V. S. Patel

EFFECTS OF REACTIVE DILUENT DIEPOXIDIZED CARDANOL AND EPOXY FORTIFIER ON CURING KINETICS OF EPOXY RESIN

Different formulations, composed of the diglycidyl ether of bisphenol-A, diepoxidized cardanol as reactive diluent, an anhydride as curing agent, and a tertiary amine as curing catalyst, with/without the use of an epoxy fortifier, were analysed. The effect of the fortifier on the diluent was also observed. The overall kinetics of curing was observed to follow a simple Arrhenius-type temperaturedependence, with an activation energy in the range 54–120 kJ/mol, with first-order kinetics up to 85% conversion. An increase in activation energy was observed with an increase of diluent content. The curing reaction was found to follow a three-step mechanism, involving a nucleophilic bimolecular displacement reaction, for which an explanation was offered. Incorporation of the fortifier lowers the curing temperature, but does not alter the final degree of reaction.ZusammenfassungEs wurden verschiedene Ausgangsgemische, bestehend aus dem Diglyzidyläther von Bisphenol A, diepoxydiertem Kardanol als reaktives Streckmittel, einem Anhydrid als Vernetzungsmittel und einem tertiären Amin als Vernetzungskatalysator mit bzw. ohne Anwendung eines Fortifyers untersucht. Der Einfluss des Fortifyers auf das Streckmittel wurde ebenfalls untersucht. Die Bruttokinetik der Vernetzung zeigt eine Temperaturabhängigkeit einfachen Arrhenius-Types mit einer Aktivierungsenergie im Bereich von 54–120 kJ/mol sowie einen Reaktionstyp erster Ordnung mit einer Konversionsrate von 85%. Ein steigender Streckmittelgehalt bewirkt ein Anwachsen der Aktivierungsenergie. Der Vernetzungsreaktion liegt ein Dreistufenmechanismus zu Grunde, der unter anderem auch eine nukleofile bimolekulare Substitutionsreaktion beinhaltet. Der Einsatz eines Fortifyers senkt zwar die Vernetzungstemperatur, verändert aber nicht die Endkonversionsrate.РезюмеИсследованы различн ые композиции, состоя щие из диглицидного эфир а бисфенолаА, диэпоксидированног о карданола, как разба вителя реакции, ангидрида, ка к вулканизирующего аг ента, и третичного ами на, как катализатора реакци и отверждения, с или без использования эп оксизакрепителя. Уст ановлено влияние закрепителя на разбавитель. Найдено, что общая кин етика реакции отверж дения подчиняется простой температурной зависимости аррениу совского типа с энерг ией активации 54–120 кдж·моль−1 и реакцией первого порядка с 85% превращени ем. Наблюдалось увели чение энергии активации с у величением содержания разбавит еля. Найдено, что реакц ия отверждения следует трехступенчатому механизму, включающе му реакцию нуклеофил ьного бимолекулярного сме рения, для которой и предложено объяснен ие. Введение закрепит еля понижает температуру отвержд ения, но не затрагивает конечну ю степень реакции.

Effect of different epoxy diluents/fortifier on the reactivity in curing and the thermal stability of epoxy resin using 2,2-bis[4-(p-aminophenoxy)phenyl]-propane as a curing agent

Abstract The curing reaction of the diglycidyl ether of bisphenol A with different diglycidyls and triglycidyls (used as diluents) using 2,2-bis[4-(p-aminophenoxy)phenyl]propane as a curing agent, with or without fortifier, has been studied by differential scanning calorimetry. The thermal stability of the cured resins has also been discussed. The overall activation energy for the curing reaction is observed to be in the range 48.1–71.4 kJ mol−1 and the order of the reaction is found to be ∼-1.0. The activation energy of decomposition of the cured resin falls within the range 48.3–84.5 kJ mol−1.

Synthesis and Characterization of Monomeric and Polymeric Disperse Dyes for Hydrophobic Fibres

Abstract Some monomeric disperse dyes based on 2-amino-5-mercapto-1,3,4-thiadiazole have been synthesized by coupling with derivatives of N-phenylacrylamide. Polymeric dyes have been prepared by free radical polymerization of monomeric dyes and were characterized by IR spectra, Intrinsic viscosity, molecular weight by Vapour Pressure Osmometry, thermogravimetry analysis, bleeding test and elemental analysis. The monomeric dves have been also characterized by IR spectral studies and elemental analysis. The purity of dyes was checked by thin layer chromatography. All the dyes were applied as disperse dyes on nylon and polyester fibres. These dyes have been found to give a wide range of colour shades with very good depth and levelness on each fibre. The percentage dye bath exhaustion on different fibres have been found to be good to very good. The dyed fibres showed good to excellent fastness to light on nylon and polyester fibres. The washing, rubbing, perspiration and sublimation fastness properties of the dyed fibres has been found to be very good to excellent.

Curing kinetics of epoxy resin using epoxidized cardanol as diluent with/without fortifier

Abstract The curing reactions of diglycidyl ether of bisphenol-A (DGEBA) with different anhydrides as curing agent and triethyl amine as curing catalyst have been studied using mono epoxidized cardanol (MEC) as reactive diluent in different molar ratios with/without the use of epoxy fortifier by differential scanning calorimetry. The overall kinetics of curing follows a simple Arrhenius type temperature dependence with an activation energy range 80–115 kJ mol−1, and first-order kinetics, at least up to 85% conversion. Incorporation of diluent lowers the reactivity of the epoxy system; however addition of epoxy fortifier accelerates the cure process.

Thiophene Based Monomeric and Polymeric Disperse Dyes for Hydrophobic Fibres

Abstract Eight monomeric dyes have been prepared by coupling 2-amino-3-carbethoxy-4,5-dimethylthiophene with various N-phenylmaleimides. Polymeric dyes have been prepared by free radical polymerization of monomeric dyes and they are characterized by IR spectra, Intrinsic viscosity, molecular weight by Vapour Pressure Osmometry, thermogravimetry analysis and elemental analysis. The monomeric dyes have been also characterized by IR spectral studies and elemental analysis. All the dyes were applied as a disperse dyes on nylon and polyester fibres. The dyed fibres showed fair to good fastness to light on nylon and fair fastness on polyester. The washing, rubbing, perspiration and sublimation fastness properties of the dyed fibres has been found to be very good to excellent.

Glass-fibre-reinforced Epoxy Composites using Epoxidized Cardanol as Diluent

Glass-fibre-reinforced epoxy composites were prepared and evaluatedfor their mechanical chemical and electrical properties. The effect of incorporating epoxidized cardanol as diluent on such properties of the composites based on the diglycidyl ether of bisphenol-A was investigated The tensile strength andflexural strength increased significantly. The composites prepared using epoxy fortifiers showed a good improvement in properties such as tensile strength, flexural strength and interlaminar shear strength.

Carbon-fibre-reinforced Composites of Epoxidized Novolac Resins

Epoxidized novolac cardanol (ENC) was prepared from cardanol-a component of cashew nut shell liquid. Various uniand bidirectional carbon-fibre-reinforced composites were fabricated using ENC and other novolac resins. Diaminodiphenyl methane was used as curing agent for the systems. The mechanical properties of the composites were determined.

Synthesis and Characterization of Thermotropic Liquid Crystalline Copolyester

Abstract The thermotropic liquid crystalline copolyesters were prepared by direct polycondensa-tion reaction of terephthalic acid, isophthalic acid, p-acetoxy benzoic acid with various diacetylated diols. All these copolyesters were characterized by their elemental analysis and spectroscopic techniques. The transition temperatures of all compounds are confirmed by DSC technique and optical texture of the copclyesters in liquid crystalline state were observed on polarizing microscope. Most of the polymers exhibit a typical nematic mesophase. All polymers have very good thermal stability.

Synthesis, optimization and characterization of graft copolymers from Leucaena glauca seed gum and methylmethacrylate

Abstract The effects of respective concentrations of hydrogen peroxide (H2O2), methylmethacrylate (MMA) and Leucaena glauca seed gum (LGG) on the graft copolymerization of LGG-MMA have been studied by evaluating the rates of total polymerization (ktp), homopolymerization (kh) and graft copolymerization (kg) at different reaction times. The study shows that the grafting depends greatly upon the rate influencing factors. The grafted products have been characterized by infra-red sepctroscopy and thermogravimetry along with the usual methods based on grafting parameters. The optimum grafting conditions derived from the investigation at 85°C are: H2O2 concentration 10 mM litre−1, a backbone to monomer concentration ratio of 0·20 for 120 min, which yielded nearly 48% of grafting.

Properties of Glass-fibre Reinforced Epoxy Composites of Tetrafunctional Epoxy Resin

Abstract The curing reaction of epoxy resin l,l,2,2-tetrakis(4-glycidyloxyphenyl) ethane(TK-GOPE) with different aliphatic and aromatic amines has been studied by differential scanning calorimetry (DSC). The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fibre reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied. Activation energies of curing reactions is in the range of 80–187.27 KJ-mol−1. The cured products have good thermal stability, the composites have good mechanical strength, electrical insulation properties and chemical resistance.