Core-shell Rubber Nanoparticles Research Articles

Temperature-Controlled Molecular Bonding Hysteresis: Interphase Dynamics of a Nanoparticle-Modified Polymer Network.

This study demonstrates the existence of temperature-induced molecular bonding hysteresis at nanoparticle-polymer interfaces in a highly cross-linked epoxy-based polymer, modified with core-shell rubber nanoparticles. This thermally induced bond hysteresis manifests itself in a hysteresis-like change of the strength of the electrical bond polarization between epoxy molecules and surface molecules of the core-shell nanoparticles. This kind of dynamic bond behavior can be controllably switched from one bond state to the other by a sufficient temperature change. The related optical remanence is evidenced by a refractive index hysteresis independent of the temperature change using the new experimental technique of temperature-modulated optical refractometry (TMOR). From the investigation of quasi-static and dynamic thermal expansion separately, TMOR allows for the conclusion that the observed hysteresis is caused by the specific refractivity and not the dipole number density.

Production of supertough and semiconductive PLA-based polymer blend nanocomposites by kinetic microstructural control

Polymer nanocomposites with superior multi-functional properties can be fabricated by tuning their morphology. In this work, a supertough and semiconductive polylactide (PLA)-based polymer blend nanocomposite (PBNANO) was produced for the first time via melt blending with a core-shell rubber (CSR) and carbon nanotubes (CNT). Reference binary blends (PLA/CSR and PLA/CNT) revealed that, when added separately, 20 wt% of CSR and 0.25 wt% of CNT were the suitable quantities to achieve a supertough and a semiconductive PLA-based material, respectively. Based on the obtained results, PLA/CSR/CNT PBNANOs with 20 wt% of CSR and CNT amounts between 0.15 and 0.50 wt% were prepared in one extrusion step. Although supertoughness was achieved in all the cases, the PBNANOs were insulating due to the selective localization of the CNT in the poly(methyl methacrylate) (PMMA) shell of the CSR and the good dispersion of the CSR nanoparticles. However, a supertough and semiconductive PLA-based PBNANO was obtained by a two-step melt compounding. Using this processing sequence, a worse dispersion of the CSR was obtained, allowing contact between some CSR nanoparticles. The differences in PBNANOs morphology prepared in one or two extrusion steps were determined by TEM and corroborated by rheological measurements. In the case of the two extrusion steps PBNANO, the CNT were located in both the PLA matrix and in the shell of the CSR. This morphological change enabled the PBNANO to be conductive, as the CNT percolation was achieved in this case while still remaining supertough.

Core-Shell Rubber Nanoparticle-Modified CFRP/Steel Ambient-Cured Adhesive Joints: Curing Kinetics and Mechanical Behavior.

Externally bonded wet-layup carbon fiber-reinforced polymer (CFRP) strengthening systems are extensively used in concrete structures but have not found widespread use in deficient steel structures. To address the challenges of the adhesive bonding of wet-layup CFRP to steel substrates, this study investigated the effect of core-shell rubber (CSR) nanoparticles on the curing kinetics, glass transition temperature (Tg) and mechanical properties of ambient-cured epoxy/CSR blends. The effects of silane coupling agent and CSR on the adhesive bond properties of CFRP/steel joints were also investigated. The results indicate that CSR nanoparticles have a mild catalytic effect on the curing kinetics of epoxy under ambient conditions. The effect of CSR on the Tg of epoxy was negligible. Epoxy adhesives modified with 5 to 20%wt. of CSR nanoparticles were characterized with improved ductility over brittle neat epoxy; however, the addition of CSR nanoparticles reduced tensile strength and modulus of the adhesives. An up to 250% increase in the single-lap shear strength of CFRP/steel joints was accomplished in CSR-modified joints over neat epoxy adhesive joints.

On the static failure behaviour of co-cured composite joints with enhanced interlaminar fracture energies via multiscale toughening

This paper is focused on the multiscale toughened co-cured composite interfaces of carbon/epoxy laminates using vacuum infusion and out-of-autoclave curing—with an emphasis on the role of enhanced interlaminar fracture energies on the static failure of laminate joints. To toughen co-cured interlaminar regions, three toughening routes are used: (i) epoxy matrix toughening with 10 wt% core–shell rubber (CSR) nanoparticles, (ii) 10 g/m2 polyphenylene sulfide (PPS) non-woven micro-fibre veil toughening, and (iii) multiscale toughening by combining epoxy matrix toughening with 10 wt% CSR nanoparticles and 10 g/m2 PPS veils. Double cantilever beam and end-notch flexure tests are conducted with the toughened interfaces for mode-I and mode-II fracture energies. Moreover, three co-cured joint configurations (viz. double-notch single lap, stepped scarf and skin-stiffener joints with the three toughening routes) are tested to characterise the role of enhanced interlaminar fracture energies on the static failure of laminate assemblies. The results show that the three toughening routes have significantly altered the R-curve behaviour and interlaminar fracture energies and that the degree of enhancement in mode-I and mode-II fracture energies is sensitive to the type of toughening route. Based on the material systems tested, the mode-I fracture initiation energy is enhanced by ∼150% with multiscale toughening, ∼65% with particle toughening, and ∼60% with veil toughening; whereas, the mode-II fracture initiation energy is enhanced by ∼85% with veil toughening and ∼35% with multiscale toughening—but reduced by ∼20% with particle toughening. The joint tests show that the toughening routes affect the static failure of the three joint configurations and that the strength and damage evolution of the co-cured joints depend on the interlaminar fracture energies. The strength of the co-cured single lap joints is increased by ∼50% with multiscale toughening and ∼40% with veil toughening; whereas, the strength of the co-cured skin-stiffener joints is enhanced by ∼35% with multiscale toughening and ∼45% with veil toughening. The failure mechanisms observed on the fracture surfaces indicate that the strength/failure behaviour of the co-cured joints depends on the dominant interlaminar fracture mode and the corresponding fracture energies. Overall, it is shown that the multiscale interlaminar toughening routes that are used to address the issue of delamination can also be effectively explored to enhance the static failure of co-cured laminate assemblies by toughening the co-cured interfaces/bondlines.

Effect of Core-Shell Rubber Nanoparticles on the Mechanical Properties of Epoxy and Epoxy-Based CFRP.

The aim of the research was to estimate the effect of core-shell rubber (CSR) nanoparticles on the tensile properties, fracture toughness, and glass transition temperature of the epoxy and epoxy-based carbon fiber reinforced polymer (CFRP). Three additives containing CSR nanoparticles were used for the research resulting in a filler fraction of 2-6 wt.% in the epoxy resin. It was experimentally confirmed that the effect of the CSR nanoparticles on the tensile properties of the epoxy resin was notable, leading to a reduction of 10-20% in the tensile strength and elastic modulus and an increase of 60-108% in the fracture toughness for the highest filler fraction. The interlaminar fracture toughness of CFRP was maximally improved by 53% for ACE MX 960 at CSR content 4 wt.%. The glass transition temperature of the epoxy was gradually improved by 10-20 °C with the increase of CSR nanoparticles for all of the additives. A combination of rigid and soft particles could simultaneously enhance both the tensile properties and the fracture toughness, which cannot be achieved by the single-phase particles independently.

Simultaneously Toughening and Reinforcing Polylactide by Regulating the Distribution of Core–Shell Rubber Particles with Carbon Black

AbstractStiffness–toughness balance is an important issue in rubber toughened polymer blends. In this work, a facile and effective route to simultaneously toughen and reinforce polylactide (PLA) by regulating the distribution of core–shell rubber (CSR) nanoparticles with carbon black (CB) is reported. The PLA/CSR/CB nanocomposites are prepared via direct melt‐blending PLA, CSR, and CB nanoparticles with different self‐aggregate capabilities. The FTIR and DFT calculation results reveal that the interactions between CB and CSR are stronger than those between CB and PLA. Thus, CB nanoparticles with high self‐aggregate capability (HCB) can drive CSR nanoparticles to join into the HCB network structures and form CSR‐HCB network structures in the PLA/CSR/HCB nanocomposites. However, for the CB nanoparticles with low self‐aggregate capability (LCB), uniform dispersion of both CSR nanoparticles and small‐sized CB clusters in the PLA/CSR/LCB nanocomposites is observed. Compared to the network structures, the uniform dispersion structure can endow PLA/CSR/CB nanocomposites with much better stiffness–toughness balance performances. Additionally, the distribution of CSR nanoparticles on the rheological properties of PLA/CSR/CB nanocomposites are studied. This work reveals significant correlations between distribution of CSR nanoparticles and properties of PLA nanocomposites, which is helpful to prepare high‐performance PLA materials.

On the R-curve behaviour of carbon/epoxy laminates with core-shell rubber nanoparticle and micro-fibre veil hybrid toughening: Carbon vs PPS veils

This paper investigates the effect of non-hybrid and hybrid toughening, via core-shell rubber (CSR) nanoparticles and non-woven micro-fibre veils, on the delamination resistance and crack migration in carbon fibre/epoxy laminates under mode-I and mode-II conditions—with an emphasis on the effect of veil fibre properties on toughening mechanisms and fracture energies. Core-shell rubber particles, varying in size from 100 nm to 3 μm, with 0–10 wt% content, are dispersed within the epoxy resin. Two non-woven veils with contrasting fibre properties (i.e. one with ∼6 mm (50 wt%) and ∼12 mm (50 wt%) short carbon fibres and another with ∼6 mm short polyphenylene sulfide (PPS) fibres) with 10 g/m2 areal weights are used to introduce hybrid toughening at the interlaminar region. Carbon fibre/epoxy laminates with five different toughening routes (i.e. CSR toughening, carbon veil toughening, PPS veil toughening, carbon veil and CSR hybrid toughening, and PPS veil and CSR hybrid toughening) are manufactured with a two-part resin using vacuum infusion and out-of-autoclave curing. Double cantilever beam (DCB) and four-point end-notch-flexure (4-ENF) specimens are tested for mode-I and mode-II fracture energies and R-curves. Fracture surfaces are investigated to characterise crack migration and energy dissipation mechanisms. The results indicate that mode-I and mode-II fracture energies are significantly enhanced (e.g. ∼275% in initiation and propagation under mode-I) with the combined core-shell rubber nanoparticle and veil toughening investigated—significantly altering micro-failure mechanisms, crack paths and R-curves. It is shown that the low modulus PPS fibre veils together with CSR particles provide stable crack growth, while high modulus carbon fibre veils with CSR particles lead to unstable crack growth.

Modeling Brittle Fractures in Epoxy Nanocomposites Using Extended Finite Element and Cohesive Zone Surface Methods.

Linear elastic fracture modeling coupled with empirical material tensile data result in good quantitative agreement with the experimental determination of mode I fracture for both brittle and toughened epoxy nanocomposites. The nanocomposites are comprised of diglycidyl ether of bisphenol A cured with Jeffamine D-230 and some were filled with core-shell rubber nanoparticles of varying concentrations. The quasi-static single-edge notched bending (SENB) test is modeled using both the surface-based cohesive zone (CZS) and extended finite element methods (XFEM) implemented in the Abaqus software. For each material considered, the critical load predicted by the simulated SENB test is used to calculate the mode I fracture toughness. Damage initiates in these models when nodes at the simulated crack tip attain the experimentally measured yield stress. Prediction of fracture processes using a generalized truncated linear traction–separation law (TSL) was significantly improved by considering the case of a linear softening function. There are no adjustable parameters in the XFEM model. The CZS model requires only optimization of the element displacement at the fracture parameter. Thus, these continuum methods describe these materials in mode I fracture with a minimum number of independent parameters.

Impact response of composite sandwich structures with toughened matrices

The mechanisms of failure of a composite sandwich structure subjected to a projectile impact have been investigated. The results reveal the complex interplay between the various damage dissipation mechanisms. The effects of modifying the matrix of the skins with polysiloxane core–shell rubber (CSR) nanoparticles and silica nanoparticles were investigated. Single cantilever beam specimens were tested to evaluate skin-core debonding. The addition of CSR nanoparticles to the matrix beyond 3 wt% causes a change in failure mechanism from sub-interface foam failure to interfacial failure when 6 and 9 wt% CSR are added. The sandwich structures were impacted with an aluminium projectile at 130 m/s. High speed cameras were used to obtain 3D digital image correlation of the back-face. Sectioning and imaging of the panels revealed damage in the form of front skin perforation and delamination, crushing and fracture of the core and back-face skin-core debonding. The impacted specimens also exhibited a transition in failure mechanism relating to rear face skin-core debonding between 3 and 6 wt%. Panels containing low amounts of CSR resulted in increased core cracking, while beyond the transition point, widespread rear face skin-core debonding was observed. At 3 wt% CSR, optimum back face deflection is achieved, and lower front skin delamination is experienced.

Toughening epoxy asphalt binder using core-shell rubber nanoparticles

Core-shell rubber (CSR) has been widely applied in the improvement of the toughness for the brittle epoxy resin. In this study, an epoxy asphalt (EA) binder has been toughened by the inclusion of CSR nanoparticles with approximately 100–200 nm in diameter. The incorporation of CSR nanoparticles significantly increased the viscosity of the pure EA during curing. Even with 5 wt% CSR, the EA blend exhibited extremely long operational lifetime (more than 2.5 h) for mixture pavements. The glassy shell of CSR nanoparticles was broken and the rubbery core of CSR nanoparticles swelled in the EA. New micro-scale CSR domains formed and uniformly dispersed in the epoxy phase of the cured EA. The inclusion of CSR nanoparticles altered the phase separation mechanism of the pure EA. The sea-island morphology of the pure EA took place through the nucleation and growth (NG) mechanism, while co-continuous microstructures in the EA blends with 3 wt% and 5 wt% CSR formed through the spinodal decomposition (SD) mechanism. Both sea-island and co-continuous microstructures via combined the NG and SD mechanisms were observed in the EA blend containing 1 wt% CSR. The glass transition temperature and thermal stability of the pure EA was improved by the inclusion of higher CSR loadings. The incorporation of CSR greatly enhanced the mechanical properties of the pure EA. In the case of 1 wt% CSR inclusion, 29% increase in the tensile strength, 60% improvement in the elongation at break and 2-fold increment in the toughness were obtained.

Epoxy based hybrid nanocomposites: Fracture mechanisms, tensile properties and electrical properties

This work explore the effect of addition of a combination of rigid nanofillers and core–shell rubber nanoparticles on the fracture mechanics, tensile, electrical and thermo-mechanical properties of epoxy resins. SiO2 nanoparticles, multi-walled carbon nanotubes (MWCNT's), as rigid nanofillers, and core–shell rubber (CSR) nanoparticles, as soft nanofillers were used with bisphenol-A based epoxy resin. Further, the rigid fillers were added systematically with core–shell rubber nanoparticles and MWCNT’s to study the combined effect of rigid nanofillers and soft CSR nanoparticles. The resulting systems will be characterized by standard methods. This includes a thorough characterization of tensile, fracture mechanics, electrical, and thermal properties. The results show that the maximum increase of fracture toughness (207%) and fracture energy (910%) was obtained for system containing 5 wt% of CSR and 10% SiO2. The electrical conductivity threshold was obtained at 0.075 wt% of MWCNT’s modified system. The introduction of CSR nanoparticles significantly increase the fracture energy of the matrix with decrease in tensile strength and tensile modulus, which was further recovered with the addition of SiO2 nanoparticles. The analysis of the fracture surfaces revealed the toughening micro-mechanisms.

High strength epoxy system modified with soft block copolymer and stiff core-shell rubber nanoparticles: Morphology, mechanical properties, and fracture mechanisms

High strength epoxy system modified with soft block copolymer and stiff core-shell rubber nanoparticles: Morphology, mechanical properties, and fracture mechanisms

Hygrothermal conditioning of wet-layup CFRP-concrete adhesive joints modified with silane coupling agent and core-shell rubber nanoparticles

The adhesive bond between externally bonded fiber-reinforced polymer (FRP) repairs and the concrete substrate can significantly deteriorate under hygrothermal conditions. The present study evaluated the epoxy adhesive toughening with core–shell rubber (CSR) nanoparticles and concrete surface functionalization with an epoxy-functional silane coupling agent as a means of improving the bond durability under hygrothermal exposure. To determine the effect of environmental degradation, beam bond test specimens were subjected to control conditions (standard laboratory conditions: 23 ± 2 °C and RH 50 ± 10%) and a hygrothermal accelerated conditioning protocol (ACP) (water immersion at 45 ± 1 °C) for 8 weeks. Bond test results indicate that CSR toughening and silane coupling agent can improve FRP-concrete adhesive bond strength retention following accelerated conditioning by up to 15% over that of neat epoxy. Following accelerated conditioning, CFRP coupons prepared with CSR-modified epoxy retain their mechanical properties, while the CFRP prepared with the neat epoxy exhibited a significant reduction in strength (40%) and elongation (54%). CSR nanoparticles demonstrated good compatibility with the base epoxy resin, as evidenced by differential scanning calorimetry (DSC) glass transition temperature measurements.

The Effect of Hybridized Carbon Nanotubes, Silica Nanoparticles, and Core-Shell Rubber on Tensile, Fracture Mechanics and Electrical Properties of Epoxy Nanocomposites.

The paper investigates the effect of adding a combination of rigid nanoparticles and core-shell rubber nanoparticles on the tensile, fracture mechanics, electrical and thermo-mechanical properties of epoxy resins. SiO2 nanoparticles, multi-walled carbon nanotubes (MWCNT’s), as rigid nanofillers, and core-shell rubber (CSR) nanoparticles, as soft nanofillers were used with bisphenol-A-based epoxy resin. Further, the rigid fillers were added systematically with core-shell rubber nanoparticles to investigate the commingled effect of rigid nanofillers and soft CSR nanoparticles. The resulting matrix will be broadly evaluated by standard methods to quantify tensile, fracture mechanics, electrical, and thermal properties. The results show that the electrical conductivity threshold is obtained at 0.075 wt. % for MWCNT-modified systems. For hybrid systems, the maximum increase of fracture toughness (218%) and fracture energy (900%) was obtained for a system containing 5 wt. % of CSR and 10 wt. % of SiO2. The analysis of the fracture surfaces revealed the information about existing toughening micro-mechanisms in the nanocomposites.

The curing behaviour and thermo-mechanical properties of core–shell rubber-modified epoxy nanocomposites

This work investigates the effects of core–shell rubber (CSR) nanoparticles on the curing behaviour and thermo-mechanical properties of an epoxy using differential scanning calorimetry and dynamic mechanical thermal analysis approaches. Interaction between CSR nanoparticles and epoxy matrix is detected at a temperature of approximately 97°C in the curing process. This results in an increase in the glass transition temperature ( Tg) of the cured nanocomposites. Given the semi-dynamic curing schedule, the curing process of all the epoxy nanocomposites consists of an abrupt onset stage followed by a slow diffusion-controlled stage. Higher temperature is required to initiate the curing for the epoxy nanocomposites with higher loading of CSR nanoparticles. This is attributed to the physical changes caused by the addition of CSR nanoparticles, such as the increase in the viscosity and the reduction in the density of the reactive groups. The storage modulus of the epoxy decreases in the glassy region but remains constant in the rubbery region due to the incorporation of CSR nanoparticles.

Curing rate effects on the toughness of epoxy polymers

In the current work, the fracture properties of epoxy polymers containing poly-siloxane core shell rubber (CSR) nano-particles were studied. The effect of different cure rates and curing temperatures on the epoxy resin was also investigated. Single edge notched bend tests were performed to evaluate the fracture energy of the polymers. The fracture energy of the unmodified epoxy polymer increased significantly from 339J/m2 to 3,922J/m2 due to the addition of 9 wt% of CSR nano-particles. Similarly, the fracture toughness for the unmodified polymer increased from 1.27MPam1/2 to 3.42MPam1/2 for an epoxy polymer containing 9 wt% of CSR nano-particles. Faster rates of curing, which can be achieved at higher cure temperatures are found to be detrimental to the toughness of the modified epoxy polymers.

Fracture behaviour of epoxy adhesive joints modified with core-shell rubber nanoparticles

The fracture behaviour of core-shell rubber (CSR) nanoparticle modified epoxy adhesives is studied using the tapered double cantilever beam (TDCB) test. The addition of CSR nanoparticles increased the fracture energy by over 10 times, and changed the fracture behaviour from stick-slip to stable. As the bond gap thickness increased, the fracture energy increased to a peak value then decreased to the value of the bulk specimens for brittle adhesives, and increased then plateaued for ductile and tough adhesives. The variation of the fracture energy with CSR content and bond gap thickness was attributed to varying plastic zone size at the crack tip.

Carbon nanotubes and core–shell rubber nanoparticles modified structural epoxy adhesives

In this study, multi-walled carbon nanotubes (MWCNTs) and core–shell rubber (CSR) nanoparticles were dispersed in an epoxy adhesive to produce conductive and tough structural adhesives. The thermo-mechanical properties, electrical conductivity, fracture toughness and lap shear strength of MWCNT–CSR–epoxy structural adhesives were studied. The addition of both MWCNTs and CSR nanoparticles into the epoxy adhesive increased the fracture energy significantly, from 397 J/m2 for the unmodified adhesive, to 2615 J/m2, for an adhesive modified with 10 wt% CSR nanoparticles and 0.3 wt% MWCNTs. The toughening mechanisms of the CSR nanoparticles were identified as cavitation of the rubber particles followed by plastic void growth and shear band yielding. The toughening enhancement of the MWCNTs was mainly attributed to the crack bridging, MWCNT break and crack path deflection. The addition of CSR nanoparticles into neat epoxy was found to affect the failure mode of the lap shear joints, from brittle, interfacial failure, to a ductile, cohesive failure. A moderate increase in the strength of the lap shear joint was also noted. The subsequent addition of MWCNTs further affected the failure mode of the lap shear joints. A mixture of interfacial and cohesive failure was observed for each joint configuration. The lap shear strength was observed to have increased significantly, by 39%, due to the addition of 0.5 wt% MWCNTs. The observed increase in lap shear strength with the addition of MWCNTs was attributed to the crack deflection caused by the MWCNTs.

Toughened carbon fibre-reinforced polymer composites with nanoparticle-modified epoxy matrices

In the current work, the microstructure and fracture performance of carbon fibre-reinforced polymer (CFRP) composites based upon matrices of an anhydride-cured epoxy resin (formulated with a reactive diluent), and containing silica nanoparticles and/or polysiloxane core–shell rubber (CSR) nanoparticles, were investigated. Double cantilever beam tests were performed in order to determine the interlaminar fracture energy of the CFRP composites, while the single-edge-notched bend specimen was employed to evaluate the fracture energy of the bulk polymers. The fracture energy of the bulk epoxy polymers increased from 173 J/m2 for the unmodified polymer to a maximum of 1237 J/m2 with the addition of 16 wt% of CSR nanoparticles. The toughening mechanisms were identified as (a) localised plastic shear yielding and (b) cavitation of the CSR particles followed by plastic void growth of the matrix. The steady-state propagation value of the interlaminar fracture energy of the CFRP composites increased with increasing nanoparticle concentration, from 1246 J/m2 for the unmodified epoxy matrix to a maximum of 1851 J/m2 with 4 wt% of silica nanoparticles and 8 wt% of CSR nanoparticles. Crack growth in the CFRP composites was dominated by fibre-bridging toughening mechanisms. The efficiency of the transfer of toughness from the bulk polymers to the carbon fibre composites was considered. The measured fracture energy of both bulk and composite materials decreased at a test temperature of −80 °C, compared with room temperature, i.e. 20 °C. Nevertheless, the toughening effects of both the silica and CSR nanoparticles on the bulk epoxy polymers and the CFRP composites, compared with the unmodified epoxy polymers, were still evident even at the lower temperature. Indeed, the toughening effect of the silica nanoparticles was greater at −80 °C than at room temperature.

Toughening of epoxy-based hybrid nanocomposites

The microstructure and fracture performance of an epoxy resin cured with an anhydride hardener containing silica nanoparticles and/or polysiloxane core-shell rubber (CSR) nanoparticles were investigated in the current work. The effect of adding a reactive diluent, i.e. hexanediol diglycidylether, to the epoxy resin was also investigated. The fracture energy of the neat (i.e. unmodified) epoxy polymer increased slightly from 125 J/m2 to 172 J/m2 due to the addition of 25 wt% of the reactive diluent to the epoxy. The fracture energy of the unmodified epoxy polymer increased to 889 J/m2 when 20 wt% of the CSR nanoparticles were added to the epoxy without any reactive diluent being present. However, the results show that the increase in fracture energy due to the addition of the CSR nanoparticles particles was much more marked in the case when 25 wt% of the reactive diluent was present, e.g. an increase to 1237 J/m2 with the addition of 16 wt% of CSR nanoparticles. Furthermore, while the subsequent addition of silica nanoparticles, to give hybrid epoxy polymer nanocomposites, i.e. which contained both silica and CSR nanoparticles, produced only modest increases in the fracture energy in the case of the epoxy with the reactive diluent additive present, some synergistic effects on the toughening were noted. No significant improvements in toughness were found for the hybrid epoxy polymer nanocomposites without reactive diluent. The measured toughness of the hybrid materials can be related to the degree of dispersion of both nanoparticle phases in the epoxy polymer matrix. The toughening mechanisms were identified and the experimentally measured values of toughness were in good agreement with modelling studies.