Toughness Of Epoxy Resin Research Articles

Tung oil-based modifier strengthening and toughening epoxy resin by sacrificial bond

Tung oil-based modifier strengthening and toughening epoxy resin by sacrificial bond

The intramolecular aggregation of phosphaphenanthrene groups and benzene-terminated effect within linear phosphonate oligomers effectively enhanced the flame retardancy and toughness of epoxy resin

To explore the potential of a flame retardant molecular structure that simultaneously enhances the flame retardancy and physical properties of epoxy resin (EP), benzene-terminated linear phosphonate oligomers Bz-DQPC-n were synthesized. Compared with the previously prepared linear bisphenol phosphonate oligomers DQPC-n, the benzene-terminated effect of Bz-DQPC-n molecules endows EP composites with better flame retardancy and toughness. In the vertical combustion (UL 94) test, Bz-DQPC-n/EP reached a V-0 rating. For the Bz-DQPC-2 molecule, the results revealed that under the same phosphorus contents, the limiting oxygen index (LOI) value of the Bz-DQPC-2/EP reached 38.2 %, which was higher than that of DQPC-2/EP. Furthermore, the peak heat release rate (pk-HRR) and total heat release rate (THR) of Bz-DQPC-2/EP were 677 kW/m2 and 83 MJ/m2. These values decreased by 54.7 % and 27.2 % in comparison to pure EP, respectively. In addition, the incorporation of Bz-DQPC-n can enhance the glass transition temperature (Tg) of EP composites. The flame retardant mechanism research demonstrated that Bz-DQPC-n molecules produced phosphorus-containing free radicals and aromatic compound fragments during gas-phase pyrolysis. These phosphorus-containing free radicals can interrupt or inhibit the combustion chain reaction process. A proportion of the aggregated phosphaphenanthrene groups decomposed to produce aromatic compounds that remained in the condensed phase, thereby enhancing the quality of the char layer. The investigation of the impact of the end-capping effect within Bz-DQPC-n molecules on the flame retardant behavior of EP composites offers a valuable reference for designing phosphaphenanthrene compounds with high flame retardant efficiency.

Preparation and properties analysis of CTBN/CeO2 co‐toughened epoxy resin composites

AbstractIn this paper, carboxyl‐terminated nitrile rubber (CTBN) and Nano cerium oxide (n‐CeO2) were used to toughen epoxy resin (EP), and the effects of toughening agents on the mechanical and thermal properties of EP were studied. Orthogonal experiments determined that the ideal toughener proportions are 20 wt% CTBN and 1 wt% n‐CeO2, under which the resin demonstrated superior mechanical characteristics. The combined application of CTBN and n‐CeO2 significantly enhanced the resin's mechanical properties, surpassing the effects of individual particle toughening. Compared with pure EP, the impact, flexural, and tensile strengths of the resin‐cured product synergistically toughened by CTBN and n‐CeO2 increased by 462%, 136%, and 110%, respectively, and the flexural and Young's moduli increased by 38% and 35%, respectively. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to characterize the cured resin. The results indicate that incorporating CTBN and n‐CeO2 reduces the reaction activation energy, thereby accelerating the curing reaction and facilitating its progression. The addition of nanoparticles enhances the maximum weight loss temperature of the cured resin, thereby improving its thermal stability. CTBN and n‐CeO2 particles create a uniform phase separation structure within the resin, enhancing its toughness and strength. Furthermore, the impact fracture mode of the cured resin transitions from brittle to tough fracture, demonstrating a significant toughening effect. This provides an effective method for the toughening modification of EP.Highlights The synergistic use of CTBN and n‐CeO2 enhances the toughness of EP. The incorporation of nanoparticles improves the thermal stability of the cured resin. The addition of CTBN and n‐CeO2 accelerates the curing reaction rate. The inclusion of toughening agents transforms the fracture mode of the cured resin from brittle to tough fracture.

Study on foaming behavior of block copolymer/inorganic particles co‐construction of toughened epoxy resin foams

AbstractLow toughness and brittleness limit its application range of thermosetting epoxy resin (EP) based foams. In current research, inorganic particles are commonly utilized as heterogeneous nucleating agents to enhance foaming quality and EP toughness. However, the increasing inorganic particle content usually leads to particle agglomeration, which negatively impacts foaming quality and reduces EP performance. Block copolymers, which appear as liquid to effectively mitigate agglomeration, are employed as toughening materials for EP. In this study, a small number of modified calcium silicate particles (MCS) were used as anchor points to induce the distribution of block copolymers (P‐F68) to improve EP toughness and effectively enhance cell nucleation, thus, EP/MCS/P‐F68 foams performance was improved. The research results showed that EP foams obtained excellent cell structure and very small foam density (0.256 g/cm3) at the P‐F68 content of 10 wt%. The continuous increase of P‐F68 content would lead to the thickening of cell wall and the increase of cell size. Simultaneously, the core‐shell structure formed by P‐F68 in EP effectively enhanced the toughness of EP foams and mitigated its brittleness, offering crucial theoretical guidance for toughening and regulating the cell structure of EP foams.

Amphiphilic block‐copolymer exfoliated transition metal dichalcogenides as novel epoxy toughening agents

AbstractExcited by the effect of amphiphilic block copolymer Polyethylene glycol‐b‐Polypropylene Glycol‐b‐Polyethylene Glycol, a triblock copolymer (TBCP) in the virgin state as well as in the grafted form with graphene oxide and multiwalled carbon nanotube in epoxy toughening, the effect of the same block copolymer in the exfoliation of graphene analogous Transition Metal Dichalcogenides (TMDs) was studied. Even though epoxy resin has several advantages, its inherent brittleness and flammability limit its application in several areas. So, there is a need for the efficient toughening of epoxy resin to make it appropriate for high‐end applications. In the present work, epoxy resin was toughened with exfoliated TMDs, especially Molybdenum sulfide and Tungsten disulfide (MoS2 and WS2). TBCP was used in the exfoliation of TMDs where the effect of these exfoliated TMDs in enhancing the properties of epoxy was evaluated. TBCP exfoliated MoS2 and WS2 exhibit fracture toughness of 483% and 636%, respectively in epoxy composites without compromising the tensile properties, which enhances the efficacy of epoxy resins towards high‐end applications. The improvement in toughness is evident from the fractography of the crack surfaces. The role of TBCP exfoliated TMDs in tuning the mechanical, thermal, and thermomechanical properties is portrayed in the manuscript, thereby unveiling the potential of yet another unique class of materials in epoxy toughening.Highlights The efficiency of amphiphilic block copolymer in exfoliating TMDs is analyzed. The effect of TBCP‐exfoliated TMDs as a toughener for the epoxy matrix is portrayed. 483% and 636% improvement in the toughness compared to neat epoxy was obtained for TBCP exfoliated MoS2 and WS2 reinforced epoxy respectively. Improved tensile properties after incorporation of TBCP exfoliated TMDs in epoxy matrix. The plasticizing effect of TBCP compromises the thermal properties.

Fabrication of polyurethane/polythiourethane core–shell microspheres via thiol-isocyanate click chemistry and their application in toughening epoxy resin

Fabrication of polyurethane/polythiourethane core–shell microspheres via thiol-isocyanate click chemistry and their application in toughening epoxy resin

Investigation on Polyether Sulfone Toughening Epoxy Vitrimer: Curing and Dynamic Properties.

Diglycidyl ether of bisphenol A crosslinking with glutaric anhydride is used to form the conventional "covalent adaptive network", polyether sulfone (PES) by coiling and aggregating on the adaptive network is used to significantly increase the uncured resin viscosity for improving the processability of epoxy resin, but inevitably affecting the curing reaction and dynamic transesterification reaction. This study investigates the crucial roles of PES in curing dynamics and stress relaxation behavior. The results indicate that although PES does not directly participate in the crosslinking reaction of polyester-based epoxy vitrimers. Moreover, the isothermal curing studies reveal that the addition of PES can greatly bring forward the reaction rate peak from conversion α = 0.6 to α = 0.2, meaning that the curing mechanism transfers from chemical control to diffusion control. Dynamic property analysis shows that the addition of PES significantly accelerates stress relaxation, especially at lower temperatures, leading to low viscous flow activation energy Eτ and relatively insensitive stress relaxation behavior to temperature. Introducing PES into vitrimer resin greatly improves crosslinking density (2.31×10⁴molm- 3), enhancing glass transition temperature (82.68°C), tensile strength (68.66MPa), and fracture toughness (6.25%). Additionally, the modified vitrimer resin exhibits satisfying shape memory performance and reprocessing capability.

Synergistic Effects of Liquid Rubber and Thermoplastic Particles for Toughening Epoxy Resin

This study aims to investigate the toughening effects of rubber and thermoplastic particles on epoxy resin (EP), and to understand the mechanism underlying their synergistic effect. For this purpose, three EP systems were prepared using diglycidyl ether of bisphenol-A (DGEBA) epoxy resin (E-54) and 4,4-Diamino diphenyl methane (Ag-80) as matrix resin, 4,4-diaminodiphenyl sulfone (DDS) as a curing agent, and phenolphthalein poly (aryl ether ketone) particles (PEK-C) and carboxyl-terminated butyl liquid rubber (CTBN) as toughening agents. These systems are classified as an EP/PEK-C toughening system, EP/CTBN toughening system, and EP/PEK-C/CTBN synergistic toughening system. The curing behavior, thermal properties, mechanical properties, and phase structure of the synergistic-toughened EP systems were comprehensively investigated. The results showed that PEK-C did not react with EP, while CTBN reacted with EP to form a flexible block polymer. The impact toughness of EP toughened by PEK-C/CTBN was improved obviously without significantly increasing viscosity or decreasing thermal stability, flexural strength, and modulus, and the synergistic toughening effect was significantly higher than that of the single toughening system. The notable improvement in toughness is believed to be due to the synergistic energy dissipation effect of PEK-C/CTBN.

Phenyl, propyl polysiloxane modified epoxy resin II: The co-continuous phase, concurrently strengthening and toughening mechanism

The applications of epoxy resins are restricted in certain areas due to their brittleness, while improving the epoxy toughness always compromises their strength. We reported a phenyl, propyl polysiloxane modified epoxy resins with excellent tensile strength and toughness before. In this study, the mechanism of strengthening and toughening are studied and elaborated. Compared to cured EP resin (EP), cured P/E resin (P/E20) significantly improved the tensile strength, elongation at break, impact strength, and critical strain energy release rate (GIc) by 45 %, 248 %, 18 %, and 512 %, respectively. Fracture analysis of the P/E20 revealed the appearance of parabolic markings, typical and convincing evidence of ductile fracture, indicating good toughness of the resin. AFM height and Young's modulus plots reveal the complex details of the dimples and the co-continuous phases, which provide the strong evidence to explain the reinforcement and toughening mechanism.

Halogen-free epoxy flame retardant & promoter with diimidazole skeleton improves overall properties of epoxy resins

In order to solve the widespread problem in the field of flame retardancy epoxy(FREP), for the deterioration of the overall properties, we designed a novel structural flame retardant & promoter DOPO-CDI and synthesized it using a simple nucleophilic addition one-step method, which exhibits remarkable flame retardant and curing promotion, the flame retardant and promote mechanism of DOPO-CDI on neat EP is illustrated in Fig 0a, which obtained excellent overall properties shown in Fig 0b. Compared with neat epoxy, it has high flame retardancy, low additives results in an limiting oxygen index(LOI) of up to 37.5 % and a V-0 rating of UL-94, a lower curing exothermic peak temperature, a shorter curing time. And in terms of mechanical properties, the excellent strength of epoxy has been further enhanced, flexural strength and tensile strength are increased by 13.3 % and 21.6 % respectively. Moreover, the toughness of epoxy, which is generally lacking, has been greatly improved, in particular, compared with neat epoxy, the impact strength of epoxy with 3 wt% DOPO-CDI increased by 103.6 %. Unlike most FREP, glass transition temperature(Tg) of the epoxy with the introduction of DOPO-CDI raises to 165.6 °C, which is a significant improvement compared to that of the neat epoxy, in terms of combustion behavior, DOPO-CDI has a considerable inhibitory effect on the combustion exotherm and smoke emission. This work explores a way to balance processing, mechanical and thermal properties when preparing FREP, which has great potential for application.

Effect of adhesive ductility on the bond behavior of CFRP-steel cohesive interfaces made with toughened epoxy resin

The strengthening of steel structures can be effectively performed using carbon fiber-reinforced polymers (CFRP) plates. Specifically, the behavior of corroded and fatigue damaged steel bridges can be significantly improved using externally bonded (EB) or unbonded composite reinforcements. For bonded composites, the bond between the reinforcement and the steel substrate is the weak link of the system. Indeed, cohesive failure within the adhesive layer represents the main failure mode, which makes the selection of a proper adhesive fundamental to achieve an improvement of the system load carrying capacity and fatigue resistance. Within this context, the use of toughened adhesives represents a promising solution. However, research regarding these adhesives is still limited. In this paper, 18 single-lap direct shear tests are performed to evaluate the cohesive behavior of toughened and traditional adhesives. For some specimens, the full-range bond behavior, including the load response snap-back, was experimentally captured. The digital image correlation (DIC) technique is adopted to evaluate the adhesives cohesive material law (CML). The effect of adhesive ductility, plate stiffness, and bonded length on the joint load response is investigated. Finally, experimental results are validated and discussed against the analytical predictions of a cohesive model based on a trapezoidal CML.

Tough epoxy resin systems for cryogenic applications

This work presents the development of new epoxy systems that combine high fracture toughness at cryogenic temperatures (▪) with a slow curing reaction (long pot life) and a glass transition temperature between ▪ and ▪, ensuring good mechanical performance at room temperature. This was achieved by incorporating varying amounts and types of short-chain alkylamines into epoxy networks based on bisphenol A diglycidyl ether (DGEBA) crosslinked with metaphenylene diamine (MPD). This modification enhanced the cryogenic fracture toughness of the base system, DGEBA crosslinked with MPD, from 2 to ▪. It has been suggested that the significantly improved cryogenic fracture toughness in systems with flexible aliphatic chain extenders might result from nano- or micro-phase separation, but X-ray scattering and dynamic mechanical spectroscopy did not provide conclusive evidence for this hypothesis.The required slow curing reaction was achieved by using a sterically hindered alkylamine (2-heptylamine) as chain extender, which increased the pot life more than twofold, resulting in resin formulations that combine a high cryogenic fracture toughness, a low viscosity and a long processing window at room temperature.

Study on mechanical properties and curing properties of shear‐thickening gel toughened epoxy resin

AbstractThe shear‐thickening gel (STG) is introduced as a toughening agent into the epoxy resin (EP) to improve the toughness and impact resistance of the EP without significantly increasing its viscosity. By utilizing the unique BO dynamic bonds present in STG, the EP/STG composite exhibits remarkable toughness at low strain rates due to the gradual disentanglement of molecular chains. Conversely, at high strain rates, the disentanglement of molecular chains is hindered, resulting in a pronounced impact hardening effect and overall superior impact resistance. Our findings reveal that when STG is added at a concentration of 15%, the EP/STG composite material attains its peak mechanical performance. Specifically, it demonstrates a tensile strength of 31.8 MPa and a modulus of elasticity of 550.6 MPa. Furthermore, compared to pure EP, the EP/STG composite experiences an increase in elongation at break and impact strength by 40% and 8.1%, respectively. Additionally, the introduction of hydroxyl and B atoms in STG promotes the ring‐opening reaction of epoxy groups during the curing process of the EP, thus accelerating the curing reaction rate. These insights provide a solid theoretical foundation for optimizing the performance of EPs in engineering applications.Highlights The STG was actively utilized to enhance the toughness of EP. The modified EP system exhibits significant improvements in toughness and impact resistance without a notable increase in viscosity. The promotional effect of STG on the curing of EP systems was revealed through curing kinetics analysis and rheological analysis.

A phosphorus/fluorine‐containing block copolymer endows epoxy with multifunctionality

AbstractIn order to achieve flame retardant, hydrophobic, and toughened epoxy resins, phosphorus/fluorine‐containing block copolymer (FBCP) was synthesized by reversible addition‐fragmentation chain transfer polymerization, and then the as‐synthesized PMADOPO‐b‐PHFBA block copolymer was used as additive to modify the epoxy resin, accompanying with a random copolymer (FRCP) serving as control group. It showed that due to the regular arrangement of molecular chains, FBPC formed a fibrous‐like structure at the fracture interface of epoxy/PMADOPO‐b‐PHFBA (EP/FBCP) samples, effectively enhancing the toughness of epoxy composite materials. The fracture energy of EP90/FBCP‐10 was higher than that of EP90/FRCP‐10 and was about twice than that of pure EP. The addition of 3 wt% FBCP could enhance the limited oxygen index (LOI) of EP97/FBCP‐3 to 33.2% and reached a V‐1 UL‐94 rating. As the addition of FBCP increased, the LOI gradually increased. When the addition of FBCP was 10%, the LOI and UL‐94 of EP90/FBCP‐10 was 38.2% and V‐0 grade, respectively. Meanwhile, the presence of fluorine element effectively reduced the surface energy of the composite EP material. Compared with pure EP, the water contact angle of EP90/FBCP‐10 was about 101° with an increasing of 20.8%. Furthermore, the flame‐retardant mechanism of EP/FBCP epoxy composites was discussed.

P/N-containing SiO2 flame retardant particles formed by in-situ hydrolysis for significantly improve the flame retardancy and toughness of epoxy resins

To obtain flame retardants with more efficient and multidimensional flame retardant modes, this work formed P/N-containing silica flame retardants (PBPSi) by hydrolysis and used them in epoxy resins (EP) to give them good flame retardant properties. The hydrolyzed SiO2 flame retardant builds an integrated flame-retardant structure and a concentrated stress-bearing point, the EP has good fire resistant properties and toughness. Allowing the addition of 7-PBPSi/EPPBPSi to enable EP to achieve a UL-94 rating of V-0, and the impact strength of 5-PBPSi/EP reached 52.9 kJ/m2. In addition, PBPSi has good performance in inhibiting heat release and toxic gas release, and the PHRR and THR of 7-PBPSi/EP were reduced by 54.6 % and 24.6 %, respectively, compared with pure EP, the content of CO and CO2 also decreased. The analysis of the flame retardant mechanism indicated that PBPSi played a flame retardant role in the biphasic phase through the catalytic carbon formation in the condensed phase and the synergistic dilution of flammable gases and trapping of free radicals by P/N synergistic.

Novel Reactive Polyhedral Oligomeric Silsesquioxane-Reinforced and Toughened Epoxy Resins for Advanced Composites.

Most toughening methods for epoxy resins are usually used at the expense of other properties. Some polyhedral oligomeric silsesquioxanes (POSSs) with both a rigid Si-O-Si structure and flexible organic chain segments could be expected to be effective toughening agents. In this study, three reactive polyhedral oligomeric silsesquioxanes with a thiol group (OMPPS), a carboxyl group (OCOPS), and an epoxy group (OGCPS) were synthesized and characterized. They were utilized as modifiers to toughen 3-(oxiran-2-ylmethoxy)-N,N-bis(oxiran-2-ylmethyl)aniline (AFG-90MH)/4,4'-methylenebis(2-ethylaniline) (MOEA) (epoxy resin) with different molar ratios to obtain hybrid resins named OMPPS-EP-i, OCOPS-EP-j, and OGCPS-EP-k. The effects of the amount of modifier added and the length of the organic chain on the cage structure on various properties of the hybrid resins were investigated. The results show that all three modifiers show good compatibility with the epoxy resin. The hybrid resins have a low viscosity at 45~85 °C and can be cured at a low temperature (110 °C). The cured hybrid resins display improved toughness. Typically, the critical stress intensity factor (KIC) and impact strength of OGCPS-EP-0.6-C are 2.54 MPa∙m-1/2 and 19.33 kJ∙m-2, respectively, which increased by 58.75% and 22.48% compared with the pristine epoxy resin, respectively. In addition, the glass transition temperature and flexural strength of the hybrid resins are basically unchanged.

Efficient toughening of epoxy anhydride thermosets with modified PVA fibers

ABSTRACT The poor interfacial properties of polyvinyl alcohol (PVA) fibers and epoxy resin seriously affect the toughening effect of PVA fibers on epoxy resin. To solve this problem, the surface of PVA fibers was modified with 3-aminopropyltriethoxysilane (KH550) and 3-glycidoxypropyltrimethoxysilane (KH560), as well as the surface of PVA fibers with tannic acid (TA) and KH560. The acid-cured epoxy resin toughening mechanism of the modified PVA fibers was systematically investigated by multiscale analysis. The experimental data showed that the epoxy resin performed best when TA and KH560 synergistically modified PVA fibers. The impact strength of the epoxy resin increased by 76.3% and the tensile strength by 20.3%. The toughening mechanism of modified PVA fibers on the epoxy resin was revealed by a series of characterizations such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). Because KH560 can participate in the curing reaction of the epoxy resin, it greatly enhances the adhesion between the fiber and the resin. The toughening mechanism of TA and KH560 working together on PVA fibers to strengthen epoxy resin is summarized through the analysis of different scales. This also offers theoretical and experimental support for using PVA fibers in composites.

Low-Velocity Impact of carbon, flax, and hybrid composites: Performance comparison and numerical modeling

In recent years, composite materials have assumed an increasingly dominant role in various industrial sectors, combining lightweight with optimal mechanical properties. In this context, natural fibers are essential for the development of eco-friendly composites, ensuring a balance between performance and sustainability via hybridization. This study provides an experimental and numerical analysis on composite laminates subjected to Low-Velocity Impact (LVI) tests at different energy levels, after an initial mechanical characterization of the materials. Carbon and flax fiber fabrics are chosen as reinforcements embedded in a toughened epoxy resin, as well as in two hybrid configurations; two different stacking sequences are also investigated, with the layers placed at 0°and in a quasi-isotropic (ISO) orientation. Hysteresis curves and energy absorption capability – in terms of specific energy absorption (SEA) – are then discussed and compared to each other, along with cross-shaped damage propagation on fracture surfaces. Numerical finite element (FE) models of tensile, compressive, and LVI tests are designed and solved using LS-DYNA software. In particular, tensile and compressive ones are carried out to calibrate the material cards, which have subsequently been adopted in the LVI models. The results obtained not only show an agreement between the experimental response and the simulated one, but also provide a complete investigation of different materials and orientations under LVI in view of future applications, highlighting the possibility of designing structural components to absorb energy in hybrid composites reinforced with natural fibers.

Effect of solid lubricant additives on solid particle erosion characteristics of rigid and toughened epoxy resins

AbstractSolid lubricants are added to polymers to upgrade their tribological properties, especially in cases where adhesive and abrasive friction are valid. However, there are not enough studies on the effects of solid lubricants on particle erosion. This study investigated the effects on solid particle erosion behavior of three different well known solid lubricants (molybdenum disulfide, polytetrafluoroethylene, and graphite). These solid lubricants were added at three different ratios (5, 10, and 15 wt.%) to the two different type (rigid and toughened) epoxy resins. Garnet abrasive particles (180–400 μm) were blasted to the sample surface under 1.5 bar for 15 s to conduct solid particle erosion tests. The erosive wear mechanisms of neat and solid lubricant‐reinforced epoxy resins were investigated in relation to the epoxy type, solid lubricant type, and solid lubricant reinforcement ratio. Statistical analysis was performed according to response surface methodology to support the experimental results, and ANOVA tables were obtained. The wear and deformations that occurred on the surface after solid particle erosion were examined using a noncontact optical profilometer system and scanning electron microscopy, and a significant relationship was detected between the deformation on the surface and particle erosion. Analysis results showed that the factor causing the greatest erosion rate change was the epoxy resin type. Finally, it has been observed that all solid lubricants reduce the erosive wear resistance, and this resistance decreases as the weight ratio increases.Highlights Investigations were conducted into the erosion behavior of two types of epoxy resins: rigid and toughened. The toughened epoxy resin exhibited greater resistance to erosion. Although it has the same type of content, on average, rigid epoxy worn 2–4 times more than toughened epoxy. The effect of adding polytetrafluoroethylene tended to increase the erosion rate of both rigid and toughened epoxy resin less than that of other solid lubricants. Graphite particles increased the erosion rate of toughened epoxy by 1.5–3 times and that of rigid epoxy by 2–3 times, depending on the value of the reinforcement ratio. MoS2 increased the erosion rate of toughened epoxy by 1.5–3 times and that of rigid epoxy by 2–3 times. Using a noncontact optical profilometer (for investigating surface topography), it was proven that there is a significant relationship between the erosion rate and roughness characteristics. Wear mechanisms were identified by SEM analysis.

Introducing rigid-flexible integrated structure and constructing sacrificial bonds to achieve mechanically robust and malleable epoxy resin

Epoxy resin (EP) is usually brittle because of highly cross-linked chemical structure, so it is necessary to carry out research on toughening of epoxy resin. Here, a modified epoxy resin with enhanced mechanical toughness and strength was prepared using a novel modifier (PEA-BA), synthesized from polyetheramine D-400 (PEA) and benzoic acid (BA). Polyether chains that represent flexible structures, and aromatic rings representing rigid structures, were integrated together into the modifier to achieve simultaneous enhancement of the toughness and strength of the resulting epoxy resin. Moreover, the aromatic rings in PEA-BA formed π-π interactions with the aromatic rings in the EP network, further increasing the ductility of the modified epoxy resin. Research results demonstrated that the modified epoxy resin exhibited significantly improved elongation at break (increasing from 6.7 % to 39.2 %), as well as higher tensile strength (from 61.9 MPa to 69.3 MPa) and impact strength (from 25.3 kJ·m−2 to 62.9 kJ·m−2). Importantly, the glass transition temperature and thermal stability of the modified epoxy resin were not markedly reduced. The above properties indicated that PEA-BA achieved a favorable combination of high strength and ductility of epoxy resin, providing a new idea for toughening epoxy resin.