Modified Epoxy Resin Research Articles

Preparation of modified epoxy resin with high hydrophobicity, low dielectric constant, toughness, and flame retardant by epoxy-functionalized siloxanes

A series of α, ω-dimethylglycidoxypropyl-terminated PDMS oligomer (PDMS-GE) oligomers with different polymerization degrees were synthesized and used to modify the bisphenol-A diglycidyl ether E51 (DGEBA) / 4,4-diaminodiphenylmethane (DDM) epoxy resin, resulting in epoxy resins with high hydrophobicity, low dielectric constant, good impact toughness, low combustion heat release rate, and low total heat release. The combustion heat release rate and total heat release of the material decreased with the increase in the loadings of PDMS-GE. Relative to pure epoxy resin, the composite E51/D30–10, which using DGEBA as the matrix, PDMS-GE with a degree of polymerization of 30 as the modifier in an amount of 10 phr relative to the mass sum of DGEBA, PDMS-GE and DDM, exhibited the best comprehensive performance with a water contact angle of 102.42°, a dielectric strength of 6.49 kV/mm, a dielectric constant of 2.93 at 14.2 GHz, the peak rate of heat release (PRHR) and total heat release (THR) are of 378.3 kW/m2 and 134.4 MJ/m2, respectively. These comprehensive performances underscore the potential of PDMS-GE oligomers in significantly improving epoxy resin properties. When the loadings of PDMS-GE oligomers are less than 5 wt%, PDMS-GE with a lower degree of polymerization can improve the toughness of epoxy resins. The impact strength of the composite E51/D24–5, which uses DGEBA as the matrix, PDMS-GE with a degree of polymerization of 24 as the modifier in an amount of 5 phr relative to the mass sum of DGEBA, PDMS-GE, and DDM, reaches 98.1 kJ/m2, which is about 28.9 % higher than that of pure epoxy resin. The results also indicated that the degree of polymerization of PDMS-GE oligomers has less influence on the dielectric properties and mechanical properties of composite materials.

Research on the Durability of Composite Epoxy Resin Modified Repair Mortars Based on Water-Oil Gradient Phase Change: From Macroscopic to Nanoscopic Scales

With the rapid pace of urbanization, global demand for concrete is increasing, shifting focus from construction to repair and maintenance. Traditional cement-based repair materials generally suffer from brittleness and poor durability, failing to meet the growing demand for durable repair solutions. We developed a water-oil gradient composite epoxy resin (CEP) modified cement-based repair mortar (MCEP) using self-synthesized water-based epoxy resin (WEP) and oil-based epoxy resin (EP). Durability tests showed that CEP-modified cement mortar exhibited improved resistance to solution penetration, shrinkage, acid corrosion, and freeze-thaw cycles, with increased CEP content positively affecting mortar durability. Notably, the addition of CEP not only enhanced the interface bonding strength between MCEP and old concrete but also maintained good bonding stability under moisture erosion. X-CT and SEM microstructural tests revealed that CEP is evenly distributed in the cement paste, forming a cement-polymer interpenetrating network structure, which improves crack resistance and reduces solution penetration in MCEP. Molecular dynamics simulations explored the adsorption of CEP on calcium aluminate hydrate (AFt), a key cement hydration product, and the moisture transport mechanisms in AFt and CEP-modified AFt nanopores. Results indicated that CEP molecules adsorb onto AFt via ionic and hydrogen bonds, demonstrating good stability. During moisture penetration, CEP reduced water transport efficiency in the nanopores. CEP modification improved the crack resistance and durability of cement repair mortars, providing valuable insights into molecular-scale enhancements in water permeability resistance. This study aims to contribute to the design and practical application of water-oil gradient epoxy resins and other polymer-modified cement-based repair materials.

High-reliable polyurethane modified epoxy photosensitive composites for solder resist applications

Developing solder resist ink (SR) with superior comprehensive performance through the chemical modification of epoxy resin (EP) using polyurethane oligomers (PU) is an effective strategy. In this study, a highly reliable SR was designed by chemically grafting -NCO terminated PU onto the -OH groups of the EP molecular chain. By adjusting the PU content, high flexibility, reliability, and adhesion of the EP-PU system were achieved. Compared to SR-0, when the PU content is 50 % of EP, under conditions of 85 % humidity, 130 °C temperature, and 1 V voltage, the failure time of SR-0.5 can be adjusted from 67.5 h to over 150 h, an increase of 150 %. This high-reliability characteristic makes it potentially useful in applications such as printed circuit board and packaging substrate manufacturing. Additionally, by adjusting the PU content in the EP-PU system, the degree of crosslinking in the EP-PU molecular chain can be controlled, resulting in excellent adhesion, alkali resistance, hydrophobicity, mechanical properties, low water absorption, and good thermal stability. The chemical modification of EP with PU provides a theoretical basis and technical support for the development of high-performance SR, while also offering more reliable material solutions for the advancement of the electronics industry.

Biobased Hyperbranched Flame Retardant for Epoxy Resin Modification: Simultaneously Improved Flame Retardancy, Toughness, and Smoke Toxicity Suppression

Biobased Hyperbranched Flame Retardant for Epoxy Resin Modification: Simultaneously Improved Flame Retardancy, Toughness, and Smoke Toxicity Suppression

Comparison of machine learning models predicting the pull-off strength of modified epoxy resin floors

Abstract It is becoming popular to replace destructive laboratory testing with related nondestructive testing (NDT) and/or machine learning (ML) techniques. Such an approach is becoming particularly desirable in operating facilities, where failing components result not only in the need for repair but also in the suspension of facility use for up to several months. Supporting construction work with artificial intelligence (AI) offers the potential for breakthroughs in this area. Commonly, this approach is already being used in the construction industry to determine compressive strength using, for example, information about the composition of a composite. Determination of pull-off strength can be approached in a similar way. In this paper, the ML model presented can be used to predict the pull-off strength of resin coatings containing granite powder and linen fibers. To obtain satisfactory results, the selected ML algorithms were analyzed on a database consisting of 140 sets of parameter values containing information about the composition of the resin coating. Indices indicating high performance (R = 0.885; RMSE = 0.138; MAPE = 3.72%) were obtained by a model based on the random forest (RF) algorithm containing 160 trees with a depth of 10 nodes. A comparison of the predicted fb pull-off strength with the strength determined by in-situ tests was developed. The results suggest that using artificial intelligence to determine the fb of resin coatings is a promising alternative.

Preparation of UV curable acrylamide modified epoxy resin and performance in 3D printing

A novel UV-curable 3D printing resin was synthesized by combining diglycidyl ether of bisphenol A (DGEBA) and acrylamide (AAM) to create a UV-curable acrylamide-modified epoxy resin prepolymer. This prepolymer was then uniformly mixed with the photoinitiator TPO and the reactive diluent hydroxyethyl methacrylate (HEMA). By adjusting the prepolymer content, UV-curable 3D printing resins were formulated with prepolymer concentrations of 30 wt%, 40 wt%, and 50 wt%, respectively. Infrared spectroscopy and nuclear magnetic resonance studies indicated that the amino groups in acrylamide reacted with the epoxy groups. When the prepolymer was added at concentrations of 30 wt% and 40 wt%, the viscosity met the requirements for UV-curable 3D printing. Upon completion of curing, these three distinct resins exhibited high mechanical strength, with tensile strength reaching up to 59.42 MPa and flexural strength peaking at 72.25 MPa. The elongation at break ranged from 2.60 % to 4.91 %. Scanning electron microscopy was used to examine the UV-cured 3D printed samples, and comparison with the design files revealed that the printed samples exhibited excellent dimensional stability. The study results indicated that this novel UV-curable epoxy vinyl resin formulation possessed excellent mechanical properties, suitable curing characteristics, and high resolution, making it a highly promising prepolymer for UV-curable 3D printing.

Synergy between biphenyl mesomorphic structure and organic crystal phenazine for improving the intrinsic thermal conductivity of epoxy

The inherent low intrinsic thermal conductivity of epoxy resin severely restricts its potential application, making it difficult to meet the growing demand of energy, electrical and electronic technologies. The liquid crystal epoxy resin, which is wildly employed to improve the intrinsic thermal conductivity of epoxy resin, is constrained by its complex molecular structure design and synthesis procedures. In this work, the rigid group of 4,4′-dihydroxybiphenyl was introduced into the main chain of epoxy resin by ring-opening polymerization (ROP) to change the molecular structure of epoxy resin. The introduction of biphenyl groups enhances the orderliness of molecular structure and forms hydrogen bonds between molecules, which further enhances the transport of intramolecular phonons. The thermal conductivity of the graft modified epoxy resin (GMR) after DDM curing is 0.30 W m−1 K−1. After adding of organic crystal phenazine (PNE) to the GMR matrix, the inherent strong crystallization behaviors of PNE can accelerate the regularity arrangement of rigid groups in GMR, and promote the nucleation and crystallization process of GMR/PNE. The thermal conductivity of GMR/PNE after DDM curing can reach 0.33 W m−1 K−1. It is 165 % of the thermal conductivity of traditional epoxy resin, which is 0.2 W m−1 K−1. This study will provide a new method to improve the intrinsic thermal conductivity of polymer materials.

Evaluation Indexes of Skid Resistance of Epoxy Chip Seal Based on Texture Features at Different Scales

Epoxy chip seals are widely used to improve the skid resistance of cement concrete pavements, which is significantly affected by surface texture. However, current methods for characterizing the surface texture structure are not precise, and the standard is not uniform. Therefore, a high-toughness modified epoxy resin chip seal structure was developed to conduct an indoor accelerated abrasion test. The elevation data of the epoxy chip seal under different abrasion times and different abrasion loads were obtained using laser scanning, and the density/sharpness combination parameters were obtained using the Hilbert–Huang transform and spectral analysis. The correlation between the texture parameters and the dynamic friction coefficient was analyzed using a stepwise multivariate quadratic polynomial method. The results showed that the texture structure of the epoxy chip seal surface is positively distributed, and the macroscopic texture occupies 49.45%, while the probability of the microscopic texture is only 4.55%. Meanwhile, the correlation coefficient between the texture parameters and the dynamic friction coefficient is 0.9307, which demonstrates that the selected texture parameters discard the texture components unrelated to skid resistance performance and reflect the distribution of the pavement texture and the skid resistance performance well.

A strategy to prepare high Tg and low CTE solder resist using alkali-soluble photosensitive polyimide

Photosensitive Solder resist (SR) materials require a high glass transition temperature (Tg > 170 °C) and a coefficient of thermal expansion matching that of copper (CTE≈17 ppm/°C) to meet the demands of manufacturing processes and application reliability. However, the commonly used epoxy resin in SR materials exhibits insufficient mechanical and thermal properties, failing to meet these requirements adequately. To address this issue, alkali-soluble photosensitive poly (amic ester) (PAE) materials were synthesized. By grafting a low-temperature curing accelerator, 6-([1,1′-biphenyl]–4-yl)–4-chloroquinoline (NQL), onto the hydroxyl groups of the PAE, the resultant grafted PAE resin was blended with an alkali-soluble photosensitive modified epoxy resin (APE) to enhance the mechanical and thermal properties of the SR composite. Research indicates that due to the low-temperature curing effect and electrostatic interactions of NQL, SR-2 (with a 10% PAE addition) exhibits a Tg of 183 °C and a CTE of 16 ppm/°C, while SR-3 (with a 30% PAE addition) achieves a Tg of 204 °C and a CTE of 20 ppm/°C. Furthermore, with the PAE addition of 5%, the lithography quality of SR is enhanced, enabling SR-1 to achieve a pattern resolution of up to 40 μm. The modification method involving PSPI blending has been shown to enhance the thermal stability, dimensional stability, and lithographic performance of SR, indicating significant potential applications in solder resist materials.

Extreme impact enhancement of epoxy using a sulfosuccinate-based anionic surfactant as a new modifier

In this study, disodium lauryl ether sulfosuccinate (DSL or sulfosuccinate), a commercially available anionic surfactant, was employed for the first time as an impact modifier for epoxy resin. Introducing only 5 phr of DLS into the epoxy matrix resulted in a remarkable 189% enhancement in impact strength without a significant detrimental effect on its tensile strength. According to FTIR and SEM results, the strong interaction between the modifier DLS and the epoxy matrix, along with the formation of a nano-blend morphology with a wide interfacial area, can be proposed as two key factors contributing to the remarkable enhancement in impact strength of epoxy/DLS hybrid. The thermal stability of the epoxy was not significantly affected by the incorporation of DLS up to 8 phr. The epoxy/DLS hybrid exhibited lower chemical stability against organic solvents, while the hybrid resistance to acids and bases remained largely unchanged. Based on the obtained results, DLS can be considered as a promising impact modifier for epoxy systems.

Preparation and characterization of waterborne silicone modified epoxy resin

AbstractSilicone modified epoxy resin was synthesized with bisphenol‐A epoxy resin (E51) and dimethyldichlorosilane (DMDCS), and waterborne silicone modified epoxy resin (WSER) was prepared. The WSER emulsion exhibited good stability with particle size ranging from 0.5 to 2 μm. Compared with waterborne epoxy resin (WER) cured film, the water resistance of WSER cured film was enhanced by the excellent hydrophobicity of DMDCS. Furthermore, the WSER cured film with 6% DMDCS showed better mechanical properties, and Shore hardness and tensile strength of that were greatly increased. Moreover, the corrosion resistance and ultraviolet (UV) aging resistance of WSER cured film were obviously improved compared to WER cured film.Highlights Dimethyldichlorosilane (DMDCS) was employed to modify bisphenol‐A epoxy resin (E51). Waterborne silicone modified epoxy resin (WSER) was prepared by phase inversion method. WSER cured films did better than WER cured film in water resistance and mechanical properties. WSER cured films showed good corrosion resistance and ultraviolet aging resistance.

A novel efficient flame-retardant curing agent for epoxy resin based on P-N synergistic effect: Bio-based benzoxazine phosphate ester

Most epoxy resins on the market have low thermal stability and flammable defects. As a potential curing agent for epoxy resin, polybenzoxazine (PBz) can effectively improve the thermal properties of the resin due to its low heat release capacity (HRC) and rigid aromatic ring support, and its raw materials can be derived from renewable resources. Here, we have successfully developed a molecular design strategy to obtain a trifunctional benzoxazine monomer with phosphate ester. Firstly, guaiacol-ethanolamine benzoxazine monomer (GE) was synthesized by Mannich condensation using guaiacol and ethanolamine as raw materials. Then trifunctional benzoxazine phosphate ester (TBP) was synthesized by the nucleophilic reaction of GE with phosphorus oxychloride. Finally, the epoxy resin DGEBA was cured by TBP to obtain a PBz modified epoxy resin (EP-TBP polymer) with Tg of 113.7 °C and char yield of 37.4 %. Due to the introduction of TBP rich in phosphorus and nitrogen, it releases phosphorus radicals and nitrogen-containing inert gases during combustion, which leads to quenching effect and dilution effect. In addition, TBP can also promote the dehydration and dehydrogenation of the polymer and accelerate the formation of the aromatic hybrid char layer. Therefore, the THR of TBP modified epoxy resin is 49.3 % lower than that of epoxy resin without TBP, and the char yield is 47 times higher. And when the phosphorus content is 1.76 %, the flame-retardant grade can reach V-0. In addition, the introduction of TBP also enhanced the mechanical properties, adhesion properties and hydrophobicity properties of the polymer. It is worth mentioning that under alkaline conditions, the phosphate ester in the structure of EP-TBP polymer will undergo ammonolysis reaction with ethanolamine, and the resulting oligomers will be dissolved in it, thereby achieving rapid degradation of EP-TBP polymer. This work is to develop a high-performance multifunctional epoxy resin flame retardant curing agent based on renewable raw materials, and provide important insights for the subsequent development of halogen-free bio-based PBz flame retardant materials.

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.

A novel strategy utilizing oxidation states of phosphorus for designing efficient phosphorus-containing flame retardants and its performance in epoxy resins

The oxidation state of phosphorus has a great influence on the flame retardant action of its flame retardants. In this study, a reactive phosphorus-containing flame retardant (POG-DOPO) with both low and high phosphorus oxidation states is synthesised and incorporated into epoxy resin. The results show that the part in high oxidation state act mainly in the condensed phase and the part in low oxidation state act mainly in the gas phase. Furthermore, the flame retardant exhibits a synergistic flame retardant effect, resulting in a higher flame retardant efficiency than that of flame retardants with a single phosphorus oxidation state. Compared with unmodified epoxy resin, the peak heat release rate, total heat release rate and total smoke release of POG-DOPO modified epoxy resin with only 3wt% phosphorus are reduced by 70.9%, 51.2% and 55.7%, respectively. Its LOI increases to 31.8% and vertical combustion test achieves UL-94 V-0 rating. This study provides a strategy for the structural design of efficient phosphorus-based flame retardants.

Molecular dynamics simulations of the micro mechanism of functionalized SiO2 nanoparticles and carbon nanotubes modified epoxy resin adhesives

AbstractThe bonding interface of carbon‐fiber‐reinforced polymer (CFRP)‐reinforced steel structure is a weak part, and nanomaterial‐modified adhesives are expected to improve its comprehensive performance. This paper investigates the micro‐modification mechanisms of nanomaterials on epoxy resin adhesives using molecular dynamics simulation method. It explores how the functionalized nano SiO2 and carbon nanotubes affects the thermal and mechanical properties of the epoxy resin adhesive. The models established using Materials Studio software include the pure epoxy resin adhesive model (EP) with varying degrees of crosslinking, the functionalized nano‐SiO2‐modified epoxy resin adhesive model (EP + SiO2/OH), the single‐walled carbon nanotube‐modified epoxy resin adhesive model (EP + SWNT), and the synergistic enhancements model of the epoxy resin adhesive with nano‐SiO2 and carbon nanotubes (EP + SWNT + SiO2/OH). Based on the aforementioned models, the Forcite module is used to calculate the free volume, glass transition temperature and mechanical properties of the adhesive. The results show that the degree of crosslinking effects significantly the mechanical performance of epoxy resin adhesive. A high degree of crosslinking restricts the movement of the molecular chain, enhancing the strength of the epoxy resin adhesive. Furthermore, the trend of the mechanical and thermal properties of the four models remains constant with the rise of temperature, and the properties decrease most significantly in the range of the glass transition temperature. Moreover, the epoxy resin adhesive doped with nanomaterials exhibits varying degrees of enhancement in mechanical and thermal properties. The epoxy resin adhesive reinforced with functionalized nano‐SiO2 and carbon nanotubes exhibits better properties compared to those with a single nanomaterial.Highlights The micro‐modification mechanism is revealed for nanomaterial modified epoxy resin adhesive. The degree of crosslinking effects significantly the mechanical performance of epoxy resin adhesive. The epoxy resin adhesive doped with nanomaterials exhibits varying degrees of enhancement in mechanical and thermal properties.

Study on the UV aging resistance of ZnO‐modified epoxy resin by experiments and MD simulation

AbstractThis study investigates the impact of zinc oxide nanoparticles on epoxy resin systems and the ultraviolet (UV) aging resistance of modified epoxy resin composites using molecular dynamics (MD) simulations and experimental methods. Initially, various epoxy resin cross‐linking models are established through MD simulations to understand the influence of different nano ZnO contents on resin modification, further validated by experiments. Subsequently, the UV radiation resistance of nano ZnO–epoxy resin composites is assessed by subjecting them to high‐intensity UV radiation equivalent to 3 years of natural environmental conditions, analyzing changes in tensile properties, impact performance, hardness, and glass transition temperature of epoxy resin before and after UV radiation exposure. The findings suggest that the addition of nano zinc oxide reduces the impact of UV radiation on epoxy resin, with optimal UV radiation resistance observed at a nano zinc oxide mass fraction of 0.3 wt%.

Development of a Superhydrophobic Protection Mechanism and Coating Materials for Cement Concrete Surfaces.

In order to further enhance the erosion resistance of cement concrete pavement materials, this study constructed an apparent rough hydrophobic structure layer by spraying a micro-nano substrate coating on the surface layer of the cement concrete pavement. This was followed by a secondary spray of a hydroxy-silicone oil-modified epoxy resin and a low surface energy-modified substance paste, which combine to form a superhydrophobic coating. The hydrophobic mechanism of the coating was then analysed. Firstly, the effects of different types and ratios of micro-nano substrates on the apparent morphology and hydrophobic performance of the rough structure layer were explored through contact angle testing and scanning electron microscopy (SEM). Subsequently, Fourier transform infrared spectroscopy and permeation gel chromatography were employed to ascertain the optimal modification ratio, temperature, and reaction mechanism of hydroxy-silicone oil with E51 type epoxy resin. Additionally, the mechanical properties of the modified epoxy resin-low surface energy-modified substance paste were evaluated through tensile tests. Finally, the erosion resistance of the superhydrophobic coating was tested under a range of conditions, including acidic, alkaline, de-icer, UV ageing, freeze-thaw cycles and wet wheel wear. The results demonstrate that relying solely on the rough structure of the concrete surface makes it challenging to achieve superhydrophobic performance. A rough structure layer constructed with diamond micropowder and hydrophobic nano-silica is less prone to cracking and can form more "air chamber" structures on the surface, with better wear resistance and hydrophobic performance. The ring-opening reaction products that occur during the preparation of modified epoxy resin will severely affect its mechanical strength after curing. Controlling the reaction temperature and reactant ratio can effectively push the modification reaction of epoxy resin through dehydration condensation, which produces more grafted polymer. It is noteworthy that the grafted polymer content is positively correlated with the hydrophobicity of the modified epoxy resin. The superhydrophobic coating exhibited enhanced erosion resistance (based on hydrochloric acid), UV ageing resistance, abrasion resistance, and freeze-thaw damage resistance to de-icers by 19.41%, 18.36%, 43.17% and 87.47%, respectively, in comparison to the conventional silane-based surface treatment.

Comprehensive performance evaluation of HGM hybrid modified resins: Excellent high resistivity terahertz shielding and impact energy absorption properties

AbstractThe development of electronic fuze has placed higher demands on encapsulation resins, which are required to provide not only insulation and protection, but also higher impact resistance and good electromagnetic shielding performance. A new composite material consisting of hollow glass microspheres (HGM) and modified epoxy resin was developed. This material exhibits significant electromagnetic shielding capabilities for terahertz (THz) waves, as well as superior impact energy absorption properties. Bisphenol A‐type epoxy resin (E‐44) was modified using Al(OH)3, red phosphorus, carbon black, and SiO2, and the material properties were optimized by adjusting the HGM content. The electromagnetic shielding effectiveness and impact energy absorption of the composite material in the THz band were comprehensively tested using THz time‐domain spectroscopy and split Hopkinson pressure bar testing systems. Additionally, a comprehensive evaluation of the mechanical and dielectric properties, thermal conductivity, and thermal stability of the material was conducted. The results showed that the electromagnetic shielding effect of 60 vol.% HGM hybrid‐modified resins was the best, reaching 43.78 dB. The 20 vol.% HGM hybrid‐modified resins not only has a specific absorption energy of 18.51 J/cm3, but also has the best overall performance. This work has advanced the design and development of multifunctional and impact‐resistant potting epoxy resins.

Modified Epoxy Resin on the Burning Behavior and Mechanical Properties of Aramid Fiber Composite.

Aramid fiber/epoxy resin (AF/EP) composite has been heavily used as an impact protection material due to its excellent mechanical properties and lightweight merits. Meanwhile, it is also necessary to concern the flammability of matrix resin and the wick effect of aramid fiber, which would constitute a fire risk in harsh environments. In this work, a multifunctional flame-retardant modifier (EAD) was incorporated into the AF/EP system to improve the flame retardation. The addition of 5 wt% EAD made the AF/EP composite exhibit a high limiting oxygen index (LOI) value of 37.5%, self-extinguishment, as well as decreased total heat release and total smoke release. The results from thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) demonstrated that the treated composites maintained good thermal stability. Due to the combined action of covalent and noncovalent bonds in the matrix-rich region, the interfacial bonding improved, which endowed AF/EP composite with strengthening and toughening effects. Compared with the control sample AF/EP, the tensile strength and ballistic parameter (V50) of the sample with 5 wt% EAD increased by 17% and 10%, accompanied with ductile failure mode. Furthermore, the flame-retardant mechanism was obtained by analyzing the actions in condensed and gaseous phases. Thanks to good compatibility and interfacial adhesion, the incorporation of EAD solved the inconsistent issue between flame retardancy and mechanical properties, which further expanded the application of AF/EP composite in the protection field.

Co-enhancement of toughness and strength of room-temperature curing epoxy adhesive derived from hydroxyl-terminated polybutadiene based polyurethane resin

Incorporation of flexible chains into epoxy adhesives facilitates toughening but usually poses an opposite effect on strengthening. Herein, by combining hydroxyl-terminated polybutadiene (HTPB) with polyether diol as soft chains, epoxy-terminated polyurethane (EHTPU) is synthesized, a strategy balancing strengthening and toughening is developed. The use of polyolefin soft chains substantially contributes to sea-island phase separation for maintaining low glass transition temperature (Tg) and high strength and toughness simultaneously. Specifically, the modified epoxy adhesive has seen a significant increase in shear strength to 19.75 MPa, tensile strength to 48.25 MPa and fracture toughness to 3.63 MPa·m1/2, with increment of 914 %, 268 %, and 149 %, respectively, compared to neat epoxy. Moreover, even under low temperatures of -45 °C, the modified epoxy resin can still maintain a high shear strength, demonstrating excellent low-temperature adhesion performance. At the same time, the incorporation of EHTPU does not significantly affect the overall thermal stability of the epoxy resin, meeting the requirements for stability in practical applications. It is worth mentioning that the adhesive exhibit excellent bonding performance under different environments and substrates, indicating that this composite material has broad application prospects in various industrial fields. These findings provide valuable insights into optimizing the performance of epoxy resins by controlling the introduction of specific modifiers and offer new ideas and methods for the development of room temperature curing epoxy resin adhesives.