Particulate Polymer Composites Research Articles

Predictive potentialities of a cylindrical structural cell for particulate elastomeric composites

A unit cell of a specified shape under specified loading conditions has been offered for predicting some basic properties of particulate polymeric composites. The stress–strain state for bonded, debonding and debonded cells as a function of the cell stretch and superimposed pressure has been calculated for various filler volume fractions, adhesive strengths and matrix extensibility. The tensile curves and volume changes have been calculated for various superposed pressures. The predictive ability of the unit cell has been exemplified by the comparison of the calculated and experimental data on the modulus/filler volume fraction curves over a wide range of concentrations.

Plasma treatment of particulate polymer composites for analyses by scanning electron microscopy: II. A study of highly filled polypropylene/calcium carbonate composites

Plasma treatment of fracture surfaces from particulate calcium carbonate/polypropylene composites has been shown to have potential as a means for exposing filler particles in the fracture surface, particularly where fracture occurs through the matrix. It has been found that the optimum time of plasma treatment is governed by the nature of the matrix and possibly by the type of filler-matrix bond. This method of exposing filler particles in composite surfaces provides a very convenient aid in the process of characterising filler particle size distributions and composite homogeneity/heterogeneity.

Modeling viscoelastic response of particulate polymeric composites with high volume fractions of fillers

A generalized self-consistent method is extended to particulate viscoelastic composites with elastomeric matrices and high volume fractions of elastic inclusions. It is shown that the effective bulk modulus of a composite coincides with the bulk modulus of particles. A quadratic operator equation is derived for an analog of the effective shear relaxation kernel. This equation is explicitly solved using the Laplace transform method. The influence of material and geometrical parameters of a composite on its effective viscoelastic moduli is analyzed numerically.

Plasma treatment of particulate polymer composites for analysis by scanning electron microscopy: I. Morphology of silica filled low density polyethylene

Scanning electron microscopy was used for investigation of brittle and ductile fractures of composites with low density polyethylene matrix filled with inorganic particle fillers. Air-plasma treatment was shown to be a suitable procedure for the etching of the fracture surface when studying the filler distribution and dispersion in particle filled composites if the fracture of the studied material is cohesive, i.e., the crack initiates and proceeds through the polymer matrix and the filler particles are covered by polymer layer.

Aligned microstructure of some particulate polymer composites obtained with an electric field

Alignment by an electric field was obtained for a variety of particles dispersed in photopolymerizable fluids. The particle shapes studied were irregular, spherical, rhombohedral, rod-like (fibres), and platelet. The sizes ranged from sub-micrometres to tens of micrometres, and the dielectric constants of the particles varied from less than that of the lquid matrix to very much greater than that of the matrix. Polymerization or hardening of the matrix was possible at room temperature, required only a few seconds, and the aligned structures obtained were able to be examined by both light and scanning electron microscopy after fracture or sectioning. Nominally equiaxed particles, containing a statistical proportion of non-equiaxed particles, could be completely aligned at 48 vol% concentration in a fluid having a viscosity of about 2.5 Pa s, but at 57 vol%, the mixture behaved as a paste, and only particle rotation and local rearrangements were possible. The rate of alignment seemed to depend generally on the magnitude of e1(aβ)2, where e1 is the relative dielectric constant of the liquid resin, a is the particle radius, and β is the particle dipole coefficient given by (e2−e1)/(e2+2e1), where e2 is the relative dielectric constant of the particles. e1(aβ)2 emphasizes the importance of particle size and the relative unimportance of the particle dielectric constant for alignment, except when e2≈e1. Platelets were more rapidly aligned than fibres.

On the Influence Zone and the Prediction of Tensile Strength of Particulate Polymeric Composites

An intended numerical investigation is carried out. The results indicate that, even if a perfect adhesive bond is preserved between the particles and matrix materials, the two-phase element cell model is unable to predict the strength increment of the particulate polymeric composites (PPC). To explore the main reinforcing mechanism, additional microscopic experiment is performed. An "influence zone" was observed around each particle which is measured about 2 to 10 micrometers in thickness for a glasspolyethylene mixture. Then, an improved computational model is presented to include the "influence zone" effect and several mechanical behaviors of PPC are well simulated through this new model.

Discrete models of failure for particulate polymer composites

AbstractA stochastic discrete model is offered that simulates the behavior of particulate composites able to generate and accumulate scattered structural microdamages to the final breakdown of the model. The model is quite transparent, which allows us to observe continuously its internal state and effective behavior. Through numerical experiments, it is established that the accumulation of the scattered damage, accompanied by the appearance of the elastic nonuniformity, ends in a loss of the elastic stability of the whole of system and macrocrack formation in the most compliant part of the body. No strength criteria are needed to describe this process. Breaking stresses and strains and their scatter in repeated experiments, as functions of the virgin system specification, can be calculated and used for safety factors or for optimization of composite properties.

Highly Predictive Structural Cell for Particulate Polymeric Composites

A unit cell of a specified shape under specified loading conditions has been offered for predicting some basic properties of particulate polymeric composites. The stress-strain state of the bonded and debonded cell has been calculated in the framework of the large deformation approach within a wide range of filler volume concentrations. Effective modulus-filler concentration curves have been predicted on the basis of the unique cell investigation for bonded and debonded cell states and have proved to be in good agreement with the available experimental data. Local strain concentration as a function of cell extension and filler volume loading has been estimated.

Evaluation of dielectric behaviour of particulate composites consisting of polymeric matrix and conductive filler

Extension of the logarithmic law of mixtures enables equations to be formulated which describe the dielectric behaviour of particulate polymeric composites containing conductive particles. These eq...

Evaluation of dielectric behaviour of particulate composites consisting of polymeric matrix and conductive filler

Extension of the logarithmic law of mixtures enables equations to be formulated which describe the dielectric behaviour of particulate polymeric composites containing conductive particles. These equations give the permittivity and dielectric loss of the composite as a function of the permittivity of the polymeric matrix, the volume fraction and aspect ratio of the inclusions, and the frequency of the applied field. The proposed equations were tested with experimental data obtained over a wide range of frequencies and temperatures from composites consisting of epoxy resin and aluminium powder. Satisfactory agreement was observed when the volume fraction of the inclusions was small, but at higher values discrepancies appeared which are attributed to the intrinsic weakness of the logarithmic law of mixtures, on which the proposed equations are based.MST/3167

Evaluation of the behaviour of particulate polymeric coatings in a corrosive environment. Influence of the concentration of metal particles

In this work pretreated steel specimens were coated by a spinning process with particulate polymeric composites consisting of an epoxy resin (DOW 331) and iron powder. Applied coatings were roughly 70 μm thick and the contained quantity of iron particles was varied (7.5, 15, 30% wt./wt.). The effect of the presence of iron particles in the coatings as well as the influence of their concentration on the evaluation of the coatings' behaviour in a corrosive environment (3.5% NaCI) was studied. Electrochemical impedance spectroscopy, corrosion potential, corrosion current density (Tafel) and dielectric measurements were performed. Minor differences in the anticorrosive behaviour of the coatings were observed irrespective of the iron content in the coating. Effective resistance inhibition action of the composite coatings was diminished with the increase of exposure time to the corrosive environment being in all cases very close to that of the pure epoxy resin coatings.

Pressure Reinforcement of Particulate Polymeric Composites Originated By Adhesive Debonding

Abstract Particulate elastomeric composites exhibit considerable reinforcement when they are extended under moderate superposed pressures. Numerous experiments have shown that this effect is provoked by pore formation and relevant matrix overstraining. The interfacial friction between the debonded matrix and filler has as well been shown to influence this phenomenon markedly. It seemed resonable first to study separately elastic and frictional contributions to reinforcement. The paper examines the reinforcement effect caused by elastic pore suppression under superposed pressure without taking into account the frictional effect. The structural element has the form of a rubber neo-Hookean cylinder (matrix) with a rigid spherical inclusion (filler) at the center. Quantitative dependence of the reinforcement on the volume suppression, pressure, degree of extension, volume content of the inclusion and modulus of the matrix has been obtained in the framework of large deformation. The analysis of these data has shown that theoretical results were in good agreement with the available experimental evidence. Some peculiarities of the phenomenon have been established such as the weakening of the extent of reinforcement with the extension, higher reinforcement under negative pressures, two different geometrical modes of the vacuole compression depending on the extension and the range of matrix moduli where the reinforcement effect becomes negligible.

Interfacial Friction in Filled Polymers Initiated by Adhesive Debonding. II. Relaxation Studies

Abstract A number of dissipative mechanisms exhibited by particulate polymeric composites are known. The viscoelasticity of matrices as a repeatable phenomenon and the Mullins effect as an irreversible one have been investigated by many researchers over a long period of time.