TEOS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 757–768, 2006     

A FOURIER TRANSFORM INFRARED SPECTROSCOPIC STUDY OF THE REACTION BETWEEN POLY (VINYL PYRIDINE)S AND EPOXY COMPOUNDS

Chemical reactions between poly (vinyl pyridine)s and 1, 4-butanediol diglycidyl ether and other epoxy compounds were studied by Fourier transform infrared spectroscopy and other techniques. The epoxy group was found to react with the pyridine side group of poly (4-vinyl pyridine), forming crosslinked networks which contain cyclic amide structures. The reaction was also observed in the interracial region of poly(vinyl pyridine) and γ-glycidoxy propyl trimethoxysilane hydrolyzate (γ-GPS) coatings on PET fiber substrates. Poly(2-vinyi pyridine) does not show the same reaction.     

Preparation of epoxy-acrylic latex based on bisphenol F epoxy resin

Bisphenol F based epoxy-acrylic latex with different amount of epoxy resin was successfully prepared by semi-continuous seeded emulsion polymerization. The resulting composite latexes had a narrow size distribution of about 105 nm in diameter. The DSC result showed that the epoxy resin and polyacrylate were grafting copolymerization. The FTIR spectra showed that the epoxy group had been introduced into the epoxy acrylic latex system, and the composite latex could be crosslinked with epoxy hardener at room temperature. The crosslinked composite latex film exhibited a high Tg compared to epoxy-acrylic latexes. The surface of the films with the epoxy resin was regular, and diffused into the polyacrylate phase in the epoxy-acrylic latexes films. Since the curing reactions occurred before latex particle coalescence stage, the surfaces of the cured epoxy-acrylate latex films had a number of interface particle. Compared with the acrylic latex, the thermal stability of the epoxy-acrylate latex was increased, and the stability of the cured film increased with increasing epoxy content.     

Surface modification of imide containing polymers I: Catalytic groups

This paper describes basic studies of the surface modification of polyimide covered wires for insulation of electrical machines. Drain-off of the impregnating resin during production should be reduced by introduction of surface catalytic groups. ¹H NMR kinetic analysis of aminolytic ring opening reaction of low molecular model compounds for polyimides showed very fast modification reactions. The catalytic effect of various functional groups on unsaturated polyester imide, acrylate and epoxy resins was investigated by DSC. Co(II)-catalysts and tertiary aliphatic amines proved highest activity for double bond containing systems and epoxy resins, respectively. Aminolytic treatment of Kapton^® slides was followed by ATR-IR spectroscopy. Plate-plate rheometer measurements of epoxy resins employing tertiary amine-treated Kapton^® slides proved significantly reduced gelling temperature.     

Toughening of nylon‐6 with epoxy‐functionalized acrylonitrile‐butadiene‐styrene copolymer

Glycidyl methacrylate (GMA) functionalized acrylonitrile‐butadiene‐styrene (ABS) copolymers have been prepared via an emulsion polymerization process. The epoxy‐functionalized ABS (e‐ABS) particles were used to toughen nylon‐6. Molau tests and FTIR results showed the reactions between nylon‐6 and e‐ABS have taken place. Scanning electron microscopy (SEM) displayed the compatibilization reaction between epoxy groups of e‐ABS and nylon‐6 chain ends (amine or carboxyl groups), which improve disperse morphology of e‐ABS in the nylon‐6 matrix. The presence of only a small amount of GMA (1 wt %) within the e‐ABS copolymer was sufficient to induce a pronounced improvement of the impact strength of nylon‐6 blends; whereas further increase of the GMA contents in e‐ABS resulted in lower impact strength because of the crosslinking reaction between nylon‐6 and e‐ABS, resulting in agglomeration of the ABS particles. SEM results showed shear yielding of the nylon‐6 matrix and cavitation of rubber particles were the major toughening mechanisms. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2170–2180, 2005