Dimethylbenzylamine Research Articles

Thermal and Mechanical Characterization of Epoxy Resins (ELO and ESO) Cured with Anhydrides

AbstractIn this work we have developed polymeric materials from epoxidized vegetable oils in order to obtain materials with excellent mechanical properties for use as green matrix composites. Epoxidized soybean oil (ESO), epoxidized linseed oil (ELO) and different mixtures of the two oils were used to produce the polymers. Phthalic anhydride (17 mol%) and maleic anhydride (83 mol%) which has a eutectic reaction temperature of 48 °C were used as crosslinking agents while benzyl dimethyl amine (BDMA) and ethylene glycol were used as the catalyst and initiator, respectively. The results showed that samples 100ELO and 80ELO20ESO could be used as a matrix in green composites because they demonstrated good mechanical properties.

Curing and characterization of oxazolidone‐isocyanurate‐ether networks

AbstractOxazolidone‐isocyanurate‐ether networks were prepared by copolymerization of mixtures of DGEBA and toluene‐2,4‐diisocyanate (TDI) in presence of benzyldimethylamine (BDMA) as catalyst. Changes during curing and final properties of the cured materials were investigated by using DSC, FTIR/ATR, TMA, DMTA, TGA, and densitometry. The influence of the molar ratio of isocyanate to epoxide groups on the properties and curing were studied. The kinetics of curing was analyzed by means of an integral isoconversional nonisothermal procedure. The fractions of oxazolidone, isocyanurate, and ether groups present in the final network were evaluated and were found to be dependent on the initial isocyanate/epoxy ratio and curing conditions. By increasing the initial proportion of isocyanate the glass transition temperature, the thermal stability, the shrinkage, and the amount of isocyanurate rings increase, whereas the fraction of ether linkages and oxazolidones decreases. It was observed that the gelation is controlled by the formation of isocyanurate rings at the beginning of the curing. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

High performance HTLNR/epoxy blend—Phase morphology and thermo‐mechanical properties

AbstractAn attempt was made to toughen diglycidyl ether of bisphenol A (DGEBA) type epoxy resin with liquid natural rubber possessing hydroxyl functionality (HTLNR). Epon 250 epoxy monomer is cured using nadic methyl anhydride as hardener in presence of N, N dimethyl benzyl amine as accelerator. HTLNR of different concentrations up to 20 wt % is used as modifier for epoxy resin. The addition HTLNR to an anhydride hardener/epoxy monomer mixture has given rise to the formation of phase‐separated structure, consisting of small spherical liquid natural rubber particles bonded to the surrounding epoxy matrix. The particle size increased with increase in rubber content. The viscoelastic properties of the blends were analyzed using dynamic mechanical thermal analysis. The Tg corresponding to epoxy rich phase was evident from the dynamic mechanical spectrum, while the Tg of the rubber phase was overlapped by the β relaxation of epoxy phase. Glass transition of the epoxy phase decreased linearly as a function of the amount of rubber. The mechanical properties such as impact and fracture toughness were also carefully examined. The impact and fracture toughness increase with HTLNR content. A threefold increase in impact strength was observed with 15 wt % HTLNR/epoxy blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Phosphorus Recovery by Liquid–Liquid Extraction

It is acknowledged that phosphorus removal is more crucial in comparison with nitrogen removal for preventing algae glooming and eutrophication. Chemical and biological methods are common methods for the P removal. Excessive sludge production and difficulties of recovering phosphorus are concerns in terms of sustainable waste management. A liquid-liquid extraction (LLE) process is thus considered for the study aiming at recovering phosphorus from wastewater in a sustainable way. The results revealed that the best extractant is a mixture of kerosene and benzyl-di-methyl-amine (BDMA) at a volume ratio of 2:1. Under the study conditions, one part of extractant can react with four parts of wastewater to transfer >97% of P to the organic phase. In addition, in the stripping step, a 1:1 ratio of extract to recycled acid can result in 96% recovered P, implying an overall 93% phosphorus recovery efficiency can be achieved by the LLE process. Most importantly, the extractant can be recycled and reused at least 5 times if the residual P concentration should be less than 4 mg/L vs. the original P concentration of 21 mg/L. A complexion between amine groups in BDMA and phosphates and the positive charge of the micelles surface when the extractant (composed of kerosene and BDMA) mixed with P containing wastewater would contribute to the P recovery and this is a novel approach to recover P from wastewater.

New Age of Polymer Nanocomposites Containing Dispersed High-Aspect-Ratio Silicate Nanolayers

A new natural mica/epoxy nanocomposite was formed through the exfoliation of a mica layer. The natural mica used was a potassium sericite (K-SE) whose interlayer was saturated with potassium cations. Powdered samples were separated through an air classifier into D50 = 13.6 µm (its median particle diameter), D10 = 7.9 µm, and D90 = 23.7 µm. An organophilic SE was prepared by an ion exchange reaction between the SE powder and alkylammonium solutions of various initial concentrations. As a typical procedure to forming a completely organically modified sample, the K-SE powder was treated with the highest alkylammonium concentration. This corresponded to an alkylammonium+/K+ mole ratio = 10.0 which was kept at 90 °C for four days. The nanocomposites were prepared by dispersing the organophilic SE in an epoxy resin (diglyxidyl ether of bisphenol A, DGEBA) with subsequent curing in the presence of nadic methyl anhydride (NMA) and benzyldimethylamine (BDMA) at 120–180 °C. Considerable exfoliation of the organical...

Comparative study on the curing kinetics and mechanism of a lignin-based-epoxy/anhydride resin system

Curing kinetics and mechanism of liquid lignin based epoxy resin (LEPL)–maleic anhydride (MA) system accelerated with benzyldimethylamine (BDMA) were studied by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). In order to investigate the difference in the curing process, heating FTIR was used to study the change of the functional group. Complete consumption of the epoxides has been observed after the heating temperature was higher than 110°C. E constant method and E variable method, to study the dynamic DSC curves, were deduced by assuming a constant and a variable activation energy, respectively. With E constant method, the cure reaction activation energy E, the frequency factor A and overall order of reaction n+m are calculated to be 59.68kJmol−1, e20.6 and 1.462, respectively. With E variable method, E is proved to decrease initially, and then increases as the cure reaction proceeds. The value of E spans from 60.16 to 87.80kJmol−1. With the E constant method, E variable method and heating FTIR spectra used together, we can have a comprehensive and profound understanding of the cure reactions of the LEPL–MA system.

Episcopal Visitation of Cathedrals in the Church of England

In December 1994 the Revd Philip LS Barrett BD MA FRHistS FSA, Rector of Compton and Otterbourne in the Diocese of Winchester, successfully submitted a dissertation to the University of Wales College of Cardiff for the degree of LLM in Canon Law, entitled ‘Episcopal Visitation of Cathedrals in the Church of England’. Philip Barrett, best known for his magisterial study, Barchester: English Cathedral Life in the Nineteenth Century (SPCK1993), died in 1998. The subject matter of this dissertation is of enduring importance and interest to those engaged in the life and work of cathedrals, and the Editor invited Canon Peter Atkinson, Chancellor of Chichester Cathedral, to repare it for publication in this Journal, so that the author's work might receive a wider circulation, but at a manageable length. In 1999 a new Cathedrals Measure was enacted, following upon the recommendations of the Howe Commission, published in the report Heritage and Renewal (Church House Publishing 1994). The author was able to refer to the report, but not to the Measure, or to the revision of each set of cathedral Statutes consequent upon that Measure. While this limits the usefulness of the author's work as a point of reference for the present law of cathedral visitations, its value as an historical introduction remains.

A study on curing kinetic of bisphenol-F using benzyl dimethyl amine by isothermal DSC

The effect of the concentration of benzyl dimethyl amine as a catalyst on the cure reaction of bisphenol-F based epoxy resin(BPF)/nadic methyl ahydride(NMA) system was studied by differential scanning calorimetery using an isothermal approach over the temperature range 115-145°C. Kinetic parameters of the curing reaction including the reaction order, activation energy and kinetic rate constants were investigated. The results were dependent on the cure temperature and catalyst concentration and proceeded through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained by the Arrhenius kinetic model. The suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetic of BPF resin compositions as a function of the catalyst content and temperature.

Epoxies Modified by Palmitic Acid: From Hot‐Melt Adhesives to Plasticized Networks

AbstractSummary: Reactions taking place in a homogeneous solution of an epoxy monomer based on the diglycidyl ether of bisphenol A (DGEBA) and palmitic acid (PA), in the presence of benzyldimethylamine (BDMA), were investigated using Fourier‐transformed infrared spectroscopy (FTIR) and size exclusion chromatography (SEC). In the stoichiometric formulations prepared with equal molar ratios of epoxy (E) to carboxyl groups, E/PA = 1, the main reaction was the carboxyl addition to the epoxy giving a β‐hydroxy ester. This reaction was followed by transesterification that occurred to a very small extent. In the formulations prepared with an epoxy excess, E/PA > 1, the transesterification reactions were very significant as well as the homopolymerization of the epoxy excess that took place to an almost complete conversion. Reaction products synthesized in the range of 1 < E/PA < 2 were solids at room temperature due to the crystallization of a fraction of fatty acid chains. Above the melting temperature, reaction products recovered the liquid state. The formulation synthesized with E/PA = 2 exhibited a good behavior as a hot‐melt adhesive of steel sheets with a single lap‐shear strength of 2.5 MPa and an interfacial‐cohesive failure. For E/PA > 3, the gelation took place leading to the networks exhibiting a single glass transition temperature (Tg) without any evidence of crystallization or phase separation. Tg varied from 90 °C for the neat epoxy to 0 °C for the formulation with E/PA = 3.Single lap‐shear strength values of hot‐melt adhesives corresponding to reaction products synthesized with E/PA = 1.6, 1.8, and 2.magnified imageSingle lap‐shear strength values of hot‐melt adhesives corresponding to reaction products synthesized with E/PA = 1.6, 1.8, and 2.

Mixed S/P Ligands from Carbohydrates: Synthesis and Utilization in Asymmetric Catalysis

New chiral mixed sulfur/phosphorus ligands derived from carbohydrates are reported. These ligands were found to be efficient catalyst precursors for palladium-catalyzed asymmetric substitution of 1,3-diphenylpropenyl acetate with dimethyl malonate or benzylamine (up to 96% ee), and for rhodium-catalyzed methyl acetamidocinnamate hydrogenation (up to 92% ee).

Study of the Effect of BDMA Catalyst in Epoxy Novolac Curing Process by Isothermal DSC

Epoxy-Novolac/Anhsydride cure kinetics have been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was Epoxy Novolac resin (DEN431), nadic methyl anhydride as hardener and benzyl dimethyl amine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants were investigated. The cure reaction was described with the catalyst concentration and the normalized kinetic model was developed for it. It is shown that, the cure reaction was dependent on the cure temperature and catalyst concentration and proceeded through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained by the Arrhenius kinetic model. The suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetic of Epoxy Novolac resin compositions as a function of the catalyst content and temperature.

Thermally Reversible Light Scattering Films Based on Droplets of a Liquid Crystal (N-4-Ethoxybenzylidene-4‘-n-butylaniline)/Polystyrene Solution Dispersed in an Epoxy Matrix

Thermally reversible light scattering (TRLS) films were synthesized by the reaction-induced phase separation of solutions of N-4-ethoxybenzylidene-4‘-n-butylaniline (EBBA; 20−50 wt %) and polystyrene (PS; 1−5 wt %) in diglycidyl ether of bisphenol A (DGEBA), using benzyldimethylamine (BDMA) (0.06 mol with respect to epoxy groups), to initiate the polymerization. The material obtained after complete reaction consisted of a dispersion of EBBA/PS droplets in the epoxy network partially swollen by EBBA. The fractionation of EBBA between both phases was estimated using a simple thermodynamic model. Due to the matching of refractive indices of the three components, the multiphasic material was transparent above the nematic−isotropic transition temperature (TNI) of the EBBA/PS droplets. Below TNI the material exhibited a sharp transition to an opaque state due to the mismatching of refractive indices when EBBA was segregated as a nematic phase inside the droplets. The PS addition produced a significant decrease of the cloud-point conversion with respect to formulations devoid of PS. This led to relatively large domains that behave efficiently as light scattering centers in the PS-modified material, enabling high contrast ratios between transparent and opaque states to be obtained. The morphologies generated, and the corresponding optical properties of the TRLS films, did not change in the course of successive cooling/heating cycles.

TTT‐cure diagram of an anhydride‐cured epoxy system including gelation, vitrification, curing kinetics model, and monitoring of the glass transition temperature

AbstractThe curing reaction of an epoxy resin [diglycidyl ether of bisphenol A (DGEBA)] combined with a methyl‐hexahydrophtalic anhydride (MHHPA) hardener and a benzyldimethylamine (BDMA) accelerator was studied over a temperature range of 60–140°C to build its isothermal time‐temperature‐transformation (TTT)–cure diagram. This includes gelation and vitrification measurements using rheological measurement techniques, monitoring of the glass transition temperature and the reaction kinetics by differential scanning calorimetry, and determination of the following critical glass transition temperatures: Tg0, GelTg, and Tg∞. A new curing kinetics model, based on the Sesták‐Berggren model, was developed including both chemical‐ and diffusion‐controlled stages of reaction. Then, the TTT‐cure diagram was built by numerical integration of the kinetics model, and good agreement was obtained by comparison with experimental data. Additionally, for the first time, this model takes into account the incomplete cure, which occurs when the thermosetting system is cured below its ultimate glass transition temperature, leading to a more realistic description of the cure evolution after vitrification. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1774–1787, 2004

Nasal lavage fluid and proteomics as means to identify the effects of the irritating epoxy chemical dimethylbenzylamine

The aims of this study were to describe the changes in the nasal lavage fluid (NLF) protein pattern after exposure to the irritating epoxy chemical dimethylbenzylamine (DMBA) and to identify the affected proteins using a proteomic approach. The protein patterns of NLF from six healthy subjects and eight epoxy workers with airway irritation were analysed using two-dimensional gel electrophoresis (2-DE) before and after exposure to 100 μg m−3 DMBA for 2 h in an exposure chamber. NLF proteins were identified by (i) comparison with a 2-DE NLF reference database; (ii) N-terminal amino acid sequencing; and (iii) mass spectrometry. In NLF from healthy subjects, the levels of immunoglobulin A increased and the levels of Clara cell protein 16 (CC16) decreased after chamber exposure, while in NLF from epoxy workers, α2-macroglobulin and caeruloplasmin increased. Two previously unidentified proteins decreased in NLF from epoxy workers after exposure; these were identified as statherin and calgranulin B. In addition, the subjects who developed high counts of eosinophils in their nasal mucosa after chamber exposure had significantly lower levels of immunoglobulin-binding factor (IgBF) before exposure than subjects with low eosinophil infiltration. These results show that short-term exposure to DMBA causes distinct changes in NLF proteins. Moreover, three proteins that have previously not been associated with upper airway irritation were identified: statherin, calgranulin B and IgBF. Further studies are needed to investigate whether these proteins may be used as biomarkers of airway irritation and to give new insight into the ways in which occupational exposure to irritants causes inflammation of the airways.

Viscoelastic Effects on the Phase Separation in Thermoplastics-Modified Epoxy Resin

The phase separation of the diglycidyl ether of bisphenol A (DGEBA)/methyltetrahydrophthalic anhydride (MTHPA) blends modified with polyetherimide (PEI) in the presence of various amounts of accelerator benzyldimethylamine (BDMA) was investigated by scanning electron microscopy (SEM) and time-resolved light scattering (TRLS). The morphologies of the blends with the accelerator are of the co-continuous type, exhibiting irregular shapes. They are quite different from that without accelerator, in which the morphology is spherical. The TRLS results display clearly that the phase separation takes place according to a spinodal decomposition mechanism and the evolution of scattering vector qm corresponding to epoxy droplets follows a Maxwell-type relaxation equation. The temperature-dependent relaxation time τ obtained for these blends can be described by the Williams−Landel−Ferry equation. It demonstrates experimentally that the coarsening processes of epoxy droplets and the final morphologies obtained in these...

Benzyldimethylamine (BDMA): Catalyst of Choice with Epoxy Embedding Media

Benzyldimethylamine (BDMA): Catalyst of Choice with Epoxy Embedding Media

Epoxy networks based on solutions of silsesquioxanes functionalized with 3-glycidoxypropyl groups in diglycidylether of bisphenol A (DGEBA)

In previous publications we reported the synthesis and characterization of silsesquioxanes derived from the hydrolytic condensation of (3-glycidoxypropyl) trimethoxysilane (GPMS) using diglycidylether of bisphenol A (DGEBA) as a solvent [1,2]. The reaction product has aliphatic epoxy groups supplied by the silsesquioxane and aromatic epoxy groups supplied by the solvent. Solutions containing 0, 25 and 50% aliphatic epoxy groups, were cured with different hardeners: methyltetrahydrophthalic anhydride (MTHPA), ethylenediamine (EDA) and benzyldimethylamine (BDMA). Silsesquioxane-modified epoxy networks showed a significant increase in the elastic modulus in the rubbery state, the abrasion resistance and the development of strain hardening in uniaxial compression tests.

ChemInform Abstract: Application of Chiral Mixed Phosphorus/Sulfur Ligands to Palladium-Catalyzed Allylic Substitutions.

A modular approach to the synthesis of a class of mixed phosphorus/sulfur ligands was designed to identify important ligand structural features for enantioselective palladium-catalyzed allylic subsitutions of acyclic and cyclic ayllic esters. After a systematic variation of the ligand substituents at sulfur, phosphorus, and the ligand backbone, ligand 11k was found to be optimal in the palladium-catalyzed allylic substitution of 1,3-diphenylpropenyl acetate with dimethyl malonate or benzylamine in high yield and excellent enantioselectivity (95−98% ee). A similar optimization of the mixed phosphorus/sulfur ligand for the palladium-catalyzed allylic substitution of cycloalkenyl acetates showed that 49g afforded the highest enantioselectivities (91−97% ee). Application of this methodology to heterocyclic substrates was developed as an efficient approach to the enantioselective synthesis of 3-substituted piperidines and dihydrothiopyrans. Models for asymmetric induction are discussed based on the absolute st...

Epoxy/anhydride networks modified by epoxy/anhydride oligomers containing SiOH groups

Epoxy/anhydride oligomers containing variable amounts of trialkoxysilane groups were synthesized from phenyl glycidyl ether (PGE), 3-glycidoxypropyl trimethoxysilane (GPMS), and methyl tetrahydrophthalic anhydride (MTHPA), using benzyldimethylamine (BDMA) as an initiator. They were hydrolyzed and partially condensed using diluted formic as a catalyst, with the last step carried out in a solution of diglycidyl ether of bisphenol A (DGEBA). By curing with a stoichiometric amount of MTHPA, in the presence of BDMA, plasticized epoxy/anhydride networks were obtained without any evidence of phase separation. These materials showed a better abrasion resistance than that of the neat matrix. The presence of free SiOH groups can be used to improve the adhesion to glass surfaces. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1365–1370, 2000

Gel-coated ion-exchange resin: A new kinetic model

Regenerable ‘gel-coated’ cationic resins with fast sorption kinetics and high sorption capacity have application potential for removal of trace metal ions even in large-scale operations. Poly(acrylic acid) has been gel-coated on high-surface area silica (pre-coated with ethylene–vinyl acetate copolymer providing a thin barrier layer) and insolubilized by crosslinking with a low-molecular-weight diepoxide (epoxy equivalent 180 g) in the presence of benzyl dimethylamine catalyst at 70°C. In experiments performed for Ca 2+ sorption from dilute aqueous solutions of Ca(NO 3) 2, the gel-coated acrylic resin is found to have nearly 40% higher sorption capacity than the bead-form commercial methacrylic resin Amberlite IRC-50 and also several times higher rate of sorption. The sorption on the gel-coated sorbent under vigorous agitation has the characteristics of particle diffusion control with homogeneous (gel) diffusion in resin phase. A new mathematical model is proposed for such sorption on gel-coated ion-exchange resin in finite bath and solved by applying operator-theoretic methods. The analytical solution so obtained shows good agreement with experimental sorption kinetics at relatively low levels (<70%) of resin conversion.