Particle Polymer Composites Research Articles

Mechanical Properties of Polymeric Composite Based on Aluminium Microparticles

The paper deals with the testing of composite materials based on aluminium microparticles. The aim of the research was to determine the influence of content of aluminium microparticle filler on the mechanical properties of the polymeric particle composite. The object of the experiments was a particle polymer composite, whose continuous phase was in the form of a two component epoxy resin and a discontinuous phase (reinforcing particles) of aluminium microparticles, which size was less than 45 μm. The influence of a tensile stress, an impact strength and a wear was experimentally investigated. Composite systems with a higher content of microparticles of aluminium from 15 to 25 volume % achieve higher values of the tensile strength at higher temperatures of environment than the composite systems with a lower content of the aluminium microparticles (or matrix). Due to the increased temperature of the environment there is a significant decrease in tensile strength. Impact strength showed increased values in composite systems that have a higher percentage of aluminium microparticles. The filler in the form of aluminium microparticles is detrimental to wear resistance. The results show that increasing the concentration of microparticles of aluminium increases the mass losses of the test materials.

Influence of Interphase Imperfection on Micro-Crack Behavior in Polymer Composites Filled by Rigid Particles

In this paper a particulate composites with polypropylene matrix and rigid mineral fillers are studied. The polymer particulate composites are frequently used in many engineering applications. Due to the physical and chemical interaction between matrix and particles a third phase (generally called interphase) is formed. The composite is modeled as a three-phase continuum. The properties of particles and interphase have a significant effect on the global behavior of the composite. On the basis of fracture mechanics methodology the interaction of micro-crack propagation in the matrix filled by rigid particles covered by the very soft interphase is analyzed. The effect of the composite structure on their mechanical properties is studied here from the theoretical point of view. The properties of particles and matrix were determined experimentally. Conclusions of this paper can contribute to a better understanding of the behavior of micro-crack in polymer particulate composites with respect to interphase.

Effect of hydroxylated multiwall carbon nanotubes on dielectric property of poly (vinylidene fluoride)/poly (methyl methacrylate)/hydroxylated multiwall carbon nanotubes blend

Poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA)/hydroxylated multiwall carbon nanotubes (MWNTs-OH) nanocomposites are prepared via solution blending and hot-press processing. The structure, morphology, crystallization behavior and dielectric properties of nanocomposites are studied. The results show that the crystallization of PVDF is affected by PMMA and MWNTs-OH. With the introduction of PMMA and increment of MWNTs-OH, the content of polar phase in PVDF increases. The dependence of the dielectric properties of the nanocomposites on both volume fraction of the fillers and frequency is investigated. The percolation threshold of the nanocomposite, 2.79 vol.% (volume fraction), is much lower than that of the common two phase particle-polymer composite. A dielectric constant of over 300 is observed at 102 Hz with 3.12 vol.% of MWNTs-OH, which is near the percolation threshold. Large enhancements of the conductivity and loss tangent are also observed near the percolation threshold. The results can be explained by the percolation theory and nanocapacitor model theory.

Thermomechanical properties of CaCO3-latex pigment coatings: Impact of modified dispersing agents

The effect of CaCO3 pigment surface modifications on the rheology, microstructure and the thermomechanical properties of porous particle–polymer composites are investigated. The incorporation of (random copolymerised) acrylamido-2-methyl-propane sulphonate (AMPS) and ethylene glycol methyl ether (mPEG) into poly(acrylic acid) dispersant reduced the dispersing efficiency. Similarly, the composite microstructure showed the concentration and size of particle aggregates were strongly dependant on the chemical nature of the dispersing agent. Dynamic mechanical thermal analysis (DMTA) showed that the incorporating of mPEG segments within the dispersant chain improves the dispersant-latex compatibility, which results in better adhesion as was confirmed through SEM imaging. The composite storage modulus of dry and water saturated samples showed a strong dependency on the properties of the latex. Composites made of high glass transition temperature (Tg), styrene acrylate (SA) latex exhibited high stiffness in dry samples. Contrarily, the cross-linking of the styrene butadiene latex (SBR) induced a low drop in stiffness under conditions of water saturation.

Molecular Dynamics Simulations of Diffusion of O2 and N2 Penetrants in Polydimethylsiloxane-Based Nanocomposites

Recently, metal particle polymer composites have been proposed as sensing materials for micro corrosion sensors. To design the sensors, a detailed understanding of diffusion through metal particle polymer composites is necessary. Accordingly, in this work molecular dynamics (MD) simulations are used to study the diffusion of O2 and N2 penetrants in metal particle polymer nanocomposites composed of an uncross-linked polydimethylsiloxane (PDMS) matrix with Cu nanoparticle inclusions. PDMS is modeled using a hybrid interatomic potential with explicit treatment of Si and O atoms along the chain backbone and coarse-grained methyl side groups. In most models examined in this work, MD simulations show that diffusion coefficients of O2 and N2 molecules in PDMS-based nanocomposites are lower than that in pure PDMS. Nanoparticle inclusions act primarily as geometric obstacles for the diffusion of atmospheric penetrants, reducing the available porosity necessary for diffusion, with instances of O2 and N2 molecule trapping also observed at or near the PDMS/Cu nanoparticle interfaces. In models with the smallest gap between Cu nanoparticles, MD simulations show that O2 and N2 diffusion coefficients are higher than that in pure PDMS at the lowest temperatures studied. This is due to PDMS chain confinement at low temperatures in the presence of the Cu nanoparticles, which induces low-density regions within the PDMS matrix. MD simulations show that the role of temperature on diffusion can be modeled using the Williams–Landel–Ferry equation, with parameters influenced by nanoparticle content and spacing.

The Estimation of Micro-Crack Behavior in Polymer Particulate Composite with Soft Interphase

The presented paper is focused on the numerical study of fracture behavior of polymer particulate composites. The polymer particulate composite is modeled as a three-phase continuum. Together with particles and matrix is considered an interphase. The interphase is created on particle-matrix interface. Non-linear matrix material properties were experimentally determined and used in calculations. The main aim is to estimate micro-crack propagation direction for the variety of matrix and interphase material properties. The results are obtained using the finite element commercial code ANSYS.

Fracture and Plasticity in Nano-Porous Particle-Polymer Composites

A fracture mechanics algorithm, used for continuum mechanics simulations of nano-porous particle-polymer composites, is described herein. The model comprises close to a thousand ceramic particles bound together by latex polymer. These packings are generated using probabilistic methods (Monte Carlo). Pore-space arises as a function of particle shape and position coupled to the concentration and distribution of latex. Since the bridges are the weakest links in the solid state continuum, an understanding of failure behaviour is paramount for the design and optimisation of these composites. The objective of this research is to statistically characterise adhesive failure at particle-latex interfaces against cohesive failure within the latex bridges. To achieve this, a novel numerical method was developed. This method solves ordinary differential equations for vectors of force and displacement in layers through the computational packing. The model includes a scheme for non-linear elastic behaviour that evolves into a plastic flow regime. The model moreover incorporates a routine for interfacial failure between particulates and binder. Geometrical features such as solid state anfractuosity, bridge orientation, material fraction and coordination numbers are calculated from the packing output. The number of bridges straining plastically within the packing is lower than those that fracture at the interface. Fracture and failure are both related to the particle-binder coordination number. There is no evidence to suggest that decreasing the contacting sizes of binder at interfaces as well as making them thinner will lead to more plastic failure and decrease fracture. Rather, both plastic failure and fracture increase as a function of decreased contacting sizes and bulk diameters. The residual elastic modulus decreases exponentially as the number of broken connections increases.

A mixtures’ model for porous particle–polymer composites

Derived herein is a mixtures’ model for porous particle–polymer composites, modified to encompass the geometrical influences of microstructure to elastic resistance. Emphasis is directed in particular to binding material contact lengths, solid state anfractuosity, pore-space influence perpendicular to the direction of loading and the effective contribution of reinforcing material. These microstructural features are contextualised within the classical Voigt model to yield a simplistic model that predicts, with greater accuracy than classical mixture-based models and contemporary porous composite models, the Young modulus for porous particle–polymer composites.

Processing, properties, and in vitro bioactivity of polysulfone‐bioactive glass composites

The mismatch between the mechanical properties of bioceramics and natural tissue has restricted in several cases a wider application of ceramics in medical and dental fields. To overcome this problem, polymer matrix composites can be designed to combine bioactive properties of some bioceramics with the superior mechanical properties of some engineering plastics. In this work, polymer particulate composites composed of a high mechanical-property polymer and bioactive glass particles were produced and both the in vitro bioactivity and properties of the system were investigated. Composites with different volume fraction and particle size were prepared. In vitro tests showed that hydroxy-carbonate-apatite can be deposited on the surface of a composite as early as 20 h in a simulated body fluid. Ionic evolution from a composite with 40% volume fraction of particles was demonstrated to be similar to bulk bioactive glasses. The mechanical properties of some of the obtained composites had values comparable with the ones reported for bone. Moreover, a physical model based on dynamical mechanical tests showed evidences that the interface of the composite was aiding in the stress transfer process.

Modeling the Al2O3 particle–polymer composites for the packaging of the shock-wave pulsed transducer

A model has been developed for the prediction of the dielectric property and the acoustic impedance of particle/polymer composite used in the plastic packaging of the shock-wave pulsed transducer. Expressions are derived for the parameters of the composite in terms of the volume fraction of particle and the polymer. The model is illustrated by analyzing composites made from Al2O3 particle and the epoxy resin, with the anisotropy of the Al2O3 taken into account. Comparisons with the rod and particle of Al2O3 are discussed. The three different polymers, polyethylene, epoxy resin and PVDF are also discussed. The model gives some physical insight into the design of the composites used in the transducer and shows good correlation between calculated and measured ultrasonic velocities.

Dielectric behavior of a metal-polymer composite with low percolation threshold

Stainless steel fiber (SSF)/poly(vinylidene fluoride) composite is prepared via simple blending and hot pressing route. The dependence of the dielectric properties of the composite on both volume fraction of the fillers and frequency is investigated. The percolation threshold of the composite, 9.4vol% (0.094 volume fraction), is much lower than that of the common two phase metal particle-polymer composite. A dielectric constant of 427 is observed at 50Hz with 10vol% of SSF. Large enhancements of the ac conductivity and loss tangent are also observed near the percolation threshold. The dielectric properties are explained by percolation theory while the dielectric anomalies are attributed to the high slenderness ratio of the SSF fillers.

Estimation of elastic properties of a particulate polymer composite using a face-centered cubic FE model

A three-dimensional (3D) finite element (FE) unit cell model is applied to studies on the elastic properties of ceramic spherical particle–polymer composite. In this model, hydroxyapatite particles (HAp) are assumed to be spherical and are arranged on a face-centered cubic (FCC) array in poly- l-lactide (PLLA) matrix surrounding. The three dimensionality of the proposed model enables simulation of elastic properties as well as developed stress states. The FE calculations provide estimates of compressive elastic modulus, shear modulus, Poisson's ratio and stress state of the composite for a range of particle volume fractions. The FCC unit cell FE models are evaluated by comparison to available experimental results, simple cubic (SC) unit cell FE calculations and Halpin–Tsai equations. In applying unit cell models for predicting elastic properties of particle-filled composites, the FCC arrangement can be observed to be more accurate compared with the SC arrangement.

Modeling plate impact response of particle–polymer composite

A recently obtained constitutive relation [Zhang et al., Phys. Rev. E 66, 051806 (2002)] is used for polymers to model plate impact experiments on a composite material consisting of elastic particles and a polymer binder. The stress relaxation in the polymer is described by a kernel in a history integral. The kernel implies a 1/t stress relaxation for a short time t, and an exponential stress relaxation for a long time. It is found that the binder behavior, especially the stress relaxation at a short-time scale, plays an essential role in the wave dispersion observed during the experiments. Although it is difficult to implement the history dependent constitutive relation directly into a numerical calculation, a mathematical approximation of the kernel is found in the form resembling a prony series. The approximation enables easy implementation of the constitutive relation into numerical calculations. While the conventional use of a prony series requires a series of experiments to determine the parameters, in the present article, the parameters in the series expansion are uniquely determined by the kernel. Furthermore, not all the terms in the series are needed for a specific problem of interest. Only those terms with the relaxation times in the range of the time scales of the physical process are important.