Application Of Epoxy Research Articles

Synthesis and characterization of PEDMCD as a flame retardant and its application in epoxy resins.

In this study, a highly effective flame retardant agent, called polybicyclopentaerythritol phosphate-O-4-imino-p-phenylmethane-4-imino-2-chloro-1,3,5-s-triazine (PEDMCD), has been prepared through a direct polycondensation reaction. PEDMCD was incorporated into epoxy resin (EP) to improve the flame retardancy of EP. The molecular structure and thermal stability of PEDMCD were analyzed by nuclear magnetic resonance spectroscopy. Further, the structural properties, composition, and thermal stability of the PEDMCD/EP composite were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). PEDMCD exhibited both high thermal stability and high flame-retardant performance; these properties were attributed to the phosphorus-containing structure on the side groups and a triazine structure as the molecular backbone, which played the role of a foaming carbon source. With the addition of PEDMCD, the flame-retardant behavior of PEDMCD/EP composites was gradually enhanced. Furthermore, the amount of char residue of the PEDMCD/EP composite at 500 °C was increased from 21% to 34%. The peak value of the mass loss rate of PEDMCD/EP decreased from 0.52 to 0.35 g s−1. Further, the TSP of the sample decreased from 44.2 m2 to 24.6 m2, and the total oxygen consumption decreased from 64.2 g to 30.4 g. Accordingly, owing to the incorporation of PEDMCD, EP begins to decompose sooner, and the carbon layer formed by decomposition reduces the decomposition rate of the EP matrix. Based on the results of characterization measurements and flame retardancy testing, it is confirmed that PEDMCD exhibits good flame retardancy when applied in EP.

Synthesis of a Novel Spiro Phosphorus–Nitrogen Concerted Reactive Flame-Retardant Curing Agent and Its Application in Epoxy Resin

Spiro-phosphorus (P)-based reactive flame retardant (SPDPT), a novel reactive flame-retardant epoxy resin (EP) curing agent, was prepared through the one-pot synthesis of triacetonediamine, pentaerythritol, and P oxychloride. The successful preparation of SPDPT was confirmed through Fourier-transform infrared spectroscopy, 1H NMR spectroscopy, 31P NMR spectroscopy, and elemental analysis. The flame-retardant epoxy thermoset (e.g., EP/ 4'4-diaminodiphenyl sulfone (DDS)/SPDPT) was prepared by using DDS as the co-curing agent. Differential scanning calorimetry results show that SPDPT can cure EP and improve the carbon residue yield of the epoxy thermoset after burning. When the P content was 1.0 wt%, the limiting oxygen index value of the EP/DDS/SPDPT-4 sample was 26.4%, and UL94 reached the V-0 rating. The tensile property of the epoxy thermoset reached 37.20 MPa, the flexural property reached 63.82 MPa, and the impact property reached 21.57 KJ·m−2.

Fabrication of eco-friendly and multifunctional sodium-containing polyhedral oligomeric silsesquioxane and its flame retardancy on epoxy resin

Considering the reduction of fire hazards associated with the application of epoxy resin (EP) composites. Herein, a novel sodium-containing polyhedral oligomeric phenyl silsesquioxane (Na-Ph-POSS) has been synthesized through hydrolysis condensation. FTIR, NMR and MALDI-TOF MS results reveal that Na-Ph-POSS is a hepta-phenyl POSS consisting of Si–O–Na and Si–OH groups. Compared to pure EP, according to the combustion results, the peak of heat release rate (p-HRR), the maximum smoke density (Ds, max) and the peak of CO production rate (p-COP) of EP/5 wt% Na-Ph-POSS significantly decrease by 45.9, 45.1 and 46.9%, respectively. Additionally, EP composites endowed with Na-Ph-POSS have low dielectric constant and dielectric loss. Therefore, eco-friendly multifunctional Na-Ph-POSS provides a promising prospect for mitigating the fire hazards of EP composites.

Comparison and Optimization of Various Coated Ceramic Insulator Artificial Coastal Thermal Power Plant Pollution

In power system, the post-insulator is a critical apparatus which carries the conductor and also provides isolation between the conductors as well as ground. Besides, it offers mechanical support. However, extreme weather and pollution cause post-insulator flashover, which results in interruption of power supply and revenue loss. Therefore, post-insulator’s pollution flashover study is necessary. The pollution flashover voltage (FOV) is directly related to dominating metrological circumstance and how this pollution severity on the surface of insulator. Mostly, anti-pollution flashover coating is deliberated to be one of the most effective means to prevent and reduce pollution flashover. This paper investigates and compares the application of Epoxy Resin and Room Temperature Vulcanize (RTV) Silicone Rubber for enhancing the performance of ceramic outdoor (near coastal thermal plant area) insulator to defeat the effect of environmental pollution. At first, a real-time pollution performance has been carried out in controlled laboratory setup. It shows that the withstand ability of post-insulator has been 25% with Silicone Rubber coating. Subsequently, Artificial Neural Network (ANN) has been used to predict the FOV of post-insulator under wet and dry condition. It shows that critical FOV has enriched with anti-reflection coating rate. After that, post-insulator has been modeled by COMSOL multiphysics software, which is used for estimating field distribution on post-insulator. From the modeling, we found that anti-reflection coated post-insulator surface has low electrical stress than that of others.

Theoretical modelling of kinetics of glass transition temperature of PEG toughened epoxy

ABSTRACT In this paper, we examined glass transition, a very important parameter that determines the properties and applications of epoxy resins by the innovative approach of kinetic study. The effect of thermoplastic filler Polyethylene Glycol-1000 (PEG-1000) on the kinetics of glass transition temperature of epoxy was analysed by varying the filler loadings and the heating rates. The differential scanning calorimetry curves were plotted at heating rates of 5, 10, 15 and 20°C, respectively and the kinetics of glass transition by varying the heat rates was investigated. Kissinger and Moynihan methods were employed to analyse the glass transition kinetics. The changes in glass transition have been interpreted remarkably with the constrained polymer region of the systems. The improvement in toughness of about ≈ 213% was obtained compared to the neat epoxy with an addition of about 1 wt-% of PEG loading. The toughening mechanisms were elucidated by analysing the scanning electron microscopic images of fractured samples.

Direct diazotization of graphite nanoplatelets with melamine and their favorable application in epoxy resins

The ease of undesirable agglomeration and a low efficiency are two problems that restrict the application of graphite nanoplatelets (GNPs) in epoxy resins (EP). Herein, a new strategy with melamine (MEL) as the precursor to functionalize GNPs chemically, which form a bonding layer that is compatible with epoxy matrix, is reported. The MEL fragments with secondary amine groups were grafted uniformly on the GNPs surface by covalent junctions to exploit the diazonium chemistry. This behavior led to a better dispersion and a stronger interaction with the epoxy matrix and resulted in an enhanced glass transition temperature and bending strength, compared with the pure EP. When only 1 wt% functionalized GNPs (f‐GNPs) was used, the Tg of the modified EP raised of about 15°C compared with pure EP, and the bending strength increased by approximately 39%. The dielectric constant of the EP with f‐GNPs was impacted slightly, and the dielectric loss decreased. At 105 Hz, the dielectric loss of the EP with 1 wt% f‐GNPs decreased by approximately 11% compared with pure EP. Therefore, diazotization modification of the GNPs is a useful approach to improve the compatibility in nanoparticle networks.

Synthesis of Diphenylphosphine Oxide Derivative and Its Flame Retardant Application in Epoxy Resin

Synthesis of Diphenylphosphine Oxide Derivative and Its Flame Retardant Application in Epoxy Resin

Synthesis of an organophosphorus flame retardant derived from daidzein and its application in epoxy resin

For the concern of sustainable and green chemical engineering, the development of flame retardants from renewable biomaterials is particularly attractive. Daidzein is an isoflavone found in large amounts in soybeans and other legumes. The structure of daidzein permits easy reaction with flame retardant groups and is beneficial for the formation of char at high temperature. A flame retardant which can work in both the gas phase and the condensed phase may be unusually effective. An organophosphorus flame retardant (DPOD) has been prepared using daidzein and diphenylphosphinyl chloride, and used to modify the flammability of epoxy (EP) resin. The structure and flame retardant mode of action of DPOD in EP were explored. The results showed that DPOD works in both the gas phase and the condensed phase and improves the flame retardancy of EP blends greatly. In addition, the DPOD doesn't deteriorate the glass transition temperature and impact strength of EP blends. This work is a useful attempt to use biobased monomers in the design of flame retardants.

Synthesis of a novel phosphorus-nitrogen flame retardant and its application in epoxy resin

A novel phosphorus-nitrogen flame retardant named as melamine phenyl phosphate (MAPPO) was synthesized successfully via the neutralization reaction between phenylphosphonic acid (PPOA) and melamine (MA). The chemical structure of MAPPO was characterized by Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (NMR) and element analysis (EA). MAPPO was introduced into epoxy resin by blending to improve the flame retardancy. Flame retardancy and combustion behavior of EP/MAPPO were investigated by limiting oxygen index (LOI) test, vertical burning (UL-94) test and cone calorimeter test. UL-94 and LOI tests results showed EP containing 18 wt% MAPPO passed the UL-94 V-0 rating and got a high LOI value of 33%. In the cone calorimeter test, compared with that of EP, the values of peak of heat release rate (HRR), total heat release (THR), peak of smoke production rate (PSPR) and total smoke production (TSP) of modified EP were reduced by 58.7%, 40%, 49% and 61.6%, respectively. By analyzing the volatile pyrolysis products of MAPPO, it was known that MAPPO mainly produced CO2, NH3, H2O and other nitrogen-containing compounds, which diluted the concentration of fuel gases and oxygen during combustion. Meanwhile, the char residue of EP/MAPPO system after combustion was also analyzed by scanning electron microscope (SEM), FT-IR and Raman tests, and the results showed MAPPO was able to promote the crosslinking of EP leading to the formation of compact char layer containing P–O–C, PO and CC, etc. In a word, the enhancement in flame retardancy was attributed to both dilution effect of non-combustible gases and barrier effect of compact char.

Synthesis of an effective bio-based flame-retardant curing agent and its application in epoxy resin: Curing behavior, thermal stability and flame retardancy

In this work, a bio-based macromolecule ammonium phytic acid named as PA-AEP was synthesized successfully via neutralization reaction between phytic acid (PA) and N-aminoethylpiperazine (AEP) and served as a monocomponent flame-retardant curing agent to improve the flame retardancy and smoke suppression of epoxy resin (EP). Curing behavior, flame retardancy and combustion behavior of PA-AEP cured epoxy resin were investigated. By comparison with EP/AEP reference sample, EP/PA-AEP samples showed good flame retardancy and smoke suppression effect because of the addition of PA-AEP. The PA-AEP cured EP sample passed UL-94 V-0 rating and achieved to a limiting oxygen index (LOI) value of 28.0% with 20 wt% PA-AEP. Cone calorimeter test results showed that, compared with EP/20% AEP reference sample, both the peak of heat release rate (PHRR), total heat release (THR), the peak of smoke production release (SPR) and total smoke production (TSP) of EP/20 wt% PA-AEP sample were decreased by 44.4%, 55%, 49% and 80.8%, respectively. In addition, by analyzing the char residues and volatile pyrolysis products, it was concluded that PA-AEP mainly played an important role in condensed phase which was associated with the formation of phosphorus-rich intumescent char layer.

A novel flame retardant derived from DOPO and piperazine and its application in epoxy resin: Flame retardance, thermal stability and pyrolysis behavior

A novel flame retardant poly (piperazine phosphaphenanthrene) (DOPMPA) was successfully synthesized via two step reactions using DOPO and piperazine as reactants and characterized by infrared spectrometry (FT-IR), nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The DOPMPA was used to enhance flame retardancy of epoxy resin (EP). When the addition content of DOPMPA in EP was 13 wt%, the EP/DOPMPA sample passed a UL-94 V-0 rating and possessed a high limited oxygen index (LOI) value of 34%. Cone calorimeter tests showed that the release of heat and smoke for EP/DOPMPA samples decreased significantly compared with neat EP. Moreover, the reduction of average effective heat of combustion (av-EHC) value with the increased addition of DOPMPA confirmed that DOPMPA had a flame-inhibition activity in gashouse phase. The analysis of the char residues after cone calorimeter test exhibited that DOPMPA promoted the swell of the sample and compacted char layer. Furthermore, the pyrolysis analysis of DOPMPA was investigated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), which illustrated that DOPMPA decomposed into many fragments with quenching effect toward combustion.

Innovative Strengthening Method for Steel Truss Nodes—Experimental Results

This article presents experimental results of steel truss nodes strengthened/refurbished with concrete encasement. Four strengthened specimens are tested in total, two encased in normal class concrete and two encased in high strength concrete C80/95. The results obtained are compared with one reference bare steel node test. All specimens are loaded with static monotonic loading except the last one, where cyclic loading is applied before it is finally loaded statically to failure. The connection between the concrete and the structural steel is ensured by the application of epoxy resin only, no mechanical elements are added. The strengthened specimens show a considerable reduction of the stresses into the steel gusset plate even for encasement in normal class concrete C40/50.

Construction of conductive three-dimensional structure by low content of silver nanowires and its application in epoxy resin

A conductive macro-network was fabricated by dip-coating silver nanowires (AgNWs) on the polyurethane (PU) sponge skeleton and a semi-conductive epoxy nanocomposite was obtained. The resulting nanostructures exhibit an effective pathway to achieve low electrical percolation threshold for a scalable 3D conductive network with low loading of fillers. The epoxy composites filled with conductive 3D foams show the enhanced thermal stability, glass transition temperature and mechanical properties. The volume resistivity of the obtained epoxy/PU@AgNWs composites decreases from 1.1 × 1017 to 1.9 × 105 Ω cm with ultralow AgNWs loading of ~ 0.14 vol%, and meanwhile thermal conductivity is improved by 45% at 0.282 W/mK compared to neat epoxy resin. This method might be a scalable and effective way for the applications in the high-performance semi-conductive engineering devices.

Push-out tests on demountable shear connectors of steel-concrete composite structures

Circular Economy refers to a move from linear business models, in which products are manufactured from raw materials, used and then discarded, to circular business models where products or parts are re-used, remanufactured or recycled. Structural steel is highly compatible with this concept; however, when steel-concrete composite structures are used, recycling becomes difficult and the potential for reuse is lost. In order to make steel-concrete composite structures reusable, bolted connections should replace the commonly used welded headed studs. Furthermore, the reusable parts should be designed to withstand repeated use.This paper presents a desktop study and the corresponding laboratory experiments on demountable shear connectors that facilitate recyclability and even provide the potential for reusing complete structural elements. In the Laboratory of Steel and Composite Structures of the University of Luxembourg 15 push-out tests have been carried out using different bolted connection systems suitable for multiple use. The shear connectors have been evaluated based on their shear strength, stiffness, slip capacity, ductility and ability of demounting. The investigated systems included pre-stressed and epoxy resin injection bolts, solid slabs and solid slabs in combination with profiled steel sheeting. The results showed that the tested demountable shear connections could provide higher shear resistance than conventional shear connections. The critical failure mode was the shear failure of the bolts, which is a brittle failure. There was no visible damage observed on the connected members. The application of epoxy resin in the hole clearance resulted in lower slip capacity. The outcome provides an important basis for the justification of the forthcoming enhancement and validation of numerical models of the demountable shear connections. The failure behaviour, the observed damages and the resulting ability of the elements for re-use are discussed in detail.

Organic-Inorganic dual modified graphene: Improving the dispersibility of graphene in epoxy resin and the fire safety of epoxy resin

Fire safety is very important in the application of epoxy resin (EP). To study the effect of fire safety, a new kind of double-modified graphene (F-RGO-CuMoO4) was synthesized in this work. Firstly, GO was modified with 3-Triethoxysilylpropylamine (KH550) through the amidation reaction between the amino and carboxyl group to obtain organic functionalized graphene F-RGO. Subsequently, CuMoO4 was introduced onto the surface of F-RGO by the electrostatic interaction. Then the prepared F-RGO-CuMoO4 was added into EP to prepare an EP composite. The TEM test results of the EP/F-RGO-CuMoO4 ultrathin section showed that F-RGO-CuMoO4 was well dispersed in EP, indicating that the dispersion of graphene in EP was obviously improved after double modification. In addition, F-RGO-CuMoO4 also effectively improved the fire safety of EP. Specifically, the total heat release (THR), peak heat release rate (PHRR), total smoke production (TSP) and smoke production rate (SPR) values of the EP/F-RGO-CuMoO4 composite were reduced to 33.4 MJ/m2, 504 kW/m2, 24.5 m2 and 0.27 m2/s, which were 43.7%, 59.9%, 62.3% and 66.7% lower than those of pure EP, respectively. The main fire safety mechanism of F-RGO-CuMoO4 was explored according to the char residue analysis.

Synthesis of a multifunctional bisphosphate and its flame retardant application in epoxy resin

A spiro-bisphosphate (MFR) was designed and synthesized via the reaction of spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) and 2,4-dihydroxybenzophenone (UV-0) with dual functions of flame retardance and ultraviolet absorption. The chemical structure was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). The flame retardancy performance of MFR was investigated in the commercial epoxy resin E−44 with respect to pyrolysis and fire behavior by thermogravimetric analysis (TGA), limiting oxygen index test (LOI), vertical burning test (UL 94) and cone calorimeter test. The results showed that EP/20%MFR thermoset (EP thermoset with 20 wt% MFR adding) passed the V-0 level in UL 94, and attained a LOI value of 32.2%. The peak heat release rate (p-HRR), total heat release (THR), average effective heat combustion (av-EHC), average mass loss rate (av-MLR) and total smoke release (TSR) of EP/20%MFR thermoset decreased compared with those of neat EP. The flame retardant mechanism of EP/MFR thermoset has been studied in detail. Adding MFR significantly increased char residues and mainly be responsible for the good flame retardancy of MFR. Besides, MFR demonstrated the better UV absorption capability than UV-0.

Synthesis of a Novel Mesoporous Inorganic–Organic Hybrid and Its Application in Epoxy Resins

A novel organic–inorganic hybrid particle (JF633-SBA-15A) was successfully prepared by solution blending method using hybrid hyperbranched polyether polyol (JF633) and surface-modified mesoporous (SBA-15). Further, JF633-SBA-15A/EP composites were fabricated by melt-blending method. The structure and morphology of JF633-SBA-15A were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry analysis, nitrogen adsorption–desorption, and scanning electron microscopy. The mechanical and dynamic mechanical properties of JF633-SBA-15A/EP were also studied. The results demonstrated that the prepared JF633-SBA-15A hybrid particles had excellent thermal stability and unique mesoporous structural characteristics. Compared with pure EP, the maximum degradation temperature of the composites decreased and the thermal stability increased at high temperature. Notably, the JF633-SBA-15A/EP composite had better comprehensive performance. The impact strength and temperature of the glass transition (Tg) of JF633-SBA-15A/EP composites with 1.0 wt% JF633-SBA-15A increased by 32% and 23 °C, respectively. SEM images of the cross-section of the composite which reinforced with hybrid particles exhibited a rough surface and multiple dimples, indicating a ductile fracture.

Experimental results of steel truss nodes strengthen by high strength concrete encasement

In the old steel truss bridges one particular point of interest are the nodes. While for strengthening/refurbishment of the elements of the truss engineers can rely on more conventional methods, usually, for the nodes unique solutions have to be adopted. One integral solution, which could be implemented in a variety of steel truss nodes, is strengthening/refurbishment by totally encasing the node in high performance fibres reinforced concrete. In order to validate this idea laboratory testing of steel truss nodes strengthened by encasement with different concrete classes was initiated. The connection between the concrete and the structural steel is ensured by application of epoxy resin, no mechanical elements are added. The results of the strengthened specimens are compared with one reference bare steel node test. The strengthened specimens show reduced values of the stresses in the gusset plate as well as increase in the load bearing capacity of the connection of the elements entering the node. These results are observed even for encasement in normal class concrete of C40/50.

Preparation and characterization of microencapsulated LDHs with melamine‐formaldehyde resin and its flame retardant application in epoxy resin

Layered double hydroxides (LDHs) are emerging as a new and green high‐efficient flame retardant. But LDHs aggregate seriously because of their hydrophilicity, which affect deeply the mechanical and flame retardant properties of their composites. For the first time in this paper, microencapsulated LDHs (MCLDHs) with melamine‐formaldehyde (MF) resin were prepared by microencapsulation technology to enhance their compatibility and dispersion within epoxy resin (EP). The mechanical and flame retardant performances of EP/MCLDH composite were studied by comparing with EP/LDH composite. Results showed that the water contact angle of MCLDHs increased from 8.9° to 122.1°, which indicated good compatibility. The particle size of MCLDHs decreased sharply, and more than one‐third were up to submicron scale, which can be conducive to dispersion. Moreover, the tensile strength and elongation at break of EP/MCLDHs with different flame retardant contents were higher than those of EP/LDHs. And the addition of MCLDHs increased the glass transition temperature (Tg) of EP/MCLDHs, which meant a strong interfacial interaction. Besides, compared with EP/LDHs, the limiting oxygen index values of EP/MCLDHs were higher, and its peak of heat release rate and total heat release decreased by 16.3% and 5.5% respectively. EP/MCLDHs achieved from V‐1 to V‐0 rate with the increasing content of MCLDHs from 20% to 30%, while LDHs/EP never passed tests. In the process of heating, H2O, CO2, and NH3 released from MCLDHs formed gaseous phase, and the remaining dense char layers and oxides produced condensed phase, which played an important role in inhibiting combustion.

Synthesis of aluminum ethylphenylphosphinate flame retardant and its application in epoxy resin

SummaryA novel flame retardant additive, aluminum ethylphenylphosphinate (AEPP), was synthesized from diethyl phenylphosphonite and aluminum chloride hexahydrate, and characterized by FTIR, 1H NMR, and 31P NMR. AEPP was added into diglycidyl ether of bisphenol A epoxy resin (EP) cured by bisphenol A‐formaldehyde novolac resin. The flame retardancy of the cured EP was investigated by limited oxygen index, UL 94 test, and cone calorimeter test. The results revealed that the EP composite containing 15% AEPP had a limited oxygen index value of 28.2% with a UL 94 V‐0 rating. The incorporation of AEPP effectively decreased the peak heat release rate and the total heat release in cone calorimeter test analysis. Scanning electron microscopy results showed that the introduction of AEPP benefited to the formation of a smooth and continuous char layer during combustion of the flame retarded EP. The thermogravimetric analysis results indicated that the incorporation of AEPP promoted the initial decomposition of EP matrix, but AEPP/EP composites had a higher char yield at high temperatures. Moreover, the flexural properties of the flame retarded EP composites were studied.