Cycloaliphatic Epoxy Research Articles

Effects of UV for Cycloaliphatic Epoxy Resin via Thermokinetic Models, Novel Calorimetric Technology, and Thermogravimetric Analysis

The cycloaliphatic epoxy resin selected for this study was 3,4-epoxycyclohexane methyl-3′4′-epoxycyclohexyl-carboxylate (EEC). Epoxy resin has numerous applications, such as varnishes, tires, and electronic materials. However, the extensive used of chlorofluorocarbon (CFC) compounds in the last century has resulted in the formation of a hole in the ozone layer. As a consequence, solar radiation is intensifying gradually; therefore, continuous irradiation by sunlight should be avoided. The results of solar radiation can exacerbate the deterioration and photolysis of compounds. Through thermogravimetry and differential scanning calorimetry, the apparent onset temperature of EEC and EEC was analyzed under UV radiation for different durations. Thermokinetic data were used to determine the parameters of thermal decomposition characteristics through simulation to assess the reaction of EEC and EEC under UV radiation for different durations. The goal of the study was to establish the parameters of thermal decomposition characteristics for the effects of UV on EEC, as well as the probability of severity of thermal catastrophe.

Accelerated hygrothermal aging of Talc/Cycloaliphatic epoxy composites

Cycloaliphatic epoxy (CE) systems are resistant to many aging mechanisms, which make them useful in applications with harsh environments. Reinforcement has been used in epoxy systems to decrease water absorption and improve aging resistance; thus, it is expected that talc would benefit CE systems in a similar manner. Neat, 10, and 20 wt% talc/CE composites were aged at 50 °C and 100% relative humidity for up to 398 hr. Three‐point bend testing and dynamic mechanical analysis were performed on the aged and unaged samples. Talc reduced the amount of water absorbed in the composites significantly, and increased the composite flexural stiffness at all aging levels. Talc does not appear to mitigate the negative effects of aging on flexural strength or glass transition temperature (Tg). POLYM. COMPOS., 40:2946–2953, 2019. © 2018 Society of Plastics Engineers

Fabrication of Thermal Conductivity Enhanced Polymer Composites by Constructing an Oriented Three-Dimensional Staggered Interconnected Network of Boron Nitride Platelets and Carbon Nanotubes.

The orientation of ultrahigh aspect ratio thermally conductive fillers can construct a heat transfer path to enhance the thermal conductivity of composite materials effectively with low filler loading. Nevertheless, single orientation (vertical or horizontal) limited the application of these materials when there was the need for isotropic heat transferring. Here we report a novel strategy to prepare thermally conductive flexible cycloaliphatic epoxy resin nanocomposites with an oriented three-dimensional staggered interconnected network of vertically aligned h-BN (hexagonal boron nitride) platelets and randomly dispersed CNT-NH2 (aminated carbon nanotubes). In this structure, h-BN platelets coated with magnetic particles could respond to the external magnetic field; however, the CNT-NH2 couldn't. The obtained composites exhibited both through-plane (0.98 ± 0.037 W/m·K) and in-plane (0.99 ± 0.001 W/m·K) thermal conductivity enhancement at low h-BN loading of 30 wt %, and also presented excellent electrical insulating properties (<1.2 × 10-12 S/cm). In addition, the equal value of thermal conductivity of two directions (in-plane and through-plane) was shown when the content of h-BN was about 26.43 wt % and of CNT-NH2 was 2 wt %, displaying no difference between the thermal conductivity of two directions (in-plane and through-plane). The infrared imaging tests showed the outstanding heat dissipation capability of the composites by capturing the surface temperature variations of a heater with the composites as the heat dissipating material.

Thermal conductivity of graphene nanoplatelet/cycloaliphatic epoxy composites: Multiscale modeling

Composite materials using cycloaliphatic epoxy (CE) resins are used in some structural applications that require resistance to aggressive environments. Specifically, CE-based composites are used for structural reinforcement in aluminum conductor composite core (ACCC) high-voltage power lines. However, CE resins have a relatively low thermal conductivity, which makes it difficult to dissipate localized heating due to transmission line faults. Graphene nanoplatelet (GNP) reinforcement can potentially improve the thermal conductivity of CE composites (∼0.2 W/m-K) due to its superior in-plane thermal conductivity (∼5300 W/m-K). In this study, the thermal conductivities of GNP/CE composites are investigated by multiscale modeling using molecular dynamics (MD) and micromechanics simulation techniques. Different levels of GNP dispersion and aspect ratio are studied and compared to experimental data established herein and in the literature. The thermal conductivity of GNP/CE composites increases with increased GNP content, dispersion, and aspect ratio. Additionally, covalently functionalized GNP/CE systems are simulated to determine the effect of functionalization on thermal conductivity. The transverse thermal conductivity of GNP/CF/CE hybrid composites is further investigated and validated with experimental values. This study establishes a unique multiscale modeling approach for predicting thermal conductivity of polymer nanocomposite materials (and hybrid composite materials) based on molecular structure of the nano-reinforcement/polymer interface.

A solid polymer electrolyte for aluminum ion conduction

We report on the synthesis and characterization of a solid polymer electrolyte for aluminum ion conduction. The solid polymer electrolyte is produced via the copolymerization of a low molecular weight polytetrahydrofuran and a cycloaliphatic epoxy. The crosslinked copolymer is swollen in THF solutions of different concentrations of aluminum nitrate as the aluminum ion source. The conductivity as a function of concentration is measured via AC impedance spectroscopy over a temperature range of 20–110 °C. We attain conductivities that increase with salt loading, reaching a value of 2.86 × 10−5 S·cm−1. Thermogravimetric analysis shows the electrolytes are stable up to 150 °C. Raman spectroscopy reveals complete dissociation of the aluminum nitrate salt in the electrolyte over the concentration range explored. This study establishes a polymer system and synthetic route towards solid polymer electrolytes for aluminum ion conduction, for the development of all solid-state aluminum ion batteries.

Synthesis and properties of cycloaliphatic epoxy resins containing imide and diphenyl sulfone

A novel variety of cycloaliphatic epoxy resins containing imide and diphenyl sulfone (named as 4,4′-bis[4-(4,5-epoxy-1,2,3,6-tetrahydro-phthalimido) phenoxy] diphenyl sulfone, BIES) is designed and synthesized through the three-step procedure. The mixtures of BIES and diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate (TDE-85) are cured with methyl tetrahydrophthalic anhydride. Fourier transform infrared spectrum and proton nuclear magnetic resonance spectrum confirm that the BIES contains the chemical structure of imide and diphenyl sulfone. The measurements of glass transition temperature ( Tg), heat distortion temperature (HDT), and the 5% weight loss temperature ( T5%) show that the co-cured BIES/TDE-85 exhibits excellent heat resistance. For the BIES/TDE-85 with mass ratio of 0.2, Tg, HDT, and T5% of the co-cured epoxy are 175°C, 162°C, and 290°C, respectively. The impact strength increases from 117 J m−1 to 139 J m−1 with the increasing of the mass ratios of the BIES/TDE-85 from 0 to 0.2.

Enhanced interfacial and mechanical properties of high-modulus carbon fiber composites: Establishing modulus intermediate layer between fiber and matrix based on tailored-modulus epoxy

Tailored-modulus epoxy matrix was designed on basis of surface analysis of high-modulus carbon fibers (HMCF), and the effects of modulus intermediate layer on interfacial and mechanical properties of HMCF composites were investigated. Narrow grooves and active functional groups were detected on HMCF surface. The modulus of epoxy was tuned by stiff organic molecular structure of cycloaliphatic epoxy (CE) and amide acid (AA). Modulus intermediate layer was established along with modulus gap shrinkage and interphase extension between HMCF and high-modulus epoxy, causing remarkable improvements in interfacial properties of composites. Schematic model of interphase reinforcing mechanism was proposed, and modulus intermediate layer with a platform in the composites with high modulus epoxy matrix could facilitate the shift in stress concentration and suppress initiation and propagation of cracks, which resulted in improved mechanical properties of HMCF composites by enhancement of interfacial bonding and stress transfer capability between fiber and matrix.

Fabrication of High‐Performance Cationic UV Curable Cycloaliphatic Epoxy/Silicone Hybrid Coatings

AbstractA series of cycloaliphatic epoxy acrylate prepolymer poly (METHB‐co‐MMA‐co‐BA) (MMB) and an epoxycyclohexyl‐modified polydimethylsiloxane (PDMS‐VCH) are prepared to fabricate hybrid coatings. The curing process, surface performance, mechanical properties, and thermal behavior are investigated by real‐time Fourier transform infrared (FT‐IR), contact angle measurements, tensile test, thermogravimetric analyzer (TGA), and differential scanning calorimeter (DSC). For the same photoinitiator (PI) concentration, both the epoxy value and the amount of PDMS‐VCH negatively affect the UV‐curing process. The contact angle of hybrid coatings increases by almost 12° with 4 wt% PDMS‐VCH's addition. The increasing ratio of soft acrylate segment can strengthen the toughness of materials markedly. Besides, thermal stability is enhanced with the increasing of epoxy value, while slight changes are found with the addition of PDMS‐VCH. Based on these properties, the hybrid coatings can be applied in various fields, including protection, decoration, and other displayed fields.

Synergistic enhancement of anisotropic thermal transport flexible polymer composites filled with multi-layer graphene (mG) and mussel-inspiring modified hexagonal boron nitride (h-BN)

In this work, we presented novel cycloaliphatic epoxy resin composites filled with multi-layer graphene (mG)/hexagonal boron nitride (h-BN) with high thermal conductivity and good electrical insulating. Firstly, the h-BN platelets were modified by mussel-inspired method with dopamine chemistry to obtain the modified filler h-BN@PDA. And the attachment of polydopamine molecule improved the interfacial adhesion between polymer matrix and filler. Secondly, the mG with fixed content was mixed with h-BN@PDA and then the hybrid filler mG/h-BN@PDA was added to the cycloaliphatic epoxy resin to obtain the polymer composites. Because of the high aspect of the filler, low viscosity of the polymer matrix, and assistance of the gravity force, the hybrid filler would stack alignment. It was found that the hybridization of the filler and alignment of the hybrid filler resulted in the enhancement of properties of the composites such as the thermal decomposition, mechanical (tensile strength = 5.50 MPa), thermal (through-plane ∼ 1.27 W/m K, in-plane ∼ 1.31 W/m K) and electrical insulating (electrical conductivity < 1.5 × 10−10 S/cm) properties. The obtained composites could be applied in thermal management area.

Anisotropic thermally conductive flexible polymer composites filled with hexagonal born nitride (h-BN) platelets and ammine carbon nanotubes (CNT-NH2): Effects of the filler distribution and orientation

High thermal conductive filler (hexagonal boron nitride and carbon nanotube) reinforced polymer composites have obtained a growing attention in the microelectronic industry for their good thermal conductivity but electrical insulating. In this work, a synergistic hybrid structure of two fillers with different dimensions had been designed and prepared by taking hexagonal born nitride (h-BN) platelets and ammine carbon nanotubes (CNT-NH2) into the flexible polymer matrix. Using cycloaliphatic epoxy resin (CER) as the polymer matrix, a serious of (a) h-BN/CER based, (b) hybrid filler h-BN@CNT-NH2/CER based, and (c) mixed filler CNT-NH2 and h-BN/CER based composites were prepared. In this structure, h-BN (and h-BN@CNT-NH2) platelets stacked along the horizontal direction under the assistance of gravity force and interactivity between the fillers. The orientation of the h-BN platelets was investigated by scanning electron microscope (SEM) of the cracked cross-section of the composite film and XRD measurement via calculating the orientation function (f). The CNT-NH2 was embedded within the network to improve the filler-filler contact or network-density. Due to the anisotropic properties of h-BN platelets and dispersion states of CNT-NH2, the composites with different structures presented different and special properties, including thermal/electrical conductivity properties, mechanical properties, and thermal decomposition properties. The analysis of structure and mechanism of thermal decomposition were then proposed to explain those interesting properties. The incorporation and dispersion states of CNT-NH2 in the composites played an important effect on the enhancement of the thermal conductivity properties both included in-plane (∼1.76 W/m·K) and through-plane (∼1.09 W/m·K) thermal conductivity. Additionally, the good electrical insulating properties and mechanical properties of the composites provided a potential application in the thermal management areas. The solvent-free procedure was environment friendly, easy operation, and suitable for the practical application in large scale.

Oligo-fluoropolymer Modified Cycloaliphatic Epoxy Resins with Excellent Compatibility, Waterproof and Mechanical Properties for LED Encapsulation

An oligo-fluoropolymer(PFM) with functional cycloaliphatic epoxy and fluorinated groups was obtained via free radical polymerization and applied to the modification of cycloaliphatic epoxy resins(CE). The chemical structure of PFM was characterized by Fourier transform infrared(FTIR) spectroscopy, gel permeation chromatogra-phy(GPC) and nuclear magnetic resonance(NMR) spectroscopy, and the effects of different PFM concentra-tions(0.5%—6%, mass fraction) on the thermal resistance, mechanical properties, surface dewettability, light trans-mission, refractive index and various cured polymer properties were studied in detail. The DSC and TGA results demonstrate that the modified epoxy resins possess a higher thermal resistance than the neat epoxy resin. The im-provements in the surface dewettability and water resistance are caused by the high crosslinking density and the enrichment of the oligo-fluorinated random copolymers dispersed in the matrix. The fracture surface morphologies of the thermosets were investigated by scanning electron microscopy(SEM) and transmission electron microsco-py(TEM). It was observed that the optical transmittance of the composites was maintained even though microphase separation occurred during the curing process. With respect to the corresponding properties of the neat epoxy resins, the 2 phr(parts per hundreds of resin) PFM thermoset exhibited relatively better comprehensive properties, making the cured material a good candidate for light-emitting diode(LED) encapsulation.

Multifunctional anisotropic flexible cycloaliphatic epoxy resin nanocomposites reinforced by aligned graphite flake with non-covalent biomimetic functionalization

High thermal conductive filler (graphite flake) reinforced polymer composites have obtained a growing attention in the microelectronic industry. In order to overcome the obstacles in surface modification, in this study, dopamine chemistry was used to achieve the facile modification of graphite flake via forming a polydopamine (PDA) shell on the surface in a solvent-free aqueous condition. The strong π-π interaction between the hexagonal structural graphite flake and aromatic dopamine molecules ensured the effective modification. The PDA coating on graphite flake enhanced the compatibility between the filler and the flexible cycloaliphatic epoxy resin (CER) matrix via hydrogen bond, and promoted the epoxy curing process by forming covalent bond. Under the assistance of gravity, the PDA@graphite flake stacked along the horizontal direction in the polymer matrix. The procedure of filler alignment and mechanism of thermal decomposition were investigated by XRD measurement and thermodynamic/kinetics analysis, respectively. The dynamic mechanical analysis (DMA) was also used to investigate the relationship between microstructure and performance. Due to the combination of surface modification and alignment of PDA@graphite flake, the prepared CER/PDA@graphite has higher in-plane thermal conductivity. In addition, excellent adhesion property and thermal stability demonstrated that the CER/PDA@graphite composites was a good candidate as thermal interface material (TIMs), which could be applied in the thermal management areas. The procedure was environment friendly, easy operation, and suitable for the practical application in large scale.

Creeping discharges features propagating in air at atmospheric pressure on various materials under positive lightning impulse voltage – part 1: noise suppression using the discrete wavelet transform approach

The acquisition of discharges data is usually affected by external interference leading to erroneous interpretations. In the viewpoint of improving computation accuracy, the discrete wavelet transform (DWT) has been used as an effective tool for de-noising purposes. In this study, creeping discharges waveforms have been investigated under the positive lightning impulse voltage over various materials. The used polymers belong to three distinct families (i) thermoplastics (namely polyamide 6 and polyamide 66), (ii) one filled cycloaliphatic epoxy resin and (iii) one unfilled ethylene propylene diene monomer (EPDM). Two approaches namely one-dimensional (1D) and 2D DWT algorithms have been adopted for de-noising signals and images, respectively. Both techniques were applied for simulated and laboratory data using various wavelet families (Daubechies, Symlet and Coiflet). The comparison of de-noising performance for signals has been achieved through the calculation of signal-to-noise ratio, normalised correlation coefficient (Norm_corr) and root mean squared errors. Moreover, the computation of power spectral density of lightning current transients using a periodogram estimator is also analysed. For images, mean square error and peak-signal-to-noise ratio assess the quality of filtering regarding the visualisation of discharges patterns. Results show that Coiflet wavelets demonstrate their effectiveness to reduce background noise and preserve the signals shape and images edges.

New epoxy composite thermosets with enhanced thermal conductivity and high Tg obtained by cationic homopolymerization

Thermal dissipation is a critical aspect for the performance and lifetime of electronic devices. In this work, novel composites based on a cycloaliphatic epoxy matrix and BN fillers, obtained by cationic curing of mixtures of 3,4‐epoxy cyclohexylmethyl 3,4‐epoxy cyclohexane carboxylate (ECC) with several amounts of hexagonal boron nitride (BN) were prepared and characterized. As cationic initiator a commercial benzylanilinium salt was used, which by addition of triethanolamine, exhibited an excellent latent character and storage stability. The effect of the formulation composition was studied by calorimetry and rheological measurements. The variation of thermal conductivity, thermal stability, thermal expansion coefficient, and thermomechanical and mechanical properties of the composites with the load of BN filler (ranging from 10 to 40 wt%) was evaluated. An improvement of an 800% (1.04 W/m·K) in thermal conductivity was reached in materials with glass transition temperatures &gt;200°C without any loss in electrical insulation. POLYM. COMPOS., 39:E1760–E1769, 2018. © 2018 Society of Plastics Engineers

Creeping discharges features propagating in air at atmospheric pressure on various materials under positive lightning impulse voltage – part 2: modelling and computation of discharges’ parameters

In this paper, the propagation mechanism of creeping discharges up to flashover for short air gaps is examined and described on various materials based on laboratory de-noised data (namely current, voltage and captured images). The main parameters considered for investigating the development of creeping discharges and their characteristics deal with the measurement, modelling and calculation of (i) their final/stopping length and morphology, (ii) their propagation velocity and (iii) the electric field distribution including the maximal magnitude ( E max ) and the geometric coefficient ( β ) estimation. The obtained results evidenced that both length and velocity of discharges are emphasised for polyamide-based materials (namely PA6/50 and PA66/50) whereas their ignition remains inhibited for filled cycloaliphatic epoxy resin (FCEP) and ethylene propylene diene monomere (EPDM) surfaces. As the electric field is concerned, both analytical and numerical models are developed and their results are compared and discussed. It has been shown that the presence of a polymer acts as a barrier when being incorporated between an electrodes gap whose dielectric strength depends strongly on the used material. Moreover, the FCEP barrier, in comparison to other materials, exhibits a marked dielectric reinforcement and an enhanced stability of the system making it suitable to provide a better protection to high-voltage equipment against discharges effects.

Investigation on the chemical structure and ageing transformations of the cycloaliphatic epoxy resin EP2101 used as stone consolidant

Abstract The commercial cycloaliphatic epoxy resin EP2101, frequently used as a structural stone strengthening agent in monuments, was tested to ascertain the related chemical nature, the mechanisms involved in the polymerization reaction and the stability under degradative environments. After a preliminary chemical characterization in the laboratory by means of GC/MS and FTIR, the resin was applied by brushing to the surface of veined Carrara marble and Vicenza white limestone specimens, and subjected to three different typologies of degradation: natural weathering, artificial accelerated ageing and resistance to mould growth. The resin's stability was monitored by microscopic observations, FTIR and SEM-EDX analysis, colorimetric and water absorption measurements. The results prompted a number of considerations, which were confirmed by those obtained from the examination of samples taken from a granite column in Murano (Venice) and a laboratory specimen of Proconnesian marble, treated in 1985 and 1984 respectively.

Cycloaliphatic epoxy-based hybrid nanocomposites reinforced with POSS or nanosilica for improved environmental stability in low Earth orbit

Abstract The purpose of this study is to demonstrate the properties of novel nanocomposites, based on cycloaliphatic epoxy resin additionally reinforced with silicon-containing nanostructures (mono- or octa-functional POSS or nanosilica). The changes in properties are discussed for the varied combinations of cycloaliphatic epoxy with a curing agent (cycloaliphatic amine or anhydride) and the nanomodifier. The influence of modification on thermal stability, curing behaviour, morphology, surface chemistry, and topography were studied with TGA, DSC, ATR-FTIR, XPS and LCM. The results show that when POSS and/or nanosilica are incorporated to the cycloaliphatic matrix they influence curing behaviour and glass transition temperatures (Tg), where mono-POSS increases Tg and octa-POSS decreases it with respect to nanosilica. Mono-POSS produces silicon-rich surfaces but tends to agglomerate and increase surface roughness. Octa-POSS and nanosilica penetrate the polymer matrix more deeply and disperse more easily. From the selected modifiers, octa-POSS shows the highest thermal stability.

Latest Development and Application of Cycloaliphatic Epoxy Resin

Latest Development and Application of Cycloaliphatic Epoxy Resin

Analysis of atomic oxygen and ultraviolet exposure effects on cycloaliphatic epoxy resins reinforced with octa-functional POSS

In this study, novel nanocomposites were created by incorporation of Silsesquioxane containing eight glycidylether groups (octa-POSS) into a cycloaliphatic epoxy cured by an anhydride. The developed resin system, with different nanoparticle concentrations, was used on the outer layers of an ultra-thin CFRP structure in order to provide better environmental resistance to the environment of low Earth orbit (LEO) which was tested in a ground-simulation facility. The developed resins were subjected to space-like degrading factors and their response to corrosion, radiation and elevated temperatures was monitored by mass loss, together with measuring changes in surface chemistry (ATR-FTIR), functionality development (contact angle measurement and XPS), roughness (scanning laser microscopy) and morphology (SEM). The influence of increasing octa-POSS content on thermo-mechanical properties was measured with DMTA and the strength and modulus of elasticity were determined by flexural test. The addition of octa-POSS in any loading improves the environmental resistance, however, the most significant retention of mass and mechanical and surface properties after space-like exposure was observed in the 20 wt% octa-POSS reinforced cycloaliphatic epoxy. The results presented here may contribute to the development of novel class of nanocomposites which can offer an extended service life in LEO.

Thermal, electrical, and mechanical properties of talc‐ and glass microsphere‐Reinforced Cycloaliphatic epoxy composites

Cycloaliphatic epoxy (CE) is used in high voltage and temperature applications because of its high glass transition temperature and resistance to ultraviolet, ozone, and hydrothermal aging mechanisms. Fillers can be used to increase the tensile modulus and thermal conductivity (TC) without a corresponding increase in electrical conductivity (1/electrical resistivity [ER]), which would be detrimental in a high voltage environment. In this study, two fillers were examined in a CE system: talc and glass microspheres (MS). Up to 20 wt% talc/CE and up to 40 wt% glass MS/CE composites were fabricated and tested for ER, TC, and tensile properties. As desired, all composites remained electrically resistive. Composite TC increased with increasing filler content from 0.15 W/m‐K for the neat epoxy to 0.25 W/m‐K for 20 wt% talc and for 40 wt% glass MS. This TC increase could be helpful to dissipate heat in high voltage and temperature applications. Tensile modulus increased from 2.7 GPa for the neat epoxy to 3.6 GPa for 20 wt% talc/CE and to 5.2 GPa for 40 wt% glass MS/CE composites. Increasing the tensile modulus is useful in the newly developed Polymer Core Composite Conductors that are used to transmit power. POLY COMPOS., 39:E1581–E1588, 2018. © 2017 Society of Plastic Engineers