Diglycidyl Ether Epoxy Research Articles

Fabricating epoxy vitrimer with excellent mechanical and dynamic exchange properties via network topology design

Epoxy vitrimers are a novel type of environmentally friendly materials that possess exceptional properties, including self-healing, recyclability, and reprocessability. They offer a solution to the issue of traditional thermosetting epoxy resins, which are not recyclable. However, the incorporation of dynamic bonds typically results in a decrease in mechanical properties. Therefore, achieving a balance between the mechanical properties and dynamic exchange capability is crucial. In this work, a series of epoxy resin systems with various topological network characteristics were prepared by adjusting the proportions of bisphenol A epoxy resin (E51) and polyethylene glycol diglycidyl ether (EGDGE) epoxy resins in combination with a curing agent containing vinylogous urethane (VU) dynamic bonds. Through further study, we found that with the increase of E51 content, the cross-linking density of the network gradually increased, and the flexibility of the macromolecular chains decreased (favorable for enhancing the material's mechanical performance). Simultaneously, the free volume of the network gradually increased, and the tightness of the macromolecular chains decreased (favorable for improving the material's dynamic exchange ability). These two effects combined to make E51-40 exhibit the lowest activation energy for dynamic covalent bond exchange and the lowest topological transition temperature. Compared to E51-0, the tensile strength and glass transition temperature of E51-40 were improved by 22.23 % and 25.30 %, respectively. After remoulding experiment at 140 °C for 1h, the material exhibited a high tensile strength recovery of 91.34 %. Therefore, starting from the design of molecular structure, adjusting the network topology is an effective means to balance the mechanical and dynamic exchange properties of epoxy vitrimers. This provides experimental guidance and theoretical insights for designing high-performance epoxy vitrimer materials.

Effect of crosslinking density on the self-healing and self-reporting properties of epoxy anti-corrosion coatings

This work developed a novel coating with self-healing and self-reporting performance by embedding polyurethane/poly-(urea-formaldehyde) (PU/UF) microcapsules in a shape memory epoxy polymer. 2’7’-Dichlorofluorescein (DCF) and linseed oil were applied as the coloring agent and healing agent, respectively, which are encapsulated into the PU/UF microcapsules (DL@PU/UF microcapsules) via a facile one-step method. To adjust the shape memory effect and the self-reporting performance of epoxy system, two kinds of curing agents (D230 and D400) were reacted with bisphenol A diglycidyl ether epoxy monomer to design a series of coating samples, finally the optimal coating system was selected by three indexes including barrier performance, residual amino content and coating hardness. When the composite coating was damaged, DCF can flow out of the broken microcapsules and react with the residual amino groups in the epoxy coating matrix, which can be recognized red signals in natural light and yellow fluorescent signals under ultraviolet light irradiation. More importantly, the excellent self-reporting property of the coating can be achieved on various metal substrates that broaden the application range of the coating. As for self-healing performance, the damaged coating can be healed quickly due to the shape memory effect of the coating as well as the filling of linseed oil in the scratched region. The Rct value of the healed coating containing 6 % DL@PU/UF microcapsules after immersing in 3.5 wt% NaCl solution for 5 days was more than 3 times that of the scratched coating, and the Rc value was about 16 times that of the scratched coating, indicating its corrosion protection performance. The novel coting not only achieve timely self-reporting ability of color and fluorescence, but also rapidly repair the coating damage, which is essential to practical applications.

Improving flame retardancy in BADGE epoxy via novel phosphorus‐functionalized epoxy integration

AbstractA novel epoxy resin, DPHP, was synthesized from diphenolic acid, which contains biobased levulinic acid, with triethylphosphite, to improve the flame retardancy of bisphenol‐A diglycidyl ether (BADGE) epoxy. Curing experiments were conducted using isophorone diamine as a curing agent for BADGE and DPHP mixtures. Variations in cure kinetics, mechanical properties, and flame retardancy were evaluated across different DPHP contents. The introduction of phosphorus functional groups into DPHP affected the polarization of epoxide CO bonds, resulting in reduced apparent activation energy for epoxy curing reactions. However, the higher epoxy equivalent weight of DPHP compared with that of BADGE led to a decrease in the tensile strength and the glass transition temperature of the cured material with increasing DPHP content. A significant increase in char yield for combustion of the epoxy blend was observed, ranging from 8.3% at 0 wt% DPHP to 20.1% at 50 wt% DPHP. Additionally, cone calorimeter measurements showed significant reductions in heat release rate and total heat release, leading to a decrease in fire spread from 1.07 MJm−2 s−1 at 0 wt% DPHP to 0.43 MJm−2 s−1 at 50 wt% DPHP. These results show that the flame retardancy of the cured material improved significantly as the DPHP content increased.

Construction of silver-epoxy adhesive with suppressed silver migration rate based on thiol-silver interaction

The silver migration limits the application of silver based conductive adhesives in wet environment. The existing methods for inhibiting silver migration in epoxy conductive silver adhesives involve one or more issues such as cost, complexity, and inhibition of conductivity. Moreover, there is currently a lack of strategies that can suppress the silver migration effect while ensuring good dispersion of silver fillers in the matrix and constructing a good filler matrix interface. Herein, a facile method was reported suppressing the silver migration in silver-epoxy conductive adhesive. Tetrafunctional thiopentaerythritol tetramercaptoacetate (PERTMA) was introduced into 1,4-cyclohexanedimethanol diglycidyl ether (CHDMGE) epoxy resin as the curing agent. This method utilized the strong interaction between silver and thiols, including coordination and covalent bonding, to achieve good compatibility between filler and matrix. By tightly combining silver with the resin system, the content of free silver atoms was reduced, capturing and inhibiting the hydrolysis of silver atoms and their migration with current, and the conductivity of the conductive silver adhesive was not greatly degraded due to the silver-thiol interaction. At the same time, the introducing of PERTMA was able to reduce the surface hydrophilicity of epoxy resin, which also helped suppressing the silver migration effect under humid circumstances. The interaction between silver and thiol was characterized, and the influence of silver content on the curing behavior, material mechanical performance, conductivity, resistivity on silver migration and flexibility was explored. The CHDMGE/PERTMA/Ag conductive adhesive based on strong thiol-silver interaction had excellent resistance to silver migration, which occurred after 3500s, which was 10.67 times longer than the control group. In addition, the silver filler enhanced the tensile strength of the matrix resin by this thiol-silver interaction. This study will provide new ideas for the design and development of silver migration resistant conductive adhesives based on matrix filler interaction.

Pyrolytic performance and kinetics study of epoxy resin in carbon fiber reinforced composites: Synergistic effects of epoxy resin and carbon fiber

Pyrolysis is recognized as a sustainable approach for recycling carbon fiber reinforced polymers (CFRP), ensuring enhanced process efficiency and resource utilization. To unveil the pyrolysis mechanism of epoxy resin and its synergistic interaction with carbon fiber in different scenarios, we conducted pyrolysis experiments on pure epoxy resin diglycidyl ether of bisphenol A cured with 4,4'-Diaminodiphenylmethane (C-epoxy), as well as three kinds of carbon fiber-resin mixtures, using TG and Py-GC/MS techniques. Isoconversional analysis (Friedman method) of C-epoxy degradation revealed three reaction stages within the temperature range of 280–540 °C, each corresponding to activation energies of 158 kJ/mol at α = 5%, 179–190 kJ/mol at the plateau of α = 10–60%, and 190–236 kJ/mol for α values surpassing 60%. The multi-Gaussian distributed activation energy model (DAEM) aptly characterized C-epoxy’s thermal decomposition, featuring two Gaussian peaks with similar contributions of 0.58 and 0.42, and activation energy distributions of 217.76 ± 3.92 kJ/mol and 233.36 ± 21.42 kJ/mol, respectively, which are close to the activation energies from isoconversional analysis at α = 10–60% and α > 60%, respectively. The presence of carbon fiber significantly influenced the kinetic parameters of epoxy resin pyrolysis, with the extent of change linked to the mixing methodology applied. Notably, carbon fiber decreased the activation energy of the reaction while accelerating the rate of weight loss. However, the synergistic effects vary depending on different synergistic scenarios. By analyzing the product distribution obtained through an analytical pyrolyzer coupled with a gas chromatography–mass spectrometry set-up (Py-GC/MS), we proposed a pyrolysis mechanism for epoxy resin, encompassing three key stages: cleavage of N–C and NC–COH bonds, phenolic O–C and vicinal C–C bonds, and disruption of the isopropylidene bridge on bisphenol A. The influence of carbon fiber on epoxy resin pyrolysis product distribution was relatively modest, manifesting predominantly within the mixture obtained by premixing before curing. Here, carbon fiber exhibited a dual effect, inhibiting oxygen-containing diphenyl products while promoting oxygen-containing monophenyl products. Ultimately, our study provides essential kinetic data for multidimensional simulation and theoretical guidance pertaining to the pyrolysis recycling of widely used carbon fiber-reinforced epoxy resin composites.

Blending Compatibility Simulation of UV-thermal Curing Solution with Epoxy Resin

To make a UV-thermal curing solution based on bisphenol A, epoxy acrylate (EA) and epoxy resin of diglycidyl ether of bisphenol A (DGEBA) were uniformly mixed. The Blends module in the Materials Studio software was used to carry out molecular dynamics simulation of blending compatibility and evaluate the rationality to achieve UV-thermal curing through interaction parameters, binding energy, and phase diagram. The binding energy distribution of DGEBA and EA is not consistent at 298 K, and the interaction parameter is 6.4335. When the temperature rises to 365 K, the interaction parameter diminishes to 3.5795. The compatibility of the UV thermal curing solution is improved by changing the molar ratio of DGEBA and EA to 0.45 and raising the temperature to 340 K. The results can be used to guide and predict the UV-thermal curing process and properties of epoxy resin.

Foaming epoxy-amine-carbamate: The effect of different neat amines on rheological and cellular morphology

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.

Adhesion Improvement of Bio‐Based Epoxy in Environmentally Friendly and High‐Performance Natural Fiber‐Reinforced Composites

AbstractDeveloping robust bio‐based epoxy against petroleum‐derived epoxy is necessary for environmentally friendly and high‐performance natural fiber‐reinforced composites. A bio‐based vanillin epoxy (VE) is synthesized from the lignin‐derived vanillin, and a thermoset resin is prepared after mixing it with a 4,4′‐diaminodiphenyl methane (DDM) hardener. Further, it is infused in high‐cellulose‐containing alkali‐treated jute fiber (TJF) mats through a simple approach to enhance the adhesion between the VE‐DDM and TJF. Bio‐based VE‐DDM resin shows better compatibility with TJF than petroleum‐derived bisphenol A diglycidyl ether (DGEBA) epoxy. The bio‐based VE‐DDM/TJF composite demonstrates the Tgis ≈165 °C, tensile strength is ≈83.12 ± 3.80 MPa, and Young's modulus is ≈2.86 ± 0.10 GPa with excellent flexural strength (138.72 ± 3.81 MPa) and flexural modulus (8.01 ± 0.11 GPa). It also shows merits regarding hydrophobicity, reduced water absorption ability, durability, and chemical resistance in an acidic medium. The natural fiber‐reinforced VE composites pave the way to produce environmentally friendly and high‐performance composites for structural applications.

Investigation of cycloaliphatic amine-cured bisphenol-A epoxy resin under quenching treatment and the effect on its carbon fiber composite lamination strength

AbstractThermosetting epoxy resin polymer with cycloaliphatic amines curing agent has been widely used for a composite matrix with carbon fiber reinforcement. The utilization was increased due to the superior performance of this epoxy resin compared to other polymers. However, a changing operational environment has potentially reduced composite performance, which most likely begins with matrix degradation. This research applies thermal treatment by the quenching process sequence to the epoxy resin matrix and its reinforced carbon fiber composite (CFRP). The composite is made by epoxy resin diglycidyl ether bisphenol-A, curing with cycloaliphatic amine as matrix and strengthening carbon fiber mat/woven. Three times quenching treatment was performed by heating the specimen around the glass transition temperature and then dipped immediately in fresh water. After quenching treatment, the epoxy resin shows a reduction in tensile strength and elongation. Under infrared observation, epoxy resin does not significantly show changes in functional groups. Investigation under X-ray refraction also indicates no difference in a crystalline structure; this epoxy resin stays in an amorphous form before and after quenching. In contrast to the matrix, the quenching treatment of the CFRP composite above the epoxy resin s glass transition temperature revealed an increase in the interlaminar shear strength (ILSS). The matrix ductility reduction after quenching should be carefully considered for application in the form of epoxy resin sheets or CFRP composite construction materials.

Biomass-based epoxy resin derived from resveratrol with high temperature resistance and intrinsic flame retardant properties

Preparing biomass-based epoxy resin with high temperature resistance and flame retardancy is still an appealing yet challenging task. Now, a high-temperature resistant and flame-retardant resveratrol-based epoxy (RESEP) has been synthesized through a facile one-step method. The structure of RESEP was established using FTIR and NMR spectroscopy. RESEP and petroleum-based epoxy diglycidyl ether of bisphenol A (DGEBA) were each cured with 4,4-diaminodiphenyl methane (DDM) to prepare RESEP/DDM and DGEBA/DDM. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, thermogravimetric analysis (TGA), thermogravimetric analysis-infrared spectroscopy (TG-IR), scanning electron microscopy (SEM), limiting oxygen index (LOI) and the UL-94 vertical burning test were used to systematically evaluate the properties of RESEP and RESEP/DDM. The glass transition temperature (Tg) of RESEP/DDM is 335 ℃, which is significantly higher than that of DGEBA/DDM (168 ℃). In addition, RESEP/DDM displays good thermogravimetric performance and flame retardancy. Typically, it displays a UL-94 V-0 rating, an LOI value was as high as 31.8%, and a char yield as high as 38.6% (800 ℃). The results reported indicate the possibility of preparing biomass-based epoxy resin with high temperature resistance, flame retardancy and mechanical properties, which is potential to be utilized in the fields of electronics and aerospace.

Correlation between cyclic topology and shape memory properties of an amine-based thermoset shape memory polymer: a coarse-grained molecular dynamics study

Defects in crosslinked networks have a negative effect on mechanical and functional properties. In this study, an epoxy resin diglycidyl ether of bisphenol A crosslinked by a hardener 4,4-diaminodiphenyl methane with various cyclic topologies was simulated to find correlations between the mechanical/shape memory properties (i.e. glassy/rubbery elastic modulus, shape recovery ratio, and recovery stress) and cyclic topologies (i.e. number of total loops, number of defective loops (DLs), etc). The effect of cyclic topology on shape memory properties was more significant than its effect on mechanical properties, altering recovery stress by more than 25% on average. After analyzing several topological fingerprints such as total number of loops, number of DLs, and number of higher order loops, we found that the effect of cyclic topology on the mechanical/shape memory properties of the systems can be best understood by the fraction of hardeners reacted with four distinct epoxy molecules (tetra-distinctly-reacted (TDR) hardeners). By increasing the number of TDR hardeners, the network is closer to ideal, resulting in an increase in the number of higher order loops and a reduction in the number of DLs, which in turn leads to an increase in rubbery elastic modulus and shape recovery ratio to a lesser degree, but a substantial increase in recovery stress. These results suggest that utilization of experimental techniques such as semibatch monomer addition, which leads to a more expanded and defect-free network, can result in a simultaneous increase in both shape recovery ratio and recovery stress in thermoset shape memory polymers (TSMPs). Moreover, topology alteration can be used to synthesize TSMPs with improved recovery stress without significantly increasing their stiffness.

A fully bio-based, anti-flammable and non-toxic epoxy thermosetting network for flame-retardant coating applications

A fully bio-based epoxy thermosetting network was prepared by curing a renewable luteolin-derived epoxy resin (DGELU) with a furan-derived hardener, 5, 5′-methylenedifurfurylamine (DFA). For comparison, a control sample was prepared by curing the petroleum-based commercial epoxy diglycidyl ether of bisphenol A (DGEBA) with a petroleum-based hardener, 4, 4′-diaminodiphenylmethane (DDM). The glass transition temperature (Tg) was found to be 216 °C for the cured DGELU/DFA, which was 67 °C higher than that of the cured DGEBA/DDM. The storage modulus at 30 °C and the tensile strength of the cured DGELU/DFA were 82.5 % and 23.2 % higher than those of the cured DGEBA/DDM. The benzopyrone unit of the luteolin structure was conducive to exceptional charring, and the char yield for thermal decomposition in the nitrogen of the cured DGELU/DFA was 3.2-fold higher than that for the cured DGEBA/DDM. As expected, the cured DGELU/DFA displays a relatively high limiting oxygen index (LOI) of 38.0 % and a UL-94 V-0 classification, whereas the petroleum-based counterpart exhibited a much lower LOI of 24.0 % and no classification in the UL-94 test. An in-vitro cytotoxicity study indicated that the cured DGELU/DFA showed no cytotoxic effect against normal fibroblast cells after 24 and 72 h. Because of these fascinating features, the DGELU/DFA thermosetting network was deposited onto wood surfaces for evaluation as a flame-retardant coating. Compared with the wood treated using the cured DGEBA/DDM coating, wood coated with the cured DGELU/DFA showed a super fire-safe property that could lead to a 55.8 %, 12.4 %, and 11.5 % decrease in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP), respectively. An anti-flammable, high strength and non-toxic bio-derived epoxy thermosetting network for highly safe epoxy coating applications has been developed.

The effect of DOPO concentration and epoxy amine stoichiometry on the rheological, thermal, mechanical and fire‐retardant properties of crosslinked networks

AbstractPresented here is an investigation into the effect of a phosphorus‐based fire retardant on the thermal, rheological and mechanical properties and flammability of an epoxyamine network prepared using stoichiometric and off‐stoichiometric epoxyamine compositions. The flame retardant 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was reactively incorporated into a blend of a bisphenol‐F diglycidyl ether epoxy resin and a polyfunctional epoxidized phenol Novolac resin, then cured with diethyltoluenediamine and accelerated using imidazole. Increased DOPO concentration improved fire retardancy, but reduced reactivity and thermal and mechanical properties. An increasing amino excess stoichiometry, however, comparatively increased reactivity and improved thermal and mechanical properties. Despite evidence of an earlier onset of degradation and higher char yield, enhanced graphitisation and reduced volatile emissions for the off‐stoichiometric networks, no significant improvements in fire resistance as a function of stoichiometry were observed using UL‐94 and limiting oxygen index measurements. © 2022 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Hot-lithography 3D printing of biobased epoxy resins

The introduction of Hot Lithography has opened new perspective in the field of additive manufacturing especially with regard to high viscous formulations. The access to elevated temperature in the 3D printing process not only reduce the viscosity of resin but it allows to achieve higher curing kinetics and degree of conversion. Therefore, it is possible to process new type of monomers which are not reactive enough at room temperature towards UV-curing expanding the formulation design and selection to the 3D-printing of a broader range of epoxy-based formulations. With regard to climate change and the limitation of fossil resources, new needs arise for the origin of the materials. In this view, we investigated the use of two bio-based epoxy monomers (furandimethanol diglycidyl ether (FDE) and resorcinol diglycidyl ether (RDE)) in Hot Lithography 3D printing. Moreover, we compared the performance of the bio-based resins with a commercial fossil-based one, the 1,4-cyclohexanedimethanol diglycidyl ether (CDE). The photocuring process was fully characterized by means of real-time NIR/photorheology and photo-DSC analysis. The thermo-mechanical properties of the final thermosets were investigated by DMTA and tensile test. Finally, the 3D printing of complex shapes was carried out to demonstrate the possibility to obtain arbitrary self-standing shapes. • Hot-lithography 3D-printing of bio-based epoxy resin. • Photocuring of Furan-dimethanol diglycidyl ether epoxy resin. • Photocuring of 1,4-cyclohexanedimethanol diglycidyl ether.

Design of New Functional Flame‐Retardant System for High‐Performance Epoxy Thermosets Enabled by Bifunctional Few‐Layer Black Phosphorus and Synergistic Strategy

AbstractIn this paper, a new highly effective functional flame‐retardant system is designed and fabricated by the combination of bifunctional amino‐functionalized few‐layer black phosphorus (BP‐NH2) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), and BP‐NH2 is utilized as both the flame‐retarded synergistic agent of DOPO and the reinforcing agent for bisphenol A diglycidyl ether (DGEBA) epoxy thermoset. The cured epoxy thermoset with a low phosphorus loading (EP/DOPO‐0.4/BP‐NH2‐0.3, P content = 0.5 wt%) passes the UL‐94 V‐0 rating with a limiting oxygen index of 34.5%. EP/DOPO‐0.4/BP‐NH2‐0.3 also shows 20.8% and 16.0% reduction in the peak heat release rate and total heat release as compared to that of pure epoxy thermoset. Furthermore, EP/DOPO‐0.4/BP‐NH2‐0.3 exhibits significant enhancements in tensile modulus and strength, which are, respectively, increased by 11.4% and 18.0%. Thus, by combining a synergistic effect strategy and the bifunctional BP‐NH2, the fabrication of epoxy thermosets with high comprehensive (outstanding flame‐resistance and mechanical properties) performance can be achieved. This paper offers a facile and scalable approach to construct a highly‐effective functional flame‐retardant system and new insight into the versatility of BP‐NH2, possessing great potential for scalable production and utilization in fire‐safe high‐performance matrix materials.

Preparation and Properties of Inkjet Waterborne Coatings

As an environmentally friendly coating, waterborne coatings have broad application prospects in paper packaging products in food and medicine. In this paper, a waterborne coating is synthesized from epoxy resin, polypropylene glycol diglycidyl ether, acrylic acid, trimellitic anhydride, maleic anhydride, and organic amine by three steps: ring opening reaction, esterification reaction, and neutralization reaction. Using viscosity, particle size, thermal stability, adhesion, and friction resistance as performance evaluation factors, the effects of the ratios of epoxy resin and polypropylene glycol diglycidyl ether in the polymerization system on the performance of synthetic waterborne coatings were discussed. Taking water solubility, water absorption, and water resistance as performance evaluation factors, the effects of the amount of ratio of anhydride groups to hydroxyl groups in the epoxy acrylic resin, which were produced in the second step of the reaction, were considered on the performance of synthetic waterborne coatings. The experimental results showed that when the molar ratio of the epoxy group in the epoxy resin and polypropylene glycol diglycidyl ether was about 1:1, and the molar ratio of anhydride in maleic anhydride to hydroxyl in the epoxy acrylic resin generated in the second step of reaction was about 0.9:1, the performance of the prepared waterborne coatings was comprehensively better. At the same time, the applicability of self-made waterborne coatings was tested. The results showed that when the coating amount was about 3.60 g/m2, the properties of the packaging base paper were greatly improved with respect to air resistance, oxygen resistance, oil resistance, and color reproducibility.

Experimental investigation of fracture toughness of nanoclay reinforced polymer concrete composite: Effect of specimen size and crack angle

This study experimentally investigates the influence of specimen size on fracture toughness properties of a polymer concrete (PC) composite. The PC was composed of a mixture of a Bisphenol A diglycidyl ether (BADGE or DGEBA) epoxy resin and its polyamine hardener as a binder, crushed basalt and silica sand as aggregates, ultrafine fly ash as a micro filler, and a montmorillonite nanoclay as a nanofiller. For this purpose, semi-circular bend (SCB) specimens in three sizes (R = 20, 30, and 60 mm), and for each size, four different crack angles (0°, 10°, 20°, and 41°), totally 12 types of specimen were fabricated. Three-point bending tests were performed to evaluate the size effect on the behavior of KIf, KIIf, Keff, T stress, and rc (length of the fracture process zone). It was shown that increasing the radius from 20 mm to 30 mm and 60 mm, increased KIf by 30.6% and 41.1%, and also increased KIIf by 10.4% and 20.7%, respectively. As the crack angle increased from 0° to 41°, KIf decreased and KIIf increased, both in almost a linear manner for all sizes, and the line slop slightly increased with the increasing specimen size. Field emission scanning electron microscopy (FESEM) analysis was performed to study the fracture surface of the PC specimen.

The effect of cell-size, cross-linking ratio, and force fields on the determination of properties of epoxy crosslinked by heuristic protocol

This research explores the effect of the cell size, cross-linking ratio, and the force fields used in the molecular dynamic simulation for determining the mechanical and thermal properties of cross-linked epoxy formed with a heuristic cross-linking procedure. The effects of the abovementioned variables on density, Young’s modulus, shear modulus, bulk modulus, and glass transition temperature values by molecular dynamics (MD) simulation were evaluated. Epoxy resin diglycidyl ether of bisphenol A and hardener diethyl toluene diamine were used in modeling the epoxy. A Heuristic method for reactive molecular dynamics (REACTER) protocol was used as the cross-linking procedure. Firstly, six structure cells were prepared in different cell sizes with a crosslinking ratio of 75%, and a mechanical analysis of all cells was performed. Then, the largest cell was prepared for three different crosslink ratios and its mechanical and thermal properties were calculated. Finally, the mechanical properties of the largest cell were calculated using the three different force fields namely the COMPASS, DREIDING, and UNIVERSAL. The results were also compared with the molecular dynamic simulation results performed using the other crosslinking procedures, and experimental results available in the literature. In comparison, it was observed that the results obtained with MD simulations coincided with the experimental data. It has been concluded that using the largest cell gives closer results to the experimental data but the processing time is also increasing rapidly. Moreover, it was also observed that the increase in the crosslinking ratio caused an increase in the mechanical properties of the epoxy and a significant increase in the glass transition temperature. Finally, compared to other force fields, it is seen that the mechanical analysis results obtained with the COMPASS force field comply more with the experimental data.

Synthesis and characterization of phenylated phenylenediamine and bisphenol a diglycidyl ether epoxy networks

AbstractA new highly aromatic hardener, phenylated phenylenediamine (PDA), was synthesized utilizing a Diels‐Alder reaction to afford a mixture of para and meta conformations. This new hardener was cured with bisphenol A diglycidyl ether (BADGE). To investigate the conformational mixture, pure 1,4‐benzenediamine and 1,3‐benzenediamine were cured with BADGE. DSC was employed to observe cure curves affording the onset (73, 74, and 146°C for 1,4‐benzenediamine, 1,3‐benzenediamaine, and phenylated phenylenediamine, respectively), peak (128, 151, and 206°C, respectively), and enthalpy change (385, 526, and 238 J/g, respectively), as well as the glass transition temperature (103, 151, and 212°C, respectively). ATR‐FTIR spectroscopy provided information on the structures of the cured network samples, including loss of oxirane and primary amine vibrations after curing. TGA and DMA were used to determine thermal stability (Td,N2 = 332, 367, and 380°C, respectively) and thermal mechanical properties including storage (E′ = 200, 150, and 350 MPa, respectively), loss modulus (E″ = 10, 10, and 40 MPa, respectively), and tan delta (102, 180, and 209°C, respectively).

A simple and highly reliable method to enhance the adhesion properties of polyethylene using Kapton-taping process

Although polyethylene (PE) is one of the most frequently used synthetic polymers in the plastics market, it is very difficult to imprint or bond PE with adhesives without pre-treatments based upon electrical, chemical and thermal processes. This is because a uniform adhesion property of PE cannot be expected without these processes. In this study, we suggest a simple, fast and cost-effective method to improve the adhesion properties of PE using a Kapton tape, which is a polyimide film generally used in flexible electronics. Specifically, by wrapping PE substrates applied with an adhesive using a Kapton tape and curing the sample using either a hot-press or a hot plate, the standard deviation of the shear strength decreased by 82.1% and 87.6%, respectively. To further improve the adhesion of PE substrates, we functionalized their surface using coupling agents, such as (3-glycidoxypropyl) methyldiethoxysilane and (3-aminopropyl) trimethoxysilane after an ultraviolet-ozone process. Using X-ray photoelectron spectroscopy and vacuum Fourier-transform infrared spectroscopy analysis, we proved that a significant improvement in the adhesion of PE occurred because of chemical crosslinking between either epoxy or amine groups functionalized on the PE substrates and epoxy-based adhesives comprising diglycidyl ether epoxy resin and triethylenetetramine hardener. This study is important, as it suggests a simple and very effective method to obtain highly reliable adhesion properties of PE using conventional adhesives. Kapton-taping can be a simple, yet very effective, method to achieve highly reliable adhesion properties of polyethylene substrates with conventional adhesives, resulting in a significant decrease in the standard deviation of shear strength, in comparison to other curing methods, such as hot plate and hot-press. • We demonstrated a method to improve the adhesion properties of polyethylene by simply wrapping samples using a Kapton tape. • Kapton taping method significantly lowered the standard deviation of the shear strength. • Functional groups that can be crosslinked with the main components of the adhesive greatly improved the adhesive properties. • The ultraviolet-ozone treatment was necessary for facile modification of coupling agents on bare PE surface.