Filled Polymer Composites Research Articles

Preparation of UV-Curable Nanocomposite Varnish with High Wear Resistance

To enhance the interfacial interaction in silica nanoparticles filled polymer composites , nano-SiO2 gel was prepared by a sol-gel route, and then it was modified in situ through a reaction of silane coupling agent with hydroxyl on the surface of SiO2. The modified nano-SiO2 gel was added to the system of light-cured varnish to prepare UV light-cured nanocomposite varnish. The structures and properties of varnish were studied using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and film performance test. The results showed that the modified nano-SiO2 was well dispersed in the varnish. After introduction of modified nano-SiO2, the fracture morphology of varnish film showed a corrugated shape, indicating the ductile fracture. The wear resistance of the varnish film increased by 50%, the coefficient of static friction reduced about 15%, and gloss improved to some extent.

Particle size – Dependent on the static and dynamic compression properties of polypropylene/silica composites

The effect of particle size is widely known as an essential factor that influences the mechanical properties of particulate filled polymer composites. However, there is a limited number of works available, on the particular under dynamic perspective. Based on this, the static and dynamic compression properties of polypropylene/silica composites, with particle sizes of 3μm, 1μm, 20nm, and 11nm, were successfully studied at different levels of strain rates (i.e., 0.01s−1, 0.1s−1, 650s−1, 900s−1, and 1100s−1) using a universal testing machine and a split Hopkinson pressure bar apparatus. Results show that the yield strength, the ultimate strength, and the stiffness properties, of polypropylene/silica composites were greatly affected by both particle size and loading rates. Furthermore, particle size also influences the rate sensitivity and the thermal activation volume of polypropylene/silica composites; where, smaller particle recorded lower rate sensitivity. Meanwhile, for the thermal activation volume, the trend was reversed.

Conductivity enhancement of silver filled polymer composites through electric field alignment

We show how an alternating electric field can be used to align silver micron or sub-micron sized particles into microscopic wires in diverse polymer matrices based on the dielectrophoretic effect. The electric field is set by an electrode pair and the wires form conductive pathways through the matrix, bridging these electrodes electrically. The matrix is cured after alignment, locking wires in permanent pathways within the polymer. The wires are then characterized by ac impedance spectroscopy. The alignment can take place either in-plane or out-of-plane, and yields a directional conductivity in the alignment direction parallel to the electric field lines. The samples can be centimeters wide containing thousands of wires in parallel, but even an individual wire can be grown and controlled. The initial mixture contains less than 1 vol.% of silver and is an electrical insulator. The bulk conductivity enhancement, due to the alignment, may be 5 orders of magnitude, typically from 1 � 10 � 5 S/m to 1 S/m as the particle alignment converts the sample conductivity from polymer dominated to silver dominated. For the aligned isolated silver wires, the jump in conductivity, confined to the volume filled by the wire can be seen to be as high as 9–10 orders of magnitude, resulting in conductivities as high as 1 � 10 5 S/m, thus approaching those

Aspects of fracture toughness modelling of particle filled polymer composites

Polymer composites filled with hard inorganic particles of nano- to micro-scaled sizes show a very complex variation of fracture toughness with increasing particle fraction. Various failure mechanisms such as particle debonding, matrix yielding and subsequent brittle or ductile matrix fracture develop during crack propagation. In this work, these failure mechanisms within a dissipation zone are considered for the calculation of composite fracture toughness. It is shown that their influencing extent depends on critical values of composite strain or stress, respectively. The variation of composite fracture toughness with material and structural properties, such as the relation between the debonding strain and matrix yield strain, matrix yielding energy and particle volume fraction, is discussed.

Role of Interface on the Thermal Conductivity of Highly Filled Dielectric Epoxy/AlN Composites

The interface between filler and matrix has long been a critical problem that affects the thermal conductivity of polymer composites. The effects of the interface on the thermal conductivity of the composite with low filler loading are well documented, whereas the role of the interface in highly filled polymer composites is not clear. Here we report on a systematic study of the effects of interface on the thermal conductivity of highly filled epoxy composites. Six kinds of surface treated and as received AlN particles are used as fillers. Three kinds of treated AlN are functionalized by silanes, i.e., amino, epoxy, and mercapto group terminated silanes. Others are functionalized by three kinds of materials, i.e., polyhedral oligomeric silsesquioxane (POSS), hyperbranched polymer, and graphene oxide (GO). An intensive study was made to clarify how the variation of the modifier would affect the microstructure, density, interfacial adhesion, and thus the final thermal conductivity of the composites. It was found that the thermal conductivity enhancement of the composites is not only dependent on the type and physicochemical nature of the modifiers but also dependent on the filler loading. In addition, some unexpected results were found in the composites with particle loading higher than the percolation threshold. For instance, the composites with AlN treated by the silane uncapable of reacting with the epoxy resin show the most effective enhancement of the thermal conductivity. Finally, dielectric spectroscopy was used to evaluate the insulating properties of the composites. This work sets the way toward the choice of a proper modifier for enhancing the thermal conductivity of highly filled dielectric polymer composites.

Deinked and acetylated fiber of newspapers

AbstractRecently, the incorporation of lignocellulosic materials as reinforcing agents or as fillers in polymer composites has received an increased attention. Although natural fibers have a number of advantages over glass fibers, the strong polar character of their surface is a limiting factor, as compatibility with strongly apolar thermoplastic matrices is very low. Such problems of incompatibility may be overcome with fiber pretreatments, which can enhance compatibility, albeit having a negative impact on the economics. In this study, the newspaper is deinked and acetylated. The effect of esterification between the acetyl groups and the hydroxyl groups of the fiber was examined by Fourier transform infrared. X‐ray diffraction and scanning electron microscopy were used to characterize the crystallinity and the surface morphology of the untreated deinked and acetylated fibers (newspaper). The thermal stability of deinked and acetylated fibers was slightly decreased. It was also shown that the deinking increased the crystallinity of newspaper fibers while acetylating decreased this crystallinity. Cellulose acetate is one of the most important cellulose derivatives and its main applications are its use in composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Use of Nutshells as Fillers in Polymer Composites

Nutshells are agricultural waste products that can be procured at relatively low cost. In this work we examined the possibility of using these biodegradable materials as fillers in poly(lactic acid) and low density polyethylene. The nutshells were ground into powder, blended with the polymer, and then injection molded with final weight varying from 10 to 40 weight %. The mechanical and thermal properties of the composites were then studied. In general, the addition of fillers caused reductions in mechanical properties to varying extents, but thermal properties were only slightly affected. The use of maleic anhydride and peroxide with the fillers had a negative effect on poly(lactic acid) but a slightly positive effect on the stiffness of polyethylene. The results suggested that polymer-nutshell composites may be usable in applications where cost is a concern and where some reductions in mechanical properties are acceptable.

Effect of Injection Molding Process on Electrical Conductivity and Mechanical Property of Nanoparticle Filled Polymer Composites

Authors investigated the relationship among processing parameters, microstructures, electrical conductivity and mechanical property of injection molded nanoparticle filled polymer composites at present study. Standard tensile specimens were injected under different injecting pressures and packing pressures. The molded specimens were removing five layers from the surface to observe the microstructures at different positions of the moldings. The electrical properties were measured with a two-terminal standard resistor under DC condition at room temperature, and the mechanical properties of the moldings were measured by INSTRON 5580 Universal testing machine. The results showed that filled nanoparticles may form the best conductive path under the higher packing pressure matched with higher injection pressure. The mechanical properties of the molding depend on not only the concentration of the nanofiller, but processing conditions as well.

Synthesis and Study of Optical and Electrical Characteristics of Single-Wall Carbon Nanotube/Gold Nanohybrid

Au nanoparticles of average size 3.0 nm have been deposited on SWCNT surfaces following a very lucid wet chemical process. The SWCNT/Au nanohybrid material has been characterized using field emission scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDAX), X-ray diffraction (XRD) study and Raman spectroscopy. Both optical and electrical characteristics of the hybrid sample have been studied. The PL emission intensity of the nanohybrid structure has been found to decrease on increasing the excitation wavelength in the plasmon absorption region. High temperature DC conductivity has increased appreciably when pristine SWCNT is treated with Au NPs. Such SWCNT- supported gold nanoparticles can serve as efficient catalysts in chemical industry. Also the tendency of gold-based nanoparticles to attach with biological molecules may make them useful in medical diagnostics. Increase in conductivity of SWCNT on decorating with Au NPs can find practical application as conducting filler in polymer composites.

Processing and Thermal Conductivity Characterization of Solid Glass Micro-Spheres Filled Polymer Composites

This paper describes the preparation and thermal conductivity characterization of solid glass micro-spheres (SGMs) filled polymer composites. SGMs of different sizes are embedded in epoxy resin to develop composites by hand layup technique. A numerical simulation of the heat-transfer within the composites is made by using finite element method (FEM). Three-dimensional spheres-in-cube lattice array models are constructed to simulate the microstructure of composite materials for various SGM content ranging from 0 to about 27 vol % and the effective thermal conductivities (Keff) of the composites are estimated. Keff values are also calculated using some of the existing theoretical models. Finally, guarded heat flow meter test method is used to measure the conductivity of these composites. The simulations are compared with Keff values obtained from experiments and it is found that the FEM simulations are fairly close to the measured Keff. This study shows that the incorporation of SGMs results in reduction of conductivity of epoxy resin and thereby improves its thermal insulation capability. Further, the size and content of SGMs influence the extent of reduction of Keff. Keywords: Composites; Glass Microspheres; FEM; Thermal Conductivity; Simulation

Dispersion and aspect ratio of carbon nanotubes in aqueous suspension and their relationship with electrical resistivity of carbon nanotube filled polymer composites

Multiwalled carbon nanotube (MWCNT)/acrylonitrile butadiene styrene (ABS) composites were prepared by a processing method using solvent–nonsolvent precipitation. Size distributions of MWCNT agglomerates in aqueous suspension were investigated in order to predict aspect ratio of nanotubes by evaluating the effects of sonication time, MWCNT content, and surfactant. Aspect ratios of MWCNTs were predicted on the basis of the size distribution measurements for MWCNT agglomerates. Sonication time or applied sonic energy has a strong effect on the size distribution of MWCNT agglomerates. Compared with simple shear mixing method, it was shown that this processing method is more suitable for the MWCNT/ABS composites. An electrical percolation threshold was observed for the weight fraction of MWCNTs in the range of about 0.5–1.0wt.%. Shorter MWCNTs are more suitable to induce fine dispersion, but lead to higher percolation threshold weight fraction. It was illustrated that fine dispersion can overcome the handicap of short length or low aspect ratio of MWCNTs.

Influence of foaming agent on wear and mechanical properties of surface modified rice husk filled polyvinylchloride

The ever increasing demand for high strength lightweight material is driving the current research efforts to develop advanced materials for a variety of structural applications. Polymer matrix composites form that group of advanced materials which are preferred in structural applications owing to their high specific strength. The concern for a safe environment further demands the optimum utilization of reinforcing agents and fillers that are derived from natural sources. In such a scenario rice husk seems promising as filler for polymer matrix composites. It is an agricultural waste produced in bulk quantity during rice milling. It has proved to be efficient agro filler for developing light weight polymer based composites. The weight of rice husk filled polymer composites can be further reduced if foaming agents are introduced. In the present study the influence of a foaming agent on the mechanical and wear behavior of surface modified rice husk filled polyvinylchloride has been studied. Six composites having 10, 20 and 30 weight percent of unmodified and surface modified rice husk having a small percent of a foaming agent have been studied and compared with foamed PVC. It was observed that with an increase in rice husk content wear resistance as well as compressive strength of composites increased. Surface treatment of rice husk by maleic anhydride improved the wear resistance due to improvement in compatibility between rice husk and PVC compound.

Processing and Thermal Conductivity Characterization of Solid Glass Micro-Spheres Filled Polymer Composites

This paper describes the preparation and thermal conductivity characterization of solid glass micro-spheres (SGMs) filled polymer composites. SGMs of different sizes are embedded in epoxy resin to develop composites by hand layup technique. A numerical simulation of the heat-transfer within the composites is made by using finite element method (FEM). Three-dimensional spheres-in-cube lattice array models are constructed to simulate the microstructure of composite materials for various SGM content ranging from 0 to about 27 vol % and the effective thermal conductivities (Keff) of the composites are estimated. Keff values are also calculated using some of the existing theoretical models. Finally, guarded heat flow meter test method is used to measure the conductivity of these composites. The simulations are compared with Keff values obtained from experiments and it is found that the FEM simulations are fairly close to the measured Keff. This study shows that the incorporation of SGMs results in reduction of conductivity of epoxy resin and thereby improves its thermal insulation capability. Further, the size and content of SGMs influence the extent of reduction of Keff. Keywords: Composites; Glass Microspheres; FEM; Thermal Conductivity; Simulation

Microwave Absorption Properties of Highly Filled Polymer Composites with Amorphous Fe–B Particles

In this study, polymer composites containing amorphous Fe­B particles with large particle size distribution were fabricated. A polymer composite of mixed particles showed a high relative permeability of ®r = 9.3 at 1GHz. In addition, the composite exhibited good microwave absorption properties (R.L. < 120 dB) in the frequency range of 0.6­1.1GHz for absorber thickness of 2.4­4.2mm. Thus, this polymer composite can be used for fabricating microwave absorbers that are effect in the 0.7­1.0GHz band, and would result in microwave absorbers thinner than any other microwave absorbers reported to date. [doi:10.2320/matertrans.MAW201203]

The Structural Model of Impact Toughness of Particulate-Filled Polymer Nanocomposites

A quantitative structural model of particulate- filled polymer composites impact toughness, based on the fractal analysis ideas, was offered. The model demonstrated good correspondence with the experimental data. It has been shown that the action of nanofiller as nucleator, resulting in crystallinity degree and amorphous phase structure change, exert the main influence on impact toughness value.

Relation between repeated uniaxial compressive pressure and electrical resistance of carbon nanotube filled silicone rubber composite

Carbon nanotube filled polymer composite can be used as sensitive material of flexible pressure sensor. By using solution mixing method, carbon nanotubes are dispersed into silicone rubber matrix to fabricate the composite. The piezoresistivities of the composite with different carbon nanotube concentrations under repeated compressions are researched quantitatively. The monotonicity of the piezoresistivity is dependent on the content of carbon nanotube and the range of the applied pressure. The reproducibility error of the piezoresistivity decreases with the increase of the compression cycles. The experimental data of the piezoresistivity are fitted by the linear combination of two exponential functions. The piezoresistive mechanism is studied qualitatively by analyzing the changes in the carbon nanotube network.

Thermal conductivity model of filled polymer composites

Theoretical and empirical models for predicting the thermal conductivity of polymer composites were summarized since the 1920s. The effects of particle shape, filler amount, dispersion state of fillers, and interfacial thermal barrier on the thermal conductivity of filled polymer composites were investigated, and the agreement of experimental data with theoretical models in literatures was discussed. Silica with high thermal conductivity was chosen to mix with polyvinyl-acetate (EVA) copolymer to prepare SiO2/EVA co-films. Experimental data of the co-films’ thermal conductivity were compared with some classical theoretical and empirical models. The results show that Agari’s model, the mixed model, and the percolation model can predict well the thermal conductivity of SiO2/EVA co-films.

Effect of the processing of injection-molded, carbon black-filled polymer composites on resistivity

To improve the application of carbon black (CB)-filled polymer composites, we investigated the relationship between the processing parameters, microstructure and electrical properties of injection moldings made from the material. Standard tensile specimens were fabricated under different injection pressures and packing pressures. Up to five layers were removed from the surfaces of the molded specimens to observe the microstructure at different positions within the moldings. Microstructures were observed with a scanning electron microscope, and electrical properties were measured at room temperature with a standard two-terminal direct current (DC) resistor. The results showed that CB particles form the best conductive path at high packing pressures combined with high injection pressures. If the packing pressure is low, the resistivity in the skin zone when loaded by high injection pressures is less than when loaded by low injection pressures, but resistivity increases in the sub-skin zone. We found that the sub-skin zone is a high-resistivity area that can be expanded under the action of higher injection pressures along with lower packing pressures. In contrast to an injection-molded single polymer, an injection–molded, CB-filled polymer composite develops a highly oriented microstructure in the core zone rather than in the skin or sub-skin zones because of the migration of CB particles. Our study explored microstructures at skin, sub-skin and core zones of injection-molded carbon black particles/polypropylene composite. Figure 3 in the paper showed the schematic map on definition of each zone. We found that strong oriented microstructure was formed at core instead of at sub-skin, especially under lower packing pressure. A band with non-continuous conductive path was found under the action of higher injection process, and it will expand with lowering packing pressure.

Fracture behavior of woven steel fiber reinforced and sand particle filled polymer composites

Woven steel fiber reinforced with various weight fractions and particle-filled polymer composite beams were manufactured. After cure treatments, initial notches with various notch-to-depth ratios a/ W = 0.1, 0.2, 0.3 and 0.4 were opened on the specimens. The fiber contents were 2%, 4% and 6%, and the polyester content was 16.5% of the total weight of the polymer composite system. Mode I fracture behavior of single edge notched composite specimens were investigated using three-point bending (TPB) tests. The critical stress intensity factors, ( K IC ) of these specimens were determined by using several methods such as J-integral, initial notch depth and compliance method, and the results were compared. As the weight fractions of steel fibers increases, both K IC and flexural strength of the composites increases.

Dielectric property and electromagnetic interference shielding effectiveness of ethylene vinyl acetate‐based conductive composites: Effect of different type of carbon fillers

AbstractCarbon black, short carbon fiber (SCF), and multiwall carbon nano‐tube (MWNT)‐filled conductive composites were prepared from ethylene vinyl acetate copolymer. The dielectric property and electromagnetic interference (EMI) shielding of carbon black, MWNT, and SCF‐filled composites were studied with different filler loadings. The dielectric constant and loss of filled polymer composites is due to the formation of interfacial polarization in the polymer matrix. It was found that the dielectric constant, dielectric loss, and EMI shielding of filled composites depends on amount and type of filler loading. The results of different experiments have been discussed in the light of break down and formation of continuous conductive network in polymer matrix. The results indicate that these composites can be used as effective EMI shielding materials. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers.