Search

A numerical model using homogenization techniques is proposed to simulate the evolution of elastic properties of nanocomposite polymer-nanoparticles, depending on the concentration of nanoparticles and the rigidity of the particle-matrix interface. To validate this model, it was confronted to several physical systems having different interface behavior, the nanocomposite systems: poly(vinylidene fluoride trifluoroethylene)/[A1.sub.2][0.sub.3] (alumina nanoparticles incorporated into copolymer of vinylidene difluoride and trifluoroethylene to form nanocomposite), PMMA/CNT (carbon nanotube/poly(methyl methacrylate) composite) and PMMA/Si[0.sub.2] with nanoparticles with or without surface treatment of silanization. For all these systems, the Young's modulus (nanoparticles and matrix) has been obtained experimentally from the elastic modulus [C.sub.11] obtained by Brillouin spectroscopy. These macroscopic measurements coupled with the theoretical model allow a multiscale approach of the elastic behavior of nanocomposite systems, providing information on the global elastic properties of polymer-nanoparticle material, and also indications about the strength of physical and chemical bonds between the nanoparticles and the matrix. Our results validate the hypothesis of the crucial role of the interface module, provided by numerical simulation which shows that incorporation of nanoparticles may lead to a strengthening or a weakening of the matrix. POLYM. ENG. SCI., 53: 1502-1511, 2013. [C] 2012 Society of Plastics Engineers, INTRODUCTION The power of nanotechnology is rooted in its potential to transform and revolutionize multiple technology and industry sectors, including aerospace, agriculture, biotechnology, energy, environmental improvement, information technology, medicine, and [...]

Contact resonance force microscopy has been used to evaluate the effect of maleated polypropylene (MAPP) concentration on interphase thickness as well as the spatial distribution of mechanical properties within the interphase of cellulose fiber-reinforced polypropylene composites. The average interphase thickness values ranged from 25 nm to 104 nm for different concentrations of MAPP. The interphase region showed a gradient in the elastic modulus, with a gradual decrease in modulus from fiber to matrix. The interphase region in the specimen containing 0% MAPP showed a narrow interphase with steep gradient in modulus from fiber to matrix, whereas the use of MAPP significantly increased the interphase thickness which resulted in a more gradual change in modulus from fiber to matrix. POLYM. ENG. SCI., 53:888-896, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION The structural integrity of a composite mainly depends on the quality of stress transfer across the interphase. Extending over lengths from nanometeis to micrometers, a well-engineered interphase is essential [...]

Different micromechanical models which account for the presence of dispersed and agglomerated nanofillers, specifically carbon nanotubes (CNTs) and cellulose nanowhiskers (CWs), in a polymeric matrix and consider the effect of a percolation threshold on the elastic modulus of the composite are derived and compared. We demonstrate that the critical filler volume fraction where a percolating network is forming marks a 'turning point' in the reinforcement efficiency. The suitability of these models is verified by comparing simulated values with experimental data from literature. The results show that the models are able to predict mechanical properties over a wide range of testing conditions. POLYM. ENG. Sd., 53:882-887, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Nanocomposites are a class of composites in which one of the dimensions of the reinforcement phase is in the range of 1-100 nm. Because of the filler nanometer size [...]

The extensional rheological properties of three grades of polyethylene melts, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE) were measured using a melt spinning technique under the test conditions with temperature ranging from 150 to 210°C and extrusion rate varying from 11.25 to 22.50 mm [s.sup.-1]. The results showed that the melt strength decreased with a rise of temperature while increased with an increase of extensional rate. With the rise of extensional strain rate and temperature, the melt extensional viscosity decreased. The extensional stress and viscosity reduced with increasing extrusion velocity when the temperature and extensional rate were constant. Moreover, the melt strength and extensional viscosity of the LDPE resin was the highest and the LLDPE was the lowest under the same experimental conditions. POLYM. ENG. SCI., 51:2490-2494, 2011. © 2011 Society of Plastics Engineers, INTRODUCTION In polymer processing, melt extensional flow is a common flow pattern, such as entrance converging flow in die extrusion or runner injection of polymer melts from an extruder barrel [...]

This paper describes various viscoelastic magnetic silicone gel bodies developed to create a new type of viscoelastic magnetic material. This material is capable of undergoing substantial changes in mechanical properties due to the large deformation caused by magnetic traction force under the application of a moderate strength magnetic field. This study performed tensile tests for various viscoelastic magnetic silicone gel bodies under a uniform steady magnetic field. The elastic moduli of the gel bodies were measured under different controlled experimental conditions. The experimental results showed that, under the applied magnetic field, the elastic moduli of the viscoelastic magnetic silicone gel bodies increased and were largely dependent upon the magnetic properties of the magnetic particles. The magnetic particle size and the material properties of the dispersant and the silicone gel also had significant effects on the moduli of the gel bodies. This paper also discusses the most appropriate combination of the materials used in this study from the standpoint of gaining a large magnetic traction force. POLYM. ENG. SCI., 50:857-862, 2010. [C] 2009 Society of Plastics Engineers, INTRODUCTION It was recently discovered that flow rate control can be performed by magnetic fluid membranes that are capable of freely changing the cross section of a pipe under a [...]

A series of polyurethane tri-block copolymers were synthesized by reacting a 4,4'-methylenebis(phenyl isocyanate) (MDI)-endcapped poly(tetramethylene oxide) (PTMO, [M.sub.n] = 2,000 g/mol) with a monoamine-diamide (6T6m) hard segment (HS). The concentration of the HS in the copolymer was varied between 9 and 33 wt % by changing the length of the soft mid-block segment. The structure of the copolymers was analyzed by nuclear magnetic resonance, the amide crystallinity was investigated by Fourier transform infra-red and the thermal properties were studied by differential scanning calorimetry. The mechanical and elastic properties of the tri-block copolymer were subsequently explored by dynamic mechanical analysis, compression set and tensile experiments, and the melt rheological behavior was studied by a parallel plate method. The amide end groups displayed a high crystallinity and the modulus of the tri-block copolymers was relatively high. The fracture strain increased strongly with the molecular weight and the copolymers demonstrated a ductile fracture behavior for molecular weights above 6000 g/ mol. Good compression set values were obtained for the tri-block copolymers despite their low molecular weight. In the molten state, the tri-block polymers displayed a gelling effect at low frequencies, which was believed to be a result of a clustering of the end-segments. POLYM. ENG. SCI., 50:747-755, 2010. [C]2009 Society of Plastics Engineers, INTRODUCTION Polyurethanes (TPU) make up an important class of thermoplastic elastomers with a wide variety of applications in industry (1-3). Generally, thermoplastic polyurethanes consist of PTMO soft segments and 4,4'-methylenebis(phenyl [...]

A knotted and interconnected skeleton structural (KISS) model is proposed for predicting Young's modulus of polymer blends. The KISS model accounts for the structure variations of polymer blends using the percolation theory and emphasizes the structural symmetry of co-continuous polymer blends. It reduces to the Maxwell-Eucken models below the percolation threshold and a symmetric interconnected skeleton structure at an intermediate component volume fraction. The KISS model satisfactorily predicts the Young's modulus of polymer blends for the entire component volume fraction range. Due to mathematical analogy, the model might equally be applied to predictions of electrical and thermal conductivity of binary mixtures. POLYM. ENG. SCI., 50:643-651, 2010. [C]2009 Society of Plastics Engineers, INTRODUCTION Mixing materials are often a cost-effective way to achieve unique physical properties that are superior to the properties of the individual materials. Polymer blends have attracted special attention for [...]

The current article describes static and frictional contact tests carried out with spherical indenter on both human skin surface and elastomeric materials. This tribological study is performed to analyze the elasticity and tactile properties of the human skin, and therefore to evaluate reliability of human skin behavior simulation through the considered elastomeric materials. Finite element analyses of indentation tests are proposed. Critical normal load was found when numerical and experimental results were confronted. Such critical force defines the limit of elastic model application. POLYM. ENG. SCI., 46: 1715-1720, 2006. © 2006 Society of Plastics Engineers, INTRODUCTION Ageing is a physiological mechanism associated with changes in skin morphology and mechanical properties, including dry state, and anisotropy of the skin relief. Moreover, cosmetic products induce tactile changes [...]

In oscillatory rheometry, since the dynamic storage modulus (G') represents the elastic component of the viscoelastic melt, it has been a rather common practice to associate it with the melt elasticity. Although this assumption might be valid in many instances, there can be exceptions as well. In the present study, we have chosen polypropylene/talc system to demonstrate an exception. For example, the melt elasticity decreases with increasing talc content as revealed by extrudate die swell, entrance pressure drop, and elastic compliance measurements; the opposite trend being reflected by G'. We can envision similar exceptions when stiffening agents are added to a polymer melt, e.g., rigid rod molecules. We are suggesting that G' represents the elastic modulus or stiffness of the melt, which in certain situations might not reflect elasticity, i.e., the ability of a melt to recover from a deformation. The implication of the present manuscript is that caution be exercised when relating G' to the melt elasticity of a polymer.