Epoxy Blends Research Articles

Influence of nanoclay as a compatibilizer and a reinforcement for polymer blends used as insulators

Polymer composite materials were prepared using kaolinite nanoclay as reinforcement in different weight fractions (3, 5 and 7) %, and blends of epoxy and polymethyl methacrylate (PMMA) as matrices. The current work aims to prepare a composite material with good thermal and acoustic insulation, besides improved mechanical properties, and the investigation of the effect of this nano additive on the compatibility between the two constituents of the blend, and how this compatibility might be beneficial to the performance of the prepared composite. The blend with an optimum mixing ratio (OMR) was chosen via impact test results; thus, the (80:20) percentage of epoxy and PMMA was chosen. The reinforced specimens showed an improvement in mechanical (impact and flexural) properties besides sound insulation and thermal conductivity, with the specimen reinforced with 7% nanoclay having the highest impact strength (97*10−3) KJ/m2 and the highest thermal conductivity value of (0.34) W/m.°C, with a sound intensity value 95.6 decibels at frequency 10,000 Hz. The scanning electron microscope images showed two separate phases in the unreinforced blend. In comparison, the 7% reinforced specimen showed a rough interface between the two polymer phases, suggesting a positive effect of nanoclay addition on compatibility. The differential scanning calorimeter showed two distinct glass transition temperatures for both reinforced and neat specimens, which belong to the glass transitions of both constituents (epoxy and PMMA). The main difference is the lower temperature gradient accompanied with the (nanoclay/blend) composite than the neat one. Although the blend remained immiscible, nanoclay had contributed to the compatibility and improved mechanical properties.

Synthesis and properties of foams from a blend of vegetable oil based polyhydroxyurethane and epoxy resin

This article aims to highlight the synthesis of foams from a blend of hydroxyurethane of castor oil and epoxy resin. An epoxidized castor oil of 4% oxirane oxygen was first converted to cyclic carbonate of castor oil at 120°C, 1 atm CO2 pressure and then it was reacted with three different aliphatic diamines to yield amine terminated Polyhydroxyurethane (PHU). Foams were prepared in a metal mould from the blend of PHU, epoxy resin, epoxy hardener and polymethylhydrogensiloxane blowing agent which releases hydrogen gas upon reaction with amine. FTIR and 1H NMR of cyclic carbonate of castor oil and PHU of castor oil were done to confirm their chemical structures. Optical microscopy and scanning electron microscopy of foams was done to assess their cellular morphology along with DSC and TGA to evaluate their thermal properties. Both flexible and rigid type of foams were synthesised in this study. Resilience of flexible foams was inspected using a ball rebound test and compression-recovery test while thermal insulation property was checked by measuring thermal conductivity, thermal diffusivity and R-values of rigid foams from heat transfer study using a heat transfer apparatus.

Properties of an Epoxy Blends Modified with a Thermoplastic Heat-Resistant Polymer and an Active Diluent for Manufacture of Reinforced Plastics

Properties of an Epoxy Blends Modified with a Thermoplastic Heat-Resistant Polymer and an Active Diluent for Manufacture of Reinforced Plastics

Highly Conductive Polymer Composite Based on Graphite-Filled Immiscible Polyolefin/Epoxy Blends

Conductive polymer composites (CPCs) based on polypropylene (PP)/epoxy (EP) and high-density polyethylene (HDPE)/EP blends filled with synthetic graphite (SG) were produced and characterized to explore their potential for high electrical conductivity applications. The polymer blends were chosen as matrices due to their immiscibility and potential to enable co-continuous morphology formation and preferential distribution of filler, which allows formation of maximized conducting networks. In-plane and through-plane resistivities of PP/EP/SG composites decreased from 0.083 Ω.cm to 0.015 Ω.cm and 10.16 Ω.cm to 0.31 Ω.cm, respectively, while for HDPE/EP/SG composites, in-plane and through-plane resistivities decreased from 0.086 Ω.cm to 0.014 Ω.cm and 5.02 Ω.cm to 0.24 Ω.cm, respectively, when SG content was increased from 30 to 80 wt%. The immiscible blend-based composites produced in this study have the potential to achieve significantly higher conductivity than filled single polymers due to concentration of filler in one of the polymer phases and the co-continuous structure of the blends. Also, resistivity anisotropy of the PP/EP/SG and HDPE/EP/SG composites generally decreased with increase in SG content, with HDPE/EP/SG composites showing lower resistivity anisotropy than PP/EP/SG composites at the same SG content.

Effects of Thermal Activation on CNT Nanocomposite Electrical Conductivity and Rheology.

Carbon-based nanocomposites featuring enhanced electrical properties have seen increased adoption in applications involving electromagnetic interference shielding and electrostatic dissipation. As the commercialization of these materials grows, a thorough understanding of how thermal activation affects the rheology and electrical performance of CNT–epoxy blends can inform quality decisions throughout the production process. The aim of this work was the identification of the effects that thermal activation has on the electrical and rheological properties of uncured epoxy mixtures and how those may be tied to the resulting cured composites. Herein, three distinct CNT-loaded composite mixtures were characterized for changes in electrical resistivity and viscosity resulting from varying activation times. Electrical conductivity decreased as activation time increased. Uncured mixture viscosity exhibited a strong dependence on CNT loading and applied strain, with activation time being found to significantly reduce the viscosity of the uncured mixture and surface profile of cured composite films. In all cases, cured composites featured improved electrical conductivity over the uncured mixtures. Factors contributing to the observed behavior are discussed. Raman analysis, optical microscopy of CNT networks, and data from silica bead mixing and dispersion studies are presented to contextualize the results.

Modelling of Phase Transitions and Residual Thermal Stress of CTBN Rubber Modified Epoxy Resins during a Pultrusion Process

Abstract The implicit finite difference and fourth order Runge-Kutta method are used both to solve the heat transfer problem in the pultrusion reaction and to calculate the temperature and conversion distributions within a thermoset composite profile. The aim of our work is to study the influence of a rubbery phase added to the epoxy matrix in production conditions. The results have shown that the rubber modified systems have a low exothermic temperature peak value, so that neither the amount of cured resin nor the final product properties are limited. First of all we will show that the phase transition (gelation and vitrification) zones within the die change as the amount of rubber varies in the resin. The relationship between the position and of these zones and the resin systems will be discussed. We calculate the residual thermal stresses for all the investigated fibre/resin systems, showing a reduction when the rubber amount increases in the epoxy blend.

Study of Mechanical Properties and Thermal Conduction of Polymer/Ceramic Nanocomposites

A composite materials were prepared using a polymeric blend of epoxy resin and unsaturated polyester as a matrix material, and using a nanoceramic powder Lead Zirconium Titanate as a reinforcement material in different adding ratios( 2wt % & 6wt % ). Impact strength, surface hardness, thermal conductivity and solutions absorption tests were carried out for the polymeric blend and composite samples. The pre-immersion results showed that adding the ceramic powder to the polymeric blend improved the surface hardness, increased thermal conductivity as well as reduced impact strength. Immersing the samples in H2SO4 acid and kerosene caused of decrease in impact strength and surface hardness as well as increase in thermal conductivity. It was also noticed an increase in the absorption rate of acid and kerosene solutions in a manner proportional to the duration of immersion.

Self-Assembled Microstructures with Localized Graphene Domains in an Epoxy Blend and Their Related Properties

Self-Assembled Microstructures with Localized Graphene Domains in an Epoxy Blend and Their Related Properties

Dynamic Mechanical and Chemorheology Analysis for the Blended Epoxy System with Polyurethane Modified Resin

As the important matrix material, epoxy resin has been widely used in the composites for various fields. On account of the poor toughness of epoxy resin limiting their suitability for advanced applications, considerable interests have been conducted to modify the epoxy resin to meet the engineering requirements. In this study, the bio-based polyurethane (PU) modified resin was adopted to modify the pure bisphenol-A epoxy by blending method with various proportions. Aiming to illuminate the curing behavior, mechanical and thermal properties, the blended epoxy systems were characterized by viscosity-time analysis, dynamic mechanical analysis (DMA) at different frequencies and temperatures, mechanical tensile test, thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. The results indicated that the introduction of PU modified epoxy was found to significantly inhibit the viscosity growth rates especially when the content of PU modified epoxy resin is higher than 60%. Notwithstanding the dynamic modulus and Tg reduced with the increment of PU modified epoxy, remarkable increment on the elongation at break was found and the flexibility was greatly promoted with the introduction of PU modified epoxy. The proportion of PU modified epoxy in the blends should be put balance considerations to obtain optimal mechanical properties. TGA results and FTIR spectrum demonstrated that the addition of PU modified epoxy did not change the thermal decomposition mechanism and chemical reaction mechanism, but the addition of PU modified epoxy inhibits the curing reaction of epoxy resin by measured and calculated the damping temperature domain ΔT from 35.7°C to 48.9°C.

Thermal, mechanical, and electrical properties of difunctional and trifunctional epoxy blends with nanoporous materials

In the present study, the aim is to synthesize the particulate nanocomposites with difunctional and trifunctional epoxy blend as matrix and synthesized nanoporous materials as fillers. Organic/inorganic hybrid networks were prepared by the novel solvent free method. Viscoelastic, thermal, and electrical properties of di- and trifunctional epoxy and the effect of different nanoparticles in the particulate nanocomposites have been studied by dynamic mechanical analyzer, thermogravimetry (TGA), and dielectric strength. Epoxy mixed with different compositions of TGPAP and particulate nanocomposites by the addition of different types of nanomaterials shows higher storage modulus than the pure epoxy. The addition of TGPAP and nanofillers decreases the thermal stability of epoxy matrix. The evolved gas analysis (TG-FTIR) was also done in order to study the products formed during degradation. An increase in dielectric strength and impact strength (4%) was also observed in the particulate nanocomposites.

A novel hyperbranched phosphorus-boron polymer for transparent, flame-retardant, smoke-suppressive, robust yet tough epoxy resins

The fabrication of fire-safe, robust yet tough polymeric materials represents a challenge for both academia and industry. In this work, a novel hyperbranched polymer (TP) based on trihydroxymethylphosphine oxide and phenylboronic acid for epoxy resin is described. The presence of 2 wt% TP afforded epoxy blend with a high limiting oxygen index of 33.2%, a UL-94 V-0 rating, 36.3% and 13.7% reductions in peak heat release rate and total smoke production, making it superior to previously described counterparts. The high efficiency of TP may be mainly attributed to its promotion of carbonization . Notably, an epoxy thermoset is strengthened and toughened due to the introduction of TP. The presence of 4 wt% of this additive increased the tensile strength , elongation at break , impact strength, and flexural strength by 54.0%, 32.8%, 32.0% and 36.9%, respectively. In addition, the high transparency of the epoxy thermoset is maintained in the presence of TP. Thus, this approach offers an integrated design for the preparation of transparent, fire-safe, strong but tough epoxy thermoset via the introduction of a hyperbranched polymer. It may be expected that this technique will find wide application in different industrial fields.

Cyanate Ester– Epoxy Blends toward Microwave Transparent Polymer Composites through Resin Film Infusion for Wideband Electromagnetic Applications

ABSTRACT Cyanate Ester–Epoxy blends and their glass–fabric reinforced composites with improved thermal, mechanical, and dielectric characteristics were developed through cost-effective out-of-autoclave process, resin film infusion. They are thermally stable at least up to 320°C with glass transition temperature up to 195°C. They have excellent structural characteristics in comparison to their pristine counterparts, and their crosslinking was validated with Fourier transform infrared. Electromagnetic properties such as ε’ (2.8–3.0), ε” (0.02–0.14), tan δ (0.008–0.051), and transmission loss of <−1.5 dB makes them ideal materials for electromagnetic transparent composites and for encapsulating applications for wideband microwave frequencies.

Roles of Small Polyetherimide Moieties on Thermal Stability and Fracture Toughness of Epoxy Blends.

Bisphenol A diglycidyl ether (DGEBA) was blended with polyetherimide (PEI) as a thermoplastic toughener for thermal stability and mechanical properties as a function of PEI contents. The thermal stability and mechanical properties were investigated using a thermogravimetric analyzer (TGA) and a universal test machine, respectively. The TGA results indicate that PEI addition enhanced the thermal stability of the epoxy resins in terms of the integral procedural decomposition temperature (IPDT) and pyrolysis activation energy (Et). The IPDT and Et values of the DGEBA/PEI blends containing 2 wt% of PEI increased by 2% and 22%, respectively, compared to those of neat DGEBA. Moreover, the critical stress intensity factor and critical strain energy release rate for the DGEBA/PEI blends containing 2 wt% of PEI increased by 83% and 194%, respectively, compared to those of neat DGEBA. These results demonstrate that PEI plays a key role in enhancing the flexural strength and fracture toughness of epoxy blends. This can be attributed to the newly formed semi-interpenetrating polymer networks (semi-IPNs) composed of the epoxy network and linear PEI.

Optimization of Glass Transition Temperature and Pot Life of Epoxy Blends Using Response Surface Methodology (RSM).

The aim of this work was to improve the processability of triglycidyl-p-aminophenol (TGPAP) epoxy resin. To achieve this improvement, a diluent, the diglycidyl ether of bisphenol F (DGEBF or BPF), was added to TGPAP, and the blended epoxy was then cured with 4, 4′-diaminodiphenyl sulfones (DDS). A response surface methodology (RSM) was used, with the target response being to achieve a blended resin with a high glass transition temperature (Tg) and maximum pot life (or processing window, PW). Characterization through dynamic mechanical thermal analysis (DMTA) and using a rheometer indicated that the optimum formulation was obtained at 55.6 wt.% of BPF and a stoichiometric ratio of 0.60. Both values were predicted to give Tg at 180 °C and a processing window of up to 136.1 min. The predicted values were verified, with the obtained Tg and processing window (PW) being 181.2 ± 0.8 °C and 140 min, respectively, which is close to the values predicted using the RSM.

Characterization of Mechanical of CTBN Liquid Rubber‐Modified Epoxy Cured by Anhydride- and Amine-Based Agent

The main purpose of this work is to reveal the effects of carboxyl-terminated butadiene–acrylonitrile (CTBN) rubber particles on the fracture and tensile behavior of anhydride-and amine-cured epoxy/CTBN blends. In this study, 1 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, 10 wt.% and 15 wt.% CTBN were added to two different epoxy-hardener systems. The CTBN/epoxy blends were prepared by ultrasonic mixing device and curing processes were determined by DSC analysis. As CTBN fraction by weight increased in both epoxy systems, a decrease in tensile strength and modulus was detected, but deformation ability improved. The fracture toughness of CTBN/epoxy blends cured with amine-based hardener increased up to 10 wt.% CTBN addition and then decreased. The average rubber particle size was found to have a significant effect on the fracture toughness of CTBN/epoxy blends. Compared to pure epoxy, fracture toughness increased approximately 3.5-fold in amine-cured 10% CTBN / epoxy blend. In CTBN/epoxy blends cured by amine-based curing agent, CTBN shifted the reaction rate and thus it was provided better control over CTBN particle size in the cured CTBN/epoxy. The toughening mechanisms induced by CTBN, such as rubber cavitation and matrix shear banding, contributed to the enhanced fracture toughness of the amine-cured CTBN/epoxy.

Carbon Nanotube Reinforced Poly(ε-caprolactone)/Epoxy Blends for Superior Mechanical and Self-Sensing Performance in Multiscale Glass Fiber Composites.

In this paper, a novel carbon nanotube (CNT) polycaprolactone (PCL), epoxy, and glass fiber (GF) composite is reported. Here, the nanoreinforced composites show a flexural strength increase of around 30%, whereas the interlaminar shear strength increases by 10–15% in comparison to unenhanced samples. This occurs because the addition of the CNTs induces a better PCL/epoxy/GF interaction. Furthermore, the nanoparticles also give novel functionalities to the multiscale composite, such as strain and damage monitoring. Here, the electrical response of the tensile- and compressive-subjected faces was simultaneously measured during flexural tests as well as the transverse conductivity in interlaminar tests, showing an exceptional capability for damage detection. Moreover, it was observed that the electrical sensitivity increases with PCL content due to a higher efficiency of the dispersion process that promotes the creation of a more uniform electrical network.

Cure Kinetics and Properties of Blends of Epoxy Resins with Polyethersulfone

In this article,polyethersulfone and flourene-coating epoxy resin were utilized tomodify both the toughness and the mechanical properties of traditional epoxy resins. The cure kineticsand the thermal stabilityof the resultedblends were tested by differential scanning calorimetry technology and thermogravimetric analysis, respectively. Additionally, the mechanical properties of resulted thermosets were discussed after tested by Dynamic Thermomechanical Analyzer.When compared to the traditional epoxides, the obtained blends exhibit much better heat resistance, thermal stability and mechanical properties.

Kinetic of Thermal Degradation of RTV Silicon Rubber Blends Reinforced With Nanoparticles by TGA and DSC Analysis Techniques

Binary and ternary polymeric blends from epoxy (EP), unsaturated polyester (UPE), with silicone rubber (room temperature Vulcanizes (RTV)) were prepared. Silicone rubber (SR) was mixed well with sufficient amount of ethanol before its adding to resins. These blends were reinforced by nano Al with 1% wt, and Al2O3 with 1% wt to develop the properties of blends. TGA and DSC were obtained from the thermal degradation computed by using Coast-Redfern technique. Kinetic and thermodynamic parameters were studied for all specimens were presented a good linear correlation coefficient close to unity using Minitab 16. DSC profiles for all composites shows there are a single endothermic peak which represents the glass transition temperature. Activation energy of binary and ternary epoxy blends decreases with increasing the percentage of SR while the addition of Al and Al2O3 nanoparticles shows an increase in the activation energy when added to binary and ternary blends for epoxy.

Electrical conductivity of polyethylene/epoxy/graphite/carbon black composites: synergy of blend immiscibility and hybrid filler

ABSTRACT Polyethylene (PE)/epoxy (EP) blends filled with graphite/carbon black (G/CB) hybrid filler were prepared and characterized in terms of electrical conductivity. As the total filler content increased, electrical conductivity of the PE/EP/G/CB composites increased while conductivity anisotropy decreased. Also, PE/EP/G/CB composites exhibited higher electrical conductivities than the filled individual polymers and PE/EP/G composites at the same filler contents. More continuous conductive networks caused by the synergistic effect of immiscible blend matrix and G/CB hybrid filler led to significant improvement in the overall electrical conductivities of the PE/EP/G/CB composites. This work provides a good insight for further explorations into conducting polymer-graphite composites.

Deeper insights into the thermal properties of epoxy thermoset resins using torsion measurements

AbstractThe glass transition temperature (Tg) of epoxy thermosets is a critical material property that depends on the component chemistry, the final cross‐link density, and processing conditions. This study incorporates dynamic mechanical analysis (DMA) testing with a torsion clamp geometry on a TA Instruments DHR‐2 and differential scanning calorimetry (DSC) to characterize five different two‐component epoxy‐amine systems. Investigation of the Tg dependence on DMA frequency and heating shows that lowering the frequency from 1 to 0.01 Hz results in a Tg very similar to that measured using DSC, while a heating rate of 0.3°C/min using DMA gives a Tg comparable to the DSC measured value at 30°C/min. The DMA technique reveals secondary relaxation transitions and peak broadening in the tan(δ) plots of poorly mixed epoxy blends, quantified using full width at half maximum (FWHM) of tan(δ) peaks, and are indicative of a non‐homogeneous cross‐linked network and off‐ratio blending, respectively. The increase in the FWHM due to poor mixing ranges from 8% to 96%. These parameters are easily measurable and quantifiable in DMA, but are not observed in DSC. The additional DMA insights are valuable for process development and failure analysis, and can improve the understanding of epoxies.