Epoxy Mixture Research Articles

Cure kinetics of a nadic methyl anhydride cured tertiary epoxy mixture

Cure kinetics of a methyl nadic anhydride cured tertiary epoxy (i.e., Diglycidyl ether of bisphenol A, a tetrafunctional epoxy and a fluorine-containing diepoxy), which is potential matrix for a polyimide fiber reinforced composites, were studied using dynamic and isothermal differential scanning calorimeter scans. Results showed that addition of the tetrafunctional epoxy and fluorine-containing diepoxy has negligible effects on the underlying cure mechanisms. Variation of glass transition temperature with extent of cure can be fitted using DiBenedetto equation. The Kamal model coupled with an empirical diffusion factor can adequately model the isothermal cure data. The Kamal model can model the reaction data well before vitrification. However, after vitrification, obvious deviation from Kamal model was observed, which have to be corrected using a diffusion factor. The apparent activation energy obtained from the Kamal model using isothermal data, agrees with that from the advanced isoconversional method, which utilizes the dynamic cure data.

Molecular Size Effect on Curing Process for Epoxy and Amine Mixture

The curing process of epoxy and amine mixtures was investigated from the viewpoint of molecular size of reactants via all-atom molecular dynamics simulation. Of four mixtures composed of either smaller or larger epoxy and amine molecules, the system of both smaller epoxy and amine reached the highest conversion at a given time, whereas the conversion for the combination of both larger epoxy and amine was the lowest. These can be explained in terms of their diffusion coefficients. In addition, the size effect on the reaction kinetics was more striking for epoxy than amine in the curing process. This was because epoxy reacted only once but amine did twice. When the primary amine reacted with epoxy, the resultant secondary amine was incorporated into the three-dimensional network. Hence, even if the primary amine had a higher mobility, the movement of the part after the reaction slowed down, making the further reaction to be the tertiary amine slow. Finally, it was shown that although the smaller epoxy reacted faster than the larger one in the mixed system of larger/smaller epoxy and amine, there was no difference in the reaction progress depending on the molecular size of amine.

Bulk Energy Transferability Linked to Critical N–H Modes of an Interfacial Nanoscale Surface Modification via Unique Isophorone Diisocyanate Amine Exchange Reaction

AbstractA surface‐modified carbon‐fiber reinforced epoxy (CF/E) via a unique isophorone diisocyanate amine (IDA) reaction produces a new interfacial epoxy‐polyurea “matrix” (IEPM) that elicits excellent mechanical energy transferability in brittle CF/E. The chemical bonding property in the IEPM molecule is produced via moieties of an epoxy mixture and N‐H‐concentrated urea molecules, where IDA thermodynamics are controlled via a curing parameter, tc (in hours). Nano‐scale properties of the IDA reaction, confirmed via fourier‐transform infrared spectroscopy and chemical mapping of molecules comprising the IEPM structure, are linked to bulk mechanical energy transferability, specifically loss modulus, E″(ω), and post‐elastic energy absorption. Using dynamic mechanical analysis (DMA) of six test specimens and a Generalized Maxwell Model – verified via Prony Series calibration of the storage modulus to DMA data to compute relaxation parameters – the ultrathin IEPM is isolated, and E″(ω) is computed as a function of tc. IEPM that is produced via tc = 0 exhibited two, six, and ten times greater loss modulus than IEPM produced via 0.5 ≤ tc ≤ 2; tc = 3.5; and tc = 24 (baseline design utilizes cured CF/E). Finally, IDA surface‐modification of CF/E improved energy absorption capacity (post‐elasticity) between 250% (tc = 0.5) and 300% (tc = 0).

Temperature-dependent electrical resistivity of macroscopic graphene nanoplatelet strips

This paper studies the temperature dependence of the electrical resistivity of low-cost commercial graphene-based strips, made from a mixture of epoxy and graphene nanoplatelets. An equivalent homogenous resistivity model is derived from the joint use of experimental data and simulation results obtained by means of a full three-dimensional (3D) numerical electrothermal model. Three different types of macroscopic strips (with surface dimensions of cm2) are analyzed, differing in their percentage of graphene nanoplatelets. The experimental results show a linear trend of resistivity in a wide temperature range (−60°C to +60°C), and a negative temperature coefficient . The derived analytical model of temperature-dependent resistivity follows the simple law commonly adopted for conventional conducting materials, such us copper. The model is then validated by using the graphene strips as heating elements by exploiting the Joule effect. These results suggest that such materials can be used as thermistors in sensing or heating applications.

A review on Graphene Reinforced Composites for Ballistic applications

The review paper emphasizes mainly on the hybridization of coir fiber and spider silk with carbon fiber and different percentage compositions of graphene, with an ultimate aim as to how the strength of these hybridized composites can contribute in the fields of material and manufacturing engineering. Firstly, there is an analysis of different properties of coir, carbon fibers, graphene and spider silk. Secondly, there is an analysis of the ballistic test performed on the specimens. In this review, some very basic yet important information is collected and discussed which will help the future researchers in the preparation of hybrid composites involving graphene. Being a natural fiber, the bristle coir fibers are pre-treated with alkali (NaOH) and then acidic treatment is done to remove the excess alkali. After the fibers become neutral, permanganate treatment is done. In case of spider silk, no pre-treatment is done. These fibers are reinforced with epoxy and different weight percentage of graphene (1wt%, 2wt%, 4wt%, 6wt %). Carbon fibre is incorporated in between using conventional hand layup technique. The epoxy and graphene mixture is sonicated to make sure that a uniform and good mixture is obtained. The review facilitates to perform ballistic test on the samples as the results from this test can substantiate to deliver a vital improvement in the field of material selection for body armors.

Corrosion Resistance Evaluation of Self-Healing Epoxy Coating Based on Dual-Component Capsules Containing Resin and Curing Agent

In this study, a self-healing epoxy coating was prepared by incorporating a dual capsule healing system including epoxy resin and its amine-based curing agent. The emulsion electrospray technique was used for encapsulating the healing agents in poly(styrene co-acrylonitrile) (SAN) as shell material. Characterizing the prepared microcapsules (MCs) by Scanning Electron Microscopy (SEM) revealed their spherical morphology with the particle size of 827 nm and 749 nm for epoxy and amine cores, respectively. Fourier Transform Infrared Spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results confirmed successful encapsulation with no side chemical reaction between the encapsulated core and shell materials. The effects of embedding MCs on the physical and mechanical properties of the epoxy coating matrix were studied by pull-off adhesion, conical mandrel bending, and gloss tests. In addition, the prepared coatings’ self-healing performance was evaluated by Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization (Tafel) experiments. The results revealed that the coating sample containing 1 wt% of core-shell MCs (a mixture of epoxy and amine-containing MCs with a 50 : 50 weight ratio) showed the best corrosion performance with 99% self-healing efficiency.

Improved mechanical performance of three-dimensional woven glass/epoxy spacer composites with carbon nanotubes

Three-dimensional polymer composites offer various features and design options due to their hollow structure and lightweight. However, to exploit their advantages, it is a must to improve their structural features and mechanical performances including out-plane direction. Although introducing thermoplastic fillers between the plies or multilayered design addresses on this critical issue, the benefits offered by the nanoparticles with superior mechanical properties come a step forward as an another engineering solution. Based on this motivation, the goal of this study is to investigate the impact of multiwalled carbon nanotubes on the mechanical and thermomechanical performances of three-dimensional woven glass/epoxy spacer composites. Therefore, multiwalled carbon nanotubes at various content were introduced into epoxy matrix, and the multiwalled carbon nanotubes–epoxy mixture was infused to three-dimensional woven fabric with the vacuum-assisted resin transfer method. The obtained results indicated that the three-point bending strength and modulus were enhanced up to 25 and 80% for warp direction and enhanced up to 44 and 85% for weft direction with carbon nanotube addition, respectively. Tensile strength developed in the warp direction by 7%, while the strength value in the weft direction did not change. The tensile strain values for warp and weft directions enhanced up to 19 and 12% with carbon nanotube addition, respectively. In addition, thermomechanical analysis has revealed that the glass transition temperature and storage modulus were also improved. Particle dispersion detection with color measurement and scanning electron microscopy analyses revealed the effectiveness of the ultrasonic mixing on the dispersion of carbon nanotubes in the epoxy matrix. The consequences of carbon nanotube addition on microscale morphology were discussed based on the fracture morphologies to nanoscale and microscale toughening mechanisms in the existence of carbon nanotube reinforcement.

Experimental Study on the Effect of Basalt Fiber and Sodium Alginate in Polymer Concrete Exposed to Elevated Temperature

Polymer concrete contains aggregates and a polymeric binder such as epoxy, polyester, vinyl ester, or normal epoxy mixture. Since polymer binders in polymer concrete are made of organic materials, they have a very low heat and fire resistance compared to minerals. This paper investigates the effect of basalt fibers (BF) and alginate on the compressive strength of polymer concrete. An extensive literature review was completed, then two experimental phases including the preliminary phase to set the appropriate mix design, and the main phase to investigate the compressive strength of samples after exposure to elevated temperatures of 100 °C, 150 °C, and 180 °C were conducted. The addition of BF and/or alginate decreases concrete compressive strength under room temperature, but the addition of BF and alginate each alone leads to compressive strength increase during exposure to heat and increase in the temperature to 180 °C showed almost positive on the compressive strength. The addition of BF and alginate both together increases the rate of strength growth of polymer concrete under heat from 100 °C to 180 °C. In conclusion, BF and alginate decrease the compressive strength of polymer concretes under room temperature, but they improve the resistance against raised temperatures.

Synthesis and characterization of polymer concrete withpumice aggregate and singkut leaf fiber as filler

Polymer concretehave been made based sand, pumice, epoxy resin, and singkut leaf fiber as fillers. The manufacture of polymer concrete uses block-shaped molds with a size of 100 mm x 20 mm x 10 mm with the press molding method using a hotpress. Variations in the composition polymer concrete of sand, pumice stone, singkut leaf fiber, and epoxy resin, namely 60:20:0:20 g, 60:18:2:20 g, 60:16:4:20 g, 60:14:6:20 g, 60:12:8:20 g, and 60:10:10:20 g. The variation in the composition was made into 2 groups of variations based on the concentration of NaOH used to singkut the leaves, namely the leaves with immersion of 5% NaOH and 13% NaOH. The polymer concrete then characterizes its physical properties (density and water absorption), mechanical properties (flexural strength, compressive strength, tensile strength), and SEM-EDX. The results of characterization carried out on concrete samples, show that the best composition is (60:18:2:20) g (5% NaOH content) with a density value of 1.74 g/cm3, water absorption of 0.34%, flexural strength. amounted to 37.07 MPa, compressive strength of 60.18 MPa, tensile strength of 8.33 MPa. The results of microstructure testing showed that the polymer concrete samples with a mixture of sand, pumice, epoxy resin, and singkut leaf fiber were mostly dominated by the element C (carbon).

Neutron and photon shielding competences of aluminum open-cell foams filled with different epoxy mixtures: An experimental study

In this study, ten open-cell aluminum foams with 30 mm thickness 2 pores/cm and 10 mm thickness 16 pores/cm pore sizes encoded A1-A5 and B1–B5 respectively were fabricated by filling with different mixtures which have Epoxy(60wt%)-B2O3(20wt%)-CeO2(15wt%)-(BaO, Cr2O3, WO3, Bi2O3, TiO2) (5wt%) chemical compositions. At first, gamma transmission measurements of the manufactured samples were achieved employing an Ultra Ge detector for 30.9, 59.54, 75, 81, 276, 303, 356, 384, and 662 keV photon energies. The foam samples were also irradiated with 6 MV energy X-rays via a linear accelerator (LINAC). The mass attenuation coefficients (MACs) of the samples and further photon protection parameters derived from MAC were computed with the data acquired from those measurements. It was found that the WO3 and B2O3 doped metal foams had the highest MAC values, whereas the lowest MAC values belonged to the TiO2 doped samples. Half Value Layers (HVL) obtained for two different metal foam samples of 30 mm and 10 mm thickness with Bi2O3 doped were found as 0.096cm-2.962 cm and 0.090 cm–2.921 cm, respectively. While the effective atomic numbers (Zeffs) of the WO3 and Bi2O3 added samples were of the highest values, the Energy absorption and Exposure Buildup Factors (EABF and EBF) calculated with Py-MLBUF in the energy range of 0.015–15 MeV were obtained as minimum compared to others. Finally, the shielding potential of the prepared samples against fast neutrons was assessed by performing equivalent dose measurements (EAD) and calculating macroscopic cross section (∑R) values. In A and B series metal foams, it was observed that the ∑R value was the highest in WO3-doped samples and got 0.1691 cm−1 and 0.1785 cm−1 values, respectively. It was also observed that the absorbed dose rates varied between 23% and 46%. It was concluded that B3 and B4 metal foams with thinner and higher pore sizes and doped with heavy oxides (WO3 and Bi2O3) could be used as an alternative shield material.

Novel conductive wearing course using a graphite, carbon fiber, and epoxy resin mixture for active de-icing of asphalt concrete pavement

Ice and snow on road surfaces can affect driving safety severely and cause accidents. Numerous active snow and ice removal technologies, such as conductive asphalt concrete, heating cables and pipes, have been developed in recent years. However, they reduce the lifetime of the pavement and cannot be applied on the existing roads. In this study, a novel conductive ultra-thin anti-skidding wearing course (CUAWC) is firstly proposed, which consists of a lower conductive layer and an upper wearing course. The conductive layer consists of a mixture of graphite, carbon fiber, and an epoxy resin adhesive. The optimal proportion of each additive was determined using an electrical conductivity test. The mass percolation threshold of graphite and carbon fiber in the conductive mixture were 25 and 4%, respectively. Freeze–thaw cycle and cyclic loading tests were conducted to evaluate the long-term skid resistance and resistivity fluctuation rate of the CUAWC. Finally, a laboratory de-icing test and a field snow melting test were performed. The CUAWC specimens had good skid resistance, good durability and stable resistivity, even after multiple freezing–thawing cycles and a million load cycles. Furthermore, the proposed CUAWC has lower resistivity and higher conductivity than traditional conductive asphalt concrete and can be laid on top of existing road surfaces.

Epoxy Doped, Nano‐scale Phase‐separated Poly‐Acrylates with Potential in 3D Printing

AbstractAn efficient method to improve the mechanical performance of a commercially available photocure resin is described wherein the resin is modified with a mixture of a cycloaliphatic epoxy and an anhydride curing agent. Photocured samples are thermally treated in a subsequent step to cure the epoxy to obtain an interpenetrated polymer network (IPN) and also complete reaction of the acrylate monomers remaining from the photocure. The latter is accomplished by a thermal radical initiator added earlier into the formulation together with the epoxy‐anhydride. The thermal properties and microstructure of the resulting IPN are analyzed. Uniform and quantitative conversions are obtained, with glass transition temperatures comparable to conventional epoxies. The liquid, uncured samples containing different amounts of epoxy are stable at 30 °C for several weeks. In the fully cured epoxy‐rich materials, nano‐scale phase separation is observed by atomic force microscopy. This is corroborated by the existence of multiple relaxations determined by dynamic mechanical analysis analysis. Specimens from a formulation containing 50% by weight of epoxy‐anhydride are 3D printed in a customized masked image processing stereolithography, thermally treated, and are subjected to compression tests. Results show that Young's modulus increases by 900% over the neat resin.

3D-Polystyrene-polymethyl methacrylate/divinyl benzene networks-Epoxy-Graphene nanocomposites dual-coated sand as high strength proppants for hydraulic fracture operations

The present work reports 3D-cross-linked polymer network-based coating onto frac sand prior to the epoxy coating to prepare dual-coated sand proppants with very high-stress resistance. The 3D-cross-linked poly(styrene-methyl methacrylate)/divinyl benzene) (PS-PMMA/DVB) coatings have been successfully prepared by the in-situ one-step bulk polymerization method with AIBN as an initiator at 70 °C. The 3D-polymer networks coated sand particles were then added with a mixture of epoxy resin and cure (4:1) along with commercial graphene (CG) and cured at 150 °C for 5 min. Interestingly, the roundness and sphericity of the sand particles have been retained even after the dual coating. The elasticity (E), hardness (H), and the fracture toughness (Kc) of the dual coating (PS-PMMA/DVB)-(Epoxy-CG) have been reached a maximum of 7.78 GPa, 0.34 GPa, and 3.22 MPa m1/2 respectively. The mechanically and thermally reinforced dual-coated sand particles with very high-stress resistance up to 12,000 psi will be successful proppants for hydraulic fracture operations.

Retracted] Investigation on Dielectric Properties of Press Board Coated with Epoxy Resin, Quartz, and Rice Husk Ash

Epoxy resin mixed with rice husk ash and quartz powder increases its dielectric strength. This paper presents the dielectric properties of the press board coated with this epoxy mixture. In this work, the press board, which is used in the transformer, is coated with three components: epoxy resin, rice husk ash, and quartz powder. The nanometer‐sized quartz powder and rice husk ash are mixed in the particular ratio with the epoxy resin. The mixture of epoxy resin, quartz powder, and rice husk ash is coated on both sides of the press board. The dielectric constant, volume resistivity, and Tan Delta (dissipation factor) of the coated press board are compared with the noncoated press board. The results reveal that the coated board is having high dielectric constant and volume resistivity when compared to the noncoated board.

Entropy-driven segregation in epoxy-amine systems at a copper interface.

The composition of an epoxy resin at the interface with the adherend is usually different from that in the bulk due to the enrichment of a specific constituent, a characteristic called interfacial segregation. For better adhesion, it should be precisely understood how epoxy and amine molecules exist on the adherend surface and react with each other to form a three-dimensional network. In this study, the entropic factor of the segregation in a mixture of epoxy and amine at the copper interface before and after the curing reaction is discussed on the basis of a full-atomistic molecular dynamics (MD) simulation. Smaller molecules were preferentially segregated at the interface regardless of the epoxy and amine, and this segregation remained after the curing process. No segregation occurred at the interface for a combination composed of epoxy and amine molecules with a similar size. These findings make it clear that the size disparity between constituents affects the interfacial segregation via the packing and/or translational entropy. The curing reaction was slower near the interface than in the bulk, and a large amount of unreacted molecules remained there. Finally, the effect of molecular shape was also examined. Linear molecules were more likely to segregate than round-shaped ones even though they were similar in volume. We believe that these findings, which are difficult to obtain experimentally, contribute to the understanding of the interfacial adhesion phenomena on a molecular scale.

Investigation of hardness & tribology behavior of Epoxy and Sio2 composite: An experimental study

In the ebb and flow research, an exhaustive trial study has been performed to investigate the properties of Epoxy grid mixture composite fortified by SIO 2 . The blending cycle was finished by Homogenizer to accomplish predictable dispersing of the filler particles into the grid. Tribological, Mechanical tests, for example, nail to ring wear test and Barcol hardness test were directed to assess the wear execution and hardness of Epoxy mixture composite. Exploratory examinations were done on a few Specimens of epoxy composite by changing the weight rates of the graphite filler from 1 to 5 at various weight %of SIO 2 and furthermore the outcomes were analyzed among themselves for various weight % tests. The mechanical and Tribological qualities, for example, hardness and wear pace of epoxy mixture composite material can be obviously enchased by the presentation of SIO 2 particles .

Anti-reflective coating by 3D PDMS stamping using two-photon lithography master

A method for the repeated manufacture of nanoscale optical features is presented. The method utilizes nanoscale 3D printing technology to create master structures that can be rapidly duplicated using a soft lithography method. Stamps are made of polydimethylsiloxane (PDMS) from the master structure and then inked with a mixture of nanoparticles and epoxy to create a 3D negative of the master structure. To demonstrate this method, an array of pyramids comprised of germanium (Ge) nanoparticles and epoxy were produced to function as an antireflective coating in the short wave infrared (SWIR). The antireflective array was tested and compared to 5 commercial low reflective coatings.

Novel BN‐epoxy/anhydride composites with enhanced thermal conductivity

A new series of high thermal boron nitride (BN) composites are prepared and characterized by several techniques. They are formed by an epoxy‐anhydride matrix and different BN contents, ranging from 30 to 80 wt%, of 120 μm agglomerates. For high BN ratio (≥60 wt%), epoxy mixtures were compressed (75 MPa) during 1 minute before curing, eliminating voids due to the high increase of viscosity, improving the compactness of the material and enhancing the thermal conductivity (TC). The curing process evolution was studied by calorimetric measurements to see if there was an influence of the filler on the curing rate. Rheological tests were performed to obtain the percolation threshold. It was observed that BN filler did not affect negatively the thermomechanical properties of the materials and allowed to enhance the TC from 0.17 W/m K in the case of the neat epoxy, to 3.06 W/m K when 80 wt% of BN agglomerates were added, which represents an improvement of 1700%.

Influence of polyethylene glycol (PEG) chain on the performance of epoxy asphalt binder and mixture

At low temperature, epoxy asphalt is a brittle material and presents insufficient resistance to deformation. In this research, a new approach was proposed by introducing PEG with number-average molecular weight (Mn) of 200,400, and 800 g/mol to improve the toughness of epoxy asphalt. The influence of PEG chain on the dynamic properties and hydrophilicity of epoxy asphalt binder, the mechanical properties and viscoelastic characteristics of epoxy asphalt mixture were investigated by experiments. The thermal stress of epoxy asphalt mixture containing PEG chains was analyzed by TSRST simulation. The results show that the performance of epoxy asphalt containing PEG with Mn of 200 g/mol is equivalent to that of commercial epoxy asphalt. With the Mn of PEG increasing, the low-temperature resistance, toughness, and hydrophilicity of binder enhance. Besides, the introduction of PEG chain has a slightly negative effect on the strength, high-temperature stability, and moisture resistance of epoxy asphalt mixture, while it has a significant improvement on low-temperature performance and toughness and a lower chance of thermal cracking damage. When PEG with Mn of 400–800 g/mol is introduced, epoxy asphalt mixture can be recommended for road and bridge deck pavement in severe cold regions.

SEM-Based Automated Mineralogy and Its Application in Geo- and Material Sciences

Scanning electron microscopy based automated mineralogy (SEM-AM) is a combined analytical tool initially designed for the characterisation of ores and mineral processing products. Measurements begin with the collection of backscattered electron (BSE) images and their handling with image analysis software routines. Subsequently, energy dispersive X-ray spectra (EDS) are gained at selected points according to the BSE image adjustments. Classification of the sample EDS spectra against a list of approved reference EDS spectra completes the measurement. Different classification algorithms and four principal SEM-AM measurement routines for point counting modal analysis, particle analysis, sparse phase search and EDS spectral mapping are offered by the relevant software providers. Application of SEM-AM requires a high-quality preparation of samples. Suitable non-evaporating and electron-beam stable epoxy resin mixtures and polishing of relief-free surfaces in particles and materials with very different hardness are the main challenges. As demonstrated by case examples in this contribution, the EDS spectral mapping methods appear to have the most promising potential for novel applications in metamorphic, igneous and sedimentary petrology, ore fingerprinting, ash particle analysis, characterisation of slags, forensic sciences, archaeometry and investigations of stoneware and ceramics. SEM-AM allows the quantification of the sizes, geometries and liberation of particles with different chemical compositions within a bulk sample and without previous phase separations. In addition, a virtual filtering of bulk particle samples by application of numerous filter criteria is possible. For a complete mineral phase identification, X-ray diffraction data should accompany the EDS chemical analysis. Many of the materials which potentially could be characterised by SEM-AM consist of amorphous and glassy phases. In such cases, the generic labelling of reference EDS spectra and their subsequent target component grouping allow SEM-AM for interesting and novel studies on many kinds of solid and particulate matter which are not feasible by other analytical methods.