Filler aggregation as a reinforcement mechanism in polymer nanocomposites (original) (raw)
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Nanofiller Aggregation as Reinforcing Mechanism in Nanocomposites
Procedia Engineering, 2011
A new approach is proposed to model the elastic properties of polymer nanocomposites taking into account agglomeration effects. In particular, the stiffening effect provided by rigid nanoparticles forming primary aggregates is modelled on the hypothesis that part of the polymer matrix is mechanically constrained within the aggregates. To validate the model, linear-low-density polyethylene (LLDPE)/silica micro-and nano-composites have been prepared by melt compounding followed by hot pressing. Electron microscopy observations indicated that the microstructure of the resulting nanocomposites clearly manifested primary aggregation of nanoparticles. Concurrently, thermal calorimetry and X-ray diffraction analyses proved that the crystallization behaviour was not affected by the presence of the filler. Dog-bone specimens have been mechanically tested under uniaxial tension and the data used to validate the model. A good agreement between theoretical predictions and experimental data was demonstrated. The results coupled with the propensity of nanoparticles to form aggregates could explain significant modulus increases in many nanocomposites systems reported earlier.
Journal of Polymer Science Part B: Polymer Physics, 2011
This paper presents a study of the polymer-filler interfacial effects on filler dispersion and mechanical reinforcement in Polystyrene (PS) / silica nanocomposites by direct comparison of two model systems: un-grafted and PS-grafted silica dispersed in PS matrix. The structure of nanoparticles has been investigated by combining Small Angle Neutron Scattering (SANS) measurements and Transmission Electronic Microscopic (TEM) images. The mechanical properties were studied over a wide range of deformation by plate/plate rheology and uni-axial stretching. At low silica volume fraction, the particles arrange, for both systems, in small finite size non-connected aggregates and the materials exhibit a solid-like behavior independent of the local polymer/fillers interactions suggesting that reinforcement is dominated by additional long range effects. At high silica volume fraction, a continuous connected network is created leading to a fast increase of reinforcement whose amplitude is then directly dependent on the strength of the local particle/particle interactions and lower with grafting likely due to deformation of grafted polymer.
Nanomaterials, 2021
In this work, the effective mechanical reinforcement of polymeric nanocomposites containing spherical particle fillers is predicted based on a generalized analytical three-phase-series-parallel model, considering the concepts of percolation and the interfacial glassy region. While the concept of percolation is solely taken as a contribution of the filler-network, we herein show that the glassy interphase between filler and matrix, which is often in the nanometers range, is also to be considered while interpreting enhanced mechanical properties of particulate filled polymeric nanocomposites. To demonstrate the relevance of the proposed generalized equation, we have fitted several experimental results which show a good agreement with theoretical predictions. Thus, the approach presented here can be valuable to elucidate new possible conceptual routes for the creation of new materials with fundamental technological applications and can open a new research avenue for future studies.
Nano-Reinforcement Effects on Tensile Properties of Polymeric Composite Materials
The main objective of this paper is to determine the effect of adding silica nanopowder (SiO2), alumina nanopowder (Al2 O3), and carbon nanofibers (CNF) on the tensile properties of epoxy. The nano particles were infused into epoxy resin with an ultrasonic liquid processor with 0.5, 1.5 and 3 wt.%of epoxy. For nanocomposites, addition of 0.5 wt.% of silica, alumina and 1.5% of carbon nano particles improves the tensile strength over neat epoxy by 29.6 %, 14 % and 0.8 %, respectively. The tensile modulus of the nanocomposites is improved over neat epoxy by 15.9%, 30.4%and 37.7% with addition of 3 wt.%of silica, alumina and carbon nano particles, respectively. The two-parameter Weibull distribution function was used to investigate the statistical analysis of the experimental tensile results. Some models for the prediction of the elastic modulus of nano-reinforced composites were evaluated. The measured moduli were compared to theoretical predictions. The Paul model shows the best agre...
Challenges in Nano and Micro Scale Science and Technology, 2016
A three-dimensional micromechanics-based analytical model is developed to study thermo-mechanical properties of polymer composites reinforced with randomly distributed silica nanoparticles. Two important factors in nanocomposites modeling using micromechanical models are nanoparticle arrangement in matrix and interphase effects. In order to study these cases, representative volume element (RVE) of nanocomposites is extended to c×r×h nano-cells in three dimensions and consists of three phases including nanoparticles, polymer matrix and interphase between the nanoparticles and matrix. Nanoparticles are surrounded by the interphase in all composites. Effects of volume fraction, aspect ratio and size of nanoparticle on the effective thermo-mechanical response of the nanocomposite are studied. Also, the effects of polymer matrix properties and interphase including its elastic modulus and thickness are theoretically investigated in detail. It is revealed that when nanoparticles are randomly distributed in the matrix and interphase effects are considered, the results of present micromechanical model are in very good agreement with experimental data.
Polymer, 2012
We report on the influence of parameters controlling filler dispersion and mechanical reinforcement in model nanocomposites. We elaborate a series of nanocomposites and present a structural characterization of silica dispersion in polymer matrix for several particle sizes and polymer matrices, at all relevant scales, by coupling Small Angle X-ray Scattering and Transmission Electronic Microscopy. The mechanical properties are investigated in the linear regime by coupling Dynamical Mechanical Analysis and plate/plate rheology. The results show that: (i) for all filler sizes and matrices, a structural transition is observed from non-connected fractal aggregates at low silica concentration to connected network at high particle content. (ii) In the dilute regime, the reinforcement implies a polymer chain contribution with different possible origins: increase of entanglements density for PS and increase of friction coefficient for PMMA. (iii) In the concentrated regime, for a given polymer, the reinforcement amplitude can be tuned by the rigidity of the filler network, which directly depends on the particleeparticle interaction.
Characterization of Polymer Nanocomposite Interphase and Its Impact on Mechanical Properties
Macromolecules, 2006
The structure of the interphase, a region between nanoparticle fillers and the bulk polymer matrix in a particle reinforced composite, was investigated using two different approaches. The polymer nanocomposite systems consists of alumina (Al 2 O 3) and magnetite (Fe 3 O 4) nanoparticles embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) matrices. The first approach utilized data from thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM) to predict the structure and density of the interphase for four nanocomposite systems. In the second approach, the nature of bonding between the polymer and the nanoparticle surfaces was analyzed using Fourier transform infrared spectroscopy (FTIR) to calculate the density of the interphase for two PMMA-based nanocomposite systems. Mechanical properties of these composites were correlated with the structure of the interface, and results from the two approaches were compared with previous studies. Moreover, by comparing results from the two characterization approaches, a new method for characterizing the degree of nanoparticle flocculation in a composite is also provided. The results indicate that Al 2 O 3 nanoparticles are more reactive with the polymer matrix than Fe 3 O 4 nanoparticles, but neither have strong interactions with the matrix, a fact that leads to low-density interphase and consequently results in more compliant composites. Tensile testing, dynamic mechanical analysis (DMA), and nanoindentation tests confirmed that these nanocomposite systems do not have the same mechanical properties as their respective pure polymer systems.
Journal of Composite Materials, 2018
In the current work, the effect of interphase region on the mechanical properties of polymer nanocomposites reinforced with nanoparticles is studied. For this purpose, a closed-form interphase model as a function of radial distance based on finite-size representative volume element is suggested to estimate the mechanical properties of particle-reinforced nanocomposites. The effective Young’s and shear moduli of thermoplastic polycarbonate-based nanocomposites for a wide range of sizes and volume fractions of silicon carbide nanoparticles are investigated using the proposed interphase model and molecular dynamics simulations. In order to investigate the effect of particle size, several unit cells of the same volume fraction, but with different particle radii have been considered. The micromechanics-based homogenization results are in good agreement with the results of molecular dynamics simulations for all models. This study demonstrates that the suggested micromechanical interphase ...