Mechanical Properties Of Epoxy Resin Research Articles

Effect of Phosphorus‐Containing Silane Coupling Agents Modified Ammonium Polyphosphate on the Flame Retardancy and Mechanical Properties of Epoxy Resin

Effect of Phosphorus‐Containing Silane Coupling Agents Modified Ammonium Polyphosphate on the Flame Retardancy and Mechanical Properties of Epoxy Resin

Investigation on the Optimized Curing Cycle of Epoxy Resin for Enhancing Thermal and Mechanical Properties of Glass Fiber Reinforced Plastic Applications

Abstract Understanding the thermal and mechanical behavior of epoxy resins under varying curing conditions is critical for optimizing the performance of fiber-reinforced plastics (FRP) in industrial applications. This study investigates the influence of curing temperature and post-curing stages on key epoxy properties, including heat distortion temperature (HDT), glass transition temperature (Tg), and crosslinking density, and evaluates their impact on the performance of glass fiber-reinforced plastics (GFRP). Two epoxy resin systems with distinct Tg were examined using differential scanning calorimetry (DSC) to asses curing behavior and dynamic mechanical analysis (DMA) to evaluate HDT, Tg, and crosslinking density. As curing temperature increased, the 1050/1056 epoxy resin system exhibited improvements in HDT, Tg, and crosslinking density (up to 69 ℃, 78.3 ℃, and 1674.6 mol/m3 respectively) with further enhancements observed after post-curing. Similarly, under the same conditions, the 1800/1805 epoxy resin system demonstrated changed value (up to 97 ℃, 108.9 ℃, 2287.6 mol/m3 respectively) with further improvements observed after post-curing. These changes in properties were validated through GFRP performance metrics, with tensile strength reaching up to 558.5 MP and shore A hardness up to 92.5 under optimized curing conditions. These findings reveal how curing conditions significantly affect both the thermal and mechanical properties of epoxy and epoxy-based composites, offering valuable insights for tailoring performance in applications such as molds, structural components, and high-precision industrial systems.

A novel DOPO-AS/M(OH)(OCH3) organic/inorganic nanohybrid for enhancing the flame retardancy and mechanical properties of epoxy

A novel DOPO-AS/M(OH)(OCH3) organic/inorganic nanohybrid for enhancing the flame retardancy and mechanical properties of epoxy

Preparation of multi-hydroxy chitosan derivative and its synergistic effect on fire performance and mechanical properties of epoxy resin

Preparation of multi-hydroxy chitosan derivative and its synergistic effect on fire performance and mechanical properties of epoxy resin

Effects of graphene nanoplatelets dispersion on the mechanical properties of epoxy resin and carbon fiber laminated composites

Graphene-related materials (GRM) show great potential as reinforcement in polymeric matrices, offering enhanced physicochemical and mechanical properties. In the aerospace sector, reinforced composites are increasingly used for their superior mechanical attributes and design flexibility. Incorporating graphene nanoplatelets (GNP) into epoxy resin (ER) is a promising approach to enhance the resin’s fracture toughness. The effectiveness of these nanocomposites depends heavily on the dispersion of nanoparticles within the matrix. Therefore, this work aimed to produce nanocomposites based on ER and GNP by evaluating different mixing processes and assessing the influence of GNP content on the resin´s properties, to determine the optimal conditions for the incorporation GNP-ER as matrix to produce hybrid laminated composites with carbon fiber fabric. Characterization of GNP powder revealed its organization in regular nanoplatelet stacking patterns, exhibiting multilayers with few defects. The characterization of nanocomposites showed that ultrasonication dispersion improved the dispersion of GNP in the resin, reducing agglomerates and increasing homogeneity. Tensile tests demonstrated that ultrasonication led to an increase of approximately 14% in the ultimate tensile strength (UTS) and up to 46% in the deformation at the break of the nanocomposites. Carbon fibers/GNP-ER composites were produced by the hand lay-up process and exhibited a decrease in UTS with the addition of GNP, suggesting that GNP may have acted as stress concentrators or even modified the viscosity of the matrix, which may have hindered the matrix´s ability to penetrate the carbon fabric, thereby reducing the mechanical properties.

Synthesis of a Novel Derivative Containing Phosphaphenanthrene and Phenyl Propargyl Ether Groups Toward Enhanced Flame Retardance and Mechanical Properties of Epoxy Resin

ABSTRACTTo achieve effective flame retardancy and improved toughness in epoxy resin (EP) without compromising strength and modulus, a new derivative containing phosphaphenanthrene and phenyl propyl ether groups (HPMD) has been developed and used as an additive. The structure of HPMD has been fully characterized, and the properties of HPMD and modified EP have been thoroughly studied. The phenyl propyl ether group in HPMD can undergo Claisen type rearrangement to form benzopyran during heat treatment and subsequently polymerize by curing via the CC bond in the benzopyran. The unique rigid and flexible structures of HPMD allow it to disperse in the EP matrix through melting. Dynamic mechanical analysis suggests that HPMD has a high degree of interpenetration in the EP matrix, resulting in a single‐phase structure for the epoxy resins containing HPMD. Notably, incorporating only 4 wt% HPMD content into the polymer matrix yields a flame‐retarded, toughened, and strengthened EP. EP containing 4 wt% HPMD (EP4; phosphorus content of only 0.33%) displays a limiting oxygen index value of 31.1% and exhibits a UL94 V‐0 rating. Compared with that of EP, the combustion of EP4 exhibits a decrease in the peak of heat release rate, maximum average heat rate emission, average heat release rate, and total heat release, along with an increase in the char yield, further indicating that HPMD effectively retards the combustion of EP. Moreover, EP4 displays improvements in tensile strength, elongation at break, flexural strength, flexural modulus, and impact strength of 18.4%, 9.7%, 14.9%, 19.1%, and 26.7%, respectively, compared with unmodified EP. Analysis of HPMD's flame‐retardant action suggests that it exhibits flame‐retardant activity simultaneously in the gas and condensed phases. Significant progress has been demonstrated toward the development of a meltable epoxy resin additive that combines flame‐retardant, toughening, and strengthening functions while avoiding phase separation from the epoxy resin.

Constructing a novel controllable interface structure through the anchoring effect of α-cyclodextrin at cryogenics to enhance and toughen the mechanical properties of epoxy resin

The fracture toughness of an epoxy resin (EP) often decreases under cryogenic conditions, primarily because of performance degradation caused by molecular chain freezing. In this study, a high-tensile-strength and high-fracture-toughness EP-based nanocomposite (EP/CPN–CuO) was synthesized using α-cyclodextrin (α-CD) for anchoring. The α-CD immobilized flexible linear polymers grafted onto the surface of CuO nanorods (NRs) with negative thermal expansion within a novel interface with the EP. The composite exhibited enhanced mechanical properties because the α-CD effectively hindered the curling of polymer chain segments and considerably improved the chemical bonding between the EP and CuO. Experimental results demonstrated the enhanced mechanical performance of EP/CPN–CuO under cryogenic conditions compared with that of other materials reported in the literature. EP/CPN-CuO-2.0 exhibited a tensile strength of 111.40 MPa, a Young’s modulus of 6.67 GPa, and a fracture toughness of 2.69 MPa·m1/2, marking increases of 67.4 %, 10.8 %, and 100.7 % compared to pure EP. Thus, this study effectively resolved the trade-off between the tensile strength and fracture toughness of an EP under cryogenic conditions, providing a new pathway for the widespread application of EPs in cryogenic environments.

Retraction of “Effects of Incorporating Silanized Nanoclay on the Barrier, Hydrophobic and Mechanical Properties of Epoxy Resin in Chloride Environment”

Retraction of “Effects of Incorporating Silanized Nanoclay on the Barrier, Hydrophobic and Mechanical Properties of Epoxy Resin in Chloride Environment”

Influence of network heterogeneity on the nanoscale mechanical properties of epoxy resins

AbstractThe presence of structural heterogeneities in glassy epoxy networks can strongly affect the adhesiveness and mechanical properties of epoxy-based materials. Recent studies have demonstrated that the size and architecture of structural heterogeneities can be monitored during the curing process, thus providing an effective way to control multiple physical properties of epoxy resins. However, because the size of heterogeneities is believed to be at the nanoscale, obtaining insights into the direct correlation between the local behavior of heterogeneities and the preparation conditions remains challenging. Here, we combine two recently developed atomic force microscopy (AFM)-based methods, bimodal amplitude and frequency modulation and nanoscale dynamic mechanical analysis (nDMA), to directly visualize and quantify the nanoscale mechanical properties of epoxy resins obtained via different curing conditions. Our AFM maps clearly show a correlation between the curing conditions and the heterogeneous behavior of the resulting epoxy networks, which is in excellent agreement with those predicted from macroscopic measurements. Notably, our nDMA results revealed a relationship between network heterogeneity and the glass transition behavior of the epoxy resins.

Graphene nanoplatelets inclusion effects on mechanical properties of the hybrid kevlar/basalt fiber reinforced epoxy composites

Abstract This study experimentally examined the effects of hybridizing Basalt and Kevlar fibers on the tensile, and flexural performance of composite materials with the inclusion of Graphene nanoplatelets (GnPs). Various hybrid composites were fabricated, incorporating Basalt and Kevlar fiber composites with 1, 3, and 5 wt% of GnPs as well as without GnPs, as well as hybrid composites featuring different weight content of GnPs reinforcing with with Basalt and Kevlar fibers. The findings of this study indicated that the mechanical properties of epoxy resin were significantly enhanced through the synergistic effects of hybridization with basalt and Kevlar fibers, as well as the incorporation of graphene nanoplatelets (GnPs). The significant increasing in mechanical properties was attributed to the strong interfacial interactions between the epoxy matrix and GnPs nanoparticles, which facilitate improved stress transfer from the fibers and nanoparticles to the matrix. This enhanced stress transfer capability accounts for the superior resistance to fiber pullout observed in composites reinforced with GnPs compared to those without nanoparticles.

Improvement of fame retardancy and thermal stability of epoxy composites by modifying salen-based polyphosphazene microspheres with Co-based metal organic frameworks

A functionalized cross-linked polyphosphazenes microsphere (Salen-PZN-Ni@Co-MOF) was fabricated by enveloping Salen-Ni-based polyphosphazenes (Salen-PZN-Ni) with a type of hybrid flame retardant (Co-MOF) to enhance the flame retardant, smoke suppression properties and mechanical properties of epoxy (EP) composites. Thermogravimetric analysis indicated that the incorporation of Salen-PZN-Ni@Co-MOF significantly enhanced the thermal stability of the EP composites. The existence of Salen-PZN-Ni@Co-MOF enhanced both the vertical burning rating and resulted in a higher limiting oxygen index. The addition of 5 wt% Salen-PZN-Ni@Co-MOF conspicuously improved the fire safety of EP, as evidenced by the results of the cone calorimeter. For instance, the peak heat release rate and total heat release rate of the EP composites were decreased by 25.3% and 44.97%, respectively. In addition, the incorporation of Salen-PZN-Ni@Co-MOF significantly inhibited the generation of toxic carbon monoxide and other volatile compounds. Furthermore, a synergistic effect between Salen-PZN-Ni and Co-MOF was observed. The proposed flame retardant mechanism of Salen-PZN-Ni@Co-MOF is attributed to the synergistic catalytic carbonization effect and the formation of thermally stable components. Consequently, enhanced fire safety in EP composites is achieved through the synergistic interaction among various components (nickel and Co-MOF) with polyphosphazene microspheres. Meanwhile, the excellent compatibility between Salen-PZN-Ni@Co-MOF and EP enhances the mechanical properties of EP composites.

Investigation the potential of imide covalent organic frameworks (COFs) to enhance the toughness and mechanical properties of epoxy resin

The inherent brittleness of epoxy resins poses a significant challenge to the mechanical performance of epoxy-based composites. Aiming to overcome this limitation, the integration of nanomaterials has been proposed as an innovative strategy to enhance toughness and mechanical properties. Among these materials, covalent organic frameworks (COFs) stand out due to their crystalline structure and potential for diverse applications. This study focused on the synthesis of imide-based COFs and it characterized their crystalline structure and surface morphology using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images. To evaluate the mechanical and thermal properties, epoxy composites containing 0.1–0.5 wt% COFs were tested. The integration of COFs resulted in substantial improvements in toughness and thermal stability. Notably, fracture energy increased by 318 %, modulus by 83 %, and tensile strength by 120.5 % at the optimal COF loading of 0.25 wt%. These findings highlight the effectiveness of COFs in significantly enhancing not only toughness but also overall mechanical performance, including tensile strength and modulus, of epoxy composites.

Novel Aryl Phosphate for Improving Fire Safety and Mechanical Properties of Epoxy Resins.

Epoxy resins (EPs) are highly flammable, and traditional flame retardant modifications often lead to a significant reduction in their mechanical performance, limiting their applications in aerospace and electrical and electronic fields. In this study, a novel flame retardant, bis(4-(((diphenylphosphoryl)oxy)methyl)phenyl)phenyl phosphate (DMP), was successfully prepared and introduced into the EP matrix. When the addition of DMP was 9 wt%, the EP/9 wt% DMP thermosets passed the UL-94 V-0 rating, and their LOI was increased from 24.5% of EP to 35.0%. With the introduction of DMP, the phosphoric acid compounds from the decomposition of DMP promoted the dehydration and charring of the EP matrix, and the compact, dense char layer effectively exerted the shielding effect in the condensed phase. Meanwhile, the produced phosphorus-containing radicals played a quenching effect in the gas phase. As a result, the peak heat release rate (PHRR) and total heat release (THR) of EP/9 wt% DMP were reduced by 68.9% and 18.1% compared to pure EP. In addition, the polyaromatic structure of DMP had good compatibility with the EP matrix, and the tensile strength, flexural strength and impact strength of EP/9 wt% DMP were enhanced by 116.38%, 17.84% and 59.11% in comparison with that of pure EP. This study is valuable for expanding the application of flame-retardant EP/DMP thermosets in emerging fields.

Influence of substrate temperature on plasma-enhanced chemical vapor deposition to improve the surface flashover performance of epoxy resin

Abstract Epoxy resin composites are widely used as insulating and supporting materials in high-voltage power systems due to their excellent mechanical and electrical properties. However, long-term operation under high-voltage direct current induces surface flashover. Plasma enhanced chemical vapor deposition (PECVD) has been shown to effectively improve the surface insulation properties of epoxy resin. However, the influence of substrate temperature on the film composition, stress, morphology, and surface flashover performance remains unclear. This study uses PECVD to treat epoxy resin, enhancing its surface flashover performance. Tetraethoxysilane is used as the precursor to deposit nano-scale SiO x films on the epoxy resin surface. The effects of different substrate temperatures on the surface flashover voltage, physicochemical properties, and mechanical properties of epoxy resin are characterized. The results show that the surface flashover voltage increases and then saturates with increasing substrate temperature, improving by 27.4% at 60 °C compared to untreated samples. The surface roughness of epoxy resin decreases after plasma deposition, while highly oxidized silicon-containing functional groups are introduced. When the substrate temperature increases from 20 °C to 60 °C, the interfacial bonding strength improves by 25.9%. This study provides a simple, efficient, and controllable method to enhance the surface flashover performance of epoxy resin, promoting the application of this technology in engineering practice.

MOF-derived strategy for in-situ assembly of nickel phyllosilicate nanoflowers: Enhancing smoke suppression, flame retardancy and mechanical properties of epoxy resins

Epoxy resin (EP) is a highly versatile polymer extensively used in high-end applications, including aerospace components, electronics encapsulation and adhesives. To custom-design flame retardant materials for high-performance epoxy resins, a MOF-derived zeolitic imidazolate framework-8@nickel phyllosilicate (ZIF@Ni-PS) was synthesized through the in-situ assembly of nickel phyllosilicate nanoflowers. The results showed that the smoke suppression, flame retardancy, and mechanical properties of the EP composites containing 5 wt% ZIF@Ni-PS were significantly enhanced. The peak heat release rate (pHRR) and the peak smoke production rate (pSPR) were reduced by 33.2 % and 12.7 %, respectively. The presence of ZIF@Ni-PS promoted the formation of a dense, high-quality carbon layer that isolated heat and oxygen transfer, effectively reducing heat release during combustion and suppressing smoke generation. Furthermore, the imidazole ring and Zn ions on the surface of ZIF@Ni-PS facilitated the formation of coordination and hydrogen bonds with the epoxy (EP), thereby enhancing the dispersion, compatibility, and mechanical properties of the epoxy resin matrix. This study presents a straightforward preparation method for high-performance EP composites, providing a novel pathway for EP research.

Recent studies on multiscale modeling of carbon fiber-reinforced composites

Multiscale modeling has garnered attention as an analytical method for investigating the mechanical behavior of composite materials. This paper introduces a comprehensive multiscale modeling approach developed by the authors’ group, which enables comprehensive analysis of the material properties from the atomic-scale reaction characteristics to laminate-scale fracture analysis; an overview of relevant literature is included as well. First, the methods of analysis at the atomic/molecular, microscopic, and mesoscopic scales are separately explained. Finally, a multiscale modeling approach that integrates these models and bridges the gaps between the scales is presented. The multiscale model is used to predict the fracture behavior of carbon fiber-reinforced composites based on the mechanical properties of epoxy resin.

Sustainable lignin-based high-efficiency flame-retardant epoxy resins with excellent mechanical properties

As an abundant natural aromatic polymer, how to realize the high-value utilization of lignin (LA) is still a difficult problem. Herein, a sustainable flame retardant (LA@APP) was synthesized through hydrogen bonding interactions between LA and ammonium polyphosphate (APP), then flame retarded alone epoxy resin (EP/LA@APP). With loading of 6 wt% LA@APP, the LOI of EP/LA@APP6 rose to 27.9 % and achieved UL-94 V0 rating. Meanwhile, EP/LA@APP6 presented a 63.5 % reduction in peak of heat release rate (pHRR) and an 51.3 % decrease in peak of smoke production rate (pSPR). LA@APP could promote the EP composites to form the denser and more continuous expanded charring residuals than APP during the combustion process, effectively shielding the underlying epoxy substrate and thus enhancing fire safety. Additionally, the shell layer of LA@APP, abundant in hydroxyl groups and methoxy groups, effectively improved the compatibility and interfacial interaction with EP. Therefore, the tensile, flexural and impact strength of EP/LA@APP6 reached 50.8 MPa, 86.1 MPa and 7.81 kJ/m2, higher than those of pure EP at 48.3 MPa, 81.5 MPa and 7.45 kJ/m2. This flame retardant with simultaneously enhanced fire safety and mechanical properties of epoxy resin was expected to realize the high-level utilization of lignin.

Influence of different composite curing agents on the rapid curing characteristics and mechanical performance of epoxy resins

To address the need for rapid in situ plugging and repair of hydraulic machinery and chemical pipelines and to resolve the issue that a single curing agent cannot simultaneously achieve rapid curing and excellent mechanical properties in epoxy resin systems, this study explores the use of composite curing agents. In particular, effective formulations are designed for mixing fast and slow curing agents, studying their effects on the curing behavior, curing quality, and mechanical properties of epoxy resins and elucidating their influence mechanisms. The results indicate that three resin systems meet the requirements for rapid curing (curing time within 30 min): 4A6B/EP, 2A8B/EP, and 0A10B/EP. Among them, 4A6B/EP exhibits the best curing quality and mechanical properties. In particular, 4A6B/EP demonstrates the lowest values of curing shrinkage rate, internal curing stress, average pore size, porosity, and cumulative pore volume. Its low internal stress and low defects reduce the stress concentration, while more efficient deflection and branching of internal cracks enhance its deformation resistance. Consequently, 4A6B/EP shows the highest microhardness, fracture toughness, tensile strength, Young’s modulus, and elongation after fracture. Based on the comprehensive evaluation of rapid curing characteristics and mechanical properties, the 4A6B/EP system offers the best overall performance. Therefore, it is recommended as the preferred resin system for rapid plugging and repair of composite materials, providing a theoretical basis and technical support for boosting the application of epoxy resin composite materials in high-tech fields.

Ionic Liquid-Modified Copper for the Enhanced Thermal Conductivity and Mechanical Properties of Epoxy Resin/Expanded Graphite Composites.

In this study, diglycidylether of bisphenol A (DGEBA)/expanded graphite (EG)/copper (Cu) powder composites with high thermal conductivity were prepared for use as thermal interface materials. To construct an excellent thermally conductive network, the Cu surface was modified using the ionic liquid 1-ethyl-3-methyl imidazolium dicyanamide. In addition, the effect of the Cu content on the thermal conductivity, thermal stability, flexural properties, impact strength, and morphologies of the DGEBA/EG/Cu composites was investigated. The results indicated that the addition of 10 wt % Cu increased the thermal conductivity of the composites from 7.35 to 9.86 W/(m·K). Conversely, the thermal stability of the composites decreased with the addition of Cu. The flexural strength and impact strength of the composites increased from 27.9 MPa and 0.81 kJ/m2 to 39.6 MPa and 0.96 kJ/m2, respectively, as the Cu content increased from 0 to 10 wt %. Moreover, the flexural modulus of the composites increased from 9632 to 11,309 MPa with the addition of 10 wt % Cu. Scanning electron microscopy analysis of the DGEBA/EG/Cu composites revealed sheet-shaped blocks with numerous microcracks on the fracture surfaces.

Research progress on high-temperature properties of carbon fiber reinforced polymer composites for cables

Carbon fiber reinforced polymer composites (CFRP) cable has advantages of lightweight, high strength, and excellent durability, providing a new materials for cables and bringing out potential breakthrough in spanning capacity of structures. At present, CFRP cable has already been applied in some engineering bridges. The fire resistance performance of CFRP cable is critical for ensuring structure safety when suffering accidental fire disaster, and clarifying mechanical performance deterioration and failure mechanism of CFRP cable at elevated temperature is fundamental for research of its fire resistance. This paper summarizes current research progress on high-temperature properties of CFRP cable from two levels, including epoxy resin matrix and CFRP composites. Firstly, at resin matrix level, mechanical properties of epoxy resin and its degradation at elevated temperatures are reviewed and analysed, and potential ways to improve high-temperature performance of epoxy resin are suggested. Secondly, at CFRP composites level, high-temperature properties test methods and mechanical performance of CFRP composites in longitudinal direction and transverse direction at elevated temperatures are summarized and discussed. In addition, research shortage of high-temperature properties of CFRP cable is summarized, and corresponding further research is recommended.