Novolac Epoxy Research Articles

Effects of microsize SiC, Al2O3, and ZnO particulates on mechanical and tribological properties of synthesized ortho- and meta-cresol novolac epoxy composites

In this paper, the mechanical and tribological properties of synthesized ortho- and meta-cresol novalac epoxy resin composites have been explored. Three microsize fillers SiC, Al2O3, and ZnO particulates (10 wt%) have been used as reinforcement for the composites. The dry sliding wear tests were conducted on the pin-on-disc apparatus at sliding velocities of 0.9 m/s, 1.8 m/s, 2.7 m/s, and 3.6 m/s) and applied normal loads of 10 N, 20 N, 30 N, and 40 N. By evaluating the mechanical and tribological properties, positive synergetic effect was found. It was also found that the coefficient of friction increases and specific wear rate decreases with an increase in the sliding velocity, whereas specific wear rate increases with an increase in the applied normal and decreases with an increase in the sliding velocity. Also, the worn surfaces of novalac epoxy composites were analyzed with the help of scanning electron microscope.

A novolac epoxy resin modified polyurethane acylates polymer grafted network with enhanced thermal and mechanical properties

This paper describes the synthesis of novolac epoxy resin modified polyurethane acrylates (EPUAs) for generating a grafted polymer network, which is different from the conventional interpenetrating polymer networks (IPN). It starts with preparing epoxy acrylate resins (EA) by the ring-opening reaction of novolac epoxy resin (EP) and acrylic acid (AA). Epoxy acrylate copolymers (EPAcs) with hydroxyl groups were prepared by the copolymerization of EA and acrylic monomers. EPUAs were obtained by reacting EPAcs with curing agents (polyisocycanate HDI-trimer and phthalic anhydride). The chemical structures of the obtained EA and EPAcs were characterized by Fourier-transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance spectra (1H NMR). The influence of EP on chemical and physical properties of EPUAs, including fracture surface morphology, thermal stability, tensile strength, elongation at break, glass transition temperature (Tg), cross-linking density, shore hardness, water absorption, adhesion, etc., were investigated as well. It is demonstrated that the incorporation of EP into EPUAs greatly enhances the above physico-chemical properties of EPUAs.

Bridged phosphorylated diamines: Synthesis, thermal stability and flame retarding properties in epoxy resins

Abstract The synthesis of different phosphorylated m -phenylenediamines is described. In this context a new synthetic pathway to 10-chloro-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-Cl) is reported. The reactivities of DOPO-Cl and 10-chloro-9,10-dihydro-9-oxa-10-phosphaphenanthrene (DOP-Cl) towards amines have been compared. Decomposition properties of the pure compounds have been determined by thermogravimetric analysis (TGA) and indicate a relationship between the chemical environment around the phosphorus atom and the thermostability of the corresponding compound. All substances were incorporated into the epoxy novolac resin system DEN438/DICY/Fenuron. Thermal as well as flame retarding properties of the cured epoxy resins have been investigated by differential scanning analysis (DSC) and UL-94 test. The changes of the glass transition temperature ( T g ) and the decomposition temperature of the cured epoxy resins are small compared to the pure epoxy resin. The synthesized 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide (DOPS), diphenylphosphine sulfide (Ph2PO) and 5,5-dimethyl-1,3,2-dioxaphosphinane 2-sulfide (DDPS) derivatives exhibit a pronounced flame retardant effect in DEN438/DICY/Fenuron.

Curing kinetics of lignin and cardanol based novolac epoxy resin with methyl tetrahydrophthalic anhydride

Lignin and cardanol based novolac epoxy resin (LCNE) was prepared by reacting epichlorohydrin with the mixture of lignin and cardanol (2/3 in weight ratio). Kinetics of the curing reaction between LCNE and methyl tetrahydrophthalic anhydride (MeTHPA) was studied by differential scanning calorimetry (DSC) and model-free kinetic (MFK) analysis. The apparent activation energy (Ea) of the curing reaction was obtained from Friedman's model-free method. The kinetic model and other kinetic parameters were determined by Málek's method and the reaction process could be simulated favorably by Sestak–Berggren (SB (m, n)) model. Furthermore, the kinetic equation obtained from nonisothermal data was applied to predict the isothermal conversion processes of the crosslinking reaction. The results demonstrated the calculated data from the obtained kinetic equation matched perfectly with the isothermal experimental data.

The Study of Low Moisture Molding Compound

This paper studied the moisture of the post-mold-cured packages with the effects of resin structure, equivalent ratio of epoxy resin to Phenolic resin (E/OH), coupling agent, stress modifier and release agent on the moisture are further studied. The results showed that the resin structure has significant effect on the moisture, the order is multifunctional epoxy resin>o-crosel novolac epoxy resin>biphenyl epoxy resin>Naphthalene epoxy resin. The moisture decreases while the ration of E/OH increased. The moisture decreases rapidly with increase of the ratio of E/OH from 0.3 to 1.0. The moisture decreases slowly when it is larger than 1.0. The highest moisture of catalyst are 2MZ-A and 2MAOK while the lowest are 2MZ and TPP. The highest moisture of wax are GMS and stearic acid, while the lowest are polyethylene wax, oxidized polyethylene wax, and Carnauba wax, and the moisture of E wax, OP wax and S wax are in the middle.

Synthesis and properties of epoxy-polyurethane/silica nanocomposites by a novel sol method and in-situ solution polymerization route

In this work, a novel nonaqueous sol method for preparing 3-methacryloxypropyltrimethoxysilane modified nano-SiO2 (MPS-SiO2) in N,N-dimethylformamide (DMF) substituting alcoholic solvents was developed, and epoxy acrylate resins (EA) based on novolac epoxy resin (EP) were prepared. Epoxy acrylate copolymers (EPAc/SiO2) with core/shell structure were prepared by one-step in-situ solution polymerization of EA, acrylic monomers and a certain amount of modified silica sol as core. Epoxy acrylate based polyurethane composites/SiO2 (EPUAs/SiO2) were finally obtained by curing action among as-prepared EPAc/SiO2, isocyanate and anhydride curing agent. The obtained EA and MPS-SiO2 were also characterized using Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectra (1H NMR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy(XPS), and surface contact angle analysis(CA). Microstructures of MPS-SiO2 and EPAc/SiO2 in DMF were observed by transmission electron microscope (TEM). Furthermore, the influence of MPS-SiO2 on the properties of EPUAs/SiO2 including fracture surface morphology, thermal stability, glass transition temperature (Tg), tensile strength, elongation at break, cross-linking density, shore hardness, water absorption, etc. were also investigated. The results demonstrate that colloidal MPS-SiO2 with DMF as solvent can be directly added into polyurethane system and has industrial application value, EPAc/SiO2 with core–shell morphologies have good individual dispersion in DMF, and incorporating MPS-SiO2 into EPUAs/SiO2 greatly enhances physico-chemical properties of EPUAs/SiO2 composites.

Synthesis and characterization of novel phosphorous‐silicone‐nitrogen flame retardant and evaluation of its flame retardancy for epoxy thermosets

ABSTRACTA novel phosphorous‐silicone‐nitrogen ternary flame retardant (FR), [(1,1,3,3‐tetramethyl‐1,3‐disilazanediyl)di‐2,1‐ethanediyl]bis(diphenylphosphine oxide) (PSiN) was synthesized with high yield via a one‐step procedure by the reaction of diphenylphosphine oxide and vinyl‐terminated silazane with triethylborane as the catalyst. The chemical structure of the target compound was confirmed by nuclear magnetic resonances, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and Flourier transform infrared measurements. The developed PSiN FR was applied in the flame retardancy of o‐cresol novolac epoxy (CNE)/phenolic novolac (PN) hardener system. Effects of PSiN on the processability, thermal properties, especially the flame retardancy properties of the composites were investigated. Experimental results revealed that addition of PSiN improved the flowability of the CNE/PN systems, while the thermal stability of the epoxy thermosets was maintained. Meanwhile, the incorporation of PSiN was in favor of the formation of char during the thermal degradation process of the epoxy thermosets. The limited oxygen index of the epoxy system increased along with the PSiN content. An UL 94 V‐0 FR rating was achieved when the weight content of PSiN in the epoxy composites reached 20 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40412.

Curing kinetics, mechanism and chemorheological behavior of methanol etherified amino/novolac epoxy systems

The curing kinetics and mechanism of epoxy novolac resin (DEN) and modified epoxy novolac resin (MDEN) with methanol etherified amino resin were studied by means of differential scanning calorimetry (DSC), Fourier transform- infrared (FT-IR) spectroscopy and chemorheological analysis. Their kinetics parameters and models of the curing were examined utilizing isoconversional methods, Flynn-Wall-Ozawa and Friedman methods. For the DEN mixture, its average activation energy (Ea) was 71.05 kJ/mol and the autocatalytic model was established to describe the curing reaction. The MDEN mixture exhibited three dominant curing processes, termed as reaction 1, reaction 2 and reaction 3; and their Ea were 70.05, 106.55 and 101.91 kJ/mol, respectively. Besides, Ea of reaction 1 was similar to that of DEN mixture, while Ea of reactions 2 and 3 corresponded to that of the etherification reaction between hydroxyl and epoxide group. Moreover, these three dominant reactions were n th order in nature. Furthermore, their curing mechanisms were proposed from the results of DSC and FTIR. The chemorheological behavior was also investigated to obtain better plastics products via opti- mizing the processing schedules.

Examining Epoxy-based Nanocomposites in Wellbore Seal Repair for Effective CO2 Sequestration

Thousands of abandoned wellbores may lie within the aerial extent of a CO2 storage operation. These wellbores represent a potential leakage pathway and a leaky wellbore needs to be re-completed or otherwise repaired to restore seal integrity and ensure containment of the stored CO2. Due to the high cost of recompleting a well, a sufficient economic incentive exists if a viable seal repair technology is available. In this paper, we examine the use of epoxy nanocomposites as potential seal repair materials that have excellent bond characteristics with both steel and cement when cured in the subsurface environment. Test results show Novolac epoxy nanocomposites incorporating nanosilica, nanoclay or nanoalumina to have acceptable flowability that enable injection in wellbore cracks and significantly higher bond strength compared with standard microfine cement.

Bamboo-type carbon nanotube solids derived from low-cost epoxy resins and their potential application for air filtration

Carbon nanotubes (CNTs) are formed in bulk solids from the thermal decomposition of catalytic amounts of Fe2(CO)9 or Co2(CO)8 in the presence of an excess amount of a novolac epoxy carbon precursor during the conversion to a shaped thermoset composition and pyrolysis to 1,000 °C. The as-pyrolyzed carbonaceous solid is composed of either Fe or Co nanoparticles embedded in the nanostructured carbon, which contains bamboo-type carbon nanotubes, MWNTs, and some amorphous carbon. The Fe and Co nanoparticles, formed in situ from thermal decomposition of the corresponding salts, are responsible for the formation of the CNTs. The amorphous carbon is removed by selective combustion leaving a high surface area, porous composition. The pore network facilitates the transport of gaseous molecules such as ammonia to the adsorptive sites at the CNT surface and at entrained Fe or Co nanoparticle sites. During the combustion, the Fe and Co nanoparticles are oxidized to the corresponding nanostructured oxides, which are more receptive to ammonia absorption relative to the reduced metal. The ability to produce nanostructured solid compositions containing CNTs in any shape or form from inexpensive, commercially available carbon precursors is facilitating the development for application such as energy, gas sorption, chemical sensor, membrane, and nanodevices.

Preparation, curing properties, and phase morphology of epoxy-novolac resin/multiepoxy-terminated low-molecular-weight poly(phenylene oxide) blend

The multiepoxy-terminated low-molecular-weight poly (phenylene oxide) (PPOE) was synthesized by modifying the terminal hydroxyl group of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with epoxy-novolac resin (EPN). The curing kinetics, phase morphology, and thermal stability of the cured EPN/PPOE blends were investigated and compared to the unmodified EPN/PPO and EPN/EPPO (epichlorohydrin-modified PPO) blends. As revealed by the Fourier transform infrared and differential scanning calorimetry analyses, PPOE took part in the curing reaction and formed a crosslinked structure with EPN. The curing rate of EPN/PPOE blends first increased and then decreased with the increase of PPOE fraction. PPOE had both catalytic and steric hindrance effects on the curing reaction. EPN/PPOE blends showed faster curing rate and higher degree of curing than the corresponding EPN/PPO and EPN/EPPO blends. The reactive blending improved the dispersion of PPOE in EPN matrix and the thermal stability of the blend. POLYM. ENG. SCI., 54:2595–2604, 2014. © 2013 Society of Plastics Engineers

Multifunctionalization of novolac epoxy resin and its influence on dielectric, thermal properties, viscoelastic, and aging behavior

AbstractIn this article, novolac epoxy was functionalized using p‐hydroxybenzoic acid as pendent groups, which offered weak acidic environment and were cured with methyl etherified amino resin (HMMM). Its chemical structure was characterized by Fourier transform infrared (FT‐IR), 1H nuclear magnetic resonance (1H NMR) and differential scanning calorimeter (DSC). To comprehensively investigate its performance, HMMM was used as a curing agent. The modified epoxy exhibited higher storage modulus, lower thermal expansion coefficient, better moisture resistance, better resistance to degradation and lower dielectric constant. Furthermore, the aging behavior was investigated using dynamic mechanical analysis and scanning electron microscopy, which showed that the activation energy of glass transition increased after aging and cured MDEN was more difficult to age. Moreover, the relation between storage modulus and curing rate was established; the low curing rate of MDEN decreased the growth rate of storage modulus and reduced the internal stress, which was beneficial for processing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40157.

Side-chain phenol-functionalized poly(ether sulfone) and its contribution to high-performance and flexible epoxy thermosets

We prepared a side-chain phenol-functionalized poly(ether sulfone) (P1) from a one-pot reaction of a 4,4′-dihydroxybenzophenone (DHBP)-based poly(ether sulfone), poly(oxy-1,4-phenylenecarbonyl-1,4-phenyleneoxy-1,4-phenylene-sulfonyl-1,4-phenylene (DHBP-PES)), with 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and phenol in the presence of sulphuric acid. The phenol linkages of P1 act as reacting sites for epoxy resins. Subsequently, flexible and light-yellow transparent films of epoxy thermosets can be achieved from the curing of P1 with cresol novolac epoxy (CNE) and diglycidyl ether of bisphenol A (DGEBA). The thermoset based on P1 and CNE (P1/CNE) shows a high Tg value (241 °C), a low coefficient of thermal expansion (44 ppm/°C), and flame retardancy (VTM-0). The moderate-to-high molecular weight of P1 is responsible for the characteristics high Tg and flexibility, which are rarely seen in epoxy thermosets based on a low-molecular weight curing agent.

Lap shear strength and thermal stability of diglycidyl ether of bisphenol a/epoxy novolac adhesives with nanoreinforcing fillers

ABSTRACTNanoreinforcing fillers have shown outstanding mechanical properties and widely used as reinforcing materials associated to polymeric matrices for high performance applications. In this study, a series of multiwalled carbon nanotubes (MWCNTs)‐, nano‐Al2O3‐, nano‐SiO2‐, and talc‐reinforced epoxy resin adhesives composites were developed. The influence of different types and contents of nanofillers on adhesion, elongation at break, and thermal stability (under air and nitrogen atmospheres) of diglycidyl ether of bisphenol A (DGEBA)/epoxy novolac adhesives was investigated. A simple and effective approach to prepare adhesives with uniform and suitable dispersion of nanofillers into epoxy matrix was found to be mechanical stirring combined with ultrasonication. Transmission electron microscopic and scanning electron microscopic investigations revealed that nanofillers were homogeneously dispersed in epoxy matrix at optimized nanofiller loadings. Adhesion strength was measured by lap shear strength test as a function of nano‐Al2O3 and MWCNTs loadings. The results indicated that the lap shear strength was significantly increased by about 50% and 70% with addition of MWCNTs and nano‐Al2O3 up to a certain level, respectively. The highest lap shear strength was reached at 1.5 wt % of nano‐Al2O3 loading. MWCNTs at all loadings (except 3 wt %) and nano‐Al2O3 have enhanced onset of degradation temperature and char yield of the adhesives. By combined incorporation of 0.75 wt % nano‐Al2O3 and 0.75 wt % MWCNTs into the epoxy novolac/DGEBA blend adhesives a synergistic effect was observed in the thermal stability of the adhesives at high temperatures (800°C). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40017.

Nanoprotective Layer-by-Layer Coatings with Epoxy Components for Enhancing Abrasion Resistance: Toward Robust Multimaterial Nanoscale Films

Layer-by-Layer (LbL) assembled films offer many interesting applications (e.g., in the field of nanoplasmonics), but are often mechanically feeble. The preparation of nanoprotective films of an oligomeric novolac epoxy resin with poly(ethyleneimine) using covalent LbL-assembly is described. The film growth is linear, and the thickness increment per layer pair is easily controlled by varying the polymer concentration and/or the adsorption times. The abrasion resistance of such cross-linked films was tested using a conventional rubbing machine and found to be greatly enhanced in comparison to that of classic LbL-films that are mostly assembled through electrostatic interactions. These robust LbL-films are then used to mechanically protect LbL-films that would completely be removed by a few rubbing cycles in the absence of a protective coating. A 45 nm thick LbL-film composed of gold nanoparticles and poly(allylamine hydrochloride) was chosen as an especially weak example for a functional multilayer system. The critical thickness for the protective LbL-coatings on top of the weak multilayer was determined to be about 6 layer pairs corresponding to about only 10 nm. At this thickness, the whole film withstands at least 25 abrasion cycles with a reduction of the total thickness of only about 2%.

Effect of epoxy resin properties on the mechanical properties of carbon fiber/epoxy resin composites

Abstract Three kinds of epoxy resins, i.e. tetraglycidyl diaminodiphenyl methane (AG80), difunctional diglycidyl ether of bisphenol-A (E51) and novolac type epoxy resin (F46) were selected as matrices for carbon fiber/epoxy composites. The objective of this work is to study the mechanical properties of fiber/epoxy composites by using these three kinds of epoxy resins with different physical and chemical performance. The results show that the composites fabricated with AG80 present the best stiffness and the composites prepared with E51 have the best toughness. The stiffness and toughness of the composites prepared with F46 are middle values located between those for AG80/epoxy and E51/epoxy composites. Thus, the mixed epoxy resin is a promising approach for industrial production.

Preparation and properties of water‐soluble‐type sizing agents for carbon fibers

ABSTRACTA water‐soluble epoxy resin was synthesized by the reaction between novolac epoxy resin (F‐51) and diethanolamine. Then, the modified F‐51 was mixed with poly(alkylene glycol allyl glycidyl ether) as a film former of a sizing agent. A series of water‐soluble sizing agents for carbon fiber (CF) were prepared. The modified F‐51 was analyzed by Fourier Transform infrared spectroscopy. The surface morphology of the CF was characterized by scanning electron microscopy. The effects of the sizing agent on the handling characteristics were investigated by abrasion resistance, fluffs, and breakage and stiffness tests. The results show that the abrasion resistance of the sized CF increased by 114.5% and reached 2344 times and the mass of fabric hairiness decreased to 3.2 mg. The interlaminar shear strength (ILSS) test indicated that the interfacial adhesion of the composite could be greatly improved. The ILSS of the sized CF composite could reach a maximum value of 42.40 MPa. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39843.

Measuring the frequency-dependent dielectric properties of microwave composites using simple measurement methods

BaTi4O9 (BT4) ceramic was sintered at 1270°C and ground into fine ceramic powder with an average particle size of 3μm, then the BT4 powder was mixed with O-Cresol Novolac (OCN) epoxy resin to form epoxy-BT4 microwave composites. Using the plate method, the dielectric constants of the epoxy-BT4 microwave composites were measured from 100kHz to 100MHz at room temperature, then from 20°C to 140°C at 1MHz. The measured dielectric constants were fitted to the values predicted by the Lichtenecker equation. The dielectric constants of the epoxy-BT4 microwave composites were also measured from 1GHz to 10GHz at room temperature using the “square cavity resonator” method. In the GHz range, the dielectric constants of the composites were almost unchanged. It is conjectured that in both measurement frequency ranges, dielectric relaxation was nonexistent in both the BT4 ceramic powder and the epoxy-BT4 composites.

Ultrafast UV-Curable Adhesives for Optical Pick-Ups

This paper describes novel ultraviolet (UV)-curable adhesives with an ultrafast curing rate which are fully cured within 8 s for optical pick-up (OPU) applications. Two kinds of oligomers (novolac epoxy acrylate and urethane acrylate), additives, and inorganic fillers were prepared for the formulation of the adhesives. In addition, three kinds of photo-initiator [2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-2-methylpropiophenone for surface curing and (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (TMDPO) for deep curing] were mixed to increase the curing rate. Photo-differential scanning calorimetry (photo-DSC) analyses showed that the newly formulated UV adhesives had faster curing rate than conventional UV adhesives. The UV adhesives were applied to OPUs for DVD/CD-RW, and five kinds of reliability tests, i.e., thermal shock, low-temperature storage, high-temperature storage, high temperature/high humidity, and nonoperation shock tests, were conducted to evaluate the adhesive reliability. According to the results of reliability tests and thermal stress simulations, the UV adhesives with lower storage modulus (E′) showed better thermal shock reliability due to lower thermal stresses. In addition, OPUs assembled using the UV adhesives passed all reliability tests. Consequently, the UV adhesives were successfully applied to OPUs in OPU production lines, contributing to mass production.

Degradation mechanism of lacquered tinplate in energy drink by in-situ EIS and EN

The corrosion process of phenolic epoxy coated tinplate in energy drink was investigated by in-situ electrochemical impedance spectroscopy(EIS) and electrochemical noise(EN) techniques. The experimental results indicate that the degradation process of novolac epoxy coated tinplate in energy drink can be divided into three main stages: organic coating wetted by the beverage; corrosion initiation beneath the organic coating; and corrosion extension process. It was proposed that the tin coating and carbon steel were mainly corroded by organic acids in energy drink through the pores of the organic coating. After the tin coating was corroded, the carbon steel started to corrode due to its higher electrochemical activity and became to be the dominated corrosion reaction.