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9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-N-Aminoethylpiperazine (DOPO-AEP), a phosphorus and nitrogen intumescent flame retardant curing agent was prepared by using acetonitrile as solvent using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and N-aminoethylpiperazine (AEP) as raw materials. The structure of the flame retardant curing agent DOPO-AEP was analyzed Fourier Transform Infrared Spectrometer (FTIR), Nuclear Magnetic Resonance (NMR) and Electrospray Ionization Mass Spectrometry (ESI-MS), and the synthesis method of the target product was determined. In addition, the content of char residue was determined by thermogravimetric analyzer, and its thermal properties were comprehensively explored, and based on the obtained results, the curable epoxy resin was selected to prepare DOPO-AEP/EP flame retardant composites. According to the amount of DOPO-AEP added product, different proportions of DOPO-AEP/EP flame retardant composites were prepared, and the actual impact of flame retardant properties and mechanical properties of epoxy resin in different proportions was explored. When the content of DOPO-AEP is 35%, the limiting oxygen index of DOPO-AEP/EP reaches 29.9, which has a significant increase compared with the limiting oxygen index of pure epoxy resin of 19.8, but compared with the content of DOPO-AEP of 30%, the limiting oxygen index of DOPO-AEP/EP is 28.7, and there is no significant increase change. Comprehensive analysis shows that when the component content of DOPO-AEP is 30%, the flame retardant system has a tensile strength of 29.0 MPa, an impact strength of 4.5Kj/m2 and a flexural strength of 73.9 MPa, and its limiting oxygen index is as high as 28.7, and the comprehensive performance of the system is the best. By testing the surface morphology of the flame retardant composites after combustion by SEM, it was found that a dense char layer was formed on the surface of the epoxy resin cured char residue and foamed obviously, indicating that the flame retardant curing performance of DOPO-AEP was good. [ABSTRACT FROM AUTHOR]

Reducing the dependence of epoxy resin preparation on petroleum resources and developing thermosetting epoxy resins with excellent comprehensive performance are important directions for the current development of epoxy resins. This article uses biomass resource magnolol as the main raw material to prepare magnolol epoxy monomer (DGEM). Then, using 4,4-diaminodiphenylmethane (DDM) as the curing agent, the DGEM and bisphenol A epoxy resin (E44) were blended and cured. The results showed a dual modification effect of DGEM on the toughening and strengthening of E44 epoxy resin. When the mass ratio of DGEM to E44 is 30:70, the bending strength of the cured blended resin is 18.7% higher than that of the E44 system, and the tensile strength is 57.7% higher. When the mass ratio of DGEM to E44 is 5:95, the cured blended resin exhibits the optimal impact strength (5.10 kJ/mol), which is 22.9% higher than the pure E44 system. However, the addition of DGEM reduced the glass transition temperature and crosslinking degree of the blended resin system. The addition of DGEM improves the heat resistance and flame retardancy of the blended resin. When the mass ratio of DGEM: E44 was 50:50, the vertical combustion reached UL-94 V-0 level. [ABSTRACT FROM AUTHOR]

The disadvantage of poor thermal performance of epoxy resin limits its application in special fields, therefore we improve the thermal performance of epoxy resin by copolymerizing it with phthalonitrile resin. A novel self-promoted curing phthalonitrile monomer containing pyridine rings and amino groups (APNH) was successfully synthesized using 2-amino-4-hydroxypyridine and 4-nitrophthalonitril, and characterized by FTIR and NMR spectra. DSC confirmed that the APNH monomer exhibits curing behavior that is self-promoting. Copolymerizing the APNH monomer with epoxy resin enhances the thermal performance of the epoxy resin. The curing behavior of the EPNH copolymer was studied using DSC, which revealed two distinct curing peaks. FTIR analysis showed that the EPNH copolymer has formed structures such as triazine, phthalocyanine, and isoindoline. The presence of cyano groups significantly enhances the thermal properties of the copolymer, surpassing those of traditional epoxy resins. This enhancement in thermal performance amplifies with an increase in the content of the APNH monomer. The research indicates that the EPNH copolymer exhibits superior thermal stability and elevated glass transition temperatures, facilitating the application of epoxy resin in specialized areas. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastic (CFRP) composites have been widely used in engineering. This paper investigates the effect of composite z-pin (polyimide fiber/epoxy resin) on flexural properties of skin/stringer composite structure with different z-pin densities and diameters. Compared with unpinned specimens, the peak loading and energy absorption of z-pinned specimens are increased by 98% and 9 times, respectively. Parameterized research indicates that the optimal z-pin density is 1.35%. And thin z-pins are beneficial to improve the peak loading and energy absorption, which attributes to more total contact area of z-pins. The statistical results present that z-pin pre-hole inserted (ZPI) process can significantly reduce initial damages of z-pinned specimens compared with Ultrasonically Assisted Z-fiber (UAZ) process. Specifically, the z-pin inclination angle is decreased by 60%, and the initial damages in eye-like zone are prominently reduced. The z-pin makes the specimen exhibit the quasi-brittle behavior under flexural loading by playing a bridging role, which makes the flexural properties of specimens prominently increased. In addition, the "snubbing effect" will enhance the bridging effect of z-pins, but it will lead to inter-fibers debonding, splitting, and shear failure of z-pins. [ABSTRACT FROM AUTHOR]

Turtle shells have evolved over millions of years, developing exceptional mechanical properties such as high relative strength and toughness, rendering them highly effective in resisting impacts. This study delves into the impact resistance of bionic turtle shell structures with various suture shapes. This article analyzes the low-velocity impact of carbon fiber epoxy resin prepreg (CF/EP) composite sandwich panels with a suture interface by using the finite element simulation. The simulations encompass closed and unclosed models featuring bonded and unbonded tips, each with diverse trapezoidal geometries (triangular, trapezoidal, anti-trapezoidal, and rectangular). The findings reveal that sandwich structures with suture interfaces demonstrate significantly enhanced impact resistance compared to those lacking sutures, displaying 3–9 times greater deformation capacity and 20–30 times higher energy absorption capacity. The impact resistance of the triangular suture interface exceeded that of other bioinspired suture shapes, with trapezoidal and anti-trapezoidal sutures also enhancing stiffness, strength, and toughness. Additionally, a 6° bonded tip angle resulted in optimal performance for the triangular suture interface across all analyzed perspectives. The simulation study in this paper provides comprehensive and reliable data on low-velocity impact results, offering fundamental insights for researchers to design composite material structures that meet specific mechanical requirements effectively. Additionally, it offers novel ideas for the connection of protective structures, such as artificial armor. [ABSTRACT FROM AUTHOR]

The development of epoxy resin (EP) with simultaneous enhancements in flame retardancy, mechanical performance, and low dielectric properties represents a significant and complex challenge. In this study, halloysite nanotubes (HNTs) were modified with melamine amino tris-methylene phosphonate (MA) to produce MA-modified HNTs (HMA), which were then integrated into EP to form EP/HMA composites. The incorporation of 1 wt% HMA significantly enhanced the flame retardancy (limit oxygen index up to 29.7%, UL-94 V-0 rating), reduced peak heat release rate by 23.4%, decreased total heat release by 11.9%, reduced total smoke production by 18.4%, and improved mechanical properties (tensile strength by 17.0%, impact strength by 61.0%) compared to pure EP. Additionally, EP/HMA showed a low dielectric constant (3.16) and a dielectric loss (0.019) at 1 GHz. This research presents a versatile strategy for creating multifunctional EP composites with high potential for applications in microelectronics, electronic packaging, and other relevant fields. [ABSTRACT FROM AUTHOR]

The use of Raman spectroscopy has rapidly been on the rise across a great number of industries where comparability, reproducibility, and reliability of the data are of paramount importance. However, controlling the intensity of the Raman signal depends on a large number of factors such as the wavelength of the laser light, the optical components of each device, or the number of molecules in the illuminated volume. For this reason, in this study, a new protocol has been applied to twin Raman devices to achieve a conversion of the signal between them, by pairing the intensity response of the units using a reference sample. The new reference material is a homogenous dispersion of a 0.5 wt% anatase (titanium dioxide, or TiO2) in an epoxy resin matrix, with deviations <2.5% in Raman intensity across the reference material. The proposed protocol for Raman-twinned devices takes a well-defined approach that leads to obtaining a correction factor that relates the differences in the signal intensity between the two Raman devices, in order to obtain the same Raman intensity counts. The performance of the proposed method was evaluated based on the data from the devices, which presented the most common user cases: twinning Raman devices of the non-confocal same model for two different wavelengths; and twinning confocal and non-confocal devices. The results obtained show that the protocol has worked for both of the Raman twinning cases, allowing the Raman intensity harmonization of Raman spectra between two different devices. [ABSTRACT FROM AUTHOR]

A novel composite tandem sandwich structure made of aramid fabric and aramid honeycomb, impregnated in a matrix of epoxy resin combined with poly (vinyl butyral), PVB, is proposed. The composite was additionally reinforced with a small concentration of titanium diboride nanoparticles, TiB2, to study its effect on impact resistance. Sandwich composite samples were fabricated by impregnating the aramid fabrics and honeycomb in subsequent layers with the system epoxy/PVB/TiB2. Their mechanical behavior was examined through three-point bending test, Charpy impact test, and compressive test. The chemical reaction between PVB and epoxy resin, and chemical inertness between the nanoparticles and the other constituents were confirmed by FTIR analysis. The flexural strength and stiffness increased by 27.6% and 62.5%, respectively, in the presence of TiB2 reinforcement. Impact tests showed increase of 104% in impact toughness in the case of samples with TiB2. Nano TiB2 did not increase compressive strength of the proposed sandwich structure, but it improved its stiffness and reduced the permanent deformation. The achieved improvements in mechanical resistance make this new composite structure a promising candidate for automotive, airspace, naval, civil engineering, sports equipment industry, and for use in defense technologies. [ABSTRACT FROM AUTHOR]

Modern science and technology constantly require new and novel materials with special properties. Over the past decade, Nanocomposites materials have received significant attention as active materials in components ranging from sensors to biomaterials, electronics devices to structural parts. These novel composites have applications in many areas, such as energy, insulation, manufacturing, and the modern building industry. However, not all applications have the same requirements in terms of acoustic insulation, so it is useful to adapt the kind of core materials and their product specifications, such as particle size and porosity, to the different applications. Furthermore, in some applications, cheaper core materials, like precipitated silica, would be a reasonable alternative to replace the time-consuming series of measurements. Because of many bad conditions that affect acoustic insulation properties in modern buildings. And to summarize recent applications of nanotechnology as they relate to textile fibers, yarns, and fabrics for improving acoustic insulation in modern buildings and civilian communities, this paper discusses the ability to apply 3D woven spacer fabric (3DWSF) composite materials reinforced with epoxy, rigid polyurethane foam, and silica nanoporous particles, which were prepared by the sol-gel technique. Four samples had been prepared, all of these samples were textile composite materials, and reinforced with two types of nano silica 99.8% SiO2; mesoporous Ns particles with porosity up to 83%, true density 0.08 g/cm³, and particle size between 100 and 2000 nm and pore size 70–150 nm, which had been prepared by Sol-gel technique, and nonporous Aerosil®200 particles with surface area 200–225 m2/g, true density 0.25 g/cm³, and particle size between 2 and 20 nm. We used rigid polyurethane foam as core material, and epoxy resin for laminating the fabric. 3D spacer E-glass fabrics, and chopped E-glass microfibers had been used. The weight percentage of silica nano particles which were used in this research was 5% by weight, which was better for economic reasons, and enough, to enhance the acoustic absorption coefficient up to R w = 99.79%. The best sound absorption could be achieved by using mesoporous silica nanoparticles, and soundproofing of an insulator using this porous structure is better than using a nonporous one. We found in this research that the thickness 45 mm and semi-porosity structure of the 3DWSF composite insulator material were enough to make a difference, with reference to the thermal and acoustic insulation guide of buildings. [ABSTRACT FROM AUTHOR]

In order to evaluate the structural performance of repaired RC beams with partially debonded longitudinal rebars, structural experiments were conducted. In the experiments, real-scale and half-scale RC beam specimens underwent cyclic loading of 1.0% or less in terms of deformation angle, repaired with epoxy resin injection method, and multiple cyclic loading again. As a result of the experiments, damage was suppressed in specimens with partially debonded longitudinal rebars even after repairs. Further, the specimens with partially debonded longitudinal rebars exhibited high recovery of initial stiffness after repair compared to the specimen with bonded longitudinal rebars. In addition, from study of the costs required to repair cracks, it was confirmed that RC beams with partially debonded longitudinal rebars used smaller quantities of materials used for repairs and could potentially reduce repair cost by approximately 50% compared to RC beams having standard bonding properties. [ABSTRACT FROM AUTHOR]

A reactive flame retardant containing biphenyl structure (DEU-2DOPO) was prepared from the bio-based raw material eugenol. The incorporation of DEU-2DOPO into the epoxy resin serves to enhance the ring-opening reaction of the epoxy. Furthermore, the inclusion of DEU-2DOPO has been found to have a positive impact on the glass transition temperature and residual carbon rate of the epoxy resin. This additive also significantly improves the mechanical properties of the epoxy resin, leading to a 49.3% increase in tensile strength, an 81.9% increase in breaking elongation, and a 15.8% increase in flexural strength. Notably, when DEU-2DOPO is introduced at a concentration of 5 wt%, it not only achieves a V-0 rating in the UL-94 test but also exhibits an impressive ultimate oxygen index of 34.5%. Additionally, the cone calorimetric testing revealed that the presence of DEU-2DOPO results in lower combustion metrics compared to pure epoxy, as evidenced by a reduction of 15.1% in total heat release (THR) and 10.8% in total smoke release (TSR). An analysis of the flame retardant mechanism elucidates that DEU-2DOPO promotes the formation of a stable and dense residual carbon, thereby impeding gas and heat exchange. Furthermore, the decomposition of DEU-2DOPO generates PO · and PO2 · radicals, which effectively neutralize reactive radicals. [ABSTRACT FROM AUTHOR]

The graphene/nanonickel composites(Ni/RGO) were prepared by liquid phase reduction method, and the graphene/nanonickel epoxy composites(Ni/RGO/EP) were prepared by in-situ polymerization method. The glass transition temperature (Tg) of the modified epoxy resin was increased by 19°C compared to EP with 2.1 wt% Ni/RGO loading. The tensile strength and hardness increased by 65% and 18%, the impact strength is increased by 10.053 KJ·m−2 compared to EP, and the shear strength reaches 34.78 MPa for the Ni/RGO/EP with 1.7 wt% Ni/RGO loading. It can be seen, that the addition of Ni/RGO greatly improves the heat resistance and mechanical properties of epoxy resin when the Ni/RGO are evenly dispersed into the epoxy resin by emulsion dispersion method. [ABSTRACT FROM AUTHOR]

Free vibrations of an axially moving multiscale composite beam in thermal environment are analyzed. The beam material is epoxy resin with variously reinforced and randomly oriented or aligned in electric field carbon nanofibers (CNFs). To describe the thermomechanical properties of the beam material, published dynamic characteristic of stationary multiscale composites were taken into consideration. Using the frequency–temperature equivalence principle, the nanocomposite material of the beam is modeled using four-parameter fractional rheological model. The dynamic characteristics of the multiscale polymer beam in the frequency domain made it possible to determine the partial equation of motion of the axially moving beam. The Galerkin method is used to solve the governing partial differential equation. The effects of various nanofiber reinforcements of randomly oriented, and aligned in electric field fibers at different temperatures, on the free vibration of the axially moving beam are investigated. [ABSTRACT FROM AUTHOR]

Agricultural by-products have long hinder farmers, and subsequently, the food supply chain. Making use of their natural by-products will both reduce waste and increase industrial production. In particular, pineapple leaf fibers (PALF) can be extensively studied. Here, the curing kinetics of chemically modified PALF/epoxy resin crosslinked by an anhydride hardener was investigated by non-isothermal and isothermal methods with the differential scanning calorimetry technique. In this study, the Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods, as well as Kamal's model, were employed to analyze the curing behavior of epoxy in non-isothermal and isothermal processes, respectively. The highest activation energies for pure epoxy and PALF/epoxy composite calculated differ when using the methods. Additionally, a decreasing trend in the activation energy values during the late stages of epoxy curing was observed. The results from Kamal's model indicate that the k1 values of the PALF/epoxy composite are only greater than those of pure epoxy at 100°C and 110°C. However, all the k2 values of PALF/epoxy are greater than those of pure epoxy. Additionally, the m value of the PALF/epoxy composite is lower than that of pure epoxy only at 100°C, while the n and m+n values of the PALF/epoxy composite are all greater than those of pure epoxy. Moreover, the results reveal that the Cure Index of the PALF/epoxy composite was larger than ΔH* and smaller than ΔT*. With PALF, it was found that the epoxy resin's curing rate was increased and the activation energy was reduced. Meanwhile, the degree of crosslinks was less than that of the virgin resin. It is speculated that the hydroxyl groups on the plant fibers and the amine groups on the coupling agent-modified fibers can promote the cross-linking reaction. However, the curing reaction of the composite is affected by steric obstacles and high viscosity resulting from the addition of PALFs. [ABSTRACT FROM AUTHOR]

Epoxy resin/cyanate ester copolymer (EC) possesses the advantages of low dielectric constant and low dielectric loss, while the easy flammability of EC restricts its applications. The effect of 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphazephenanthrene-10-oxide (DQ) and copper hydroxystannate (CuHS) on the flame retardancy, smoke suppression, mechanical properties and thermal decomposition behavior of EC was studied. The EC composite containing 7 wt% DQ and 3 wt% CuHS (EC/7DQ3CuHS) passed the UL-94 V0 rating with a limiting oxygen index of 32.0% The peak heat release rate and total heat release of EC/7DQ3CuHS fell by 41.9% and 35.0% respectively, compared with those of pure EC. The total smoke release of EC/7DQ3CuHS was reduced by 36.0% in comparison with that of the EC composite containing 10 wt% DQ. The tensile and impact strengths of the EC composite with 9 wt% DQ and 1 wt% CuHS increased by 16.9% and 19.2%, respectively in contrast with pure EC. The dielectric constant and dielectric loss of the EC composites maintained at relative low values. The as-prepared EC composites have application prospect in electronic packaging industry. [ABSTRACT FROM AUTHOR]

The development of novel nanomaterials with superior reflection loss (RL), thin thickness, wide bandwidth, and low density has recently received significant attention in an effort to increase their effectiveness in electromagnetic (EM) microwave absorption while maintaining an easy manufacturing process. Naturally, using conventional materials with magnetic or dielectric loss makes it difficult to achieve the last criterion and limitations the thickness of the absorber and mass production. In this work, microwave nanocomposites samples were prepared on epoxy resin with different percentages of the nanoparticles of aluminum oxide (epoxy/Al2O3) with surfaces treated by amino propyl and silane. The surface treatment was carried out to improve the adhesion, morphology, and EM properties of the samples to enhance the microwave absorption and the Shielding Effectiveness (SE). Therefore, the treated sample can be considered as potential candidate for high frequency EM absorption applications. Then, the study is followed by structural, morphological, thermal, and electrical characterization of the prepared samples in order to enhance the performances of the latters. The EM absorption and the shielding effectiveness were done in the X band frequency (8 GHz-12 GHz). The obtained results confirmed that the nanocomposites treated samples exhibit higher EM absorption performance and better electrical characteristics. Overall, these results put forward the role played by the addition of the nanoparticles films as high-performance materials in electronic devices and EM applications. [ABSTRACT FROM AUTHOR]

Environmental issues have geared the interest of researchers toward the use of naturally occurring materials for various applications in recent times. Hydroxyapatite particles (HAp) for biomedical applications were synthesized from egg and snail shells and used for the fabrication of bio-composites in this research. The shells were prepared by thoroughly cleaning before subjecting to calcination as well as wet-chemical precipitation treatment to obtain 50 µ sized hydroxyapatite particles that were used for the development of the bio-composites. The composites were fabricated with an open mold stir casting technique after mixing the constituents in predetermined proportions. Mechanical, wear, and physical properties evaluations were carried out on the composites and control samples while the images of the fractured surfaces were examined using a scanning electron microscope. It was revealed from the results that the addition of hydroxyapatite to epoxy improved the properties of the composite where most of the optimal values emerged from 15 wt% HAp-reinforced samples. It was discovered that snail shell HAp-based composites had superior enhancements than the eggshell HAp-based composites which showed that the source of the animal shell influences the characteristics of the ensuing properties. Flexural strength and modulus were 63.95 and 774.64 MPa, respectively; hardness was 40.25 HS, wear index was 0.07, and thermal conductivity was 0.545 W/mK for the snail shell HAp-based composites. Hence, synthesized HAp from snail shells is more structurally stable than eggshell-based and can be used for biomedical applications. [ABSTRACT FROM AUTHOR]

In this study, the intermediate of SPDPC flame retardant curing agent was successfully synthesized through the reaction between phosphorus oxychloride and pentaerythritol under the catalysis of 4-dimethylaminopyridine. Using 1,2-propylenediamine and the prepared SPDPC, a novel phosphorus and nitrogen flame retardant curing agent named poly1,2-propylenediamine pentaerythritol diphosphate (PDS) was successfully synthesized. The target product was subjected to characterization using infrared spectroscopy, mass spectrometry, hydrogen NMR spectroscopy and thermogravimetric analysis. The molecular structure of the product was determined and its decomposition temperature curve obtained, leading to the conclusion that it could be cured at high temperatures. DDS was selected as the curing agent for epoxy E-51, the specific curing conditions were obtained by DSC test. Subsequently, E-51, DDS and PDS were mixed for high temperature curing resulting in obtaining test spline of PDS-E-51 flame retardant composite material. Then, the flame retardancy and mechanical properties of the spline were tested. It was observed that pure EP cured by DDS had an LOI of only 19.5%, indicating its flammability. However, upon addition of PDS as a flame retardant, the LOI significantly increased with 20 parts resulting in an LOI of 29.7%. The addition of 25 parts results in an increase in limiting oxygen index to 30.3%, while the tensile strength and impact strength are measured at 38.27 MPa and 5.087 kJ/m2 respectively. The CCT test shows that the addition of PDS can significantly reduce the HHR and THR of the system. CCT digital photos show that the addition of PDS can make the combustion residue of the system expand obviously, showing a good expansion and flame retardant effect. TG-FTIR gas phase infrared absorption indicates that the addition of PDS can reduce the concentration of combustible gas in the combustion process. Test results indicate that the mechanical properties of PDS-E-51 flame retardant composites experience a certain degree of decline, but with increasing amounts of PDS curing agent added, their flame retardancy is significantly enhanced. [ABSTRACT FROM AUTHOR]

Egg shells and fish scales are two abundantly available by-products from food industries which can be used as filler materials to reinforce polymer composites. The bulk of discarded chicken eggshells and fish scales are disposed of in landfills, which cause environmental issues. The present research work focuses on the water absorption, mechanical and tribological properties of epoxy composites reinforced with chicken eggshells and catla fish scale particles. Hybrid composites incorporating both fillers were also made and evaluated. Results from the water absorption tests showed that the addition of fillers decreased the water absorption of the composites than neat epoxy. Tensile and impact tests revealed that the inclusion of fillers reduced the tensile and impact strength of the composites compared to neat epoxy, but improved the tensile modulus. The hybrid composite (EFREC) showed improvement in both flexural strength and modulus in comparison to neat epoxy. Also, the results from the wear tests revealed that the addition of fillers improved the wear resistance of the composites. Among all the mechanical and wear tested composite specimens, the hybrid composite (EFREC) showed the best performance. This was also validated from the SEM images of the fracture and wear surfaces of the composites. [ABSTRACT FROM AUTHOR]

Reactive polyimide (PI) containing phenolic hydroxyl groups was prepared by the polymerization of 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane and mixed thiodiphthalic anhydride. A series of epoxy resin composites were obtained by adding reactive PI to N,N,N′,N′ -tetraglycidyl-4,4′-diamino-diphenylmethane (TGDDM) epoxy resin in different proportions. The effect of PI content on curing behavior, thermal properties, and mechanical properties was carefully investigated. Even a small amount of PI addition improved the mechanical properties and heat resistance of the epoxy resin, particularly the fracture toughness. Among them, epoxy resin composites EP-PI-1.5 with the addition of 1.5 wt% PI showed the best mechanical properties, whose impact strength, fracture toughness, and tensile strength were increased by 114%, 59%, and 34%, respectively. The phase morphology was also investigated to illustrate the fracture mechanism by scanning electron microscope (SEM) characterization. [ABSTRACT FROM AUTHOR]

To gain insight into more about how flame retardants containing phosphorus, sulfur, and nitrogen affect epoxy resin (EPs), a multicomponent flame retardant (Sp-ACDH) containing P/N/S was synthesized from sodium p-aminobenzene sulfonate (Sp-A), cinnamaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and applied to epoxy resin. Sp-ACDH enables the epoxy resin to achieve the desired flame retardancy. For example, with the addition of 10 wt% Sp-ACDH, the epoxy composite passed the UL-94 V-0 rating and achieved an LOI of 32.7%. Additionally, Sp-ACDH effectively slowed down EP's ability to release heat, with EP-15 Sp-ACDH exhibiting a peak heat release rate (PHRR) that was 680 kW/m2 rather than pure EP's 1204.4 kW/m2. Eventually, the samples were characterized using Scanning electron microscopy (SEM), Raman spectroscopy, and Thermogravimetric analysis-fourier transform infrared spectroscopy (TG-FTIR) spectra, and the samples were analyzed, it revealed that Sp-ACDH's flame-retardant properties were active in both the gas and condensed phases. [ABSTRACT FROM AUTHOR]

A high effective P/N-containing flame retardant additive CDD was triumphantly synthesized with nitrogen-rich 3,5-Diamino-1,2,4-triazole, DOPO and cinnamaldehyde. With the help of 4 wt% CDD, Epoxy resin (EP) sample succeeded in UL-94 V-0 test, and improved its LOI value to 33.5%. EP/4 wt%CDD sample also performed very well in cone calorimeter (CC) test. For example, the peak of heat release rate of EP/4 wt%CDD decreased to 603 kW/m2, which was 56.8% of EP sample without flame retardants. All these details showed that CDD was highly effective in fire resistance. Besides, the addition of CDD also drastically improved mechanical strength of EP. Tensile strength, flexural strength and izod iMPact strength of EP/4 wt%CDD sample was increased to 102 MPa, 124 MPa and 38 kJ m−2, which was 118.6%, 129.2% and 126.7% of control group. At last, the flame-retardant mechanism of CDD was studied by FTIR, XPS, Raman spectra, and SEM. The results showed that CDD's perfect performance in fire resistance was ascribed to the generation of phosphorus-rich char layer in condensed phase. [ABSTRACT FROM AUTHOR]

Epoxy resins (EP) have been commonly used, but their poor flame retardant properties have prevented their widespread use. In order to improve the flame retardant properties of EP, an organic-inorganic composite flame retardant (HKDC) containing multi-element P/N/Si was successfully synthesized in this work using a typical aldehyde amine condensation reaction. This flame retardant utilizes the synergistic effect of multiple elements to simultaneously perform the flame retardant function of each element, and it can achieve excellent flame retardant effect by using low addition amount in EP. At the same time, this flame retardant can not only reduce the migration of molecules through the structure of inorganic substances, but also the C = C reaction in EP can form large molecules and increase the compactness with the EP matrix. The flame retardants were then quantified by measuring their flame retardant properties, combustion behavior and thermal stability. When the flame retardant HKDC is added, the flame retardant performance of EP is improved and the vertical combustion test achieves a V-0 rating. Most importantly, the addition of flame retardant HKDC effectively suppressed the toxic gas and smoke emissions of EP, with TSP values much lower than those of pure EP, and CO and CO2 emissions were suppressed. [ABSTRACT FROM AUTHOR]

A P/N containing flame retardant DOPO-QN was synthesized by a reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 8-hydroxyquinoline (QN). Its chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) like 1H, 13C, 31P NMR, and high-resolution mass spectrometry (HRMS) techniques. The synthesized DOPO-QN was employed as an additive type flame retardant in combination with clay nanomer 1.34TCN (NC) in diglycidyl ether of bisphenol A/4,4ʹ-diaminodiphenlsulfone (DGEBA/DDS) to synthesize epoxy thermosets. The fire behavior of synthesized epoxy thermosets was studied by UL-94, limiting oxygen index (LOI), and cone calorimeter tests. The EP/DOPO-QN (1.5%P)/NC sample passed the UL-94 test with a V-0 rating and LOI value of 26.5%. A decrease in peak heat released, carbon monoxide, and carbon dioxide emissions was observed in the cone calorimeter test. Thermogravimetric analysis (TGA) of epoxy thermosets showed an increase in thermal stability at a higher temperature range on the formation of nanocomposites. Also, a remarkable improvement in storage modulus was observed for the EP/DOPO-QN (1.5%P)/NC sample containing 2.0% NC in dynamic mechanical analysis (DMA). [ABSTRACT FROM AUTHOR]

Polymeric epoxy-based nanocomposites have tremendously grown in electronic and indoor high-voltage insulation applications over the last two decades. The interface between the epoxy resin and inorganic fillers surprisingly improves the performance compared to neat epoxy and conventional ceramic insulators. However, several configurations, including the filler loading, filler size, and synthesis process, substantially impact performance. Dielectrics employed in power equipment are often exposed to corona discharges, causing surface erosion and may cause flashover due to prolonged exposure to the discharges. Also, dielectrics must continuously endure heat from leakage currents or surrounding temperatures. The present work examines various configurations of the epoxy/ZnO composites for the corona discharge resistance and thermal stability: the effect of filler loading, preparation method of nanocomposites, and co-filling of nano-micro fillers. The ZnO nanoparticles were disseminated in the epoxy resin using a probe and bath sonicator with and without solvent. It also includes the impact of heated nanoparticles. The corona discharge tests were performed using a set-up similar to CIGRE working group D1.24. The studies of surface degradation were conducted using surface roughness metrics obtained from an optical 3D profilometer. Differential scanning calorimetry (DSC) was used to perform the thermal analyses as per ASTM E1356. It was found that compared to all the filled specimens, the neat epoxy experienced more severe erosion. In addition, the specimen filled with ZnO nanoparticles endured positive corona discharges compared to negative and AC discharges. The specimen prepared with heated nanoparticles without solvent using a probe sonicator showed high heat energy and heat capacity leading to thermal instability. Besides, the interface between nano-micro particles and the host material increases corona discharge resistance and thermal stability. [ABSTRACT FROM AUTHOR]

In this research, diglycidyl ethers of bisphenol-A (BADGE) and polyethylene glycol (PEGDGE) were binarily cured with a mixture of diamine curing agents including isophorone diamine and polyethylene glycol diamine (PEGDA) in the absence/presence of aminated graphene oxide nanoplatelets (AGNPs, 0.5 wt.%). Four molar ratios of diglycidyl ethers and curing agents were used stoichiometrically in isothermal curing systems. The films prepared from the epoxy networks were entirely strong and pliable. All epoxy thermosets were evaluated using field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and diffuse reflectance-ultraviolet/visible spectroscopy (DR-UV/vis). The absorption coefficients of the epoxy and AGNPs-loaded epoxy materials decreased with increasing the molar ratio of PEGDGE resin and polyethylene glycol diamine curing agent. According to dynamic mechanical analysis no phase heterogeneity occurred in the structure of the prepared thermostats. When the thermoset materials were loaded by AGNPs filler, the peaks associated with alpha relaxations shifted to higher temperatures. Moreover, thermogravimetric analysis demonstrated that the thermal stability of the prepared epoxy thermosets slightly increased after the addition of the nanoplatelets. In addition, the thermal resistance of the prepared thermosets decreased to some extent by increasing the participation rate of monomers containing polyoxyethylene. Graphical Abstract [ABSTRACT FROM AUTHOR]

In the present paper, a novel combined damage-based failure criterion is being proposed for predicting failure stresses in unidirectional fibrous composite laminas or laminates having a nonlinear material behavior. The present model incorporates the effect of a quantitative damage factor on the final stresses at failure. This is achieved through a new term called the quantitative directional damage-index (QDD-I) which assesses the contribution and effectiveness of damage in each principal material direction on the present failure criterion. From the QDD-I, it is proved that the principal material-direction with a linear or nonlinear stress-strain behavior showed a quantitative damage response on the proposed failure criterion. In a composite lamina, the contribution of fiber-damage and matrix transverse-damage are proved to have minor effects on the failure criterion, while in-plane shear-damage has the major effect. In order to verify the suitability and applicability of the criterion, results are tested using various theoretical and experimental data available from the literature. Furthermore, the model is compared with other failure criteria under both uniaxial and biaxial loading cases from a worldwide comparison, which showed reasonable accuracy and good agreement. Three types of fibrous composite materials are used; Graphite/Epoxy 4617/Modmore-II, Carbon/Epoxy AS4/3501-6, and Boron/Epoxy Narmco 5505. [ABSTRACT FROM AUTHOR]

The generation of electronic waste generation has led to significant attention towards metal recovery from urban sources. Due to scarcity, finite resources, and geopolitical constraints, tantalum recycling from capacitors is essential. In this study, sequential separation involving the removal of tightly bound epoxy resin and metallic impurities is carried out. Pyrolysis as a pre-treatment and its response on phase transformation, resin decomposition and metal enrichment are investigated. Pyrolysis effectively liberates the tantalum–rich sintered core from outer resin which is followed by mild organic acid leaching. The manganese impurity was removed from the core to obtain Ta recovery of ∼94.8% with ∼96% purity in the leach residue. The separated resin component was subjected to conventional sink-float separation for the recovery of metallic values (silver, tantalum). It is found that 100 g (666 units) of Ta capacitors can yield 34 g of Ta, equivalent to 0.28 tons of primary ore. [ABSTRACT FROM AUTHOR]

N,N′-Tetraglycidyldiaminodiphenyl methane (TGDDM) was reinforced with various weight fractions (0.5, 1, and 1.5 wt%) of amine functionalized nano alumina (F-Al) were cured with diaminodiphenyl-methane (DDM). FT-IR analysis revealed that formation of functionalized nano alumina (F-Al) structure, was brought about via coupling agent APTES. Furthermore, the morphology of TGDDM epoxy nanocomposites was studied using X-ray Diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microscopic analysis and an atomic force microscope (AFM). We found a bonding relationship between TGDDM epoxy and F-Al in TGDDM/F-Al nanocomposites It was interesting to note that the values of tensile, flexural and impact strength of 1 wt% F-Al reinforced TGDDM epoxy nanocomposites were found to be 141.5, 192.5 MPa, and 92.4 J/m2, respectively., which resulted in a substantial improvement in the dynamic mechanical analysis (DMA) to 4.3 and 5.5 for 0.5 and 1 wt% F-Al reinforced TGDDM epoxy nanocomposites and the glass transition temperature (Tg) increased from 210°C to 225°C as the F-Al content increased. The initial degradation temperature (IDT) of 0.5, 1, and 1.5 wt% F-Al reinforced TGDDM epoxy nanocomposites were significantly enriched to 328°C, 345°C, and 335°C respectively from 290°C of neat (TGDDM) epoxy matrix. Likewise, the char yield for the neat (TGDDM) epoxy matrix was 13% and that for 0.5, 1, and 1.5 wt% F-Al reinforced TGDDM epoxy nanocomposites were 17%, 25%, and 20% respectively. It is feasible to state unequivocally that considerable F-Al diffusion within the TGDDM epoxy can only occur at low weight percentages. The results clearly showed that F-Al reinforced TGDDM epoxy nanocomposites may be investigated for advanced high performance industrial engineering applications. [ABSTRACT FROM AUTHOR]

In this work, the epoxy resin cured with chlorinated fluorene amine as the curing agent was obtained, which significantly increased the resin modulus and did not reduce the impact toughness, compared with the common curing system. Al2O3 nanoparticles were used to stiffen the new curing epoxy system, which did not reduce the compression strength of the resin but increased the compression modulus. The microscopic morphology showed that the rigid particles were uniformly dispersed in the resin matrix, and the addition of rigid particles mildly affected the reactional and rheological properties of the resin system. The minimum viscosity of the matrix increased with the additional number of particles. The composite was prepared using the nanoparticle-modified epoxy resin with carbon fiber (CF), and the compression strength of the composite was significantly improved by nearly 30% compared with that composed of the common epoxy system. [ABSTRACT FROM AUTHOR]

Two effective flame retardant additives hsalaminopyridine phosphaphenanthrene (HAD) and methoaminopyridine phosphaphenanthrene (MAD) were respectively prepared with DOPO, aminopyridine, salicylaldehyde and 3-Methoxysalicylaldehyde. Subsequently, HAD and MAD was added into epoxy resin (EP) respectively, and flame retardancy of EP/HAD and EP/MAD thermosets were dramatically enhanced. The result of cone calorimeter (CC) test revealed that both HAD and MAD showed perfect smoke suppression performance. In respect of transmittance and mechanical properties, there was a huge difference between HAD and MAD. The introduction of HAD dramatically harmed transmittance and mechanical properties of EP, while, EP/10%MAD was transparent and nearly possessed the same mechanical properties with pure EP. [ABSTRACT FROM AUTHOR]

The use of carbamate to foam epoxy depends significantly on the precured modulus to stabilize the cellular structure. The optimum precured modulus is developed from the reaction of epoxy resin and the neat amine. The selection of the neat amine relies on its reaction temperature with epoxy, which is required to be below the decomposition temperature of carbamate. This study investigates the effect of three different neat amines on the rheological behavior of foaming epoxy-carbamate-amine. They are bisphenol-A diglycidyl ether epoxy (DGEBA), isophorone diamine carbamate (IDPA.CO2), N-aminoethylpiperazine (AEP), 2,4-Diamino-1-methyl-cyclohexan (DMC) and isophorone diamine (IDPA). The mixtures of DGEBA-amine-carbamate are filled in 25% and 75% of the volume of a closed mold. Precuring is carried out at 60°C for 2 h. The foaming and complete curing are conducted at 180°C for 1 h. Having H-active at piperazine, AEP reacts with DGEBA faster and develops a higher precured modulus compared to DMC and IDPA. It is important to note that DGEBA-AEP-IDPA.CO2 exhibits viscoelastic behavior beyond 138°C, seen by its rheological storage modulus lower than loss modulus and its tan delta larger than 1. The reaction between DGEBA and the H-active piperazine of AEP leads only to linear linkage and is unable to further crosslink compared to the primary amine (-NH2). This results in a lower glass transition temperature Tg of DGEBA-AEP-IPDA.CO2. The effect of amine on foaming is more obviously at 25% filling level. DGEBA-AEP-IPDA.CO2 has more spherical and homogeneous cellular structure and the density of 285 kg/m3. Having quite similar chemical structure, both DGEBA-DMC-IPDA.CO2 and DGEBA-IPDA-IPDA.CO2 produce the epoxy foams having cell-interconnection and coalescence; their densities are also similar 301 kg/m3 and 305 kg/m3, respectively. All the foams are closed-cell at 75% of filling level. The cell morphologies are well reflecting the foaming modulus and tan delta behavior. [ABSTRACT FROM AUTHOR]

Four siloxane benzoxazines containing different rigid segments were successfully synthesized and characterized herein, including a benzene ring, a biphenyl, a naphthalene ring, and a diphenyl sulfone group. Different rigid segments had different effects on polymer properties. The introduction of the naphthalene ring and sulfone group considerably reduced the curing temperature of benzoxazine. Although the benzoxazine with the naphthalene ring exhibited low heat resistance, all the four samples showed a high char yield at 800°C under nitrogen atmosphere. In addition, during copolymerization with AG-80 epoxy, the introduction of epoxy promoted the curing of the benzoxazines containing the naphthalene ring and sulfone group. The heat resistance of all copolymers was considerably improved, especially for the copolymer containing the naphthalene ring, whose 5% thermal weight loss temperature (T d5) increased from 248°C to 321°C under nitrogen atmosphere. The copolymer containing the biphenyl structure had the highest glass transition temperature, reaching 259.1°C. Copolymerization with epoxy also considerably improved the tensile strength and elongation at break of the copolymers, which were much higher than those of traditional bisphenol A-aniline based benzoxazine (BA-a). Compared with the neat benzoxazine prepared using siloxane and bisphenol A, the developed copolymers also had better tensile properties, and the copolymer containing the sulfone group showed the greatest improvement (from 49 to 69 MPa, from 3.1% to 9.12%). [ABSTRACT FROM AUTHOR]

Previous studies on linear epoxy (bisphenol A epoxy) resin/benzoxazine composites showed that with the addition of epoxy (EP) resin, the resulting copolymers exhibited an increased glass transition temperature (T g) (T g reached a maximum value at a specific content), improved flexural strength, lower heat resistance, and reduced tensile strength. Herein, branched EP resin (AG-80)/benzoxazine copolymers featuring novolac (N-box) and siloxane (Si-box) chains were prepared without any external curing agent. In both systems, the EP resin endowed the copolymers with an increased crosslinking density; however, T g continued to increase with increasing EP content. In addition, the heat resistance of the copolymers gradually enhanced. Different types of benzoxazines have various effects on the properties of copolymers. In terms of mechanical properties, AG-80/N-box copolymers exhibited brittle fracture characteristics; with increasing EP content, the flexural strength of the copolymer decreased while the tensile strength increased. AG-80/Si-box copolymers exhibited ductile fracture characteristics, with gradual increases in flexural and tensile strengths. Furthermore, with increasing EP content, the molecular chain migration ability and network homogeneity of the AG-80/N-box copolymers decreased gradually. Alternatively, in the case of the AG-80/Si-box copolymers, the molecular chain migration ability remained unchanged and network homogeneity improved. Hence, the developed copolymers can be used as resin matrices for the fabrication of advanced composites. [ABSTRACT FROM AUTHOR]

Polymer composites, in particular aramid-epoxy composites, are widely used in fields such as aerospace, transportation, electronics, etc. due to their excellent mechanical and dielectric properties. This article presents studies of modification and combined reinforcement on the mechanical properties of aramid-epoxy composites. The influence of matrix (epoxy resin) and reinforcing filler (aramid fabric) mass ratio and ways to increase strength characteristics and impact toughness of the composite were studied. Comparative results for composites made by vacuum forming and vacuum infusion methods are presented. Mass ratio of reinforcing filler and matrix varied in the range of 50:50%, 60:40%, 65:35%, and 75:25%. It was found that modifying epoxy resin with polyurethane rubber plasticizer, together with combined reinforcement of aramid fabric/aramid roving, resulted in composite strength up to 720 MPa and impact toughness of 426 kJ/m2. Modification of epoxy resin with tricresyl phosphate leads to composite strength up to 710 MPa and impact toughness of 475 kJ/m2. Thus, it is shown that modification and combined reinforcement of aramid-epoxy composites are the most effective methods to increase strength and adhesion to epoxy resin. [ABSTRACT FROM AUTHOR]

Silica aerogel (SA) is used as an additive in composite production to improve their thermal–mechanical properties, owing to their excellent properties such as high porosity, low density, and low thermal conductivity. All these unique properties make it attractive to be used for improving sound absorption and thermal insulation properties of composite materials. However, there are very limited studies on both improvement of sound and thermal insulation properties of glass fiber fabric epoxy composite by adding silica aerogel. With this aim, this study investigates the effect of incorporation of SA as a filler in glass fiber fabric epoxy composite (GFEC) and epoxy plate used in a wide variety of structural and engineering applications such as buildings, constructions, communication, aerospace and transportation, on sound absorption and thermal insulation. Results indicate that SA addition decreased the thermal conductivity coefficient from 0.55 to 0.48 W/mK for GFEC, and from 0.25 to 0.23 W/mK for epoxy plate, providing improvement on thermal insulation. Silica aerogel increased the maximum sound absorption coefficient (SAC) from 0.27 to 0.65, shifting the frequency from 4000 to 400 Hz for GFEC. The maximum SAC value increased from 0.28 to 0.41 at 800 Hz and decreased from 0.54 to 0.47 at 2000 Hz in SA incorporated-epoxy plate with 1 cm air gap thickness. The results reveal that SA has an improvement effect on low-frequency sound absorption for both GFEC and epoxy plate. [ABSTRACT FROM AUTHOR]

This paper includes the curing of previously synthesized multifunctional bio-based epoxy resins (PEMPAE/TMPAE) with rosin-based imidoamine curing agents (IAMDK/IASDK/IAEDK) which are nucleophilic addition reaction products of diamino diphenyl ether (DDE) and dimaleopimaryl ketone (DMPK), a dehydrodecarboxylated derivative of MPA. Curing dynamics of rosin-based epoxy resins (PEMPAE/TMPAE) with rosin-based imidoamine curing agents (IAMDK/IASDK/IAEDK) were evaluated using differential scanning calorimetry. For comparison, the bio-based epoxy resins were also cured with rosin derivative dimaleopimaryl ketone (DMPK) and commercial-based diamino diphenyl ether (DDE). The universal testing machine and thermogravimetric analyzer) were used to measure the mechanical properties and thermal stability of the cured epoxy samples. The samples' chemical resistance was assessed by calculating the weight loss in percent after they were submerged in solutions of NaOH, HCl, and NaCl. We also used scanning electron microscopy (SEM) to examine the morphological changes. Rosin-based epoxy cured with imidoamine curing agents outperformed the commercial epoxy in terms of performance. [ABSTRACT FROM AUTHOR]

To investigate a new type of bionic energy-saving sandwich plate—the beetle elytron plate (BEP), the compressive mechanical properties of short basalt fiber reinforced epoxy resin composite BEPs and honeycomb plates with different polyvinyl chloride foam densities and height-to-thickness ratios were investigated. The mechanism of the coupling effect of the core structure, foam density and height-to-thickness ratio was revealed by observing the failure mode of the outer and inner ring honeycomb walls. This study can provide useful instruction for designing lightweight sandwich structures and accelerate the application of BEPs in engineering. [ABSTRACT FROM AUTHOR]

The aim of the present study is the thermal characterization of laboratory-scale carbon fiber/epoxy-based prepregs by incorporating single-wall carbon nanotubes (SWCNTs). Investigation of the cure behavior of a prepreg system is crucial for the characterization and optimization of the fiber reinforced polymeric (FRP) composite. To affect dispersion characteristics, SWCNTs were functionalized by oxidizing their surface with carboxyl (-COOH) group using an acid treatment. The modified resin system contained 0.05, 0.1, and 0.2 wt. % functionalized SWCNTs (F-SWCNTs). Carbon fiber (CF) reinforced prepregs containing various amount of F-SWCNTs were prepared using drum-type winding technique. FTIR was performed to identify new bonding groups formed after the functionalization of SWCNTs. Cure kinetics of prepregs prepared with/without F-SWCNTs were investigated using isoconversional methods. [ABSTRACT FROM AUTHOR]

To explore thermal and mechanical properties of epoxy material, difunctional aromatic epoxy--divinylbenzene dioxide (DVBDO) had been synthesized by epoxidizing divinylbenzene, using the metal acetylacetone compound grafted Fe3O4 particles as the catalyst. The catalyet had high conversion and epoxy selectivity and could be recyclable. Then the polymerization of DVBDO with different diamine curing agents were reported. The structure and viscosity of DVBDO were firstly characterized. Because it had low molecular weight and viscosity, DVBDO had excellent liquidity and formability. Subsequently to clarify the properties of epoxy thermosets, experiments to determine thermal and mechanical performances were carried out, such as differential scanning calorimetry (DSC), thermal gravimetric (TGA), dynamic mechanical analysis (DMA) and tensile test. It could be observed that the thermoset polymers using DVBDO as epoxy matrix had excellent thermal (Tg was about 201°C) and mechanical properties (tensile strength was 131.99Mpa). Possibly considering that this kind of thermoset polymers had higher rigidity and crosslink density. In conclusion, a new type of one-component liquid epoxy encapsulant material with low viscosity, good filling fluidity, strong heat resistance and excellent storage performance had been developed. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymers, especially carbon fiber reinforced polymers, are expected in the future to contribute more than 50% of the structural mass of an aircraft. With increasing application and experience increased attention is paid to carbon-fiber reinforced composites with improved advanced properties, such as mechanical, structural and electrical, allowing them to displace the more conventional materials, such as metal alloys. In this paper, we used the Design of experiment methodology to investigate the design and properties of newly developed unique porous carbon-fiber reinforced composites intended for electromagnetic shielding purposes. The main goal was therefore to fabricate a composite with low thickness, high permeability to air and water vapor with a satisfactory ability to shield electromagnetic fields, whereas the investigation of the influential variables of the reinforcement and the investigation of the influence of the matrix on the overall shielding efficiency of the composite belongs to the sub-objectives. Furthermore, other important properties of the composites including heat and mass transfer, mechanical and electrical properties were evaluated. A quality index evaluation approach using weighted and normalized data was implemented to choose a composite with properties, which best fits to its intended use. The highest quality index was achieved by the composite containing reinforcement with warp and weft sett 18 dm−1 using carbon tape 2 mm wide. This composite provides electromagnetic shielding 36 dB at 1.5 GHz, having high air permeability 1000 mm/s, relatively low bending rigidity of around 2.5 Nmm and thickness of only 0.37 mm. [ABSTRACT FROM AUTHOR]

An agro-waste such as coffee beans has been used to generate cellulose particles. Coffee roast which is brown in color, was treated with 6% sodium chlorite solution, followed by alkali treatment. This chemically treated mass was subjected to acid treatment with 20% sulfuric acid. Cellulose microwhiskers were released. These micro particles were examined by an X-ray diffractometer (XRD). X-Ray diffraction study of these white cellulose particles and the residue showed a highly crystalline nature of the cellulose particles. The fourier transform infrared (FTIR) spectra were carried out to further investigate any structural changes after chemical treatment. The spectra of the treated powder showed lesser peak intensity at 1630 cm−1. This peak is related to the aromatic ring of lignin. Thus, indicating that the removal of aromatic rings of lignin and polysaccharides after hydrolysis process, simultaneously increases degree of crystallinity. Composites of epoxy resin with a conventional amide-type hardener reinforced with renewable materials were investigated in the presence of castor oil (CO). The renewable material was extracted from coffee beans using various chemical agents. The extracted renewable material has been incorporated into epoxy resin. The composites were evaluated by FTIR to check any interactions. The remarkable hint is the increased intensity of the peak located at 3941 cm−1 being assigned to the –NH2 of the amine cured epoxy. The increment in the intensity is being attributed to the enhanced degree of interaction between the multifunctional CO and the amine cured epoxy resin as mentioned earlier. Tests of tensile and impact strength properties were carried out and Izod impact was determined at room temperature. It has been found that the incorporation of CO has significantly increased the elongation at break. The impact resistance of the composites with CO has significantly increased as compared to the control and the samples without CO. Scanning electron microscopy (SEM) images were taken to assess the effects of reinforcement and homogenization of the composites. It was noticed that the incorporation of the CO has turned the topography of the samples to a smooth surface with respect to rugged phase of the samples without CO. [ABSTRACT FROM AUTHOR]

Tetra functional epoxy resin namely tetraglycidyl 1,4'-bis (4-amine-phenoxy) sulphone benzene epoxy (TGBAPSB) was developed via 1,4'-bis (4-amine-phenoxy) sulphone benzene (BAPSB) and epichlorohydrin. TGBAPSB was reinforced with polyhedral oligomeric silsesquioxane (POSS) nanomaterial in various weight percentages (1–2 wt%) and polyamidoimidazoline (Aradur 140) was used as curing agent. FT-IR results validated the molecular structure of the synthesized POSS. Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) evaluated the thermo-mechanical and thermal behaviour of TGBAPSB epoxy matrix and its organic-inorganic hybrid epoxy nanocomposites (TGBAPSB/POSS). X-Ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) investigated the surface morphological behaviour of the organic-inorganic hybrid epoxy nanocomposites. TGBAPSB epoxy resin with optimized POSS reinforcement exhibited excellent thermo-mechanical, thermal, mechanical, dielectric, and water absorption properties, making it a suitable material for advanced high-performance applications. [ABSTRACT FROM AUTHOR]

Owing to the requirement for environmental protection, water-based coatings have become a significant trend in the development of coatings. The water-based epoxy curing agent has also become a hot research topic. In this study, a B-A-B epoxy compound with a long hydrophobic alkyl chain connected to the intermediate nitrogen atom was synthesized at both ends of a molecule using ethylene glycol diglycidyl ether and 3,4-dimethoxyaniline as raw materials. Subsequently, the epoxy compound was sealed with triethylenetetramine. A nonionic, water-based epoxy resin curing agent with amino groups at both ends of the molecule was prepared. The target product structure was confirmed by infrared spectroscopy (IR), Mass spectrum (MS), and Nuclear magnetic resonance hydrogen spectroscopy (1H-NMR). Additionally, through three factors and three levels of orthogonal experimental design, the optimum experimental conditions were confirmed, the optimum yield was 82.83%. The thermogravimetric analysis (TGA) indicated that the monomer exhibited a significant weight loss in the temperature range of 320–450°C. The pencil hardness, flexibility, and impact resistance of the waterborne epoxy resin coating film prepared by the non-ionic water-based epoxy curing agent reached or exceeded those of similar products at China and foreign countries. [ABSTRACT FROM AUTHOR]

Today, advanced materials like fibrous composites are widely used in the industry due to their favorable strength-to-weight ratio, corrosion resistance and many other suitable properties. Buckling phenomenon may occur in a thin composite structure subjected to high compressive loads. Moreover, the buckling strength of polymer based composites such as glass/epoxy decreases due to sunlight radiation. In this research, the effect of adding zinc oxide (ZnO) nanoparticles as a reinforcement to the matrix material of glass/epoxy composite on the critical buckling load of the beam specimens is investigated experimentally. In addition, samples are exposed to simulated sunlight irradiation and the effect of adding nanoparticles is investigated. Rectangular composite beams are made and reinforced with 1 wt. % of ZnO nanoparticles. Beams are clamped under tensile testing machine for buckling test. Compressive load is applied to the beams in the longitudinal direction and force-displacement graphs are plotted. Results indicate that the addition of ZnO nanoparticles into the epoxy resin increases the critical buckling load of these beams. As the results show, the critical buckling load of ZnO reinforced glass/epoxy specimens increases by %39.4 with respect to that of glass/epoxy samples. Moreover, to investigate the effect of adding nanoparticles after sunlight irradiation, some samples were placed in the accelerated weathering system for 24 h. Buckling test results represent a remarkable increase in the amount of critical buckling load for ZnO/glass/epoxy specimens even after the irradiation. SEM images of the break section of ZnO reinforced glass/epoxy specimens illustrate homogeneous dispersion of ZnO nanoparticles in the epoxy resin. [ABSTRACT FROM AUTHOR]

Composites were manufactured from glass fiber, bagasse fly ash, and epoxy matrix and examined their mechanical and physical properties. The percentages of bagasse fine ash, glass fiber, and matrix were designed at 10%, 15%, 20%, 25%, and 30% with 30% glass fiber and conducted density, flexural strength, hardness, absorption of water, and swelling properties of thickness. Composites were prepared by manual layering. ASTM standards were followed in preparing the samples. According to the results, the bagasse fine ash percentage variation was significant in the composite but had no linear effects on its hardness and flexural strength. A 20% bagasse fine ash composite had the highest flexural strength and hardness at 27.65 MPa and 52.86 HRA, respectively, which are significantly (>0.002) higher than composites of 30% bagasse fine ash, along with the highest density. This study measured water absorption and swelling of composite samples immersed in distilled water for 192 h. As the bagasse ash content increases, these values were linearly increased until saturation occurs. [ABSTRACT FROM AUTHOR]

The present study fabricated high-performance silica/epoxy resin nanocomposites having a low coefficient of linear thermal expansion (CTE) and a high glass transition temperature (T g). This was accomplished by dispersing colloidal silica nanospheres having hydrophilic surfaces in epoxy resins, which limited the motion of the polymer chains. Nanocomposites were produced wherein isolated primary particles of colloidal silica without silane surface modification were dispersed uniformly. These particles were generated via the breakdown of loosely bound agglomerates of spherical silica particles during the agitation of a dispersion in an epoxy resin solution. Hydrogen bonding between hydroxyl groups on the hydrophilic surfaces of the dispersed silica nanoparticles and the cross-linked epoxy polymer network evidently limited thermally-induced motion of the polymer chains, resulting in a considerable reduction in the CTE and an increase in the T g for the nanocomposite. Graphical Abstract [ABSTRACT FROM AUTHOR]

Quasi static compressive response of crumb rubber-epoxy composites was examined by varying the crumb rubber composition (0, 10, 20 and 30 vol.%). All the composites, irrespective of the strain rates, depict elastic regions tailed by a wide plateau area that is credited with the densification of rubber particulates. Higher strains to failure of composites were revealed as compared with neat epoxy signifying higher energy absorption ability of constituents. The modulus of elasticity of composites was noted to be lower than neat epoxy specimens, irrespective of the strain rates. Irrespective of strain rates, the strength of all the composites were inferior to neat epoxy specimens. Energy absorption of EC-30 was higher compared to EC-20 and EC-10 and noted to be increased in the range of 6–14% for 0.1 mm/min strain rate while it increases in the range of 5–9% for 0.01 mm/min strain rate, respectively. Rubber-toughening mechanism was credited with the increase in energy absorption of composites. Higher energy absorption of composites was mainly due to higher strain realisation indicating more deformation ability. Fracture features of specimens were analysed by scanning electron microscope. [ABSTRACT FROM AUTHOR]

The coupling effects of high and low temperature-humidity-applied load on the longitudinal tensile mechanical properties and the durability performance of epoxy resin-based carbon fiber reinforced composites (EP-CFRP) are studied in this paper. It considers two high and low alternating temperature ranges [-40°C~40°C]/[-40°C~25°C], two humidity conditions (soaking in water and anhydrous), and three load levels of unstressed state or 30% and 60% of the ultimate load. The results indicate that all these three factors have a significant impact on the durability of EP-CFRP. The tensile strength varies with the high and low temperature alternating cycle, showing a trend of first decreasing, then increasing, and then decreasing; however, the peak and valley values appear in the quite different alternating cycle. The coupling effects of these factors have less influence on the tensile modulus. The microcracks generated at the interface between the resin matrix and the fiber have been proved to be the main reason for the strength reduction at the later stage. The coupling effect of humidity and load promotes the expansion of cracks and exacerbates the damage to EP-CFRP. Based on the cumulative damage theory, the residual strength damage model of EP-CFRP under the three-factor coupling action of "high and low temperature cycling-humidity-load" is calibrated by nonlinear fitting method. [ABSTRACT FROM AUTHOR]

Natural bamboo fibers (BFs), which were treated by silane coupling agents, reinforced epoxy resin (EP)–based composite were synthesized. Effects of the coupling agents on the chemical structures of the BFs were characterized by Fourier Transform Infrared Spectroscopy. The mechanical properties, such as tensile strength, flexural strength, impact strength, and hardness of the BFs/EP-based composites were improved significantly, which could be attributed to the excellent strengthening effect of the BFs. Simultaneously, experimental investigations on the thermal behaviors of the BFs/epoxy composites were also presented, indicating that the thermal decomposition temperature of the polymer materials was lowered but the flame retardancy was improved. The bamboo fiber breakage and fiber split were also observed on the impact fracture surface of the composites, which indicate energy dissipation during fiber debonding and pullout process. Moreover, the erosive wear tests have also been carried out to analyze the erosive wear properties of the natural bamboo fibers which modified the epoxy matrix composites. The results indicate that the erosive wear resistance of the EP-based composite was improved greatly when the natural bamboo fibers content was 15 wt. %. [ABSTRACT FROM AUTHOR]