Viscosity Epoxy Research Articles

Comparison of carbon‐reinforced composites manufactured by vacuum assisted resin infusion with traditional and fully recyclable epoxy resins

AbstractThis study presents a comparative analysis of carbon fiber reinforced polymer (CFRP) composites manufactured through vacuum assisted resin infusion (VARI) using a traditional epoxy resin (E), a fully‐recyclable epoxy resin system with (BBR10) and without (BBR) the addition of a reactive diluent (R*Diluent). Various mechanical and thermal tests were conducted to assess their performance. The BBR10 laminate, incorporating 10 wt% R*Diluent, exhibited competitive mechanical performance, comparable to traditional (E) and fully‐recyclable laminates (BBR). Despite a slightly lower ultimate tensile strength (UTS) compared with BBR, BBR10 demonstrated improved flexural strength and modulus. Low‐velocity impact testing confirmed comparable strength between VARI‐produced composites with the recyclable matrix (BBR and BBR10) and the traditional one (E). X‐ray mCT investigations revealed distinct void arrangements in the CFRP laminates. Additionally, a chemical approach was employed for recovering high fractions of fibers from CFRP laminates with a recyclable matrix (BBR and BBR10). Chemical recycling achieved an almost 100% yield for long carbon fibers.Highlights Comparative analysis of CFRP composites manufactured through VARI. Diluent addition allowed to tailor the recyclable epoxy viscosity. Mechanical characterization of traditional and fully recyclable epoxy resins. Investigation by X‐ray mCT of potential flaws and manufacturing defects. Chemical recycling of CFRP laminates with a recyclable matrix.

The effect of processing/curing temperature and viscosity of epoxy resins on the flexural/tensile properties of GNP-epoxy resin nanocomposites

Despite the problem of graphene aggregation in cured epoxy resin, no studies have clarified the tendency of graphene aggregation in a wide variety of material systems and process. We hypothesized that the use of epoxy resins at high temperatures leads to an extreme decrease in resin surface tension and viscosity of epoxy, which would cause re-aggregation of graphene once dispersed. So, we examined process/material with/without high temperature treatment and epoxy resins of different viscosities, and properties of nanocomposites were evaluated by flexural/tensile test. Experiments revealed that the process not including high temperature treatment suppressed graphene re-aggregation and maintained the high mechanical properties of nanocomposites. In particular, the increased tensile modulus by 18.44% and flexural strength by 2.81% (@ 1 wt% graphene loading), which were quite high for non-functionalized graphene, were recorded when epoxy was treated and cured at 20 ˚C at all times to keep the surface tension of epoxy desirable.

Advancements in emerging MXene-integrated nanocomposite coatings: Unraveling defect-free microstructure for superior tribological, mechanical, and anti-aging features

This study explored the enhancement potential of MXene, a novel two-dimensional material, in epoxy-based nanocomposites; which comprehensively examined the influence of MXene on epoxy's viscosity, void formation, aging resistance, mechanical properties, and anti-wear properties. MXene nanofillers, labeled as 25C and 80C, fabricated via different acid-etching methods, were incorporated into epoxy resin at varying weight percentages (0.1–2.0 wt%). Observations revealed that for both varieties of MXene, inclusion of 1.0 wt% MXene led to the mitigation of void content, whereas the incorporation of 2.0 wt% MXene yielded maximal enhancements in both tensile strength and abrasion resistance. Additionally, the integration of 1.0 and 2.0 wt% MXene displayed superior aging resistance, with around 80 % reduction in free radical formation compared to the unmodified epoxy, while maintaining its excellent mechanical properties after QUV exposure. Therefore, both MXene types significantly enhanced the performance of epoxy composites, with the 80C-MXene displaying marginally superior enhancement due to its smaller particle size and higher purity, as identified by SEM and TEM images.

The effect of different GNP/BNNP foam structures in the infiltration of epoxy resin: A fundamental study

AbstractHierarchical 3D architecture of nanoplatelets, also known as foams, has arisen as a promising alternative to overcome agglomeration and promote mechanical reinforcement and electrical and thermal conductivity of polymer composites. Freeze‐drying is a cost‐effective method to manufacture foams with different structures and tailored thermal and electrical properties. This study used freeze‐drying to produce graphene (GNP), boron‐nitride (BNNP), and hybrid foams of different ratios. The interaction between these structures and high‐temperature epoxy grade was investigated via contact angle analysis. The foams were also infiltrated with epoxy to achieve a fully dense nanocomposite. The contact angle monitoring reveals solid loading content, composition, and structure as the main factors affecting wettability. Despite the slight variation in porosity among the foams, all the samples achieved a densification above 96%, suggesting that the epoxy viscosity of 2.34 Pa∙s combined with optimized infiltration parameters can successfully produce dense nanocomposites. The contact angle analysis is a suitable method to compare the infiltration quality of freeze‐dried foams and can be applied to evaluate the production feasibility of other polymer/foam nanocomposites. Furthermore, preliminary thermal data shows a clear temperature increase for the epoxy/foam structures, with GNP and 50:50 GNP:BNNP being the most thermally conductive compositions. This study serves as a starting point for freeze‐dried foams/polymer nanocomposite investigation and may broaden the possibilities for manufacturing and future application of these structures.Highlights The freeze‐dried foams were successfully fabricated and infiltrated with high‐temperature epoxy, obtaining densifications above 96%. The main factors affecting infiltration are foam morphology, porosity, and chemical affinity between polymer and foam platelets. Thermal conductivity has significantly improved by adding GNP and BNNP foam network to epoxy matrix.

Role of Bio-Based and Fossil-Based Reactive Diluents in Epoxy Coatings with Amine and Phenalkamine Crosslinker.

The properties of epoxy can be adapted depending on the selection of bio-based diluents and crosslinkers to balance the appropriate viscosity for processing and the resulting mechanical properties for coating applications. This work presents a comprehensive study on the structure-property relationships for epoxy coatings with various diluents of mono-, di-, and bio-based trifunctional glycidyl ethers or bio-based epoxidized soybean oil added in appropriate concentration ranges, in combination with a traditional fossil-based amine or bio-based phenalkamine crosslinker. The viscosity of epoxy resins was already reduced for diluents with simple linear molecular configurations at low concentrations, while higher concentrations of more complex multifunctional diluents were needed for a similar viscosity reduction. The curing kinetics were evaluated through the fitting of data from differential scanning calorimetry to an Arrhenius equation, yielding the lowest activation energies for difunctional diluents in parallel with a balance between viscosity and reactivity. While the variations in curing kinetics with a change in diluent were minor, the phenalkamine crosslinkers resulted in a stronger decrease in activation energy. For cured epoxy resins, the glass transition temperature was determined as an intrinsic parameter that was further related to the mechanical coating performance. Considerable effects of the diluents on coating properties were investigated, mostly showing a reduction in abrasive wear for trifunctional diluents in parallel with the variations in hardness and ductility. The high hydrophobicity for coatings with diluents remained after wear and provided good protection. In conclusion, the coating performance could be related to the intrinsic mechanical properties independently of the fossil- or bio-based origin of diluents and crosslinkers, while additional lubricating properties are presented for vegetable oil diluents.

Magnetic field induced alignment of graphene nanoplatelets in epoxy resin to develop model nanocomposite

In this work, a mathematical model is developed to optimize the alignment parameters of Graphene Nanoplatelets (GNP) and Fe3O4-GNP applying a weak DC magnetic field (0.05 T), considering rotation, translation, migration, and slackening mechanisms of the nanoparticle in the epoxy. The characteristic magnetic, viscosity and hydrodynamic parameters required by the mathematic model are determined experimentally by synthesizing the magnetite ferric oxide (Fe3O4) and attaching them to GNP to increase its magnetic susceptibility. A highly aligned Fe3O4-GNP nanocomposite is fabricated at 0.05 T magnetic field and 40 Pa-s dynamic viscosity of epoxy, as evident from the optical image analysis. The mass magnetic susceptibility for the nanoparticles are determined at different magnetic field. Time needed for the alignment process at 0.05 T and viscosity range 10–50 Pa-s are compared among the rotation, chaining, migration and the slackening phenomena. The procedure demonstrated to prepare fully cured nanocomposite with aligned Fe3O4-GNP can be used in advanced structures.

Mechanical properties and durability of injected SCC panels by epoxy against freezing and thawing

Repairing cracks in concrete structures exposed to freezing and thawing cycles by injecting epoxy resin and the main factors affecting it, such as epoxy viscosity, crack width, and the crack's moisture content, has been studied in a few research.This paper utilized commercial epoxy resins with high, medium, and low viscosities to inject through simulated cracks. In addition, repair methods were tested and evaluated by injecting epoxy resins in dry, damp, wet, and water-filled conditions. Furthermore, two crack widths (0.5 and 0.8 mm) were simulated on the specimens, and the effects of the repairing materials' thickness on the rehabilitation success were examined. The specimens’ durability with 24 cycles of freezing and thawing was investigated.Results demonstrate that water's presence in different situations, especially the water-filled ones in the interfacial zone, deteriorates the bond characteristics; Contrastly, the results were better in the wet situation. It can be concluded that injecting in the dry situation is optimized. The results showed that curing in lower temperatures takes longer than in higher temperatures. Moreover, a correlation was observed between the viscosity and its effect on tensile bond strength and actual shear strength in the slant shear test. It was found that the low-viscosity resin showed better performance than the high-viscosity resin overall. Moreover, the low-viscosity resin achieved 25% more shear strength in the slant shear test than the high-viscosity. In the freezing and thawing cycles, the injection was stable only in dry cracks, and in other moist conditions, the samples failed the freezing and thawing cycles.

Verification of Utilizing Nanowaste (Glass Waste and Fly Ash) as an Alternative to Nanosilica in Epoxy

Silica is considered one of the most prevalent components in the Earth’s shell and is synthesized for use in technological applications. Nevertheless, new methods for finding a better, cheaper, and more ecologically friendly supply of silica with less energy consumption are unavoidable. This study investigates whether nanopowders made from waste with a great silica amount (fly ash and glass) can be utilized as fillers in an epoxy glue to enhance its characteristics. Four different contents (5, 10, 15, and 20 wt%) of nano–fly ash, nanoglass, and nanosilica powder were introduced into the samples. Fourier transform infrared analysis, differential scanning calorimetry analysis, viscosity testing, and microhardness testing were conducted for nanoglass/epoxy and nano–fly ash/epoxy samples, which were compared with the silica/epoxy samples. Results indicated that the nanoglass and nano–fly ash powder have the same impact as nanosilica on the characteristics of epoxy. The hardness and viscosity of epoxy increased with the increase in the added filler. At 20 wt%, the hardness value of the nanoglass/epoxy composites was greater than that of the nanosilica/epoxy and fly ash/epoxy composites by about 15% and 7%, respectively. The results also indicated that the highest viscosity values were obtained when using nano–fly ash powder of 20 wt%. Furthermore, the modification of the epoxy by the nanoparticles had no significant effect on the values of the glass transition temperatures.

Self-healing microcapsules modified by montmorillonite for modulating slow-release properties

Slow-release type self-healing microcapsules (RHM) are fabricated by the solvent evaporation process with a core of epoxy resin (E-44 and E-51) modified by montmorillonite and a wall of ethyl cellulose (EC). Rotational rheometer, environmental scanning electron microscope, high performance liquid chromatography, and UV–vis spectrophotometer are utilized to characterize the composite viscosity, microscopic morphology, encapsulation rate, and slow-release performance, while the rate of strength healing is utilized to characterize the healing performance. The results demonstrate that the viscosity of epoxy resin (E-44 and E-51) can be improved effectively and the sensitivity of its viscosity to temperature can be reduced when epoxy resin (E-44 and E-51) is modified by montmorillonite. There is a good appearance in RHM. With the addition of montmorillonite, the encapsulation rate of the microcapsules increases slightly, while the rate of slow-release decreases gradually. When montmorillonite doped at 9% of E-44, the cumulative release of RHM is 121%, which is lower compared to E−51 RHM at 48 h. The strength healing rate of cement-based materials increases firstly and then decreases with the increasing montmorillonite doping. The RHM modified by E-44 with 6% montmorillonite could reache a maximum strength healing rate of 34.4%. Slow-release type self-healing microcapsules with epoxy resin (E-44 and E-51) modified by montmorillonite (RHMM) can better regulated the slow-release characteristics and have a more significant effect on cement-based self-healing materials.

A multilayer transparent wood prepared by laminating two kinds of tree species

AbstractTransparent wood (TW) is a new material with a certain light transmission performance, which can be widely used as new energy‐saving material. However, the application and development of TW are limited by material and thickness. In this work, the representative species of softwood and hardwood were selected for lamination. After chemical treatment, the lignin in natural wood was removed, and then the epoxy resin with a similar refractive index to the cell wall was impregnated in vacuum. By using the viscosity of epoxy resin itself, the single‐layer materials could be effectively laminated together to prepare a new type of multilayer transparent wood (MLTW). By testing the optical properties, mechanical properties. and surface properties of MLTW materials, we found that the optical transmittance and mechanical properties can be effectively controlled and selected through the selection of materials and assembly methods. Besides, the surface properties of MLTW are mainly related to its surface material. In short, MLTW is a new composite material prepared by simple lamination at the macro level. The properties of the material can be controlled through the selection of single‐layer materials and assembly methods. Compared with the traditional TW, MLTW has better performance regulation ability.

A novel method to improve the settlement stability of epoxy resin-based cementing fluid

Compared with cement stone, epoxy resin has a higher compressive strength, lower elastic modulus, and better seepage capacity in repairing cement sheath or cementing in special formations. The viscosity of epoxy resin is significantly affected by temperature, which causes a serious decrease in the settlement stability. In this study, the effects of the diluent, solid epoxy resin and rheological agents on the slurry viscosity, and settlement stability were evaluated. The results indicate that fumed silica and organic bentonite have a good effect on improving the settlement stability, but have negative effects on pumpability. Therefore, a method to improve the settlement stability of epoxy resin-based cementing slurry was developed. Fumed silica and organic bentonite were compounded to increase the settlement stability and lower dosage (fumed silica less than 3 wt.%) can avoid too much negative effect on pumpability. Viscosity tests showed that diluent work more effectively at low temperatures while solid ER and Xanthan gum are more effective at high temperatures. When they use together, the viscosity at 90 °C is increased by 33% while decrease by 86% at 25 °C. When the temperature increases downhole, the viscosity of diluent is closed to ER, and tackifying materials dominate, increasing the viscosity at high temperatures. Based on the method proposed in this paper, the epoxy resin-based cementing slurry can increase the settlement stability to less than 0.01 g/cm3 when the slurry density is less than 1.3 g/cm3 and a settlement stability of less than g/cm3 when slurry density is less than 1.59 g/cm3 .

Investigation of the effects of silica aerogel particles on thermal and mechanical properties of epoxy composites

Aerogel particle filled epoxy was fabricated in this work by investigating the effect of resin viscosity on pore infiltration and density of resulting composites. Aerogel porous structure was successfully preserved by carefully selecting epoxy viscosity for mixing procedure. The effect of aerogel content and particle size was subsequently investigated on thermal conductivity and compressive properties of epoxy composites. The results showed that incorporating aerogel particles into the resin could lead to over 40% reduction in both density and thermal conductivity. However, there was a linear trade-off between compressive properties and thermal conductivity of silica aerogel/epoxy composites. A wide range of aerogel particle sizes was also studied and it was found that the size effect was dependent on the aerogel content. Overall, the results of the presented work allow conclusions to be drawn regarding the usefulness of delayed wet mixing technique and the impact of particle size and loading on aerogel filled resin composites.

Detailed experimental and theoretical investigation of the thermomechanical properties of epoxy composites containing paraffin microcapsules for thermal management

AbstractMicroencapsulated phase change materials (PCMs) are being increasingly employed as functional fillers in polymer matrices for thermal management. Therefore, the effect of PCM microcapsules on the rheological, microstructural, thermal and mechanical properties of the host polymer matrices must be understood. This work concerned the preparation of epoxy polymers filled with PCM microcapsules (MC) in various concentrations and their subsequent characterization. The MC phase increases the viscosity of epoxy before curing, thereby reducing castability and hindering elimination of air bubbles. The latter was reflected in an increase in porosity for highly filled compositions, as elucidated by density measurements and microscopic investigation. SEM micrographs showed that the adhesion between the capsule shell and the epoxy matrix was not optimal. The interfacial weakness and the intrinsic low stiffness and strength of MC caused a reduction in mechanical properties, as evidenced by the Nicolais‐Narkis and Pukanszky models. On the other hand, at zero or low deformation levels, the interface presents no gaps and is able to transfer load and heat, as demonstrated by the data of elastic modulus, modeled with the Halpin‐Tsai and Lewis‐Nielsen models, and those of thermal conductivity, in excellent agreement with the Pal model. POLYM. ENG. SCI., 2020. © 2020 Society of Plastics Engineers

Designing epoxy viscosity for optimal mechanical performance of coated Glass Textile Reinforced Mortar (GTRM) composites

Preliminary epoxy coating of the reinforcing fabric provides an effective approach for improving matrix-to-fabric strength in inorganic matrix composites. We investigate the effect of epoxy resin dilution in acetone on uni-axial tensile performance of coated alkali-resistant (AR) glass fabric embedded in a lime-based matrix. Remarkably, it is found that dilution has a mixed effect on performance and this trend is consistently retrieved for strength, ductility and energy dissipation. Indeed, performance initially decays and then it suddenly raises to a level close to or even exceeding that of the undiluted specimens. It is postulated that this behaviour is caused by resin viscosity, that falls off exponentially with the dilution degree. Once a viscosity threshold is breached, epoxy is capable of penetrating inside the yarn and thereby prevents telescopic failure, that is the sliding of the outer over the inner glass filaments. Furthermore, the interphase surface area increases dramatically and this enhances performance and narrows scattering. Besides, optimal viscosity is reached at an unexpectedly high dilution degree, whence material cost is significantly reduced. A cost-to-performance comparison of common strengthening technologies is presented, which shows that diluted epoxy composites score comparably to FRPs. It is concluded that epoxy coating optimization plays an important role in designing inorganic matrix composites.

A Study on the Fabric Substrates With Fine-Pitch Laminated Cu Metal Patterns Using B-Stage Adhesive Films

Cu pattern-laminated fabric substrates using epoxy-based B-stage adhesive films were demonstrated. Fine-pitch Cu electrical patterns were fabricated on B-stage adhesive films and then laminated to fabrics. As a result, fabric substrates having minimum Cu line width of $80~\mu \text{m}$ were successfully fabricated without any Cu lines displacement and fabric damages. First, the effects of the curing properties of adhesive films on fine-pitch Cu patterning were investigated by Fourier transform infrared (FTIR) spectroscopy and a 90° peel adhesion test. In addition, the morphology of the Cu pattern-laminated fabric substrates was observed depending on the viscosity of epoxy laminating adhesive film. Finally, the effects of film moduli on the dynamic bending fatigue properties were investigated experimentally and theoretically.

Anomalous Effects of Changes in the Viscosity of Epoxy Resins and the Plasticity of Bitumen when Introducing Carbon Nano-Tubes

Anomalous Effects of Changes in the Viscosity of Epoxy Resins and the Plasticity of Bitumen when Introducing Carbon Nano-Tubes

The effect of carbon nanotubes on the curing process and the strength of epoxy resin

The influence of carbon nanotubes of “Taunit-M” of various modifications (carboxylated, carboxyl-hydroxylated, amidated) on the viscosity of the liquid state, gelation, and the strength of the cured epoxy resin “Inject-T” was investigated. For the first time it was found that the introduction of carbon nanotube in epoxy resin at 25 °C increases the viscosity by 4-55 %, at 50 °C it increases by 5-52 %, at 70 °C – by 6 %. The most discernable effect on the viscosity of epoxy resin is obtained for amidated carbon nanotubes. Gel time at 150 °C epoxy resin was 6.3 minutes, with the introduction of carbon nanotube increased to 11.3-13 minutes. Increasing pot life is very important for the technology of using epoxy resin. The first 3 minutes of gelation of the epoxy resin were studied, while the energy loss modulus of the epoxy resin gel without carbon nanotubes monotonically increases over time from 0 to 0.05 MPa, with the introduction of carbon nanotube into the epoxy resin, the loss modulus increases within the first 1-2 minutes from the start of the gel time to the values of 0.14-0.38 MPa (depending on the modification of carbon nanotube), then falls sharply. This means that after the gel time the carbon nanotubes substantially accelerate the process of solidification of the epoxy resin. The strength of the cured epoxy resin was 172 MPa, the introduction of carbon nanotubes increased the strength to 210 MPa. Thus, the introduction of carbon nanotube in epoxy resin slightly increases its viscosity in the liquid state, substantially prolongs the gelation time, accelerates hardening from the moment of gelling, increases the strength of the cured epoxy resin.

Warpage Behaviors of System-in-Packages on a Substrate Strip

Abstract In this paper, the impact of two different types of warpage, strip warpage and system-in-packages (SiP) module warpage, are considered and studied, both experimentally and numerically. An advanced material characterization method is also conducted to study the curing reaction and Pressure-Volume-Temperature-Cure (PVTC) kinetics of the packages. The curing reaction of epoxy resins, as a function of temperature and activation energies, is experimentally determined. During the curing process, the viscosity of epoxy resins change with temperature and conversion rate. The Castro-Macosko model is adopted to describe the rheological properties of epoxy resins. Experimentally, we have prepared substrate strip samples with different component density and molding compound materials. Each substrate strip contains eighteen system-in-packages. The warpages of all substrate strips and all the system-in-package modules were measured, compared, and correlated.

Chemo-Rheological Study of Hardening of Epoxy Modified Bituminous Binders with the Finite Element Method

The chemical irreversible hardening of epoxy modified bitumen is affected by various physical factors and the successful application of this technology is directly linked with full understanding of chemo-rheological material characteristics. This study proposes a model to describe the material viscosity evolution during hardening of epoxy modified bitumen. The findings from numerical analyses performed to assess the mechanical response of epoxy modified bituminous binders are presented. Information of the chemical interaction of epoxy within a bituminous matrix was collected and all the influential factors have been determined. The proposed chemo-rheological model accounting for the polymerization of the epoxy in the bitumen was formulated and the sensitivity of material parameters, such as activation energy, reaction order and extent of hardening reaction until the gel point of epoxy modified binders, was demonstrated. Results of the analyses suggest that lower levels of activation energy increase the degree of hardening and the rate of viscosity development. By decreasing the hardening reaction until the gel point the achieved viscosity of epoxy modified bitumen was increased showing the importance of gel reaction extent on material viscosity evolution. The numerical studies have shown also that the polymerization rate in the epoxy modified bitumen is highly dependent on the temperature under various (non-) isothermal conditions. Also, the polymerization rate should be considered through all the material curing processes to avoid unwanted variations in the mechanical properties.

A Facile Solid-Phase Micro-Extraction Fiber Based on Pine Needles Biochar Coating for Extraction of Polychlorinated Biphenyls from Water Samples

In this study, a facile route for the preparation of biochar coated fiber via dip method was built. The uniform biochar was produced by thermal decomposition of pine needles under limited or absence of oxygen. The robust adhesion of biochar to the etched stainless steel support was ensured by the viscosity of epoxy resin. The obtained fiber was utilized for headspace solid-phase micro-extraction (HS-SPME) of polychlorinated biphenyls (PCBs) from aqueous solution. The results of orthogonal experiment suggested that the maximum extraction efficiency for the target PCBs compounds was obtained when the extraction temperature, extraction time and the pyrolysis temperature of biochar were 60 °C, 30 min and 400 °C, respectively. Under the optimized conditions, the developed method showed good linearity between 40 and 320 ng L−1 with correlation coefficients (R) in the range of 0.9817–0.9936. The limits of detection (LOD) ranged from 12.3 to 24.3 ng L−1. The reproducibility for fiber-to-fiber obtained on two fibers was in the range of 9.5–20.4 %. The precisions for run-to-run found for 5 extraction times using one fiber in 1 day was less than 27.8 %. The relative standard deviations (RSD) for day-to-day achieved for 5 days was less than 22.4 %.