Soy-based adhesive cross-linked by melamine–glyoxal and epoxy resin

To develop a soy-based adhesive with good water resistance, non-toxic melamine–glyoxal resin (MG) prepared in the laboratory was used as a cross-linker of soy-based adhesive. The FT-IR and ESI-MS results showed that there was a reaction between melamine and glyoxal. The resulted –CH–OH– groups could be the possible reactive groups for the cross-linking of soy-based adhesive. The wet shear strength of soy-based plywood indicated that the water resistance of soy adhesive cross-linked by MG improved with respect to that with no cross-linker, although it was not good enough to satisfy the relative standard. With the optimized preparation procedures for plywood, specifically, press temperature 180?°C, press time 3 min and resin loading 280 g m^?2, type I soy-based plywood could be prepared with a hybrid cross-linker, namely 12%MG + 2% epoxy resin (EPR). The DSC results showed that the reaction between soy-based adhesive and the hybrid cross-linker MG + EPR was very complex.     

Preparation and properties of bisphenol A epoxy resin microcapsules coated with melamine–formaldehyde resin

Microcapsules containing epoxy resins have potential applications, such as in adhesive, electronic packaging, and self-healing polymeric composites. A series of microcapsules were prepared by in situ polymerization with poly(melamine–formaldehyde) as the shell materials and a mixture of diglycidyl ether of bisphenol A and epoxy diluent as the core substances. Morphology, chemical structure, mean particle size, and thermal properties of the microcapsules were studied by means of optical microscope, Fourier transform infrared spectroscopy, laser particle size analyzer, and microcomputer differential thermal balance, respectively. Effects of kind of epoxy diluent, surfactant type, emulsifier concentration, and emulsifying rate on the physical properties of microcapsules were investigated. Results indicate that the formation of microcapsules is affected by the epoxy diluent type and surfactant type. The highest core content of the resultant microcapsules is about 88 wt% and average diameters of the capsules range from 67 to 201 μm, which can be adjusted by changing the emulsifier concentration and emulsifying rate. Thermo gravimetric analysis indicated that the prepared microcapsules experienced excellent stability up to 235 °C.     

Synergistic toughening effects of nucleating agent and ethylene–octene copolymer on polypropylene

The synergistic toughening effect of nucleating agent (NA) and ethylene–octene copolymer (POE) on polypropylene was studied in the present work. Two different nucleating agents, such as α-form nucleating agent 1,3 : 2,4-bis (3,4-dimethylbenzylidene) sorbitol (DMDBS, Millad 3988) and β-form nucleating agent aryl amides compounds (TMB-5), were selected to blend with PP or PP/POE blends, respectively. The results show that PP containing 0.5–0.25 wt % DMDBS or 0.5–0.25 wt % TMB-5 has relatively low impact strength. For PP/POE blends, although the impact strength increases gradually with the increasing of POE content, high content of POE is needed to obtain the available PP toughness. However, once nucleating agent and POE are simultaneously added into PP, PP/POE/NA blends show great improvement of toughness even at low POE content. Furthermore, the synergistic toughening effect of POE/TMB-5 is more apparent than that of POE/DMDBS. SEM results show that whether DMDBS or TMB-5 has no apparent effect on the morphologies of POE in the PP/POE/NA blends. Further investigations using DSC and POM indicate that both DMDBS and TMB-5 induce the apparent enhancement of the crystallization temperature of PP and the sharp decrease of spherulites size of PP in the PP/POE/NA blends. The possible synergistic toughening mechanism is discussed in the work. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrical properties of a composite comprising epoxy resin and α-hematite nanorods

Electrical properties of pure epoxy and epoxy-hematite nanorod composites have been investigated. The nanorods were synthesized by the forced hydrolysis method and further mixed with epoxy to obtain the nanocomposite. TEM analysis revealed that they have an average diameter of about 8 nm, with an average aspect ratio of 25. DC-conductivity and DC-current relaxation measurements showed a significant influence of Fe₂O₃ nanorods on the DC-electrical properties of the epoxy matrix. However, the observed effects of the filler below and above the glass transition are different. Because of their high specific surfaces, nanorods affected segmental mobility of epoxy molecules to a large extent, which resulted in an increase in the glass transition temperature (T_g) and a decrease in the real part of dielectric permittivity in high frequency/low temperature region. It is further observed that at elevated temperatures (above T_g) and low frequencies the real part of dielectric permittivity of the nanocomposite exceeds that of the pure matrix, i.e. there is a transition towards microcomposite-like dielectric behaviour.     

Microstructure and thermal properties of silyl-terminated polycaprolactone–polysiloxane modified epoxy resin composites

With a direct nucleophilic addition between  OH groups of polydiol and  NCO of a silane, a blend of silyl-terminated polycaprolactone PCL-Si and silyl-terminated polydimethylsiloxane PDMS-Si oligomer, PCS-2Si, were firstly prepared, and then blended with a commercial epoxy resin (diglycidyl ether of bisphenol-A, DGEBA) to form a ternary composite. The formed ternary composites of different content of DGEBA were cured using a polyamidoamine as a curing agent and a sol–gel process at ambient temperature. The microstructures and properties of the cured composites were investigated by SEM, TGA, and energy dispersive spectroscopy. The results showed the compatibility between DGEBA and PDMS increased with increasing content of PCS-2Si, but higher content of PCS-2Si resulted in a slight enrichment of silicon in the surface of the cured film. TGA showed that incorporating PCS-2Si into epoxy resin altered the composites' thermal stability and degradation characteristics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of XeCl excimer laser treatment of Vectran® fibers and their adhesion to epoxy resin

Vectran^® fibers, made using liquid crystalline polyester, were treated with pulsed XeCl excimer laser (308 nm) to alter their surface characteristics and, thus, improve their adhesion to epoxy resin. The treatments were carried out in air using varying numbers of pulses at different laser fluences. The effects of laser treatment on the fiber surface topography, chemistry and wettability have been investigated. Fiber/epoxy resin interfacial shear strength was measured using the microbead test. The surface roughness was characterized qualitatively and quantitatively using scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Changes in the surface energy were characterized using the Wilhelmy technique. Based on the SEM micrographs, the threshold fluence for the formation of surface structure was found to be less than 36 mJ/(pulse ? cm²). The laser treatments at fluences higher than the threshold fluence introduced periodic roll (wavy) structures on the fiber surface transverse to the fiber axis. From the AFM results, the fiber surface roughness was found to increase by up to 3.5 times the control fiber after the laser treatment. The dispersion component of the surface energy decreased, while the acid–base component of the surface energy increased significantly from 0 to 8.8 mJ/m² after the laser treatment. The Vectran^® fiber/epoxy resin IFSS increased by up to 75% after the laser treatment. This improvement is mainly attributed to higher surface roughness of the fiber.     

Investigation of the curing kinetics of alkyd–melamine–epoxy resin system

Properties of coatings based on alkyd resin can be improved via blending with other suitable resins. Recent studies assessed that many properties could be improved by blending with epoxy resins as well as with melamine resins. The aim of this work was to investigate the effect of epoxy resin content on the curing process in alkyd–melamine–epoxy three component blends. The coatings with two mixing ratios of alkyd/melamine (70:30 and 80:20) were formulated. They were made into baking enamels by blending with 3 and 5 wt% of epoxy resin on total resin solid. Curring kinetics was investigated by differential scanning calorimetry (DSC) and application of Ozawa isoconversional method. Fourier transform infrared spectroscopy (FTIR) was used to follow major curing reactions. The absorbance of –OH and –N–CH₂R, showed significant reduction and confirmed that the epoxy resin reacts and inserts in enamel structure. It was found that resin system with alkyd/melamine ratio of 70:30 and 3 wt% of epoxy resin has the lowest apparent activation energy of 141.5 kJ mol⁻¹ and needs the shortest time of 34.2 min to reach final apparent degree of cure. Isothermal DSC experiments have confirmed these findings. The samples with 30 wt% of melamine resin had higher hardness of baked enamels then samples with 20 wt%. They also showed an increase of hardness with the increase of epoxy resin content.     

Flame-retardant epoxy resin with good smoke-suppression endowed by chitosan–cobalt/phosphorus complex

Chitosan-based flame-retardant CS–Co–DOPA (CCD) was synthesized by the neutralization reaction of 10-hydroxy-9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide (DOPA) with chitosan-cobalt complex and fully characterized by scanning electron microscopy (SEM), energy-dispersive spectrometer, x-ray diffraction, X-ray photoelectron spectroscopy (XPS), optical emission spectrometer, and Fourier transform infrared (FTIR) characterizations. The epoxy resin (EP) modified with CCD exhibited good flame retardancy. With the addition of 5 wt% CCD, the EP/CCD achieved UL-94 V-1 rating and possessed limiting oxygen index (LOI) value of 30%. Cone calorimetry (CC) test demonstrated that EP/CCD resulted in a remarkable reduction of peak smoke production rate (pSPR) and total smoke production (TSP) by 63% and 40%, respectively, showing an outstanding smoke suppression. The char residue obtained from the CC test was further characterized using SEM, FTIR, Raman, and XPS techniques. The results revealed that CCD facilitated the formation of a dense and compact char layer on EP during combustion, thereby impeding gas and heat transfer. In addition, TG-IR was employed to investigate the gas-phase flame-retardant effect of EP/CCD composites, which revealed that CCD promotes the release of water, CO_2, and other incombustible gases, altering the decomposition path of EP.     

Effect of different zeolitic imidazolate frameworks nanoparticle-modified β-FeOOH rods on flame retardancy and smoke suppression of epoxy resin

A simple method was used to load zeolitic imidazolate frameworks (ZIFs) onto β-FeOOH nanorods to ameliorate the flame retardancy and smoke suppression of epoxy resin (EP). The morphology and structure of ZIF-8-β-FeOOH (Z8Fe) and ZIF-67-β-FeOOH (Z67Fe) nano hybrids were systematically characterized by field emission scanning electron microscope, Fourier transform infrared and X-ray diffraction (XRD) spectra, which proved the successful preparation of the hybrids. 3 wt% of Z8Fe and Z67Fe were added to the EP matrix, and their combustion properties were studied, respectively. The results showed that the composites' limiting oxygen index values were ameliorated to 27.3% and 28.1%, respectively. Their UL94 flame retardant rating was improved, their peak heat release rate and total heat release were reduced, their flame retardant performance was considerably improved, and their generation of toxic smoke was significantly suppressed. Further, through X-ray photoelectron spectroscopy, XRD and laser Raman spectroscopy analysis of the char residue, their potential mechanism of flame retardancy and smoke suppression were studied.     

Preparation of the organic–inorganic double-shell microencapsulated aluminum hypophosphite and its improved flame retardancy and mechanical properties of epoxy resin composites

To develop the functional particles with better flame-retardant and compatibility with epoxy resin (EP) matrix, organic–inorganic double-shell microencapsulated aluminum hypophosphite (MSiAHP) was prepared by situ polymerization. The water contact angles of MSiAHP (62.4°) is significantly larger than that of aluminum hypophosphite (34.4°), which shows that the organic shell material of MSiAHP endows excellent hydrophobicity and water resistance. With the incorporation of MSiAHP, EP/30%MSiAHP composite exhibits limiting oxygen index value of 27.3% and V-0 rating. Furthermore, the cone calorimetry test reveals that MSiAHP reduces the peak heat release rate, total heat release and total smoke release of EP matrix by 33.3%, 24.4% and 56.6%, respectively. Besides, due to the unique organic–inorganic double-shell structure of MSiAHP particles, EP/30%MSiAHP composite achieves greater thermal stability and higher char yields than pure EP. The investigation of the products in the gas and condensed phase demonstrates that MSiAHP is beneficial to the generation of a high-density and compact carbon layer structure with a high graphitization degree, and delay the generation time of pyrolysis products in the gas phase, which can improve the fire safety of EP composites effectively. Furthermore, preeminent dispersion and compatibility of MSiAHP lead to EP/MSiAHP composites with excellent mechanical properties.     

Synthesis and characterization of epoxy resin of 9,9′-bis-(3,5-dibromo-4-hydroxyphenyl) anthrone-10 and its jute composite

Epoxy resin of 9,9′-bis-(3,5-dibromo-4-hydroxyphenyl) anthrone-10 (EANBr, EEW 490) was synthesized and was characterized by IR and ¹HNMR . EANBr and EPK3251 cured resin (EANBrC) were characterized by DSC and TGA at 10°Cmin^?1 under nitrogen atmosphere. Broad DSC endothermic transitions of EANBr (265.3 °C) and EANBrC (291.4 °C) are due to some physical change and further confirmed by no weight loss in their TG thermograms. EANBr and EANBrC are thermally stable up to 340 °C and 310 °C, respectively. EANBr has followed single step degradation kinetics, while EANBrC has followed two step degradation kinetics. EANBr followed apparently zero order kinetics, while EANBrC followed apparently second order (1.80) and first order (0.89) degradation kinetics, respectively. Ea and A values of EANBrC (299.7 kJmol^?1 and 6.32?×?10²⁰ s^?1) were found higher than that of EANBr (201 kJmol^?1 and 2.45?×?1013 s^?1) due to more rigid nature of EANBrC. The ΔS^* value of the first step degradation of EANBrC (146.3 JK^?1 mol^?1) was found much more than that of EANBr (4.6 JK^?1 mol^?1). Jute – EANBr composite (J-EANBr) was prepared by compression molding technique at 120 °C for 5 h and under 20 Bar pressure. The observed tensile strength, flexural strength, electric strength and volume resistivity of J-EANBr are 24.7 MPa, 19.0 MPa, 1.8 kVmm^?1 and 3.5?×?10¹² ohm cm, respectively. Water absorption in J-EANBr was carried out at 30 ± 2 °C against distilled water, 10% NaCl, 10% HCl, 10% HNO₃, 10% H₂SO₄, 10% NaOH, and 10% KOH and also in boiling water. The equilibrium time and equilibrium water content for J-EANBr in different environments are 384–432 h; 12.7–15.2%, respectively. The observed equilibrium water content and diffusivity trends of J-EANBr are KOH>H₂SO₄>HCl>NaOH>H₂O>NaCl and H₂O>NaCl>NaOH>H₂SO₄>HCl>KOH, respectively. Good thermo-mechanical, electrical properties and excellent hydrolytic stability of J-EANBr may be useful for high temperature applications in diverse fields.     

Effect of N–Ni coordination bond on the electrical and thermal conductivity of epoxy resin/nickel-coated graphite

The agglomeration of nickel-coated graphite (NCG) in epoxy resin (EP) composites leads to low electrical conductivity of EP composites, which limits their development in electronic devices and multilayer circuits. In order to improve the electrical and thermal conductivity of NCG/EP composites, ethylenediamine (EDA) was used to modify NCG and compared with pure NCG-filled EP composites. It was found that the conductive effect of modified composites with 20 wt% filler is better than that of unmodified composites with 40 wt% filler. The results of Fourier transform infrared spectroscopy and thermogravimetric analysis of EDA-modified NCG (ENCG) showed that a coordination adsorption reaction occurred between EDA and NCG, forming N–Ni coordination bonds. When the filling amount of ENCG was 40 wt%, the conductivity and thermal conductivity of the composite are improved most significantly. The volume resistivity was reduced from 2.636 to 0.109 Ω cm, a decrease of 95.85%, and the thermal conductivity was improved from 0.517 to 0.968 W/(m K), an increase of 87.23%, respectively. Meanwhile, ENCG has better dispersion in the EP matrix than NCG.     

Self-healing semi-IPN materials from epoxy resin by solvent-free furan–maleimide Diels–Alder polymerization

Novel self-healing Diels–Alder (DA) polymer and the corresponding semi-interpenetrated polymer networks (semi-IPNs) were synthesized and characterized. Initially, a furan-functionalized resin (FFR) was synthesized through the ring-opening reaction of a conventional epoxy resin [diglycidyl ether bisphenol A (DGEBA)] with furfuryl alcohol as a bio-based compound. Subsequently, semi-IPNs with different compositions were obtained through the blending of DGEBA, FFR, 4,4′-diaminodiphenylmethane, and 1,1′-(methylenedi-1,4-phenylene) bismaleimide in the molten state by following a predetermined time–temperature program. Fourier transform infrared and nuclear magnetic resonance analyses confirmed the successful synthesis of the materials. Thermoreversibility via retro-DA (rDA) reaction was evidenced by differential scanning calorimetry (DSC) and sol–gel transition tests. Repeated DSC cycle was successfully performed thrice on the DA polyadduct which corroborated repeatability of the DA/rDA association/dissociation. Self-healing and mechanical properties were preliminarily evaluated by scanning electronic microscopy and flexural testing analyses, respectively. The self-healing efficiencies were around 80 and 95% for semi-IPN and DA polyadduct, respectively, based on flexural strength. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48015.     

Thermal,mechanical and γ-ray shielding properties of micro- and nano-Ta2O5 loaded DGEBA epoxy resin composites

In this work, we have investigated the synergistic effect of micro- and nano-Ta₂O₅ fillers in the epoxy matrix on the thermal, mechanical, and radioprotective properties of the composites. Morphological analysis revealed uniform dispersion of fillers in the matrix. Both the thermal stability and tensile properties of matrices have enhanced in the presence of fillers. Although the nanocomposites showed significantly higher tensile strength and Youngs modulus compared to micro-composites, the enhancement in these properties was predominant at low loadings. Dynamic mechanical analysis indicated good interfacial adhesion and positive reinforcing effect on the matrix even at higher loading (30 wt%) of nano-Ta₂O₅. γ-Ray attenuation studies performed in the energy range of 0.356–1.332 MeV revealed better γ-ray shielding ability of nanocomposites compared to microcomposites at same weight fraction of fillers. In particular, γ-ray attenuation at 0.356 MeV for 30 wt% nano-Ta₂O₅ loaded epoxy composite was enhanced by around 13% compared to the microcomposite at the same loading. Increased surface-to-volume ratio of nanofillers and consequent increase in matrix-filler adhesion and radiation-matter interaction have manifested in an overall enhancement in the thermal, mechanical, dynamic mechanical, and radiation shielding characteristics of nano-Ta₂O₅/epoxy composites, proving them as promising γ-ray shields.     

Characterisation and modelling of CNT–epoxy and CNT–fibre–epoxy composites

Abstract

This research presents an experimental and theoretical investigation on the effects of carbon nanotube (CNT) integration within neat epoxy resin (nanocomposites) and a carbon fabric–epoxy composite (multiscale composites). An approach is presented for the prediction of mechanical properties of multiscale composites. This approach combines woven fibre micromechanics (MESOTEX) with the Mori-Tanaka model which was used for the prediction of mechanical properties of nanocomposites in this research. Nanocomposite and multiscale composite samples were manufactured using cast moulding, resin infusion, and hand lay-up process. The CNT concentrations in the composite samples were from 0 to 5 wt-%. The samples were characterised using tensile, shear and flexural tests. The discrepancy between the theoretical predictions and the experimental observations was hypothesised to be due to dispersion and bonding issues and SEM images are presented in support of the hypothesis.     

Inclusion complexes of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs with α-CD, β-CD, γ-CD,HP-β-CD,M-β-CD,and maltodextrin along with their characterizations through experimental and computational methods

The aim of this research is a comparison of the efficiency of six commercially available cyclodextrins (CDs) to improve the solubility and oral bioavailability of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs in aqueous media. Inclusion complexes of both drugs with non-toxic α-CD, β-CD, γ-CD, HP-β-CD, M-β-CD, and maltodextrin were prepared in a 1:1 stoichiometry via the kneading method. To reach the best CD, various experimental and computational analyses were performed including phase solubility, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), hydrogen-1 nuclear magnetic resonance (¹HNMR), carbon-13 nuclear magnetic resonance (¹³CNMR), and molecular docking calculations. The M-β-CD turned out to be the best substrate for the micro-encapsulation of both drugs. Also, ATV showed a higher tendency than ROV to form inclusion complexes with CDs. Molecular docking studies showed that HP–β–CD and M-β-CD are the most suitable substrates for the formation of inclusion complexes, respectively. Our research showed that the β-CD is not necessarily the most efficient substrate for increasing solubility based on previous reports in the literature; meanwhile, the other employed substrates in this study can show acceptable performances in this regard. According to our results, M-β-CD is the best substrate for the micro-encapsulation of both drugs, which increases their solubility in water.     

Buckypapers of 4,4′-oxydianiline-modified polyvinylchloride and functional nano-filler obtained by resin infusion method

This study provides information on the fabrication and characterization of polyvinylchloride (PVC) buckypaper composite using resin infusion method. PVC modified with 4,4′-oxydianiline (ODA) was infiltrated through buckypapers made of purified multi-walled carbon nanotubes (P-MWCNTs) and functionalized MWCNTs (F-MWCNTs). The increases in P-MWCNT and F-MWCNT contents were investigated on the physical properties of BP-PVC-ODA/PEG (polyethylene glycol)/P-MWCNT and BP-PVC-ODA/PEG/F-MWCNT buckypaper composites. Fourier transform infrared spectroscopy was used for the functional group confirmation which proved the PVC modification and functionality of MWCNTs. The scanning electron micrographs of BP-PVC-ODA/PEG/F-MWCNT showed that intercalation of cross-linked polymer with nanotube produced a polymer-coated F-MWCNT mesh. The maximum degradation temperature (T _max) of functional composite BP-PVC-ODA/PEG/F-MWCNT 0.05 (484 °C) was higher than that of non-functional BP-PVC-ODA/PEG/P-MWCNT 0.05 (473 °C). The glass transition temperature (T _g) of BP-PVC-ODA/PEG/F-MWCNT 0.05 was 225 °C, while BP-PVC-ODA/PEG/F-MWCNT 0.03 yielded a lower T _g of 214 °C. Tensile strength of the functional buckypaper was also found to increase to 37.3 MPa with filler loading. According to X-ray diffraction, the amorphous character of buckypaper showed a trend towards crystal formation with filler loading. P-MWCNT-based buckypaper showed an electrical conductivity up to 4.12 × 10^?1 S/cm; lower than the electrical conductivity of functional buckypaper (1.98 S/cm). The results demonstrated that the resin infusion technique was a successful method to achieve high performance buckypapers compared with F-MWCNTs.     

Research on selective laser sintering of Kaolin–epoxy resin ceramic powders combined with cold isostatic pressing and sintering

In order to fabricate traditional products with complex shapes consisting of Kaolin ceramic, selective laser sintering (SLS) combined with cold isostatic pressing (CIP) process was used to consolidate Kaolin powder with additive of epoxy resin E06. To begin preparing the material, epoxy resin (10 wt%) and Kaolin were combined through mechanical mixing, which provided a good fluidity for SLS. Investigations on the shrinkage and micro topography of Kaolin–epoxy resin SLS samples were conducted to optimize the laser sintering parameters. It was found that SLS samples represented acceptable shrinkage and high density when laser energy density was 0.3300–0.3763 J/mm². Then the SLS samples were processed by CIP to eliminate the pores in green ceramics. Finally, the optimized SLS/CIP Kaolin samples were debinded and sintered to produce crack-free Kaolin ceramics. The “Yellow Duck” Kaolin ceramic product was fabricated by combining SLS/CIP with colored glazing. The study shows a novel and promising approach to fabricate complex traditional ceramic products via SLS combined with CIP and sintering.     

Preparation of organic–inorganic intumescent flame retardant with phosphorus,nitrogen and silicon and its flame retardant effect for epoxy resin

According to the requirement of fire life cycle assessment (LCA), chitosan ethoxyl urea phosphate (CEUP), an organic–inorganic intumescent flame retardant (IFR) containing phosphorus, nitrogen, and silicon, was synthesized by the reaction of chitosan, phosphorus pentoxide, and urea. FTIR, ¹H NMR, SEM, and XRD were employed to characterize the compounds. As a result, CEUP was successfully prepared with higher thermal stability, favorable to enhance fire resistance. Combined with OMMT, the organic/inorganic IFR was applied as EP flame-retardant agents. The combustion behavior of EP composite was investigated by LOI, UL-94, CCT, SEM, TGA, and TG-IR. It was observed that using 15% CEUP and 3% OMMT (EP3), LOI value reached 34.8% and passed the UL-94 V-0 rating, while THR and TSP of EP composite reduced 65 and 72% compared with pure EP. The char residue of EP composite was up to 22.4%. The thermal decomposition mechanism was traced from 100 to 600°C by TG-IR. It was suggestive that CEUP decomposition commenced at 100°C to create phosphoric acid and sublimation of urea occurred at 300°C. EP3 exhibited a strong thermal stability, namely even at 600°C, the volatile substances were detectable. Dense and expanded carbon layer was confirmed in SEM images.     

Improving the interfacial properties of carbon fiber–epoxy resin composites with a graphene-modified sizing agent

We successfully prepared a graphene-modified carbon fiber (CF) sizing agent with good dispersity and stability by dispersing reduced graphene oxide (RGO) into an emulsion-type sizing agent. RGO was obtained by the reduction of graphene oxide (GO) with the help of gallic acid. The influence of the graphene-modified sizing agent on the interfacial properties of the CF–epoxy resin composites was investigated with microbond testing and the three-point bending method. The results show that optimized interfacial properties were achieved when the size of the modified graphene was less than 1 μm, the content of RGO was 20 ppm, and the pH value of the sizing agent was 10.5. The interfacial shear strength of the composites reached 92.3 MPa, which was 29.6% higher than that of the composites with unmodified CFs. Compared with commercial-CF-fabric-reinforced composites, the interlaminar shear strength of the composites treated with the RGO-modified sizing agent increased by 21.5%. Both the interfacial and interlaminar failure morphologies of the composites were examined with scanning electron microscopy (SEM). The results show that a large amount of residual resin adhered to the surfaces of the CFs treated with the RGO-modified sizing agent; this indicated good interfacial properties between the CFs and the resin matrix. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47122.