Epoxy Phenol Novolac Research Articles

A latent curing agent for rapid curing of phenolic epoxy resin at low temperature

AbstractDeveloping effective latent curing agent for rapid curing of epoxy resins at low temperatures remains challenging. This study reports a latent curing agent, ortho‐cresol phenolic epoxy resin‐bisphenol A (EOCN‐BPA), prepared through the addition reaction of o‐methyl phenolic epoxy resin with BPA. When blended with dicyandiamide (DICY) in a 1:3 molar ratio, EOCN‐BPA/DICY is used to cure a linear epoxy phenolic novolac (EPN) resin (epoxy equivalent: 550 g eq−1, softening point: approximately 82°C), at an onset curing temperature of 90°C, which is considerably lower than the onset curing temperature of DICY with EPN (160°C). However, EOCN‐BPA does not react with EPN without a catalyst. Therefore, this latent curing system is successfully applied in powder coatings, rapid curing at 120°C within 3 min without an additional catalyst, outperforming the EPN/EOCN‐BPA system using cocatalyst 2‐methylimidazole. Consequently, DICY catalyzes the curing reaction between the phenol hydroxyl group and epoxy resin and participates in it. The prepared powder coating exhibits excellent storage stability, maintaining its properties for over 3 months at room temperature. These findings demonstrate the excellent latent properties of EOCN‐BPA/DICY, highlighting its potential as a highly effective latent curing agent.

Red mud waste/nanoclay/polystyrene‐modified epoxy hybrid composites: Mechanical, thermal, and flammability properties

AbstractIn this study, bisphenol A‐type epoxy (ER) and epoxy phenol novolac resins (EPN) with two amine‐type curing agents (KH 816 and IPOX EH 2041) having different total amine values were selected. The mechanical properties and density of the EPN resin were found higher in the case of both curing agents. EPN was modified with polystyrene (EPN‐PS) and used as a matrix using an IPOX hardener. Nano‐ and hybrid composites were prepared with pristine and modified with tetramethylammonium chloride nano montmorillonite (NC and MNC), and red mud waste (RMW). The chemical structure was elucidated by the Fourier transform infrared (FT‐IR). The composites were characterized by scanning electron microscopy and x‐ray diffraction. Appropriate PS and NC ratio was accepted as 4% and 2% by weight, respectively. Curing degrees calculated from the FT‐IR spectra of ER, EPN, and EPN‐PS were 99.3%, 99.9%, and 86.5%, respectively. A comparative study of the two binary systems; (i) 2 wt% NC‐(15–35) wt% RMW; and (ii) 2 wt% of MNC‐(15–35) wt% of RMW on the mechanical, thermal, and flammability properties of EPN‐PS matrix was carried out. The appropriate RMW ratio was 30 wt%. Hybrid composites with 25–30 wt% RMW can be considered self‐extinguishing materials.

Epoxy phenol novolac resin: A novel precursor to construct high performance hard carbon anode toward enhanced sodium-ion batteries

Although hard carbon has been considered as one of the most promising anodes for sodium-ion batteries, however, the poor performance and ambiguous sodium storage mechanism limit the further development. Herein, a novel epoxy phenol novolac resin is used as precursor for the first time to construct excellent electrochemical performance anode by pyrolyze it at different temperature. The results demonstrate that the plateau region in discharge curve of hard carbon is ascribed to Na insertion into the long-range ordered carbon structure. Improving ordering degree with suitable interlayer distance can both enhance the plateau capacity and total capacity. With the increasing of pyrolysis temperature, the graphitization degree of hard carbon is gradually enhanced. The cured epoxy phenol novolac resin pyrolyzed at 1800 °C delivers the reversible capacity of 480.3 mAh g−1 at 50 mA g−1, high initial coulombic efficiency of 84.6%, and capacity retention of 92% after 1000 cycles at 500 mA g−1. The “adsorption-intercalation mechanism” for Na storage in EPNHC-1800 is verified by in-situ Raman spectroscopy analysis. We believe that the sodium storage mechanism of hard carbon is “adsorption-intercalation-filling”, namely, the adsorption of Na-ions on the surface of carbon layers providing the slope capacity, the intercalation of Na-ions between carbon layers and filling in the nanopores providing the plateau capacity. This study offers a novel precursor to synthesize low cost and high-performance hard carbon anode material for sodium-ion batteries, delivering great opportunity for the commercialization of anode.

Microstructure and mechanical properties of epoxy resin-reinforced geopolymer exposed to high temperatures

This study investigated the performance of fly ash/slag-based geopolymer composites at ambient and extremely high temperatures. Two types of commercially available epoxy resins, bisphenol F epoxy resin and phenol novolac epoxy resin with incorporating amounts of 1 and 2.5 mass%, were used to produce geopolymer composites. The heat resistance test was carried out at 500 °C, 750 °C, and 950 °C. The microstructure and mechanical strength of geopolymers unexposed and exposed to heat were examined. The results show that incorporating a small amount of epoxy resin could improve strength and reduce crack formation. Although the epoxy resin is sensitive to high temperatures, incorporating it into the geopolymer system did not significantly affect the high-temperature resistance of the geopolymer. This finding indicates that geopolymer reinforced with epoxy resin has the potential to be used in the application where exposure to high temperature is required.

Processing method, properties and application of functionally graded polymer materials based on the mixtures of poorly compatible epoxy resins

In this study, the method of manufacturing of functionally graded polymer materials based on the mixtures of poorly compatible epoxy resins is suggested. A novel processing method allowing to control the filler distribution across the section of graded materials depending on the operating conditions was developed. The essence of the method is self-settling of the blend consisting of two liquid epoxy resins with different viscosities and densities. Depending on mixing and injecting order the functional additive having antifriction, anti-adhesive or heat-protective properties can be distributed either homogenously or nonuniformly. In the latter case after curing the functionally graded material can be produced. Based on the formulations of poorly compatible phenol novolac epoxy resin NPPN-638 and active diluent triglycidyl phosphate (TGP), new functionally graded polymer materials with continuous change of composition and properties were developed. The functional additive (graphite, glass microspheres, polytetrafluoroethylene powder) concentrates in the top layer of the self-settled epoxy mixture while the bottom layer is enriched by TGP which possess advantaged adhesion to various substrates. As a result, antifriction, anti-adhesive, heat-protective and intumescent flame retardant coatings with improved performance were obtained.

Phosphazene as an effective flame retardant for rapid curing epoxy resins

A rapid curing, low viscosity epoxy amine resin developed for high pressure resin transfer moulding composite fabrication possessing good thermal and mechanical properties and excellent flame retardancy after cure is presented here. The resin system consists of diglycidyl ether of bisphenol F (DGEBF), an epoxy phenolic novolac resin and diethyl toluene diamine (DETDA), while rapid cure is enabled by 2-ethyl-4-methylimidazole (2E4MI) catalysis. The fire-retardant additive, a crystalline powder, hexaphenoxy cyclotriphosphazene (HPCTP) produces only a small increase in viscosity and regardless of additive concentration, the formulations are less than 200 mPas at processing temperatures of between 80 and 125 °C. Using the UL-94 vertical burn test, a V0 rating and a limiting oxygen index (LOI) of 36.2% were achieved using only 10 phr HPCTP. Indeed at 20 phr of HPCTP an LOI of 43.6% was achieved. The HPCTP additive remains miscible in the network after cure which reduces reactivity modestly and the glass transition temperature (Tg), but the flexural properties, including modulus, strength and strain to failure, either increase modestly or were unaffected.

Chemical ageing effects on the ply and laminate strength of a filament wound cross-ply GFRP

This work presents a numerical approach to multi-routines based on experiments, and, with a target to analyse strength of a cross-ply glass fibre reinforced plastics (GFRP) composite after immersion in sulphuric acid solution under pressure (5% H2SO4 solution, 95 °C, 15 bar). Two alternative vinyl ester resins (bisphenol A diglycidyl ether and epoxy phenol novolac) were investigated. After 0.5, 1, 1.5 and 2 years of conditioning, the specimens were mechanically tested. The multi-scale definition of the material system and its virtual conditioning were performed in a finite element (FE) model. The Hashin 3D failure criterion was implemented by coding the UMAT subroutine when using the Abaqus software. The experimental results demonstrated better performance of the bisphenol A vinyl ester resin-based GFRP when a thin barrier layer is used. The numerical results indicated that the shear strength property was the most susceptible at weak zones to present a tendency for degradation after one year of conditioning.

Thermo Mechanical behaviour of Phenol Novolac Resin and Unsaturated Polyester Toughened Epoxy using nano Bentonite and Silica Nanoparticles

Phenol novolac epoxy resin is a polymer matter which its properties can be modified for industrial needs. In this research, nanocomposites of phenol novolac epoxy resin and unsaturated polyester are made nano Bentonite and silica nanoparticles as filler. For this purpose, effect of nanoparticles percent on nanocomposite formation is studied and their physical, mechanical and thermal properties are obtained. The presence of unsaturated polyester in this process forms a cross-link capable of improving the physical and mechanical properties of epoxy resin. Fracture behavior was determined by a SEM device. Moreover, TGA, DSC, impact tests and bending test were applied for data analysis. When process ability is growing, moisture absorption decreases. Fracture toughness was also evaluated in a stoichiometric network. Physical and mechanical properties improve significantly with increasing nanoparticles. The most important reason for using this nanocomposite is its high resistance to corrosion.

Nanoclay dispersion and colloidal stability improvement in phenol novolac epoxy composite via graphene oxide for the achievement of superior corrosion protection performance

In this study, Graphene oxide (GO) nanosheets were studied to improve nanoclay (NC) exfoliation in a phenol novolac glycidyl ether and improve coating performance. Particle characterizations are performed by FT-IR, Raman spectroscopy, and FE-SEM methods. EIS measurements confirmed denotative stability in impedance values, more significant than 1010 ohm·cm2, after prolonged immersion time (18 weeks). Complementary characterizations, salt spray test, pull-off, and cathodic disbondment test, revealed that such enhancement in the clay dispersion has significantly improved the coatings protection function.

Chemical modification of apricot kernel shell waste and its effect on phenolic novolac epoxy composites

AbstractApricot kernel is one of the most abundant types of agro‐waste in the eastern Anatolia regions of Turkey. In this study, apricot kernel shells (AKShs) were chemically modified using levulinic acid (LA) for the first time, and their potential for developing biobased composites was evaluated. Phenol novolac epoxy resin was used as matrix owing to its high thermal and superior adhesion properties. Shell treatments to improve interfacial bonding were carried out using alkali, acetic acid, and LA. These treatments were aimed at improving the mechanical properties, wettability, and bonding of the composites. Moreover, these treatments could prevent the deterioration of the fiber/matrix interface (hydrophilic and hydrophobic effect) and mitigate damage to the fiber during production, which is one of the main reasons for the reduced strength of the composites. The thermal characteristics, crystallinity index, chemical composition, and surface morphology of the untreated and chemically modified AKShs and composites were studied by thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, respectively. In addition, the composites were analyzed in detail using mechanical tests and contact angle measurements. The chemical treatment using LA resulted in composites with superior mechanical behavior.

Functionalized graphene oxide-epoxy phenolic novolac nanocomposite: an efficient anticorrosion coating on mild steel in saline medium

The present paper reports the fabrication of efficient anticorrosion coating material on mild steel using epoxy phenolic novolac (EPN) polymer. The EPN was prepared by refluxing the mixture of phenol formaldehyde amine and epoxy in a 1:1 weight ratio and characterized by 1H NMR and FT-IR spectral studies. The graphene oxide (GO) was functionalized using 2-{4-[2-hydroxy-3-(propan-2-ylamino) propoxy] phenyl} acetamide and thoroughly characterized by FT-IR, Raman, and energy dispersive X-ray spectroscopies and TEM techniques. The anticorrosion performance of the coated mild steel (MS) samples was studied by electrochemical impedance spectroscopy and potentiodynamic polarization techniques in 3.5 wt% NaCl medium. The results revealed that the anticorrosion ability of EPN coating was significantly enhanced by the incorporation of functionalized graphene oxide (FGO). The corrosion inhibition efficiency of 99.99% is achieved with 0.2 wt% FGO-grafted EPN matrix.

Mechanism of the temperature-responsive material regulating porous morphology on epoxy phenolic novolac resin microcapsule surface

Porous microcapsules (MCs) with tailorable surface morphology are indispensable in practical applications because of their large surface area and controlled release. In this study, epoxy phenolic novolac resin MCs were prepared with temperature-responsive 2,4,6-tris(dimethylaminomethyl)phenol (DMP) as crosslinker. Reaction temperature was proved to generate distinct effects on MC porous morphology, shell thickness, mechanical strength and release behavior. The MC surface varied from nonporous to dense small pores (ca. 237 nm in diameter) with increasing temperature from 40 °C to 70 °C, but they showed decreasing tendency at higher temperature (＞70 °C). The encapsulation process illuminated that DMP aggregates formed and deposited on the loose shells at 60 °C and 70 °C (close to the so-called cloud point (Tscp) of DMP), leading to porous morphology. Nevertheless, at temperature far below or above the Tscp of DMP (＜50 °C or ＞70 °C), DMP kept its solubility in water or insufficiently deposited on the shells, which resulted in no pores existed. Higher temperature promoted the reactivity to generate thicker shells and larger mechanical strength, further leading to prolong payload release. The present work provided an insight about the reaction temperature to prepare tunable MCs, which can be employed to encapsulate lipophilic components in agriculture field.

Tunable thermal, mechanical, and controlled-release properties of epoxy phenolic novolac resin microcapsules mediated by diamine crosslinkers.

Diverse shell structures can endow microcapsules (MCs) with a variety of properties. In this study, four kinds of MCs encapsulated with epoxy phenolic novolac resin (EPN) were obtained using diamines as crosslinkers. The FTIR and CLSM confirmed that the EPN-shell was successfully synthesized. SEM results suggested that all four of the MCs possessed smooth and imporous surfaces, and they displayed uniform size distribution, with the average size ranging from 11.2 to 14.8 μm. Specifically, the MCs synthesized with the crosslinkers of hexamethylene diamine (HAD) and isophorone diamine (IPDA) were more stable and could maintain their spherical shapes in a dry environment, while those synthesized with ethylene diamine (EDA) and triethylene tetramine (TETA) exhibited poorer thermal stabilities and faster release profiles. Lipophilic diamines can form thicker shell thickness, and have smaller d-space values and higher Young's modulus values. Therefore, the lipophilicity of the diamine agents is the key factor that influences the specific properties of the MCs. The hybrid approach was validated as a flexible strategy to meet diverse requirements. The present study can provide a comprehensive understanding of diamine crosslinkers in the synthesis of EPN-MCs, and such MCs can be extended to a wide range of fields because of their broad tunable performance.

Modification of Physical, Mechanical and Electrical Properties of Reinforced Epoxy Phenol Novolac with Nano Cobalt Acrylate and Carbon Nanotubes

The research associated with optimal manufacturing procedure for composites strengthened with carbon nanotubes has became an important stage inside the early levels of discovery of fantastic physical properties of carbon nanotubes. The particular increasing interest has been brought by swift developments in nanotechnology and composites production techniques. This particular document brings together a study of two processes for production reinforced epoxy phenol novolak (EPN) with multi wall carbon nanotubes (MWCNT) and nano cobalt acrylate and evaluation of their physical properties. Shear mixing method and solution process are techniques that were used to produce plates and thin films of composites containing different weight fractions of unpurified and purified multiwall nanotubes. The first method consist in processing the pure combination of (EPN) and nanotubes in a reactor and the subsequent technique utilizes ultrasound to improve dispersion of nanotubes in the matrix through solvent medium. In this case, solution process showed a better dispersion of the encouragement in the matrix, but physical qualities did not show significant improvements. Mechanical qualities, for instance tensile strength, Young's modulus, fracture toughness, and hardness do not show relevant improvements. The explanation for this behavior is the poor adhesion at the interface carbon nanotube-matrix, attributable to tendency of MWNTs to agglomerate into bundles, which generate discontinuities in the last composite. The electrical Conductivity measurements indicate a percolating network formed only by inner metallic tubes of the nano composite.

Reconfigurable Shape Memory and Self-Welding Properties of Epoxy Phenolic Novolac/Cashew Nut Shell Liquid Composites Reinforced with Carbon Nanotubes.

Conventional shape memory polymers (SMPs) can memorize their permanent shapes. However, these SMPs cannot reconfigure their original shape to obtain a desirable geometry owing to permanent chemically or physically crosslinked networks. To overcome this limitation, novel SMPs that can be reconfigured via bond exchange reactions (BERs) have been developed. In this study, polymer composites consisting of epoxy phenolic novolac (EPN) and bio-based cashew nut shell liquid (CNSL) reinforced by multi-walled carbon nanotubes (CNTs) were prepared. The obtained composites exhibited shape memory and self-welding properties, and their shapes could be reconfigured via BERs. Their shape memory mechanisms were investigated using variable-temperature Fourier transform infrared spectroscopy and dynamic mechanical analysis. The EPN/CNSL composite containing 0.3 wt % CNTs showed the highest shape fixity and shape recovery ratio. Furthermore, shape memory behavior induced by irradiation of near-infrared (NIR) light was also observed. All samples showed high shape recovery ratios of nearly 100% over five cycles, and increasing the CNT content shortened the recovery time remarkably. The ability of shape reconfiguration and stress relaxation affected the photo-induced shape memory properties of reshaped samples. Additionally, the self-welding properties were also influenced by stress relaxation. The hindrance of stress relaxation caused by the CNTs resulted in a decrease in adhesive fracture energy (Gc). However, the Gc values of EPN/CNSL composites were comparable to those of epoxy vitrimers. These results revealed that the material design concepts of thermal- and photo-induced shape memory, shape reconfiguration, and self-welding were combined in the EPN/CNSL composites, which could be feasible method for advanced smart material applications.

Porous epoxy phenolic novolac resin polymer microcapsules: Tunable release and bioactivity controlled by epoxy value.

Microcapsules (MCs) prepared with diverse wall material structures may exhibit different properties. In this study, MCs were fabricated with three kinds of epoxy phenolic novolac resins (EPNs), which possessed unique epoxy values as wall-forming materials by interfacial polymerization. The effects of the EPN types on the surface morphology, particle size distribution, encapsulation efficiency, thermal stability as well as release behavior and bioactivity of the MCs were investigated. In all three samples, the MCs had nearly spherical shapes with fine monodispersities and sizes in the range of 7-30 μm. Scanning electron microscopy (SEM) images showed that some small pores (ranging from 50 nm to 400 nm) appeared on the microcapsule surfaces and that the porosity decreased with an increasing of epoxy value. The X-ray diffractometer (XRD) analysis indicated that the cured EPN shells had larger degrees of crosslinking with higher epoxy values, leading to better thermal stabilities. Moreover, the release rate of the core material (pendimethalin) decreased with an increasing of epoxy value and thus resulted in a lower herbicidal control efficacy. The results of our research will enhance the potential application of EPNs as smart wall-forming materials to prepare porous MCs for controlled release.

Solution spray synthesis and surface modification of SiO2 nanoparticle for development of UV curable concrete coatings

SiO2 nanoparticles (SNP) were synthesized using patented solution spray reactor using precursor tetraethylorthosilicate (TEOS) while ammonium hydroxide as precipitant in presence of Tween-80 surfactant at room temperature and the surface modification was carried out with functional organosilanes (e.g. γ -methacryloxypropyltrimethoxy silane (GMPTS)). The functional group, crystal structure, morphology and size of SNP were characterized using FTIR, XRD and FESEM analysis, respectively. Spherical shape particles of SNP of average particle size 30–80 nm were obtained. Transparent UV curable nanocomposite coatings for concrete were formulated using SNP in multifunctional acrylated epoxy phenol novolac oligomer and cured under UV light. Effect of SiO2 nanoparticles was evaluated for performance properties of nanocomposite coatings.

Modification of Phenol Novolac Epoxy Resin and Unsaturated Polyester Using Sasobit and Silica Nanoparticles

Nanocomposites containing phenol novolac epoxy resin (PNER) were modified by unsaturated polyester resin (UPR) and then reinforced using sasobit and silica nanoparticles at different filler loadings via a multi-step manufacturing procedure. Afterward, effect of sasobit and silica loadings either on mechanical and thermal properties or on morphology of nanocomposites were examined. Results showed that increase in silica nanoparticles loading can improve both thermal and mechanical properties, but increase in silica loading more than 3 wt% can lead to decrease in the mechanical properties. In this case, addition of sasobit along with silica not only can improve the mechanical and thermal properties but also it can lead to improve in dispersion quality and morphology of nanocomposites. Eventually, with affordable and environmentally friendly materials such as sasobit, either production procedure or the overall quality and properties of nanocomposites can be improved.

Synthesis of Dodecyl Phenol Novolac Epoxy Resin and Physical Properties of Coatings

Synthesis of Dodecyl Phenol Novolac Epoxy Resin and Physical Properties of Coatings

Effect of stoichiometric ratios for synthesized epoxy phenolic novolac (EPN) resins on their physicochemical, thermomechanical and morphological properties

Purpose The purpose of this paper is to study the effect of various stoichiometric ratios for synthesised epoxy phenolic novolac (EPN) resins on their physicochemical, thermomechanical and morphological properties. Design/methodology/approach In the present study, EPN (EPN-1, EPN-2, EPN-3, EPN-4 and EPN-5) resins were synthesised by varying five types of different stoichiometric ratios for phenol/formaldehyde along with the corresponding molar ratios for novolac/epichlorohydrin. Their different physicochemical properties of interest, thermomechanical properties as well as morphological properties were studied by means of cured samples with the variation of its stoichiometric ratios. Findings The average functionality and reactivity of EPN resin can be controlled by controlling epoxy equivalence as well as cross-linking density upon its curing as all of these factors are internally correlated with each other. Research limitations/implications Epoxy resins are characterised by a three-membered ring known as the epoxy or oxirane group. The capability of the epoxy ring to react with a variety of substrates imparts versatility to the resin. However, these resins have a major drawback of low toughness, and they are also very brittle, which limits their application in products that require high impact and fracture strength. Practical implications Epoxy resins have been widely used as high-performance adhesives and matrix resins for composites because of their outstanding mechanical and thermal properties. Because of their highly cross-linked structure, the epoxy resin disables segmental movement, making them hard, and it is also notch sensitive, having very low fracture energy. Social implications Epoxy resin is widely used in industry as protective coatings and for structural applications, such as laminates and composites, tooling, moulding, casting, bonding and adhesives. Originality/value Systematic study has been done for the first time, as no exact quantitative stoichiometric data for the synthesis of EPN resin were available on the changes of its different properties. Thus, an optimised stoichiometric composition for the synthesis of the EPN resin was found.