Thermal Properties Of Epoxy Resin Research Articles

Effect of Mechanically Exfoliated Graphite Flakes on Morphological, Mechanical, and Thermal Properties of Epoxy

Carbon-reinforced polymer composites form an important category of advanced materials, and there is an increasing demand to enhance their performance using more convenient and scalable processes at low costs. In the present study, graphitic flakes were prepared by the mechanical exfoliation of synthetic graphite electrodes and utilized as an abundant and potentially low-cost filler to fabricate epoxy-based composites with different additive ratios of 1–10 wt.%. The morphological, structural, thermal, and mechanical properties of these composites were investigated. It was found that the thermal conductivity of the composites increases by adding graphite, and this increase mainly depends on the ratio of the graphite additive. The addition of graphite was found to have a diverse effect on the mechanical properties of the composites: the tensile strength of the composites decreases with the addition of graphite, whilst their compressive strength and elastic modulus are enhanced. The results demonstrate that incorporating 5 wt% of commercially available graphite into epoxy not only raises the thermal conductivity of the material from 0.223 to 0.485 W/m·K, but also enhances its compressive strength from 66 MPa to 72 MPa. The diverse influence of graphite provides opportunities to prepare epoxy composites with desirable properties for different applications.

Mechanical and Thermal Properties of Epoxy Resin upon Addition of Low-Viscosity Modifier.

Thermoset-based polymer composites containing functional fillers are promising materials for a variety of applications, such as in the aerospace and medical fields. However, the resin viscosity is often unsuitably high and thus impedes a successful filler dispersion in the matrix. This challenge can be overcome by incorporating suitable low-viscosity modifiers into the prepolymer. While modifiers can aptly influence the prepolymer rheology, they can also affect the prepolymer curing behavior and the mechanical and thermal properties of the resulting matrix material. Therefore, this study investigates the effects that a commercial-grade low-viscosity additive (butyl glycidyl ether) has on a common epoxy polymer system (diglycidyl ether of bisphenol-A epoxy with a methylene dianiline curative). The weight percentage of the modifier inside the epoxy was varied from 0 to 20%. The rheological properties and cure kinetics of the resulting materials were investigated. The prepolymer viscosity decreased by 97% with 20 wt% modifier content at room temperature. Upon curing, 20 wt% modifier addition reduced the exothermic peak temperature by 12% and prolonged the time to reach the peak by 60%. For cured material samples, physical and thermo-mechanical properties were characterized. A moderate reduction in glass transition temperature and an increase in elastic modulus was observed with 20 wt% modifier content (in the order of 10%). Based on these findings, the selected material system is seen as an expedient base for material design due to the ease of processing and material availability. The present study thus provides guidance to researchers developing polymer composites requiring reduced prepolymer viscosity for successful functional filler addition.

Optimal Molecular Dynamics System Size for Increased Precision and Efficiency for Epoxy Materials.

Molecular dynamics (MD) simulation is an important tool for predicting thermo-mechanical properties of polymer resins at the nanometer length scale, which is particularly important for efficient computationally driven design of advanced composite materials and structures. Because of the statistical nature of modeling amorphous materials on the nanometer length scale, multiple MD models (replicates) are typically built and simulated for statistical sampling of predicted properties. Larger replicates generally provide higher precision in the predictions but result in higher simulation times. Unfortunately, there is insufficient information in the literature to establish guidelines between MD model size and the resulting precision in predicted thermo-mechanical properties. The objective of this study was to determine the optimal MD model size of epoxy resin to balance efficiency and precision. The results show that an MD model size of 15,000 atoms provides for the fastest simulations without sacrificing precision in the prediction of mass density, elastic properties, strength, and thermal properties of epoxy. The results of this study are important for efficient computational process modeling and integrated computational materials engineering (ICME) for the design of next-generation composite materials for demanding applications.

Synergistic effect of positive temperature coefficient and thermally conductive micro‐nano fillers on electrical and thermal properties of epoxy resin

AbstractThis study investigates the effect of positive temperature coefficient (PTC) fillers, i.e., barium strontium titanate (BST‐60) and nano hexagonal boron nitride (h‐BN) fillers, on thermal and dielectric insulation properties of epoxy (EP). The electrical resistivity, DC breakdown strength, space charge, thermal conductivity, thermogravimetric analysis, and glass transition temperature (Tg) of EP composites were measured. Results indicate that, below curie temperature, the EP composites containing 0.5 and 1 wt% of BST and 5 wt% of h‐BN have superior electrical resistivity, breakdown strength, and thermal conductivity. However, above curie temperature, the EP composites containing 2 and 2.5 wt% of BST and 5 wt% of h‐BN have superior insulation properties than the pure EP and other composites. While the thermal properties of EP improve with an increase in h‐BN loading to 10 wt%, its dielectric properties are slightly compromised due to the presence of tiny defects in the composite material. It is hypothesized that the BST‐60 suppresses the negative temperature coefficient effect (NTC) of EP by regulating the electrical resistivity above the curie point, whereas nano h‐BN enhances the thermal conductivity of EP by constructing a heat dissipation path. The proposed mechanism for charge dynamics along with heat conduction‐dissipation explains the fillers' behavior at different temperatures.Highlights Analysis of epoxy composites with polydopamine‐modified BST and h‐BN fillers. PTC fillers are used to mitigate the negative temperature effect of epoxy. Optimal fillers wt% improves dielectric and thermal properties. This study shows that optimized epoxy composites can be used for packaging.

Halogen‐free boron‐based hybrid system for enhancing flame retardancy, mechanical and thermal properties of epoxy

AbstractThis study aims to increase the flame retardancy of epoxy‐based composites by using various flame retardants together with colemanite filler (CLM), which is a very mineral‐rich boron type. As a flame retardant, aluminum hydroxide (Al(OH)3) and boron‐containing compounds: borax (BRX) and natural minerals (tincal (TNC) and colemanite (CLM)), as well as barium metaborate (BaMB) synthesized by us were used. Scanning electron microscopy (SEM), x‐ray powder diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), contact angle (CA), and particle size analysis were used to characterize the composites and additives. All boron compounds increased the thermal stability of the composites. Except for the ER/CLM‐BaMB composite, other composites' surface contact angles were over 90°. In terms of both combustion and thermal properties, the best CLM‐BaMB‐Al(OH)3‐TNC ratio was determined as 15:5:15:15. The tensile strength, self‐extinguishing time, estimated and experimental Limited Oxygen Index (LOI) values for this composite were determined as 96 MPa, 65 s, 29.6%, and 25%, respectively. In addition, ANOVA was applied to determine the effect of hybrid filler type and different weight ratios on the mechanical properties of composites.

Functionalization of nano-objects in living anionic polymerization-induced self-assembly and their use for improving thermal properties of epoxy resins

Using LAPISA or LAPICA, stabilized PDVB@(PI-b-PS) and PDVB@(PI-b-PS/PS) nano-objects were prepared, functionalized and used as additives for epoxy resin, providing improved Tgs, integrated interfaces, uniform distributions, and scalable applications.

Hybrid Epoxy Nanocomposites: Improvement in Mechanical Properties and Toughening Mechanisms—A Review

This article presents a review on the recent advances in the field of ternary diglycidyl ether of bisphenol A epoxy nanocomposites containing nanoparticles and other modifiers. Particular attention is paid to their mechanical and thermal properties. The properties of epoxy resins were improved by incorporating various single toughening agents, in solid or liquid states. This latter process often resulted in the improvement in some properties at the expense of others. The use of two appropriate modifiers for the preparation of hybrid composites, possibly will show a synergistic effect on the performance properties of the composites. Due to the huge amount of modifiers that were used, the present paper will focus mainly on largely employed nanoclays with modifiers in a liquid and solid state. The former modifier contributes to an increase in the flexibility of the matrix, while the latter modifier is intended to improve other properties of the polymer depending on its structure. Various studies which were carried out on hybrid epoxy nanocomposites confirmed the occurrence of a synergistic effect within the tested performance properties of the epoxy matrix. Nevertheless, there are still ongoing research works using other nanoparticles and other modifiers aiming at enhancing the mechanical and thermal properties of epoxy resins. Despite numerous studies carried out so far to assess the fracture toughness of epoxy hybrid nanocomposites, some problems still remain unresolved. Many research groups are dealing with many aspects of the subject, namely the choice of modifiers and preparation methods, while taking into account the protection of the environment and the use of components from natural resources.

Epoxy-Functionalized POSS and Glass Fiber for Improving Thermal and Mechanical Properties of Epoxy Resins

To improve the thermal and mechanical properties of epoxy resins, epoxy-functionalized POSS (E-POSS) and glass fiber (GF) were used to reinforce epoxy resin (E51) composites. The tensile, thermo-mechanical, fractured, and thermal tests were carried out to characterize these hybrid materials. The results show that E-POSS and GF could significantly improve the mechanical and thermal properties of epoxy resins due to high crosslink density of resin matrix and synergistic interaction between the epoxy resin, E-POSS, and GF. Compared with the pure E51 resin, the tensile strength of the E51 + E-POSS (10%) + GF (16%) sample increased by 257.6%, and the thermal decomposition temperature (Td5%) of the E51 + E-POSS (10%) + GF (16%) sample increased by 32 °C to 378 °C.

Investigating the use of natural hollow fibers from common milkweed to improve the mechanical and thermal properties of epoxy resin

AbstractMilkweed floss was used as a reinforcement to develop lightweight epoxy composites with enhanced thermal insulating properties. Seed fibers from Asclepias Syriaca harvested in Quebec were used for this study. Some fibers were treated with acetone to remove their protective hydrophobic coating. Epoxy resin was blended with 15% w/w of native or acetone‐treated milkweed floss to form prepregs. The prepregs were casted into molds, degassed, and compressed to produce the composites. The composites were passed through a post‐curing phase before characterization. The composites and the epoxy resin alone were characterized to determine their density, porosity, thermal conductivity, thermal degradation, mechanical resistance, and thermo‐mechanical behavior. The composites reinforced with native or acetone‐treated milkweed floss were 7.4% and 10.3% lighter than the epoxy resin, respectively. The specific elastic modulus of the resin increased by 9.6% and 20.1% with the addition of native or acetone‐treated fibers, respectively. The thermal conductivity of the epoxi decreased by 7.8% and 15.6% with the use of native or acetone‐treated milkweed floss, respectively. Due to their low weight and reduced thermal conductivity, the milkweed‐reinforced epoxy composites may find applications in the production of structural and insulating elements for vehicles and buildings.

Characterization of the mechanical properties and thermal conductivity of epoxy-silica functionally graded materials

<abstract> <p>A functionally graded material (FGM) was prepared using epoxy resin reinforced with silicon dioxide with a particle size of 100 μm and weight percentages of 0, 20, 40, 60, and 80 wt%. In a gravity-molding process using the hand layup technique, specimens with international standard (ASTM)-calculated dimensions were created in a mold of poly(methyl methacrylate), which is also known as acrylic. Tensile, flexural, impact, infrared wave, and thermal conductivity tests, and X-ray diffraction (XRD) were conducted on specimens of the five layers of the FGM. The XRD and infrared spectroscopy demonstrated that the compositions of the silica particles and epoxy had a strong association with their physical structures. The findings of experimental tests indicated that increasing the ratio of silicon dioxide enhanced the mechanical properties, and the increase in modulus of elasticity was directly related to the weight percentage of the reinforcement material. The composite with 80% silica had a 526.88% higher modulus of elasticity than the pure epoxy specimen. Both tensile and flexural strengths of the composite material were maximal when 40 wt% of the particle silicon dioxide was utilized, which were 68.5% and 67.8% higher than those of the neat epoxy, respectively. The test results also revealed that the impact resistance of the FGM increased when the silica proportion increased, with a maximum value of 60 wt% silica particle content, which was an increase of 76.98% compared to pure epoxy. In addition, the thermal properties of epoxy resin improved when SiO<sub>2</sub> was added to the mixture. Thus, the addition of silica filler to composite materials directly proportionally increased their thermal conductivity to the weight ratio of the reinforcement material, which was 32.68–383.66%. FGM composed of up to 80% silica particles had the highest thermal conductivity.</p> </abstract>

Metal-organic framework nanoparticles as a free radical scavenger improving the stability of epoxy under high dose gamma irradiation

Understanding the degradation mechanism of epoxy resin under irradiation and enhancing the radiation resistance of epoxy resin are of great significance for its application in aerospace and nuclear industries. In this study, we investigated the radiation resistance of epoxy reinforced by UIO-66-OH metal-organic framework. Outstanding radiation resistance was achieved by using UIO-66-OH nanoparticles as radical scavengers to retard epoxy degradation. The introduction of UIO-66-OH reduces the content of free radicals generated after irradiation by 88.17%. UIO-66-OH also improves the mechanical and thermal properties of epoxy before and after irradiation. The scavenging radicals mechanism of hydrogen atom transfer of UIO-66-OH is more dominant than that of graphene oxide and carbon nanotubes. The radiation resistance of UIO-66-OH nanoparticles is related to hydroxyl functionalization and porous structure. This work provides a new idea and method for improving the stability of epoxy resin under gamma ray radiation.

Synergistic Effect of Nano-Silica and Micro-Silica Fillers on the Rheological and Thermal Properties of Epoxy Resins

This article aims to improve nanofiller dispersion in epoxy resins by using an electrostatic disperser (ED), as well as reduce costs by using a combination of microfillers and nanofillers. The ED method aids in homogenized mixing of nanofillers in epoxy resin, due to its jet elongation and shearing effect on a polymer mix. In this article, two concentrations (7.5 wt% and 5 wt%) of nanosilica are used with resin, and the rheological properties of hybrid composites are tested before and after the addition of 50 wt% microsilica. It is observed that the electrostatic dispersion method aids in the network formation of nanosilica, unlike the high shear (HS) method, wherein clusters of nanosilica are formed. Hence, the ED method aids in reducing the viscosity values with the addition of microsilica, which is helpful in the product molding process. A plausible mechanism of filler dispersion is explained for ED and HS methods. The morphological analysis showed that the composites are brittle due to the high silica content, and that the silica fillers are dispersed well within the epoxy matrix. The flexural strength lies in the same range for both composites prepared using ED and HS methods. Thermal conductivity depends both on nanosilica and epoxy matrix dispersion, while heat deflection temperature, thermal diffusivity and specific heat depend on the dispersion method.

Effect of the Addition of Thermoplastic Resin and Composite on Mechanical and Thermal Properties of Epoxy Resin.

When the thermoplastic composites reach the service limits during the service, the recovery and utilization are the key concerns. Meanwhile, the improvement of strength, toughness and durability of epoxy resin is the effective method to prolong the service life of materials and structures. In the present paper, three kinds of thermoplastic resins (polypropylene-PP, polyamide 6-PA6 and polyether-ether-ketone-PEEK) and composites (carbon fiber-PEEK, glass fiber-PA6 and glass fiber-PP) were adopted as the fillers to reinforce and toughen the epoxy resin (Ts). The mechanical, thermal and microscopic analysis were conducted to reveal the performance improvement mechanism of Ts. It can be found that adding thermoplastic resin and composite fillers at the low mass ratio of 0.5~1.0% brought about the maximum improvement of tensile strength (7~15%), flexural strength (7~15%) and shear strength (20~30%) of Ts resin. The improvement mechanism was because the addition of thermoplastic fillers can prolong the cracking path and delay the failure process through the load bearing of fiber, energy absorption of thermoplastic resin and superior interface bonding. In addition, the thermoplastic composite had better enhancement effect on the mechanical/thermal properties of Ts resin compared to thermoplastic resin. When the mass ratio was increased to 2.0~3.0%, the agglomeration and stress concentration of thermoplastic filler in Ts resin appeared, leading to the decrease of mechanical and thermal properties. The optimal addition ratios of thermoplastic resin were 0.5~1.0% (PEEK), 1.0~2.0% (PA6) and 0.5~1.0% (PP) to obtain the desirable property improvement. In contrast, the optimal mass ratios of three kinds of composite were determined to be 0.5~1.0%. Application prospect analysis indicated adding the thermoplastic resin and composite fillers to Ts resin can promote the recycling and reutilization of thermoplastic composites and improve the performance of Ts resin, which can be used as the resin matrix, interface adhesive and anti-corrosion coating.

Synthesis of a novel star-shaped polyethylene-co-polystyrene copolymer by using ATRP and click methods and investigation of its effects on mechanical thermal properties of epoxy resins

Synthesis of a novel star-shaped polyethylene-co-polystyrene copolymer by using ATRP and click methods and investigation of its effects on mechanical thermal properties of epoxy resins

Mechanical responses of epoxy/cloisite nanocomposites

Polymeric nanocomposites based on nanoclay are extensively utilized in various structural applications. In this work, the effect of organically modified nanoclay (cloisite 20A) on the chain confinement, mechanics, structure, and thermal properties of epoxy resin cured with diamino diphenyl sulphone (DDS) was analysed. The viscoelastic properties were analysed by dynamic mechanical analysis (DMA). The stiffness parameter and the peak parameters from loss modulus and tan δ indicate effective adhesion of nanoclay with the polymer matrix. The filler-matrix confinement has created a constrained zone around the polymer-matrix interface resulting in the immobilization of polymer chains near the fillers. The chain confinement was determined from tan δ curve. The heterogeneity of the cloisite 20A/epoxy nanocomposites was analysed by Cole-Cole plots. Fine dispersion of cloisite 20A was achieved by intercalation of nanoclay as observed by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. Finally, the thermal properties of the nanocomposites were analysed by thermogravimetric analysis (TGA).

Investigating optimal region for thermal and electrical properties of epoxy nanocomposites under high frequencies and temperatures

This research investigates the optimal region to achieve balanced thermal and electrical insulation properties of epoxy (EP) under high frequency (HF) and high temperature (HT) via integration of surface-modified hexagonal boron nitride (h-BN) nanoparticles. The effects of nanoparticle content and high temperature on various electrical (DC, AC, and high frequency) and thermal properties of EP are investigated. It is found that the nano h-BN addition enhances thermal performance and weakens electrical insulation properties. On the other side, under HF and HT stress, the presence of h-BN nanoparticles significantly improves the electrical performance of BN/EP nanocomposites. The EP has superior insulation properties at low temperature and low frequency, whereas the BN/EP nanocomposites exhibit better insulation performance than EP under HF and HT. The factors such as homogeneous nanoparticle dispersion in EP, enhanced thermal conductivity, nanoparticle surface modification, weight percent of nanoparticles, the mismatch between the relative permittivity of EP and nano h-BN, and the presence of voids in nanocomposites play the crucial role. The optimal nanoparticle content and homogenous dispersion can produce suitable EP composites for the high frequency and high temperature environment, particularly solid-state transformer applications.

Effect of Dopamine-Functionalized Nano-h-BN on the Charge Dynamics and Thermal Properties of Epoxy Resins at High Temperatures for Potential Power Module Encapsulation Application

This paper investigates the charge dynamics and thermal properties of epoxy and its nanocomposites [(10 and 20 wt % of nano-hexagonal-boron nitride (h-BN)]. Two indigenously developed setups of the integrated charge [Q(t)] measurement and high-temperature space charge measurement are used to analyze the charge dynamics of the prepared samples under different testing conditions. The dispersion of dopamine-functionalized nano-h-BN is characterized by transmission electron microscopy and scanning electron microscopy. The thermal properties are measured using differential scanning calorimetry and thermal conductivity measurements. The results show that the charge property of the 10 wt % EP nanocomposite is the best under all testing conditions. The uniform dispersion of nano-h-BN can improve both the electrical and thermal properties of epoxy. A proposed mechanism explains the effect of the dopamine-functionalized nano-h-BN particles on the enhancement of nanocomposite properties.

Space charge performance of epoxy composites with improved thermal property at high temperature under high electric field

AbstractThis article investigates the high‐temperature space charge dynamics of epoxy composites consisting of micro and nano‐AlN fillers under a high electric field. The test temperatures are selected for the space charge measurement based on the glass transition temperature. An indigenously designed pulse electro‐acoustic system measures the space charge distribution up to 150°C. The stepwise‐increasing field is applied to the test samples from 20 to 100 kV/mm at the rate of 20 kV/mm. The epoxy hybrid composites show negligible space charge accumulation at room temperature and low electric fields, which increases at high temperatures and high electric fields. The hybrid composite with 1 wt% nanoparticle has a dielectric breakdown at 100 and 150°C under 100 kV/mm with an evident amount of accumulated charges. In the hybrid composites with 3 and 5 wt% nanofillers, the breakdown is observed under 80 and 100 kV/mm, respectively, at 150°C. Notably, the micro‐nano filler addition significantly improves the thermal conductivity of the epoxy resin. The uniform dispersion of the fillers affects the electrical and thermal properties of the epoxy. The charge dynamics‐related mechanism is proposed on the basis of morphological characterization and thermal properties of epoxy and its composites.

Study the Thermal Properties of Epoxy Resin Reinforced with Calcium Oxide Fibers

ABSTRACT Poor tensile strength and brittle nature are considered to be a major weakness in epoxy resin. Herein, thermogravimetric decomposition is used to investigate the effect of the addition of calcium oxides on the thermal degradation of the epoxy resin. Four composites with 5%, 7.5%, 10%, and 15 wt % calcium oxide are prepared with epoxy resin as a matrix substance. Arrhenius equation is used to evaluate the activation energies of the composites and the findings are tabulated. The findings indicate that the addition of calcium oxides as a filler contributes to an enhancement in the thermal stability of the components by inhibiting the process of thermal decomposition of epoxy resin. The composition with a ratio of 10% by weight of calcium oxide/epoxy shows a good and distinct stability, which is evidenced by the increasing in the thermal decomposition of the composite 10% CaO filler/epoxy at 400°C compared with other composites.

Sandwich-structured graphene oxide@poly (aminophenol-formaldehyde) sheets for improved mechanical and thermal properties of epoxy resin

We propose a wet chemical method to synthesize sandwich-structured graphene oxide@poly (aminophenol-formaldehyde) (GO@PAPF) sheets. It uses GO as the shape-directing agent, 3-aminophenol as the precursors of polymer layer, formaldehyde as crosslinking agent, and ammonia as catalyst. Morphology characterization shows that the prepared GO@PAPF sheet has a sandwich-like structure with a thickness of 40 nm. It has good dispersion stability in acetone and epoxy resin diluted with acetone. After standing for 48 h, no obvious precipitation was observed. The effects of GO@PAPF loading on the physicochemical properties of epoxy composites have been systematically investigated. The resulting GO@PAPF/epoxy composites demonstrated an improved tensile strength and impact strength. When the loading of GO@PAPF sheets was 1.5 wt%, the tensile strength reached the maximum of 121.6 MPa, which is 62.1% higher than that of pure epoxy resin. The corresponding elongation at break was 5.77%. In addition, the introduction of GO@PAPF sheets also improves the thermal stability of epoxy composites. The glass transition temperature of the epoxy composite containing 1.5 wt% GO@PAPF sheets has been increased from 169.5 °C for pure resin to 184.1 °C. Big interfacial area, strong interfacial force between GO@PAPF sheets and epoxy matrix, good dispersion of GO@PAPF sheets in epoxy matrix were responsible for the enhanced mechanical and thermal properties.