Novolac Epoxy Research Articles

Dynamic mechanical analysis of randomly oriented short bagasse/coir hybrid fibre-reinforced epoxy novolac composites

Hybrid composites of epoxy novolac reinforced with short bagasse fibres and short coir fibres were prepared. The mechanical and dynamic mechanical properties of these bagasse-coir hybrid fibres reinforced epoxy novolac composites were investigated with reference to different layering patterns of the composites. The tensile properties of the tri-layer composites are recorded higher than those of the bi-layer composites, whereas the flexural properties of the tri-layer composites are lower than bi-layer composites. The tensile strength of the intimate mix composite is comparable with trilayer composite having bagasse as skin material. The effect of layering pattern on storage modulus (E′), damping behavior (tan δ), and loss modulus (E″) was studied as a function of temperature and frequency. The E′ values of the bi-layer composites are recorded lower than those of tri-layer (bagasse/coir/bagasse) and intimately mixed hybrid composites. The minimum E′ value is obtained for the composites made with coir as skin layer. Bi-layer composite shows maximum damping property. The theoretical modeling showed good correlation with experimental results at above glass transition temperature (Tg), while theoretical model deviates experimental data at lower Tg. The Arrhenius relationship has been used to calculate the activation energy of the glass transition of the composites.

Photocure Kinetics of Thermally Stable Photoreactive Prepolymers with Cinnamate Moiety

New thermally stable photoreactive prepolymers were synthesized by the reaction of t-cinnamic acids (CAs) with different functional groups and two kinds of epoxy resins which are a biphenyl type epoxy resin and a novolac type epoxy resin with furan ring. Their photocure reaction rates and the extent of reaction conversion were measured with Fourier transform infrared spectroscopy, and their photocure reactions were analyzed in terms of nth-order kinetic reaction equation. Their optical and thermal stability were investigated with UV-Visible spectroscopy and thermogravimetric analysis (TGA). Their photocure reaction rates and the extent of reaction conversion increased with the intensity of UV irradiation. The photoreactive cinnamate prepolymers synthesized from FPREP epoxy resin showed a lower reaction conversion rate and a reaction constant than those of the photopolymer systems based on EBPXA epoxy resin. The reaction conversion rates of these photopolymers with hydroxyl group as a functional group of cinnamate were lower than those of only cinnamate moiety. Thermal stability was studied by observing changes in the transmittance of the photocured polymer films upon heating and by measuring weight loss with temperature using TGA. These photoreactive prepolymers with a biphenyl group showed good thermal properties, with almost no transmittance change in the visible range even after they were heated at 250°C for 1 hour, and these cinnamate photopolymer systems exhibited little weight loss up to about 300°C.

Novel Thermally Stable Epoxy-polyurethane Composites: Preparation, Characterization

A novel series of hydroxyl terminated bisphenol-A type novolac epoxy resins modified with propionic acid (MEP) were prepared by one-step ring-opening reaction process in the presence of tetramethylammonium bromide catalyst. The obtained MEP was characterized using FTIR, 1HNMR analyses. In addition, Intercross-linked epoxy-polyurethane composites networks were also obtained by curing reaction among MEP, cross linker polyisocyanate IL1351 and phthalic anhydride. The thermal characteristics of the epoxy-polyurethane composites were determined by thermogravimetric analysis (TGA). The thermal stability of the cured MEP with different ring-opening rate and cured alkyd polyol A450 were compared. The results showed that the obtained epoxy-polyurethane composites had much better thermal stability than the conventional polyurethane system A450/IL1351, and the thermal stability of them was correlated to the content of MEP.

Mechanical Properties of Oil Filter Paper Impregnated by a Novel Waterborne Novolac Epoxy Emulsion

A novel cationic waterborne epoxy emulsion for oil filter paper was synthesized. Hydrophilic groups were introduced into a multifunctional bisphenol-A novolac epoxy resin (NEP) by chemical modification, while maintaining the epoxy groups as many as possible, which were neutralized to form the equably water dispersed epoxy resin. The structure of modified NEP in different rate of ring-opening was characterized by Fourier Transform Infrared Spectroscopy (FTIR). The emulsion particle dispersion and micromorphology of waterborne bisphenol-A novolac epoxy resin (WNEP) was detected by granularity measured instrument and TEM. Mechanical properties and microstructure of oil filter papers impregnated by five different waterborne epoxy emulsions were tested and observed by SEM. From the results it can be shown that oil filter paper impregnated by WNEP emulsion has comprehensive properties better than other four commercialized products, exhibiting the best air permeability and improved bursting strength15% higher than that impregnated by poly-styrene-acrylate (PSA) latex.

Thermal-oxidative aging of DGEBA/EPN/LMPA epoxy system: Chemical structure and thermal–mechanical properties

The evolvement of chemical structure and thermal–mechanical properties of diglycidyl ether of bisphenol-A and novolac epoxy resin blends cured with low molecular polyamide (DGEBA/EPN/LMPA system) during thermal-oxidative aging were investigated by Attenuated Total Reflectance Fourier Transform Infrared spectrometry (ATR-FTIR) and Dynamic Mechanical Thermal Analysis (DMTA). The results revealed that the chemical reactions during thermal-oxidative aging contained oxidation and chain scission. Some possible chemical reaction processes were given. There was a new compound formed during aging processes and the change of its glass transition temperature ( T g) with aging time followed an exponential law. In addition, the changes of dynamic mechanical behavior of this epoxy system aged at four different temperatures (110 °C, 130 °C, 150 °C, 170 °C) were compared. An empirical formula was obtained through kinetic analysis and this formula can be used to predict the oxidative degree of the surface at different aging temperature.

Effect of CTBN Concentration on Thermal and Morphological Properties of Binary Copolymers of o-Cresol Novolac Epoxy Resin and Bismaleimide

Reactive rubber is the most used material to improve toughness of epoxy resins. Allylated o-cresol novolac resin with certain allylation degree was prepared and characterized, then was used to cure o-cresol novolac epoxy resin and 4,4′-Bismaleimide to prepare a heat-resistant epoxy resin. So, CTBN was introduced to improve its toughness. The effect of CTBN on thermal stability and morphology were studied. With the increase of CTBN, the storage modulus of BACC resins was increased basically indicating that CTBN was homogeneously dispersed in the matrix, and there were two glass transition temperatures of BACC resins indicating that the poor compatible between BACC and CTBN than between epoxy resin and CTBN. From the morphology of BACC resins, the effect of CTBN was similar to the other terminally reactive rubber. When the content was small, there was homogenous distribution of smaller CTBN particles in cured BACC matrix, and then the phase inversion occurred with the increase of CTBN. So, in order to improve toughness of cured BACC resin, a homogenous distribution of smaller CTBN particles is necessary. These conclusions revealed that the properties of BACC resins can be tailored and it must be useful to direct design of materials.

Study of effect of epoxynovolac oligomer on rheokinetics of curing of epoxyamine composition

The effect of epoxynovolac resin on hardening process in ED-22 epoxide oligomer is studied using the method of rotational viscometry.

Removal of Azo Dye Molecules from Aqueous Solution Using Novolac Resin Based Network Polymer

Abstract Synthesis of novolac resin based novel network polymer 1 based on the reaction between novolac epoxy resin and ethylenediamine has been achieved for the first time and its sorption characteristics toward methyl orange as azo dye source have been investigated.

Synthesis, characterization, and thermal stability studies of bisphenol-A type novolac epoxy-polyurethane coating systems for in-mould decoration ink applications

Recently, In-mould decoration (IMD) ink has gained considerable attention, which is used for decorating plastic surfaces through IMD craft. In this work, series of hydroxyl terminated bisphenol-A type novolac epoxy resins modified with benzoic acid (BAMEP) were synthesized in the presence of tetramethylammonium bromide catalyst. The chemical structures of the obtained BAMEP were characterized using FTIR, 1H NMR analyses. Epoxy-polyurethane coatings (BAMEP-PUs) were also obtained by curing reaction among BAMEP, cross linker polyisocyanate IL1351 and phthalic anhydride, which is desirable for IMD ink applications. The cured BAMEP-PUs, unmodified bisphenol-A type novolac epoxy resins (EP) and alkyd polyol A450 were determined by thermogravimetric analyzer, and their thermal stability were also compared. The results showed that the obtained BAMEP-PUs had much better thermal stability than the conventional polyurethanes, and the thermal stability of them at different temperature stage depended largely on the content of BAMEP and cross linker IL1351.

The Synthesis of Silicon-Containing Epoxy Resin and its Application in Environmentally-Friendship Epoxy Molding Compound for IC Packaging

Silicon-containing epoxy resin (CNE-Si) was synthesized from diphenylsilandiol (DPSD) and ortho-cresol novolac epoxy resin using SnCl2 as catalyst. The chemical structure of CNE-Si prepared in this paper was characterized by 1H-NMR and FTIR. The thermal stability was analyzed by TGA. The result showed that the –Si- group enhanced the thermal stability of the epoxy resin. The curing kinetics of the system was studied by non-isothermal DSC. The kinetic parameters of the curing reaction including the activation energy were calculated using Kissinger and Ozawa method. The results showed that the system containing CNE-Si has lower curing temperature and more quick curing speed compared to CNE, which can be used for manufacturing the quick-curing EMCs or afterward-curing-free EMCs.

Chemorheological study of phosphorylated flame retardant epoxies

The aim of this work is to study the chemorheology of the phosphorylated novolac epoxy used in flame retardants. The rheological properties are measured by a parallel plate viscometer and are combined with the kinetics of the curing reaction to explore the conversion dependent character of the viscosity. It was found that dynamic viscosity is a unique function of the effective shear rate over a wide range of frequencies and strains after being corrected for temperature. The effective shear rate dependence of the viscosity is described with a power law with an exponent that depends on the conversion. The effect of temperature is described with an Arrhenius type equation with conversion dependent parameters. Differential scanning calorimetry was applied to determine the kinetic equation that is used, in combination with the thermal history, to obtain the conversion during the rheological measurements. Time–cure–temperature modelling was applied to study a variety of factors that had an influence on the chemorheology. It was also found that the Cox–Merz relation can be utilised to correlate the dynamic viscosity data to the shear viscosity data. The Castro–Macosko model is proposed when considering the combination effects of shear thinning viscosity and reaction kinetics.

Development of Siliconized Epoxy Resins and Their Application as Anticorrosive Coatings

The present work involves the development of siliconized epoxy resin to overcome the drawback of epoxy resin like poor impact strength, high rigidity and moisture absorbing nature because of which they are not applied as corrosion resistant coating. By embedding silicone into the back bone of polymeric resin the above drawback can be reduced to substantial level. For achieving this, siliconised epoxy resins were prepared by reacting amine terminated silicone resin with novolac epoxy resin and meta-phenylenediamine was used as curing agent. The applied films of coating were baked at 150oC. Cured films were evaluated for their thermal, mechanical, chemical and corrosion resistance properties to ascertain the commercial utility of these eco-friendly resin for use in anti corrosive formulations. The siliconized epoxy resins system was found to exhibit good thermal and anticorrosive properties.

Influence of some vegetable oils on the photocrosslinking of coatings based on an o-cresol novolac epoxy resin and a bis-cycloaliphatic diepoxide

The influence of cashew nut shell oil (CNO), epoxidized soybean oil (ESO), castor oil (CO), and dioctyl phtalate (DOP) on the photocrosslinking kinetics of UV curable mixtures containing an o-cresol novolac epoxy resin (CNE), a bis-cycloaliphatic diepoxide monomer (BCDE), and a triarylsulfonium salt (TAS) as a cationic photoinitiator has been studied. The formulation with a weight ratio CNE/BCDE/TAS of 60/40/5 was found to have the highest cure rate and the greatest final conversion of epoxy groups upon UV exposure. The presence of an unsaturated oil or of DOP in the UV curable formulation, at a content ranging from 0.07 to 0.79 mol/kg, was shown to increase the initial polymerization rate of the epoxy groups from 12 up to 31 mol/kg s, and the epoxy conversion after 18 s UV exposure from 80 up to 95%. It was found that the UV cured coatings containing CNO or DOP at concentrations between 0.3 and 0.6 mol/kg and ESO at concentrations between 0.12 and 0.19 mol/kg exhibit the best performance. These results were explained by a number of competitive factors, mainly the effects of the chemical structure and content of the oils and of DOP on the polarity, viscosity, compatibility, and internal filter effect of the UV curable resins, as well as by the characteristics of the tridimensional polymer networks formed upon UV exposure. The materials produced under the optimal conditions determined in this study can be used as high performance decorative and protective coatings and also as adhesives in different sectors of applications.

Plasma Surface Modification of Silica and its Application in Epoxy Molding Compounds for Large-Scale Integrated Circuits Packaging

The surface modification of silica for epoxy molding compounds (EMC) was conducted by plasma polymerization using RF plasma (13.56MPa), and the modification factors such as plasma power, gas pressure and treatment time were investigated systematically in this paper. The monomers utilized for the plasma polymer coatings were pyrrole, 1,3-diaminopropane, acrylic acid and urea. The plasma polymerization coating of silica was characterized by FTIR, contact angle. Using the silica treated by plasma as filler, ortho-cresol novolac epoxy as main resin, novolac phenolic-formaldehyde resin as cross-linking agent and 2-methylmizole as curing accelerating agent, the EMCs used for the packaging of large-scale integrated circuits were prepared by high-speed pre-mixture and twin roller mixing technology. The results have shown that the surface of silica can be coated by plasma polymerization of pyrrole, 1,3-diaminopropane, acrylic acid and urea, and the comprehensive properties of EMC were improved.

Synthesis and curing properties of a novel curing agent based on N‐(4‐hydroxyphenyl) maleimide and dicyclopentadiene moieties

AbstractA new type of epoxy resin curing agent, containing pendant phenol functions, was synthesized by the free‐radical copolymerization of N‐(4‐hydroxyphenyl) maleimide with dicyclopentadiene (DCPD) monomer in the presence of a radical initiator. The chemical structure was characterized with Fourier transform infrared spectroscopy and nuclear magnetic resonance. The molecular weight of the new curing agent was determined by gel permeation chromatography. The activity and activation energy of this new curing agent with o‐cresol formaldehyde novolac epoxy (CNE) was investigated with a nonisothermal differential scanning calorimetry technique at different heating rates. The thermal properties of the cured polymers were evaluated with thermogravimetric analysis, and the results exhibit good thermal stability. In addition, this new curing agent with CNE showed low moisture absorption because of the hydrophobic nature of the DCPD structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Facile, one‐pot synthesis of aromatic diamine‐based phosphinated benzoxazines and their flame‐retardant thermosets

AbstractThree aromatic diamine‐based, phosphinated benzoxazines (7–9) were prepared from three typical aromatic diamines—4,4′‐diamino diphenyl methane (1), 4,4′‐diamino diphenyl sulfone (2), and 4,4′‐diamino diphenyl ether (3) by a one‐pot procedure. To clarify the reaction mechanism, a two‐pot procedure was applied, in which the reaction intermediates (4–6) were isolated for characterization. The structures of intermediates and benzoxazines were confirmed by high resolution mass, IR, and 1D and 2D‐NMR spectra. In addition to self‐polymerization, (7–9) were copolymerized with cresol novolac epoxy (CNE). After curing, the homopolymers of P(7–9) are brittle while the copolymers of (7–9)/CNE are tough. Dynamic mechanical analysis shows the Tgs of (7–9)/CNE copolymers are 187, 190, and 171 °C, respectively. Thermal mechanical analysis shows the CTEs of (7–9)/CNE copolymers are 46, 38, and 46 ppm, respectively. All the (7–9)/CNE copolymers belong to an UL‐94 V‐0 grade, demonstrating good flame retardancy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Preparation and characterization of epoxy/kaolinite nanocomposites

AbstractEpoxy/kaolinite nanocomposites were prepared by adding the organically modified layered kaolinite to an epoxy resin [biphenyl phenol novolac epoxy resin (BPNE)] with 4,4′‐diamino biphenyl sulfone (DDS) as a curing agent. The dispersion state of the kaolinite within crosslinked epoxy‐resin matrix was examined by X‐ray diffraction (XRD) and transmission electron micrograph (TEM). The effects of kaolinite on thermal properties were investigated and discussed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Experimental results show that BPNE/kaolinite nanocomposites exhibit improved thermal than pure BPNE. When the kaolinite content is 5 wt %, the BPNE/kaolinite nanocomposites show the best thermal properties. These results indicate that nanocomposition is an efficient and convenient method to improve the thermal properties of BPNE. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermal Properties, Fracture Toughness and Water Absorption of Epoxy-Palm Oil Blends

Epoxidized palm oil (EPO) was blended with cycloaliphatic epoxide, epoxy novolac and diglycidyl ethers of bisphenol-A. The fracture toughness and thermal properties of epoxy/EPO blends were characterized using single-edge notched bending tests and differential scanning calorimetry. Increased EPO loading improved the fracture toughness (K IC ) of the epoxy blends. The epoxy blends with higher EPO loading exhibited higher degree of conversion. The glass transition temperature (T g ) of the epoxy blends shifted to higher temperature as the increasing of DSC heating rate. Water absorption caused T g reduction of epoxy blends but it was determined that the water molecules absorbed were totally reversible.

Study of DGEBA and Novolac Adhesive Solutions between Ceramic and Steel Substrates

The industrial application (under a confidential clause) concerns a ceramic/steel assembly. This PhD research is concerned with providing a reliable industrial bonding between ceramic and steel using structural adhesive. This industrial joint shall withstand a wide range of temperatures with brutal thermal changes. This paper focuses on the adhesive formulation. Indeed, we needed to compromise the adhesive flexibility: soft enough to resist the thermal stresses and compensate the coefficient of thermal expansion mismatch between the two substrates. We find this good compromise with DGEBA and Novolac epoxy based adhesive separated or blended. The influence of the different formulation parameters on the initial properties was studied by chemical, rheological and thermal tests on adhesive samples. Depending on those formulations, we observed different behaviours in term of glass transition temperature, cross-linking time and flexibility.

Preparation and properties of epoxy-based cross-linked sulfonated poly(arylene ether ketone) proton exchange membrane for direct methanol fuel cell applications

Sulfonated poly(arylene ether ketone) bearing pendant carboxylic acid group (C-SPAEK) had been prepared for direct methanol fuel cell applications, and subsequently cross-linked by a thermal curing reaction using hexafluoro-bisphenol-A novolac epoxy resin (HFANER) as a cross-linker. The cross-linked network structure caused significant enhancement in the mechanical properties and oxidative stability. Meanwhile, water uptake, swelling ratio and methanol permeability substantially decreased with increasing the content of cross-linker. Notably, the water uptake of C-SPAEK was 506.9% at 80 °C, but after cross-linking, Cr-SPAEK-17 exhibited a water uptake of 32.3%. Meanwhile, a 12.1% of swelling ratio was obtained which was lower than that of Nafion 117 (17.2%). Although the proton conductivities of the cross-linked membranes were lower than that of the pristine membrane, the higher selectivity defined as the proton conductivity to methanol permeability was obtained for the cross-linked membranes.