Mechanical and Morphological Properties of Bio-Phenolic/Epoxy Polymer Blends

Polymer blends is a well-established and suitable method to produced new polymeric materials as compared to synthesis of a new polymer. The combination of two different types of polymers will produce a new and unique material, which has the attribute of both polymers. The aim of this work is to analyze mechanical and morphological properties of bio-phenolic/epoxy polymer blends to find the best formulation for future study. Bio-phenolic/epoxy polymer blends were fabricated using the hand lay-up method at different loading of bio-phenolic (5 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt%) in the epoxy matrix whereas neat bio-phenolic and epoxy samples were also fabricated for comparison. Results indicated that mechanical properties were improved for bio-phenolic/epoxy polymer blends compared to neat epoxy and phenolic. In addition, there is no sign of phase separation in polymer blends. The highest tensile, flexural, and impact strength was shown by P-20(biophenolic-20 wt% and Epoxy-80 wt%) whereas P-25 (biophenolic-25 wt% and Epoxy-75 wt%) has the highest tensile and flexural modulus. Based on the finding, it is concluded that P-20 shows better overall mechanical properties among the polymer blends. Based on this finding, the bio-phenolic/epoxy blend with 20 wt% will be used for further study on flax-reinforced bio-phenolic/epoxy polymer blends.     

High mechanical and thermal performance of Sasobit-modified epoxy resin,prepared via vacuum shock technique

In this study, thermal and mechanical properties of novel nanocomposite, epoxy resin reinforced with octadecylamine functionalized graphene oxide (GO-ODA) and Sasobit, prepared via creative vacuum shock technique, were investigated. By introducing 1, 3 and 5 wt% Sasobit to the neat epoxy resin, the tensile strength increased remarkably by 104%, 315% and 266%, respectively due to the unique stiff and crystalline structure of Sasobit. In addition, considerable enhancement of 125% in Young's modulus, 351% in toughness, 562% in impact resistance, ~19 °C in thermal stability and ~7 °C in glass transition temperature of epoxy resin with 3 wt% Sasobit loading was demonstrated. The composite containing 3 wt% Sasobit alone, were found to have even superior properties than GO-ODA/epoxy nanocomposite, as surprisingly 3, 2.9, 2.2 and 2 times more improvement, respectively in tensile strength, toughness, impact strength and thermal stability of epoxy resin compared to reinforcement with GO-ODA were obtained.     

The maleimide modified epoxy resins for the preparation of UV‐curable hybrid coatings

In the present study, maleimide‐modified epoxide resin containing UV‐curable hybrid coating materials were prepared and coated on polycarbonate substrates in order to improve their surface properties. UV‐curable, bismaleimide‐modified aliphatic epoxy resin was prepared from N‐(p‐carboxyphenyl) maleimide (p‐CPMI) and cycloaliphatic epoxy (Cyracure‐6107) resin. The structure of the bismaleimide modified aliphatic epoxy resin was analyzed by FTIR and the characteristic absorption band for maleimide ring was clearly observed at 3100 cm^?1. Silica sol was prepared from tetraethylorthosilicate (TEOS) and methacryloxy propyl trimethoxysilane (MAPTMS) by sol–gel method. The coating formulations with different compositions were prepared from UV‐curable bismaleimide‐based epoxy oligomer and sol–gel mixture. The molecular structure of the hybrid coating material was analyzed by ²⁹Si‐CP/MAS NMR spectroscopy techniques. In the ²⁹Si CP/MAS NMR spectrum of the hybrid coating, mainly two kinds of signals were observed at ?68 and ?110 ppm that correspond to T³ and Q⁴ peaks, respectively. This result shows that a fully condensed structure was obtained. The thermal and morphological properties of these coatings materials were investigated by using TGA and SEM techniques. Hardness and abrasion resistance properties of coating materials were examined and both were found to increase with sol–gel precursor content of the coating. The photopolymerization kinetics was investigated by using RT‐IR. 70% conversion was attained with the addition of 15 wt% of BMI resin into the acrylate‐based coating formulation. It was found that the UV‐curable organic–inorganic hybrid coatings improved the surface properties of polycarbonate. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of an epoxy functionalized spiroorthocarbonate used as low shrinkage additive in cationic UV curing of an epoxy resin

The synthesis of an epoxy functionalized spiroorthocarbonate (SOC) is reported. The obtained monomer has been used a slow shrinkable additive in cationic UV curing of a commercially available dicycloepoxy resin. A polymer network flexibilization was evidenced by increasing the SOC content in the photocurable formulation. It has been demonstrated that SOC acts as shrinkage reduction additive reaching expansion on volume after polymerization in the presence of 10 wt% of the functionalized spiroorthocarbonate.     

Resistance of Nanoclay Reinforced Epoxy Composites to Hyperthermal Atomic Oxygen Attack

Due to outstanding mechanical properties, heat resistance, and relatively facile production, nanoclay reinforced epoxy composites (NCRE composites) have been suggested as candidate materials for use on external surfaces of spacecraft residing in the low Earth orbit (LEO) environment. The resistance of the NCRE composites to bombardment by atomic oxygen (AO), a dominant component of the LEO environment, has been investigated. Four types of samples were used in this study. They were pure epoxy (0 wt% nanoclay content), and NCRE composites with different loadings of nanoclay—1 wt%, 2 wt%, and 4 wt%. Etch depths decreased with increasing nanoclay content, and for the 4 wt% samples it ranged from 28% to 37% compared to that of pure epoxy. X-ray photoelectron spectroscopy (XPS) indicates that after AO bombardment, relative area of C-C/C-H peak decreased, while the area of the C-O, ketones peaks increased, and the oxidation degree of surfaces increased. New carbon-related component carbonates were detected on nanoclay containing composite surfaces. Scanning electron microscopy indicates that aggregates formed on nanoclay-containing surfaces after AO bombardment. The sizes and densities of aggregates increased with nanoclay content. The combined erosion depths, XPS and SEM results indicate that although all the studied surfaces got eroded and oxidized after AO bombardment, the nanoclay containing composites showed better AO resistance compared to pure epoxy, because the produced aggregates on surface potentially act as a physical “shield”, e ectively retarding parts of the surface from further AO etching.     

Evaluating the effect of addition of nanodiamond on the synergistic effect of graphene-carbon nanotube hybrid on the mechanical properties of epoxy based composites

Addition of carbon nanotubes (CNT) to Graphene (Gr) is seen to have synergistic effect as reinforcement to polymer matrix. This is possible as CNTs inhibit stacking of Gr sheets, thus providing larger surface area nanophase to get bonded with polymer matrix and providing mechanical support through load sharing and crack growth inhibition. However, tube like morphology and high aspect ratio of CNT often lead to entanglement, which restricts their effect in exfoliating Gr. The aim of the present study is to investigate the potential of ND in improving the synergistic effect of Gr-CNT hybrid as a reinforcement to epoxy matrix. This study utilizes the power of ultrasonication technique, which is very simple and scalable, for dispersing and incorporating nanofillers into epoxy matrix. Addition of ND to Gr-CNT epoxy composite improved the tensile strength from ~46% with 0.5 wt% (75Gr:25ND) to ~51% with 0.8 wt% (25Gr:25CNT:50ND) as compared to neat epoxy. While the fracture toughness improved from ~140% with 0.5 wt% (25Gr:75CNT) to 165% with 0.8 wt% (25Gr:50CNT:25ND). Fractured surfaces of composites revealed improved dispersion and strong interfacial interaction with addition of ND to Gr-CNT hybrid. NDs attaches to the surface of Gr inhibit the stacking of Gr sheets by restricting π-π stabilization. NDs also help in bridging the ends of CNTs together into long chains, thereby increasing the aspect ratio of the fiber like reinforcement. This increases the total available surface area of CNTs and Gr, to interact with epoxy matrix, improves the overall efficiency of Gr-CNT hybrid as a reinforcement, resulting into improvement in mechanical properties of the composite structure.     

A vanillin-derived flame retardant based on 2-aminopyrimidine for enhanced flame retardancy and mechanical properties of epoxy resin

In order to give epoxy resin good flame retardance, a novel bio-based flame retardant based on 2-aminopyrimidine (referred to as VAD) was synthesized from renewable vanillin as one of the starting materials. Its structure was confirmed by NMR and mass spectra. The epoxy resins containing VAD were prepared by utilizing 4,4-diaminodiphenylmethane (DDM) as a co-curing agent, and their flame-retardant, mechanical and thermal properties and corresponding mechanisms were studied. VAD accelerated the cross-linking reaction of DDM and E51 (diglycidyl ether of bisphenol A). 12.5 wt% VAD made the epoxy resin achieve UL-94 V-0 rating and its limited oxygen index (LOI) value increase from 22.4% to 32.3%. The cone calorimetric testing results revealed the decline in the values of total heat release (THR) and peak of heat release rate (pk-HRR) and the obvious enhancement of residue yield. A certain amount of VAD enhanced the flame inhibition, charring and barrier effects, resulting in good flame retardance of the epoxy resin. Furthermore, the tensile strength, flexural strength and flexural modulus of the epoxy resin with 12.5 wt% loading of VAD were 6.5%, 14.9%, 15.2% higher than those of EP, indicating the strengthening effect of VAD. This work guarantees VAD to be a promising flame retardant for enhancing the fire retardancy of epoxy resin without compromising its mechanical properties.     

Curing behavior and properties of high biosourced epoxy resin blends based on a triepoxy monomer and a tricarboxylic acid hardener from 10-undecenoic acid

Renewable propane-1,2,3-triyl tris(9-(oxiran-2-yl) nonanoate) (EGU, 100 wt% biogenic) and a tricarboxylic acid triglyceride (CGTU) hardener (85.7 wt% biogenic) were synthesized from 10-undecenoic acid (10-UDA) and used to produce epoxy resins with 52–92 wt% biobased carbon. CGTU was prepared by thermally activated thiol-ene coupling of thioglycolic acid onto propane-1,2,3-triyl tris(undec-10-enoate), (GUD) in the absence of solvent. The characterized CGTU was used as a green hardener of blends based on EGU and a conventional bisphenol A-based epoxy pre-polymer (DGEBA) at various mass percentages (0–100 wt%) with an stoichiometric epoxy/acid equivalent ratio. Calorimetric studies revealed higher peak temperature, lower reaction heats, and longer gelation times in resins with high EGU proportion, evidencing the lower reactivity of aliphatic EGU compared with aromatic DGEBA. Cured resins were yellowish transparent rubber-like materials with glass transition temperatures (Tg) varying from −14 °C to −42 °C and tensile strength in the range of 1750 kPa–790 kPa, for 0 and 100 wt % EGU, respectively. The soluble fraction of all resins was less than 4.3%, reflecting a high level of crosslinking. Thermosets with high biobased content showed both UV-light protection and visible light transparency.     

Preparation of modified multi‐walled carbon nanotubes as a reinforcement for epoxy shape‐memory polymer composites

Effectively improving the mechanical properties and thermal resistance of epoxy shape‐memory polymers (ESMPs) without affecting their shape‐memory performance is necessary to expand these polymers in practical applications. In this article, modified multi‐walled carbon nanotubes (MWCNTs) were prepared and used as efficient reinforcement for enhancing the comprehensive properties of ESMPs. Increases of nearly 289% to 444% for impact strength and 112% to 184% for tensile force were obtained by adding only 0.1 to 1 wt% epoxy‐modified MWCNTs. The addition of unmodified and carboxyl‐modified MWCNTs was also investigated but showed less impact on the mechanical properties of the ESMPs than epoxy‐modified MWCNTs. Thermogravimetry analysis (TGA) and dynamic mechanical analyses (DMA) showed that less than 1 wt% modified MWCNTs can enhance the heat resistance of ESMPs greatly. Although the shape recovery time for composite materials increased upon adding the MWCNTs, the entire recovery time was still less than 1 minute, and the shape recovery rate was relatively high, nearly 100%.     

Improving surface structure of photocatalytic self‐cleaning membrane by WO3/PANI nanoparticles

To create a self‐cleaning feature and improve antifouling property, polysulfone (PSf) membranes were modified with WO₃ and polyaniline (PANI) nanoparticles (0–2 wt%) via phase inversion method for ultrafiltration of landfill leachate. The mass ratio of WO₃ nanoparticles was varied between 0, 40 and 60 wt% in different loadings. All synthesized membranes were tested with and without UV irradiation to evaluate the self‐cleaning feature. The synthesized PANI was analyzed with scanning electron morphology (SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). The surface hydrophilicity of the modified membranes increases with increasing the nanoparticle loadings (0–2 wt%). The membrane morphology indicated higher porosity and more finger like pores for the modified membranes. The porosity of 86.8% was achieved for the membrane containing 2 wt% PANI. The flux recovery ratio (FR) of membranes without UV radiation was increased by increasing the ratio of PANI to WO₃ nanoparticles, while the antifouling ability of membranes including WO₃ nanoparticles improved and reached to 98.87% after UV radiation. The highest COD removal before (76.65 %) and after (78.42%) UV radiation was obtained for the membrane containing 2 wt% nanoparticle loading. Copyright © 2016 John Wiley & Sons, Ltd.     

Responses and thermal conductivity measurements of multi-wall carbon nanotube (MWNT)/epoxy composites

In the present study, the MWNT/epoxy composites are prepared with three weight percentages (0.0, 0.3, and 0.5%) of multiwall carbon nanotube (MWNT). The temporal response of multi-wall carbon nanotube (MWNT)/epoxy composite with different wt% of multi-wall carbon nanotube (MWNT) is measured by experiment. Also, a cavity-type measuring system is designed to experimentally measure the surface temperatures and obtain the thermal conductivity of these composites at different heating rates. It is found that the responses of the 0.3 and 0.5% weight percentage of multi-wall carbon nanotube (MWNT)/epoxy composites are found to be about 25 and 47.8%, respectively, faster than that of the pure epoxy resin. Both the responding characteristics and the variation trends of the measured surface temperatures of these composites can be well predicted by the lumped-heat capacity model. Besides, the higher the weight percentage (wt%) of multi-wall carbon nanotube (MWNT) in the composite, the larger is the thermal conductivity. Relative to the pure epoxy, the thermal conductivities for the composites with 0.3 and 0.5% of multi-wall carbon nanotube (MWNT) increase by 15.9 and 44.9%, respectively. For the weight percentages studied, the thermal conductivity of these composites is found to increase mildly at low heating rates; however, it remains nearly constant at high heating rates.     

Aligned electrospun cellulose fibers reinforced epoxy resin composite films with high visible light transmittance

Uniaxially oriented cellulose nanofibers were fabricated by electrospinning on a rotating cylinder collector. The fiber angular standard deviation (a parameter of fiber orientation) of the mats was varied from 65.6 to 26.2^o by adjusting the rotational speed of the collector. Optically transparent epoxy resin composite films reinforced with the electrospun cellulose nanofibrous mats were then prepared by the solution impregnation method. The fiber content in the composite films was in the range of 5–30 wt%. Scanning electron microscopy studies showed that epoxy resin infiltrated and completely filled the pores in the mats. Indistinct epoxy/fiber interfaces, epoxy beads adhering on the fiber surfaces, and torn fiber remnants were found on the fractured composite film surfaces, indicating that the epoxy resin and cellulose fibers formed good interfacial adherence through hydrogen-bonding interaction. In the visible light range, the light transmittance was 88–92% for composite films with fiber loadings of 16–32 wt%. Compared to the composite films reinforced with 20 wt% randomly oriented fibers, the mechanical strength and Young’s modulus of the composite films reinforced with same amount of aligned fibers increased by 71 and 61%, respectively. Dynamical mechanical analysis showed that the storage moduli of the composite films were greatly reinforced in the temperature above the glass transition temperature of the epoxy resin matrix.     

Thermo-oxygen degradation mechanisms of POSS/epoxy nanocomposites

A series of polyhedral oligomeric silsesquioxane/epoxy nanocomposites (POSS/EP) containing 0 wt%, 5 wt%, 10 wt% and 15 wt% content of POSS were prepared. Mechanical properties were used as the index to show the effect of POSS on the thermo-oxygen degradation resistance of epoxy resin. And the thermo-oxygen degradation mechanism was investigated by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Results showed that the incorporation of POSS into epoxy networks enhanced the thermo-oxygen resistance of epoxy. POSS led to the formation of inert layer on the surface of materials which could protect the internal structure from decomposition. As a result, the retention of mechanical properties of EP/POSS hybrids increased with the POSS content increasing.     

Effect of preheat and encapsulation of steel particles on the interaction with Bisphenol A composites

In this study, the mechanical and thermal behavior of the steel particles (SP) fabricated epoxy-based composites were investigated. The purpose of using SP was to find out their suitability and compatibility to be used as low-cost fillers for epoxy-based composites. A special steel-cast metal mold was used to fabricate the composites via self-casting method. The effect of SP concentration (10, 20, 30 and 40 wt%) on various properties of the epoxy/SP composites was explored. Another sample was prepared using the optimum loading with a special treatment using heat and encapsulation of the SP. Mechanical properties of the composites were analyzed through tensile, flexural and impact testing. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to examine the structural and morphological properties. In addition, thermal properties of the composites were analyzed with the thermogravimetric analyzer (TGA). Results indicated that the addition of PS into epoxy improved both tensile and flexural strength up to 98.5% and 147.6%, respectively, compared to the neat epoxy (NE). The decomposition temperature was raised nearly 18 °C for adding 30 wt% SP which was the maximum among all other composites. Results showed that 30 wt% of SP was the optimum loading for the better properties of the composites. In addition, the preheat treatment of the particles and the encapsulation process established a better interaction between the epoxy and the particles which resulted in the superior performance of the composites compared to the other samples. Overall, the improved mechanical and thermal properties of the SP-fabricated epoxy composites indicate that the epoxy/SP composite is a good candidate for structural and high temperature applications.     

The coating performance of adipic acid modified and methacrylated bisphenol- A based epoxy oligomers

In the present work adipic acid modified and methacrylated bisphenol A based epoxy resins were prepared. The structures of oligomers were characterized by FT-IR. UV curable clear coatings were applied on aluminum substrates. The physical and mechanical properties of UV-cured coatings such as gel content, solvent resistance, hardness, gloss, flexibility and tensile tests were examined. In addition, the thermal behavior of coatings was also evaluated. It is observed that the tensile properties and thermal stabilities of modified epoxy methacrylate coatings mainly depend on the adipic acid content. The best results were obtained with 5 wt% adipic acid modification. Copyright © 2007 John Wiley & Sons, Ltd.     

Metal compound-enhanced flame retardancy of intumescent epoxy resins containing ammonium polyphosphate

A series of intumescent flame-retardant epoxy resins (IFR-EPs) were prepared only by adding a 5 wt% total loading of ammonium polyphosphate (APP) and metal compounds. All the samples could achieve V-0 rating and did not generate dripping during UL-94 testing. The limiting oxygen index (LOI) values of the samples with 4.83 wt% APP and 0.17 wt% CoSA increase from 27.1 to 29.4, compared with epoxy resin containing 5 wt% APP. The samples also showed excellent water resistance of flame retardancy in 30 °C and 70 °C water for 168 h. The LOI results show that the composition of metal compounds (metal ions and ligands/anions) and the mass ratios of APP to metal compounds affect the flame retardancy of the samples. TG results indicate that the catalytic effect of CoSA on the decomposition of both APP and the epoxy resins containing APP is better than that of CuSAO. The fire behavior of epoxy resin and epoxy resins containing APP with/without CoSA were investigated by cone calorimeter. Cone calorimeter parameters of the samples such as HRR, THR, TSP and COP indicate that the addition of APP and CoSA improves the fire safety of epoxy resin significantly, and CoSA shows an obvious catalytic effect.     

High impact resistance epoxy resins by incorporation of quadruply hydrogen bonded supramolecular polymers

A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-(propylene glycol) bis(2-aminopropyl) ether chains and 2-ureido-4[1H]-pyrimidinone moieties (UPy) self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.     

Development and thermo‐mechanical behavior of nanocomposite epoxy adhesives

Two kinds of organo‐modified (OM) clays were dispersed in an epoxy resin for the preparation of nanocomposite adhesives at various filler amounts. XRD tests evidenced the formation of intercalated structures, increasing the intercalation degree with the clay hydrophilicity. The original transparency of the samples was retained up to a filler content of 3 wt%, and then decreased due to filler agglomeration. The glass transition temperature of nanocomposites filled with the more hydrophilic clay (30B) raised up to a filler content of 3 wt% and then decreased, probably because of the concurrent and contrasting effects of the physical chain blocking and reduction of the cross‐linking degree. Also elastic modulus, stress at break, and fracture toughness were sensibly improved by nanoclay addition up to filler loadings of 0.5–1 wt%. For higher concentrations the positive contribution of clay nanoplatelets was counterbalanced by the presence of agglomerated tactoids in the matrix. Mechanical tests on single‐lap composite (epoxy/glass) bonded joints evidenced an enhancement of the shear strength by about 25% for an optimal filler content of 1 wt%. Therefore, it was concluded that the addition of a proper amount of OM clay to epoxy adhesives could represent an effective way to improve the shear resistance of adhesively bonded composite structures. Copyright © 2011 John Wiley & Sons, Ltd.     

The application of highly soluble amine-terminated aromatic polyimides with pendent tert-butyl groups as a tougher for epoxy resin

Polyimides(PIs) with various molecular weights synthesized via the reaction of aromatic diamine monomer containing tert-butyl groups with aromatic dianhydride were highly soluble in common organic solvents and some epoxy resins at room temperature. These PIs can be incorporated in the absence of organic solvent into epoxy resin E51 with the loading below 2 wt% forming EP-PI composites. No phase separation is observed by SEM on cryogenically fractured surfaces of EP-PI composites. The PI can improve mechanical properties, especially impact strength. Adding 2 wt% PI-1.5W, the impact strength reaches to 55 k J/m2 with the increase in tensile and flexural strengths by 14% and 3%, respectively. SEM analyses for the fracture surface suggest that PI reduces the crosslink density, improves the plasticity of epoxy resin and changes the mode of fracture from fragile to ductile. Moreover, the glass transition temperature of EP-PI composites was found to increase to a significant extent.     

Enhancement of water barrier properties and tribological performance of hybrid glass fiber/epoxy composites with inclusions of carbon and silica nanoparticles

Water barrier properties and tribological performance (hardness and wear behavior) of new hybrid nanocomposites under dry and wet conditions were investigated. The new fabricated hybrid nanocomposite laminates consist of epoxy reinforced with woven and nonwoven tissue glass fibers and two different types of nanoparticles, silica (SiO₂) and carbon black nanoparticles (C). These nanoparticles were incorporated into epoxy resin as a single nanoparticle (either SiO₂ or C) or combining SiO₂ and C nanoparticles simultaneously with different weight fractions. The results showed that addition of carbon nanoparticles with 0.5 and 1 wt% resulted in maximum reduction in water uptake by 28.55% and 21.66%, respectively, as compared with neat glass fiber reinforced epoxy composites. Addition of all studied types and contents of nanoparticles improves hardness in dry and wet conditions over unfilled fiber composites. Under dry conditions, maximum reduction of 47.26% in weight loss was obtained with specimens containing 1 wt% carbon nanoparticles; however, in wet conditions, weight loss was reduced by 17.525% for specimens containing 0.5 wt% carbon nanoparticles as compared with unfilled fiber composites. Diffusion coefficients for different types of the hybrid nanocomposites were computed using Fickian and Langmuir models of diffusion. Copyright © 2017 John Wiley & Sons, Ltd.