Novolac Epoxy Research Articles

Facile, one‐pot synthesis of aromatic diamine‐based benzoxazines and their advantages over diamines as epoxy hardeners

AbstractThree aromatic diamine‐based benzoxazines were successfully prepared by a facile, clean, one‐pot procedure from 1,4‐phenylenediamine (1), 4,4′‐diaminodiphenyl ether (2), and 4,4′‐diaminodiphenyl methane (3), respectively. Their structures were confirmed by NMR spectra and single crystal diffractogram. The effect of the reactivity of diamines on the purity of the resultant benzoxazines was discussed. The resultant benzoxazines were applied as hardeners for cresol novolac epoxy (CNE). The processing window, the latent curing characteristic, and the miscibility of benzoxazine/CNE systems were discussed. Compared with diamines (1 and 3), (1 and 3)‐based benzoxazines show latent curing characteristic as epoxy hardeners, and wide processing windows can be obtained. Compared with diamine (2) which is immiscible with CNE in the molten state, (2)‐based benzoxazine shows good miscibility with CNE. Dynamic mechanical analysis shows the Tgs of the benzoxazine/CNE thermosets are as high as 242–243 °C. Thermogravimetric analysis shows the outstanding thermal stability of the resultant thermosets. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2430–2437, 2010

Laminates based on vinyl ester resin and glass fabric: A study on the thermal, mechanical and morphological characteristics

The effects of variation of styrene content on the thermal, mechanical and morphological behaviours of epoxy novolac vinyl ester resin (EVER)/glass fabric laminate have been investigated. The vinyl ester resin matrix was synthesized indigenously using epoxy novolac resin and methacrylic acid catalyzed by triphenylphosphine at a temperature of 85°C in nitrogen atmosphere. Fourier-transform infra-red spectroscopic (FT-IR) analysis was used to see the structural changes during the synthesis of the EVER. Differential scanning calorimetric (DSC) technique was used to investigate the curing behaviour of the EVER matrix. Exothermic peaks (Tp) appeared in the range of 117–127°C for all the samples of epoxy resin and EVERs. Thermal stability of the prepared samples was analyzed by dynamic thermogravimetric runs. The TG/DTG trace of epoxy showed two-step mass loss decomposition behaviour whereas that of vinyl ester resin exhibited a single step mass loss. Mechanical properties such as tensile, flexural and impact strengths of the prepared laminates were determined and it was found cured resin containing 40% styrene showed the best balance of properties and EVER/glass fabric laminates exhibited better properties as compared to the epoxy/glass fabric laminates Dynamic mechanical analyses of the samples were done to determine the viscoelastic properties. Tg decreased significantly with increased styrene concentration due to increase in cross-linking density. Cross-sections of the cured samples, which failed during impact testing, have been critically studied through scanning electron microscopic (SEM) analysis to gain insight into the phase morphology.

Curing kinetics of Benzoxazine–epoxy copolymer investigated by non-isothermal differential scanning calorimetry

The reaction of epoxy novolac resin cured with benzoxazine resin (BA-a) was investigated under non-isothermal DSC at different heating rates. The kinetic parameters and the kinetic models of the curing processes of the benzoxazine-epoxy novolac mixtures were examined utilizing isoconversional methods, Flynn-Wall-Ozawa and Friedman methods. The benzoxazine-epoxy novolac mixture exhibits two dominant curing processes. The reaction 1 at lower temperature is attributed to the reaction among the benzoxazine monomers, while the reaction 2 corresponds to the formation of an etherification between hydroxyl group of polybenzoxazine and epoxide group or homopolymerization reaction of epoxide group at high temperature. The average activation energies of the reaction 1 and reaction 2 were determined to be 81 kJ mol −1 and 118 kJ mol −1, respectively. The autocatalytic kinetic model was found to be the best description of the investigated curing reactions. In addition, the predicted curves from our kinetic models fit well with the non-isothermal DSC thermogram.

Method development for epoxy resin analysis

Epoxy resin based negative photo resists are showing interesting properties which are useful for a series of applications in electronic industries (Mark et al. in Encyclopedia of polymer science and engineering, Wiley, New York, 1986; Potter in Epoxide resins, Springer, New York, 1970; May and Tanka in Epoxy resin chemistry and technology, Marcel Dekker, New York, 1973; Bauer in Epoxy resin chemistry, vol 114, American Chemical Society, Washington, 1979; Hood in RAPRA Rev Rep 38:4, 1990). Especially in micro system technologies they promise a high potential. To adjust the properties for the particular application modification of the chemical composition and crosslinker system must be performed. An actual problem is the constancy in behaviour during the LIGA-process of the resist mixture. In this work analytical techniques are used to get a detailed insight into the chemical composition of a commercial available epoxy novolac resin. Methods like size exclusion chromatography (SEC), matrix assisted laser desorption-time of flight (MALDI-ToF) and fourier transform infrared spectroscopy (FTIR) offer information about the molecular weight and functionality. The results reveal a distribution in molecular weight and functionality. Due this the resin was chemically modified. After processing a dependency of molecular weight and therefore the amount of epoxy groups existent was obtained.

Relationship of Particle Content and Size of Spherical Silica with the Flowability of Epoxy Molding Compounds for Large-Scale Integrated Circuits Packaging

The melting viscosities of different kinds of epoxy resins have been investigated in this paper. The results showed that tetramethyl biphenyl epoxy resin(TMBP) has very low melting viscosity(0.02Pa•s at 150°C) and can be blended with ortho-cresol novolac epoxy resin(ECN) in order to decrease the melting viscosity of epoxy molding compound(EMC). When the content of TMBP in the blend of ECN/TMBP was up to 40wt%, the viscosity of the blend decreased to 0.15 Pa•s from 0.8 Pa•s of ECN. In addition, the effects of the content, particle size of silica on the flowability of EMC have been researched systematically in the paper. The results showed that the melting viscosity of EMC increased greatly with the filling increasing of silica, and the particle size and the match of silica with different particle diameter had markedly influenced on the flowability of EMC. The melting viscosity of system with higher filling content of silica changed complicatedly with the increasing of shear rate, i.e., the viscosity of the system decreased with the increasing of shear rate in the range of low shear rate, then increased with the increasing of shear rate in the range of high shear rate, but decreased again with the increasing of shear rate in the range of higher shear rate. The system filled by silica with small particle diameter had low melting viscosity at low shear rate and high melting viscosity at high shear rate, but the melting viscosity of the system filled by silica with large particle diameter changed by contraries.

Hygrothermal Aging of Silane-Laced Epoxy Coatings

The impact of silane on the hygrothermal stability of epoxy coatings was investigated by specular neutron reflectivity (NR). By comparing the hygrothermal degradation behavior of neat novolac epoxy coating and corresponding bis[3-(triethoxysilyl)propyl]tetrasulfide-laced epoxy coating, the role of silane was elucidated. Accelerated aging was achieved by exposing the samples to 80°C liquid water. For the pure epoxy coating, degradation occurs at the coating–substrate interface, which makes the coating vulnerable to adhesion failure. For epoxy–silane coating the addition of silane imparts resistance to the interfacial degradation observed in the neat epoxy coating.

An approach to develop high-Tg epoxy resins for halogen-free copper clad laminates

A series of advanced epoxy resins (2) were prepared by the nucleophilic addition of cresol novolac epoxy (CNE) with a benzoxazine monomer (1), which is prepared by a one-pot procedure using 2-hydroxybenzaldehyde, 4-aminophenol and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) as starting materials. The nucleophilic addition was monitored by epoxy equivalent weight titration and NMR analysis. Based on this approach, the overall number of functionality of the resulting epoxy resins was retained because a curable benzoxazine linkage was also incorporated after the nucleophilic addition. As a result, high-Tg thermosets qualified for the UL-94 V-0 rating can be achieved after curing. When an UL-94 V-0 rating was achieved, Tg as high as 245°C (DMA data) was obtained for 4,4′-diaminediphenyl sulfone (DDS)-cured systems. The corresponding phosphorus content for the UL-94 V-0 rating was as low as 0.61wt%. The flame-retardant nature of oxazine linkage and nitrogen–phosphorus synergistic effect might be responsible for the low phosphorus content required for flame retardancy.

Study on the preparation and properties of novolac epoxy/graphite composite bipolar plate for PEMFC

In this study, the graphite/polymer composite bipolar plate was manufactured by a bulk-molding compound process. Low-cost novolac epoxy was chosen to compound with natural graphite and black carbon. The electrical properties and mechanical properties of composite bipolar plate were studied. The aging behavior was characterized according to the changes in property before and after the immersion test. The results show that the composite bipolar plates have good corrosion resistibility in the simulated solution of 0.005 mol L −1 H 2SO 4 + 2 × 10 −6 mol L −1 HF. TGA result shows that the novolac epoxy/NG composite has excellent thermal stability. The optimum processing conditions for preparing composite bipolar plate are: resin content about 15 wt.%; molding pressure 200 MPa; curing temperature 180 °C; graphite particle size −200 mesh. Under the optimum conditions, the composite bipolar plates have been produced, the electrical conductivity can attain to 120 S/cm and flexural strength is higher than 38 MPa.

Dynamic cure kinetics of epoxy–novolac compounds as studied by differential scanning calorimetry

AbstractThe cure kinetics of epoxy–novolac compounds were studied by means of differential scanning calorimetry with a dynamic approach. On the basis of a modified version of our previously reported kinetic model, a procedure aiming at the phenomenological description of the cure kinetics was developed. The reactions were found to be autocatalytic in nature for both commercial epoxy–novolac molding compounds and silica‐free imidazole‐cured epoxy–novolac systems. The weak extent of autocatalysis in the epoxy–novolac molding compounds was likely due to their high content of silica fillers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Dielectric Behavior of Epoxy/(Ba0.9Sr0.1)(Ti0.9Zr0.1)O3 Composites

The (Ba0.9Sr0.1)(Ti0.9Zr0.1)O3 (BSTZ) dielectric ceramic powder is mixed with O-Cresol Novolac (OCN) epoxy resin to form epoxy/BSTZ composites. As the content of BSTZ ceramic powder increases from 0 to 70 wt%, the dielectric constants of epoxy/BSTZ composites increase from 5.72 to 25.23 and the loss tangents are almost unchanged as measured frequency increases. The dielectric constants of epoxy/BSTZ composites first increase as measured temperature increases and are unchanged as measured temperature is higher than the Cure temperature of BSTZ ceramic. This research proves that we can develop the epoxy/BSTZ composites with stable temperature- and frequency-dependent characteristics.

Kinetic Analysis of UV-Curable Epoxy Resins for Micromachining Applications

Multifunctional epoxy resin series Epiclon HP-7200 is classified under the high performance series and is well known for its application in electrical encapsulation as it exhibits excellent mechanical and electrical properties. In addition, they have an advantage of an ultra low moisture absorption compared to other conventional cresol novolac (ECN) and biphenyl epoxy resins, which potentially makes it the next new mainstream of epoxy resins in electronics application. In this paper, kinetic study of various concentration of Epiclon HP-7200 (40-70 wt %) with divinyl ether (DVE) as the reactive solvent has been performed by Photo-Differential Scanning Calorimetry (DPC). The thermal stability of the Epiclon HP-7200 solutions has been analyzed by DSC and TGA.

The development of prediction method for the permittivity of epoxy/(Ba0.9Sr0.1)(Ti0.9Zr0.1)O3 composites

The relative permittivity of O-cresol Novolac epoxy resin/(Ba0.9Sr0.1)(Ti0.9Zr0.1)O3 (epoxy/BSTZ) composites with various contents of BSTZ ceramic powder was measured at 10 kHz to 1 MHz. As the content of BSTZ ceramic powder increases from 0 to 70 wt%, the permittivity increases from 5.72 to 25.23. Four different mixing rules are used to predict the variation of permittivity of epoxy/BSTZ composites, and the Lichtenecker equation fits the measured results. The permittivity of epoxy/BSTZ composites slightly increases as the measured temperature increases, and is unchanged when the measured temperatures are higher than the Curie temperature of BSTZ ceramic. This research proves that we can develop the epoxy/BSTZ composites with characteristics of stable temperature and frequency dependence.

Synthesis and properties of poly(urethane‐imide) diacid/epoxy composites cured with an aziridine system

AbstractA poly(urethane‐imide) diacid (PUI), a diimide‐diacid with a soft structure unit, was directly synthesized from the reaction of trimellitic anhydride and isocyanate terminated polyurethane prepolymer. FT‐IR and NMR were used to characterize its chemical structure. Then PUI was blended with two types of epoxy resins with different chemical structures, diglycidyl ether of bisphenol A (DGEBA) and novolac epoxy (EPN). After curing the blends with polyfunctional aziridine CX‐100, novel polyurethane/epoxy composites were obtained as transparent yellowish films. Thermal, chemical, and morphological properties of the cured composites were investigated using thermal analysis, SEM, TEM, chemical resistance, respectively. All experimental data indicated that epoxy modified PUI composites possessed higher thermal stability than that unmodified PUI, and that modified PUI had much better chemical resistance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Preparation and properties of halogen-free flame retardant epoxy resins with phosphorus-containing siloxanes

Novel epoxy resin modifiers, DOPO–TMDS and DOPO–DMDP were synthesized by addition reaction of divinylsiloxane with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Halogen-free flame retardant epoxy resins were obtained through modification of o-cresol novolac epoxy resin cured by phenol novolac resin using DOPO–TMDS and DOPO–DMDP which were characterized by 1H NMR, 13C NMR, 31P NMR and FT-IR measurements. Effects of the phosphorus-containing siloxanes on thermal stabilities, mechanical properties and flame retardant properties of the epoxy resins were investigated. The cured epoxy resins exhibited better mechanical properties and greatly improved flame retardant properties due to the presence of phosphorus-containing siloxanes. The cured epoxy resins with phosphorus loading of 2.0 wt% showed LOI values of 32–33 and achieved UL94V-0 ratings.

Bismaleimide Modified Epoxy-Diallylbisphenol System – Effect of Bismaleimide Nature on Properties

The properties of the ternary matrix system (EPB), obtained by the reactive blending of epoxy resin - diallyl bisphenol and a bismaleimide, depend on the structure and properties of its components. The influence of the structural variations of bismaleimide on the thermal, physical and mechanical properties of the ternary blend was examined. EPB compositions were prepared using novolac epoxy, diallyl phenol A and three different bismaleimide systems viz. 2, 2-bis 4-(4 maleimidophenoxy) phenyl propane-BMIP, bis (4-maleimidophenyl) methane-BMIM and bis (4-maleimido phenyl) ether-BMIE. The EPB systems with different types of bismaleimides were processed and characterized for their thermal, physical and rheological properties. EPB-glass composites processed using these matrix systems were characterized for their thermo-physical and mechanical properties. High temperature properties of these systems were assessed by their adhesive strength retention at different temperatures. The EPB system formed by the reactive blending of epoxy- phenol system with BMIP was found to yield the blend with improved mechanical performance at ambient conditions, while that with BMIM proved to be the best for high temperature application.

Investigation of cure kinetics and storage stability of the o-cresol novolac epoxy nanocomposites with pre-intercalated phenolic hardeners

The cure kinetics of the epoxy-layered, silicate nanocomposites were studied by differential scanning calorimetry under isothermal and dynamic conditions. The materials used in this study were o-cresol novolac epoxy resin and phenol novolac hardener, with organically modified layered silicates. Various kinetic parameters, including the reaction order, activation energy, and kinetic rate constants, were investigated, and the storage stability of the epoxy-layered silicate nanocomposites was measured. To synthesize the epoxy-layered silicate nanocomposites, the phenolic hardener underwent pre-intercalation by layered silicate. From the cure kinetics analyses, the organically modified layered silicate decreased the activation energy during cure reaction in the epoxy/phenolic hardener system. In addition, the storage stability of the nanocomposite with the pre-intercalated phenolic hardener was significantly increased compared to that of the nanocomposite with direct mixing of epoxy, phenolic hardener, and layered silicate. This was due to the protective effect of the reaction between onium ions and epoxide groups.

Synthesis, Characterization and Application of Coatings Based on Epoxy Novolac and Liquid Rubber Blend

Phenol‐based novolac resins were synthesized with different mole ratios of phenol‐to‐formaldehyde. These novolac resins were epoxidized with molar excess of epichlorohydrin at 120 °C in basic medium. Novolac and epoxy novolac resin were characterized by FTIR, NMR and GPC analysis. Molecular weight was found to be 838. The epoxidized novolac resins were separately blended with different weight ratios of carboxyl‐terminated polybutadiene liquid rubber ranging between 0‐25 wt % with an interval of 5 wt %. All the blends were cured at 150 °C with 40 wt % polyamide. The cured films of blend samples were checked for use them in coating applications.

Synthesis and characterisation of an epoxy resin containing fluorene moieties and its cured polymer

Purpose – The paper's purpose is to optimise lab‐size synthesis process of a fluorene‐containing epoxy resin, characterise structure of the resulting epoxy resin and evaluate mechanical properties of the cured fluorene‐containing polymers.Design/methodology/approach – The synthesis of the fluorene‐containing epoxy resin was accomplished by the polycondensation of 9,9‐bis(4‐hydroxyphenyl)‐fluorene and epichlorohydrin in the presence of quaternary ammonium salt and composite solvent under vacuum. The chemical structure of epoxy resin thus obtained was characterised with FTIR, NMR and MS. The shear strengthes of cured fluorene‐containing epoxy resin were determined and compared with that of cured E‐44 bisphenol A epoxy resin and F‐44 novolac epoxy.Findings – The epoxide equivalent weight (EEW) of the fluorene‐containing epoxy resin reached 240‐246 g/mol under optimal epoxidising condition. The resulting epoxy resin exhibited approximate high temperature performance relative to F‐44 novolac epoxy, much better...

Facile preparation of novel epoxy curing agents and their high‐performance thermosets

AbstractTwo flame‐retardant epoxy curing agents, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl‐tris(4‐hydroxyphenyl)methane (1) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl‐ (4‐aminophenyl)‐bis(4‐hydroxyphenyl)methane (2), were prepared by a facile, economic, one‐pot procedure. The structures of the curing agents were confirmed by IR, high‐resolution mass, 1‐D, and 2‐D NMR spectra. A reaction mechanism was proposed for the preparation, and the effect of electron withdrawing/donating effects on the stabilization of the carbocation was discussed. (1‐2) served as curing agents for diglycidyl ether of bisphenol A (DGEBA), dicyclopentadiene epoxy (HP‐7200), and cresol novolac epoxy (CNE). Properties such as glass transition temperature, coefficient of thermal expansion, thermal decomposition temperature, and flame retardancy of the resulting epoxy thermosets were evaluated. The resulting epoxy thermosets show high Tg, low thermal expansion, moderate thermostability, and excellent flame retardancy. The bulky biphenylene phosphinate pendant makes polymer chains difficult to rotate, explaining the high Tg and low thermal expansion characteristic. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7898–7912, 2008

Highly processable ternary systems based on benzoxazine, epoxy, and phenolic resins for carbon fiber composite processing

AbstractEffects of resin compositions in ternary systems of benzoxazine, epoxy, and phenolic novolac resins on processability, and thermomechanical properties of their carbon fiber‐reinforced composites are investigated. At suitable range of resin mass ratios, the ternary mixtures can provide a relatively wide processing window ranging from 50 to 200°C by maintaining their low A‐stage viscosity for a relatively long time which is crucial in the fiber preimpregnating process. Furthermore, relatively long shelf‐life of the ternary mixtures stored at room temperature (∼ 30°C) up to 270 days is obtained with minimal effect on their processability. The optimum mass ratio of B : E : P was determined to be 3 : 6 : 2, i.e., BEP362 resin. Finally, the carbon fiber composite based on BEP362 was found to exhibit substantial enhancement in its mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009