Novolac Epoxy Research Articles

Preparation of conducting poly N-methylaniline microsphere and its antibacterial performance to sulfate reducing bacteria

Microspheres of conducting polymers poly N-methylaniline (PNMA) were successfully synthesized through oxidation of N-methylaniline without any template. The average diameter of the microspheres with a smooth surface was about 0.40 µm when 0.2 M N-methylaniline was oxidized with 0.2 M ammonium persulfate in 0.2 M of HClO4 solution. The size of microspheres can be controlled by changing reaction time and temperature. The acid concentration was critical for the formation of microspheres with smooth surfaces. The excellent antibacterial performance of PNMA in novolac epoxy coating to sulfate reducing bacteria was demonstrated. Moreover, in API media, PNMA inhibited growth of SRB and then reduced the corrosion rate of carbon steel remarkably.

Load Dependence of Dynamic Viscoelasticity of Epoxy Resin and its Composites

The load dependences of dynamic viscoelasticity of casting novolac epoxy 648 and its composites, reinforced by glass fiber (GFRP) or carbon fiber (CFRP), were investigated by dynamic mechanical thermal analysis under high loads. The fiber property and load pattern were considered to analyze the complicated variations in storage modulus and loss tangent with the change of loads. The load effects are comprehensively addressed by a phenomenological theory about suppression effect of static load on the motion of microstructure units, combined with the influence of shear stress and interface properties between fiber and resin.

New type of low-dielectric composites based on o-cresol novolac epoxy resin and mesoporous silicas: fabrication and performances

A series of o-cresol novolac epoxy (o-CNER)-based composites containing various amount of SBA-15, SBA-16, and MSU-X type mesoporous silicas were prepared, and their performances were evaluated. Morphological investigation by SEM reveals that the mesoporous silicas achieve a good dispersion in the o-CNER matrix due to an effective surface modification. The dielectric constants of all the composites were measured in the frequency range of 50–1,000 kHz. The investigation suggested that the dielectric constant could be reduced from 4.0 of the pure thermosetting o-CNER to 3.71, 3.73, and 3.73 by incorporating 5 wt.% SBA-15, SBA-16, and MSU-X, respectively. The reduction is attributed to incorporation of air voids stored within the mesoporous silicas, the air volume existing in the gaps on interfaces between the mesoporous silica and the matrix, and the free volume created by introducing large-sized domains. The composites present stable dielectric constants across the wide frequency range. An improvement of thermal stability of the o-CNER is achieved by incorporation of the mesoporous silica materials, while the enhanced interfacial interaction between the surface-modified mesoporous silica and the o-CNER matrix has also led to an improvement of toughness.

Thermal deformation properties of oligoepoxide-based binders

Crosslink density and a number of other physicochemical parameters of composites are investigated as functions of the initial mixture composition by the example of materials comprising bisphenol A-based epoxy oligomers with different molecular masses, nitrogen-chlorine-containing oligoepoxide, epoxy novolac block copolymer, epoxyurethane modifier, and amine and anhydride curing agents. It is shown that the incorporation of elasticizers into densely crosslinked polymers reduces the free kinetic volume of the latter. The modification of binder makes it possible to obtain composites that are both well deformed and capable of recovering initial shape at T ≥ T g. The properties of glass-and carbon-reinforced plastics prepared using the developed elasticized binders by the contact molding are described. This method ensures defect-free bending deformation that exceeds that achieved in the case of compression molding. A rubber-like deformation technology is elaborated that enables one to employ blow molding for the production of open-contour items from cured blanks and closed-contour items that cannot be produced by winding because of their configuration.

Studies on the Modification of Commercial Epoxy Resin using Cardanol-based Phenolic Resins

Bisphenol A epoxy resin is blended with different phenolic novolac resins for property modification. The phenolic resins employed are (a) novolac resins derived from phenol/formaldehyde (PN) and cardanol/ formaldehyde (CDN) condensation and (b) condensation products of cardanol—phenol mixtures with formaldehyde (CPNs). Cardanol is the main constituent of cashew nut shell liquid (CNSL), a renewable resource. Epoxy resins containing 2.5—20 wt% of the above novolacs are prepared and tested for mechanical properties, water absorption, etc. Blends containing 5—10 wt% of novolacs show substantial improvement in properties. These properties show a declining trend with higher novolac loading. The stoichiometric ratio between phenolic material and formaldehyde in the novolacs is optimized (1:0.8) for maximum property enhancement. Among the novolacs studied, those prepared from cardanol—phenol mixtures of different molar ratios (CPNs) yield comparatively higher energy absorption at break and this property increases with increase in cardanol content in the modifier resin up to 40%. The property profiles of these epoxy—novolac blends imply a toughening action by novolac resins, especially phenol—cardanol—formaldehyde resins.

High performance wood composites based on benzoxazine-epoxy alloys

Wood-substituted composites from matrices based on ternary mixtures of benzoxazine, epoxy, and phenolic novolac resins (BEP resins) using woodflour ( Hevea brasiliensis) as filler are developed. The results reveal that the addition of epoxy resin into benzoxazine resin can lower the liquefying temperature of the ternary systems whereas rheological characterization of the gel points indicates an evident delay of the vitrification time as epoxy content increased. The gelation of the ternary mixtures shows an Arrhenius-typed behavior and the gel time can be well predicted by an Arrhenius equation with activation energy of 35–40 kJ/mol. For wood-substituted composites from highly filled BEP alloys i.e. at 70% by weight of woodflour, the reinforcing effect of the woodflour shows a substantial enhancement in the composite stiffness i.e. 8.3 GPa of the filled BEP811 vs 5.9 GPa of the unfilled BEP811. The relatively high flexural strength of the BEP wood composites up to 70 MPa can also be obtained. The outstanding compatibility between the woodflour and the ternary matrices attributed to the modulus and thermal stability enhancement of the wood composites particularly with an increase of the polybenzoxazine fraction in the BEP alloys.

Novel efficient DOPO‐based flame‐retardants for PWB relevant epoxy resins with high glass transition temperatures

AbstractNovel derivatives of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) were obtained by a simple synthetic route and incorporated in epoxy resins, consisting of epoxy novolac (DEN 438), dicyandiamide (DICY), and fenuron. The thermal and fire‐retardant properties of DICY‐cured DEN 438 epoxy samples containing the novel DOPO‐based additives were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the UL 94 test. The obtained results were compared to those of specimens containing commercially available phosphates as flame‐retardants. UL 94 tests showed that nitrogen‐containing substituents at the phosphorus atom increase the fire‐retardant efficiency of DOPO‐based additives. Two nitrogen‐substituted DOPO derivatives 4,4′‐Diaminodiphenylmethane (DDM)‐(DOP)2 and DDM‐(DOP)2‐S were found to be very powerful fire‐retardants in DICY‐cured DEN 438 epoxy resins. The V0 rating was achieved at approximately 1% phosphorus in the resin and the glass transition temperature (Tg) was maintained at the high level of the pure DEN 438/DICY epoxy material (Tg = 180–185°C). These novel DOPO derivatives are the first non‐reactive additives having no influence on the Tg of the epoxy material. They not only surpass the capabilities of the other additives used in this work, but also those of all commercially available flame‐retardants for epoxy resins. Therefore, DDM‐(DOP)2 and DDM‐(DOP)2‐S are expected to be qualified for high‐Tg resins commonly used in printed wiring boards (PWB) for high‐performance applications. Copyright © 2008 John Wiley & Sons, Ltd.

Properties of Glass Laminates of Novolac Epoxy - Diallyl Bisphenol a - Bismaleimide Resins

The high temperature properties of a novolac epoxy (EPN) – 2,2'diallyl bisphenol A (DABA) resin system was improved on co-curing it with bisphenol A bismaleimide (BMI). The concentration of BMI in the stochiometric blend of EPN and DABA was varied from 0.5 to 2.0 per equivalent of allylphenol. This ternary blend was used for processing glass laminates and their performance was evaluated through thermal, mechanical and dynamic mechanical characterisation. The incorporation of BMI in an epoxy-phenol system yielded a matrix system with comparable mechanical properties, improved high temperature stability and high temperature strength retention. The increase in BMI concentration beyond the stochiometric equivalent caused deterioration in mechanical properties including fracture toughness, and stress relaxation of the laminate. But the high temperature performance of the system evaluated through the interlaminar shear strength retention of their glass laminates showed systematic improvement with increase in BMI concentration. Toughening with polyethersulphone improved its mechanical properties, with a marginal penalty on its glass transition temperature.

Miscibility, crystallization behavior and specific intermolecular interactions in thermosetting polymer blends of novolac epoxy resin and polyethylene glycol

AbstractThermosetting polymer blends of novolac epoxy resin (EPN) and polyethylene glycol (PEG) were studied. The miscibility and crystallization behavior of the blends before curing reaction were investigated by polarized optical microscopy and differential scanning calorimetry (DSC). Overall uncured blend compositions were homogeneous in amorphous state. Single composition‐dependent glass‐transition temperature (Tg) for each blend could be observed, and the experimental Tg's of blends with EPN content ≥40 wt% could be explained well by the Gordon–Taylor equation. Thermal properties of blends cured with 4,4′‐diaminodiphenylmethane were also determined by DSC. The capability of PEG to crystallize in cured blends was different from that in uncured ones because of the topological effect of highly crosslinking structure. On the basis of Fourier transform infrared spectroscopy results, it was judged that there were intermolecular hydrogen‐bonding interactions between EPN and PEG in both cured and uncured blends. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Studies on bismaleimide co-cured Novolac epoxy–diallyl bisphenol-A system

The novolac epoxy (EPN)–2-2′-diallyl bisphenol-A (DABA) system was modified by reactive blending with bisphenol-A bismaleimide (BMI) to improve its high temperature properties. Molar concentration of BMI in the stochiometric (1:1) blend of EPN and DABA was varied and the cure conditions were optimized for these systems by DSC, DMA and rheological studies. The glass composites processed using these ternary blends were characterized for their thermal, mechanical and dynamic mechanical properties. The incorporation of BMI into the epoxy–phenol system yielded a matrix system with improved glass transition temperature and comparable mechanical properties. The increase in BMI molar concentration beyond 1.0 resulted in deterioration in the mechanical properties and fracture toughness. But the high temperature performance of the composites, determined from their inter-laminar shear strength retention, showed systematic improvement with concentration of BMI in the system. The toughening of the system using polyether sulphone improved its mechanical properties with a marginal penalty on its glass transition temperature. The dependence of properties of composites on the type, orientation and stacking sequence of the laminates was investigated. The influence of the nature of the bismaleimide on the properties of the ternary reactive blend and its glass laminates was also examined. On changing the BMI, it was seen that the rigidity of the molecular backbone of the bismaleimide contributed to the high temperature properties of the ternary blend, while BMI with better flexibility has improved the mechanical properties of the resultant composite systems.

A simple imide compound as a curing agent for epoxy resin. I. Synthesis and properties

A simple imide compound, 4-amino-phthalimide (APH), was synthesized as a curing agent for epoxy resin. APH was prepared from the hydration of 4-nitro-phthalimide, which was prepared from the nitration of phthalimide. The chemical structure of APH was verified by IR and 1H-NMR spectra. The thermal properties and dielectric constant (e) of a phosphorus-containing novolac epoxy resin cured by APH were determined and compared with those of epoxy resins cured by either 4,4′-diamino diphenyl methane (DDM) or 4,4′-diamino diphenyl sulfone (DDS). The results indicate that the epoxy resin cured by APH showed better thermal stability and a lower e than the polymer cured by either DDM or DDS. This was due to the introduction of the imide group of APH into the polymer structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Phosphorus‐containing terephthaldialdehyde adducts—Structure determination and their application as flame retardants in epoxy resins

AbstractTwo novel phosphorus‐rich prepolymers based on epoxy novolac and terephthaldialdehyde and potential flame retardants, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and 2,8‐dimethyl‐phenoxaphosphin‐10‐oxide (DPPO) were synthesised. The resultant flame‐retardant epoxy resins were cured with 4,4′‐diaminodiphenylmethane (DDM) and 4,4′‐diamino‐dicyclohexylmethane (PACM). Their flammability and burning behavior were characterised by UL 94 and LOI and compared with analogue prepolymers based on diethylphosphite (DEPP). The glass transition temperatures were determined by DSC measurements. Furthermore, the structures of two exemplary molecules based on p‐tolylaldehyde adducts were examined by XRD and NMR analysis to determine the possibilities of linking the two novel DOPO and DPPO derivatives to the backbone of the epoxy resin. Additionally, the char yields were determined by TG analysis and thermal desorption mass spectroscopy of the thermosets used and compared with each other to obtain more information about the possible mode of flame‐retardant action of the different phosphorus compounds. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Triphenyl Phosphine Catalyzed Curing of Diallyl Bisphenol A‐Novolac Epoxy Resin System—A Kinetic Study

The kinetics of triphenyl phosphine (TPP) catalyzed phenol‐epoxy reaction in the blend of 2,2′‐diallyl bisphenol A (DABA) and an epoxy novolac (EPN) was investigated using differential scanning calorimetry (DSC). The kinetic parameters viz., activation energy (E) and the pre‐exponential factor (A) were calculated by the multiple heating rate methods of Ozawa and Kissinger. The effect of catalyst concentration on the kinetic parameters of the cure reaction was studied and E and A were found to depend on catalyst concentration. The apparent activation energy values normalised to a fixed A value decreased systematically and the corresponding rates of reaction showed an increasing trend with increase in catalyst concentration. The iso‐conversional kinetic analysis done for different catalyst concentrations and for different conversion levels implied that the overall kinetics does not vary much with conversion level. The activation parameters were used to predict the cure profile of the resin under given conditions of temperature and catalyst concentration.

Synthesis of bisphenol a novolac epoxy resins for coating applications

AbstractBisphenol A novolacs were synthesized in both melting and solution processes using p‐formaldehyde and formalin solution in presence of oxalic acid catalyst, respectively. Hydrogen nuclear magnetic resonance, 1H NMR, investigations show a high methylene bridge contents in the novolacs synthesized in a melting process. These novolacs were analyzed by gel permation chromatography (GPC) and fourier transform infrared spectroscopy (FTIR). The bisphenol A novolac was cured with 1‐(2‐amino ethyl) piprazine (AEP) as a curing agent for epoxy resins. The cured resins were evaluated as organic coating for steel. The mechanical properties of the cured epoxy resins were evaluated. The chemical resistances of the cured resins were evaluated through salt spray resistance, hot water, solvents, acid and alkali resistance measurements. The data indicate that the cured epoxy resins have excellent chemical resistances as organic coatings among other cured resins. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Thermal and thermo-oxidative degradation of flame retardant high impact polystyrene with triphenyl phosphate and novolac epoxy resin

Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene (HIPS) with triphenyl phosphate (TPP) and novolac type epoxy resin (NE) were characterized using thermo-gravimetric experiment. And the flammability was determined by limited oxygen indices (LOI). The LOI results show that TPP and NE had a good synthetic effect on the flame retardancy of HIPS. Compared with pure HIPS, the LOI values of HIPS/NE and HIPS/TPP only increased by about 5%, and the LOI value of HIPS/TPP/NE reached 42.3%, nearly 23% above that of HIPS. All materials showed one main decomposition step, as radical HIPS scission predominated during anaerobic decomposition. TPP increased the activity energy effectively while NE affected the thermal-oxidative degradation more with the help of the char formation. With both TPP and NE, the materials could have a comparable good result of both thermal and thermal-oxidative degradation, which could contribute to their effect on the flame retardancy.

Diallyl bisphenol A—novolac epoxy system cocured with bisphenol‐A‐bismaleimide—cure and thermal properties

AbstractNovolac epoxy (EPN)—2,2′‐diallyl bisphenol A (DABA) resin system was modified by cocuring it with bisphenol A bismaleimide (BMI). Molar concentration of BMI in the stochiometric blend of EPN and DABA was varied from 0.5 to 2.0. The cure optimization was done using DSC, IR spectroscopy, and rheological studies. The curing proceeded by phenol‐epoxy and Alder‐ene reactions. The performance of the ternary Epoxy‐Allyl phenolic‐Bismaleimide system was evaluated through their thermal and dynamic mechanical characterization. BMI improved the overall thermal stability and the modulus of the resultant composites. The increase in BMI concentration in the system resulted in enhanced glass transition temperature with a consequent improvement in high temperature performance typically estimated by their lap shear strength at high temperatures. The high temperature performance of the epoxy‐phenol‐bismaleimide (EPB) system was found to be far superior to the epoxy‐phenol (EP)system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Synthesis, characterization, and properties of novel novolac epoxy resin containing naphthalene moiety

A series of novel novolac epoxy resins containing naphthalene moiety with different molecular weights were synthesized via condensation of bisphenol A and 1-naphthaldehyde, followed by epoxidation with epichlorohydrin. The chemical structure of the naphthalene epoxy thus obtained was characterized using FTIR, 1H NMR spectra and GPC analyses. The naphthalene epoxy was cured with 4,4′-diaminodiphenyl sulfone (DDS) and the cured products were characterized with thermogravimetric analysis, dynamic mechanical analysis, and X-ray diffraction. Compared with the diglycidyl ether of bisphenol A (DGEBA), the cured naphthalene epoxy resin showed remarkably higher glass transition temperatures ( T gs), enhanced thermal stability and better moisture resistance. When the molar ratio of 1-naphthaldehyde to bisphenol A was 0.67, the optimal thermal resistance was observed.

Effect of Structure of Bridging Group on Curing and Properties of Bisphenol-A Based Novolac Epoxy Resins

Three bisphenol-A based novolac epoxy resins with different bridging groups: methylene, methine-phenyl and methine-naphthyl, respectively, between bisphenol-A phenyl rings were prepared to study the effect of structure of bridging group on curing and properties of the epoxy resins. The structures of the obtained epoxy resins were characterized using FT-IR and 1H NMR spectra, the molecular weight and polydispersity index were determined using GPC. The effect of bridging groups on the curing kinetics, thermal mechanical properties, thermal stability, and moisture resistance of the synthesized epoxy resins cured with 4,4′-diaminodiphenyl sulphone (DDS) were investigated by dynamic differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, X-ray diffraction and moisture absorption measurement. It was concluded that the methylene-bridged epoxy resin possessed the highest curing reaction reactivity toward DDS and the methine-naphthyl-bridged epoxy network possessed the highest storage modulus, glass transition temperatures, thermal stability, and moisture resistance.

Multistep Synthesis on SU-8: Combining Microfabrication and Solid-Phase Chemistry on a Single Material

SU-8 is an epoxy-novolac resin and a well-established negative photoresist for microfabrication and microengineering. The photopolymerized resist is an extremely highly crosslinked polymer showing outstanding chemical and physical robustness with residual surface epoxy groups amenable for chemical functionalization. In this paper we describe, for the first time, the preparation and surface modification of SU-8 particles shaped as microbars, the attachment of appropriate linkers, and the successful application of these particles to multistep solid-phase synthesis leading to oligonucleotides and peptides attached in an unambiguous manner to the support surface.

Synthesis and properties of flame‐retardant epoxy resins based on DOPO and one of its analog DPPO

AbstractTwo phosphorus‐containing heterocyclic flame retardants ‐9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and 2,8‐dimethyl‐phenoxaphosphin‐10‐oxide (DPPO) ‐ and their derivatives were characterized and incorporated in the backbone of epoxy novolac to obtain flame‐retardant epoxy resins. The structures and spectroscopic data including high‐resolution mass spectroscopy of these flame retardants were determined. Flame‐retardant epoxy resins with a phosphorus content of up to 2% based on heterocyclic DOPO and DPPO were cured with 4,4′‐diaminodiphenylmethane (DDM), and their features were examined by UL 94, LOI, and DSC. In this manner, high‐performance polymers with glass transition temperatures around 190°C and the UL 94 rating V0 were obtained. These polymers were compared with epoxy resins incorporating diphenyl phosphite and diphenyl phosphate, which are nonheterocyclic and do not pass the UL 94 test up to 2% phosphorus. DPPO has a similar flame retardancy like the commercially available DOPO. Furthermore, to explain the difference in the efficiency of the tested flame retardants, key experiments for the determination of the active species during the flame‐retarding process were performed and the PO radical was identified. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.