Volume Concentration Of Filler Research Articles

Composite Feedstock Filaments for Fused Deposition Modeling (FDM) of Microwave Interconnects

Improved manufacturing methodology of ceramic-thermoplastic composite feedstock filaments using solvent assisted dispersion is presented with one of the highest reported ceramic particle filler volume concentration of 50%. Relative permittivity values up to 12.35 along with a low loss tangent of 0.003 have been achieved for newly developed feedstock filaments. They have been employed for fuse deposition modelling (FDM) of test specimens for characterization of complex permittivity, which exhibited dielectric loss tangent in the range of 0.001-0.007 at frequencies ranging from 4 GHz to 12 GHz. This is on par with that of the best microwave laminates. Also, surfactant-assisted ball milling was used to downsize ceramic fillers, while simultaneously applying a surface treatment by a strategically chosen surfactant to improve the interfaces between organic matrix and inorganic particles. The effect of the surfactant surface treatment on the dielectric and loss properties of the composite feedstock materials has been explored, which is compared with analytical model predictions. Two 40 mm-long dielectric rod waveguides (DWG’s) were 3D printed by using an in-house developed composite filament and a commercial counterpart. The former exhibited a much lower attenuation of 0.012 dB/mm as compared to 0.038 dB/mm shown by the latter. Measurements were compared to 3D EM simulation results to extract effective permittivity of DWG fabricated by FDM printing using in-house developed composite feedstock filament, which agrees very well with measured permittivity values.

A comparative analysis of engineering and economical suitability of bituminous mastics containing waste fillers

This novel study focused on comparing the effect of waste glass powder (GP), waste-dried Kota stone slurry (KS), glass-hydrated lime composite (GL), and conventional stone dust (SD) fillers on the engineering and economical performance of bituminous mastics. Bituminous concrete mixes incorporating the fillers mentioned above at multiple proportions (4%, 5.5%, 7.0%, and 8.5% by weight) were prepared and characterized. The filler-bitumen ratio corresponding to each bituminous mix was determined and used to design its corresponding bituminous mastic. The rheological characteristics of bituminous mastics were compared by investigating their engineering performance against rutting, fatigue, and long-term ageing, using a series of sophisticated tests, namely multiple stress creep and recovery (MSCR), linear amplitude sweep (LAS), and ageing index (AI) analysis, respectively. It is inferred that an increase in filler volume concentration in the bituminous mastics leads to its enhancement in resistance against rutting and long-term ageing. More specifically, GL mastics outperformed in terms of rutting and ageing resistance, followed by GP, KS, and SD mastics. Considering fatigue resistance, SD mastics indicated higher fatigue life than the mastics prepared with waste fillers. In terms of economic performance, using a higher amount of fillers in mastics tends to reduce the cost-benefit ratio (C/B). In particular, utilizing GL mastic seems to deliver better engineering performance in a more economical manner, followed by GP, KS, and SD. These inferences were further validated using statistical analysis, confirming the significant influence of filler type and filler content over the analyzed engineering parameters.

Alignment of silver nanoparticles in polysiloxane crosslink network under direct electric field

Silver nanoparticles in polydimethylsiloxane (PDMS) composite was aligned under direct current electric field in the range 3.3 kV/cm to 10 kV/cm. It recorded a constant increase in thermal conductivity displaying an average improvement of 95% conductivity with maximum of 0.391 W/mK in longitudinal direction compared to 0.301 W/mK in lateral direction. This anisotropic conductive behaviour is attributed to the mechanism of exclusion, agglomeration and alignment of the filler during in situ curing process. The observed change in thermal conductivity with filler volume concentration corroborated well with the improved model based on Effective Medium Theory (EMT). By considering Kapitza and filler-filler interface resistance, the predicted values of thermal conductivity of the filler-matrix interface к0int is 0.04 W/mK whilst thermal conductivity of the filler-filler interface к0cont is 0.8 W/mK respectively.

Assessing the effect of fillers on LVE properties of asphalt mastics at intermediate temperatures

This study aims at examining the performance of asphalt mastics in the Linear Viscoelastic (LVE) domain incorporating three Indian and three Austrian fillers. The various physical, morphological, and chemical properties of the fillers were analyzed with the help of respective characterization tests. In addition to the particle size distribution curve and fineness modulus, a new parameter called Filler Grain Coefficient (FGC) has been introduced in this study to quantify the distribution of particles in the system. This paper also attempts to find a correlation between various physical parameters. There are two variables i.e., $$\left| {G^{*} } \right|_{\text{LVE}}$$ and $$\left| {G^{*} } \right|_{\text{ratio}}$$ in order to quantify the Linear Viscoelastic complex modulus. The effects of both volume and surface area of fillers have been manifested by three ratios denoted as V/FM, V/FGC, and V/RV. To compare the outcome of the study, the Strategic Highway Research Program Linear Viscoelastic strain criteria is also included, which examines the applicability of the criteria to the asphalt mastics. The research incorporates a wide range of fillers with variable properties, as confirmed by the test results. Filler parameters Rigden Voids and Filler Grain Coefficient were found to be strongly correlated with almost all physical properties. On the grounds of variation in LVEM with volume concentration of filler, the highest rank can be attributed to Red Mud and LimeStone, respectively, followed by other fillers with Marble Dust being the lowest. The reinforcing effect of fillers and higher surface area contributed to the exponential increase in $$\left| {G^{*} } \right|_{\text{LVE}}$$ , with an increase in volumetric concentration. The variation of both variables: $$\left| {G^{*} } \right|_{\text{LVE}}$$ and $$\left| {G^{*} } \right|_{\text{ratio}}$$ , presented V/FM as the most worthy parameter, as it illustrated variation at different temperatures. The Linear Viscoelastic limits obtained from the study were relatively conservative compared to those from the SHRP study, this confirms the unsuitability of applying SHRP equations to the asphalt mastics. Moreover, the relationship instigated in the study can be used to reckon the LVE strain limit and to further analyse asphalt mastics.

Rheology of uncured magnetorheological elastomers

The aim of this paper is to study rheological properties of uncured magnetorheological elastomers comprising iron particles dispersed in silicon elastomer in relation to particle rearrangement by external magnetic field into oriented structures as this process is strongly affected by viscosity. Studied systems vary in used filler volume concentration (0 to 30 vol. %). From measured flow curves flow consistency index is extracted first by fitting experimental data to Herschel-Bulkley model followed by applying two concentration dependency models (Maron-Pierce and Krieger-Dougherty) to normed consistency. Results and model predictions are discussed.

Influence of Gmelina Wood on Mechanical Properties and Morphology of Epoxy Composites

Lignocellulosic filler such as gmelina wood flour is an alternative of synthetic reinforcements which is ecofriendly, abundant in nature and inexpensive. This research aims to investigate the effects of gmelina wood filler addition on tensile properties, impact strength and morphology of epoxy composites. Filler volume fractions evaluated were10, 20, 30 and 40 percent with 30 mesh filler size. Hand lay-up method was used to manufacture the composites. Tensile strength, tensile modulus, elongation and impact strength were determined based on ASTM standard. Results show that filler addition up to some extents improves the mechanical properties of materials. The optimum tensile properties and impact strength are achieved when 10 percent filler is added into epoxy matrix. Further addition of filler degrades the tensile and impact properties of composites. This phenomenon is due to the existence of weak interfacial interaction between the gmelina wood filler and epoxy matrix for higher filler volume concentration beyond 10 vol. %. The scanning electron micrograph of tensile fracture surface reveals that there are voids, agglomeration and pull-out mechanism which are the cause of the composites failure.

INFLUENCE OF ALBASIA WOOD ON MECHANICAL PROPERTIES AND MORPHOLOGY OF EPOXY COMPOSITES

This research aims to investigate the effects of albasia wood filler as alternative reinforcement for extravagant and non-renewable filler being used in epoxy composites. The filler size used was 30 mesh and various filler volume fractions were 10, 20, 30 and 40 percent. Composites were manufactured using hand lay-up method. Properties such as tensile strength, elongation, modulus elasticity and strain energy absorption were determined based on ASTM standard. The results show that filler volume content significantly affects the tensile properties and impact strength of albasia wood-epoxy composites. The optimum tensile properties are achieved when 10 percent filler is added into epoxy matrix. The impact test also shows the same results. Further addition of filler decreases the mechanical properties of composites due to the existence of weak interfacial interaction between the albasia wood filler and polymer matrix for higher filler volume concentration beyond 10 vol. %. The scanning electron micrograph reveals that there are voids and pull-out mechanism on tensile fracture surface which are the cause of the composites failure.

Unexpected maximum in the concentration dependency of the relaxation frequency of Brownian stress in a colloidal suspension

Concentrated and semidiluted sheared suspensions of silica nanoparticles in Diglycidyl Ether of Bisphenol A have recently been shown to exhibit a low-frequency relaxation process of the shear moduli measured by oscillatory rheology. This process, which is slower than the structural α-process of the matrix, was interpreted as Brownian stress relaxation resulting from strain-induced perturbations of the isotropic filler distribution. In this paper, we extend the rheological investigation of the low-frequency anomaly to ultra-diluted DGEBA/silica suspensions. We illustrate that the Brownian relaxation process depends in a complex manner on the filler volume concentration: For very dilute systems, the relaxation frequency increases with the concentration, whereas for semidilute or concentrated systems, the opposite behavior can be observed. This nonmonotonic dependency of the relaxation frequency leads to a maximum of the relaxation frequency at a volume concentration around 0.133. It can no longer be modeled by Peclet frequencies, since the classical Peclet frequencies depend only on a single concentration dependent physical quantity, viz., the suspension viscosity. A modified Peclet frequency depending on the suspension viscosity and the average surface-to-surface distance between the fillers as a structural, concentration dependent length scale allows for an accurate description of the Brownian relaxation for all concentrations.

Research on the absorbing characteristics of cement matrix composites filled with carbon black-coated expanded polystyrene beads

A new cement matrix composite filled with carbon black-coated expanded polystyrene (EPS) beads was developed. The electromagnetic reflection loss of this composite in the frequency range from 2·6 to 8 GHz was studied experimentally. It was shown that filling with carbon black (CB)-coated EPS beads can improve the reflection loss of plain cement-based materials greatly, and the EPS filler ratio and sample thickness all have remarkable effects on the electromagnetic wave reflection loss of this cement matrix composite material. With a CB-coated EPS filler volume concentration of 80% and sample thickness of 20 mm, the reflection loss can reach −24 dB in the range 2·6-8 GHz and the bandwidth for −10 dB reaches 3 GHz. This composite material still has a relatively low bulk density and can be handled easily.

Influence of untreated and novel electron beam modified surface coated silica filler on rheometric and mechanical properties of ethylene-octene copolymer

Surface modified silica fillers have been developed by coating these with a silane coupling agent, triethoxyvinyl silane (TEVS) followed by electron beam irradiation at room temperature. These have been incorporated in an ethylene-octene copolymer rubber. Rheometric, mechanical, volume swelling and aging properties of the gum as well as the filled elastomers have been studied in details. A significant improvement in the above properties has been noticed for these vulcanizates, which clearly emphasizes that novel surface modified silica improves polymer-filler adhesion by the introduction of covalent bonds between the filler surface and the rubber chains. Filler-filler and polymer-filler interactions have been quantified with the help of a mathematical model correlating the modulus and the volume concentration of filler. The influence of electron beam treatment on silanized silica filler has also been demonstrated from the above model.

Thermoelastic Behavior of Filled Molding Compounds: Composite Mechanics Approach

Reliability of epoxy molding compounds used in plastic packages of integrated circuit (IC) devices depends to a great extent on the level of thermal stresses. These are due primarily to the thermal expansion (contraction) mismatch of the epoxy and the silicon materials. In this analysis we assess the effect of silica fillers on the level of thermal stresses. We conclude that thermal stresses in the compound can indeed be reduced by the application of appropriate fillers. We found that the filler volume concentration does not have to be larger than 30 percent to keep the thermal stresses at a sufficiently low level. This number is close to the filler volume concentration of 30–40 percent in commercially available molding compounds. The obtained results and recommendations can be helpful in the analysis of stresses in, and physical design of, plastic packages.

Influence of filler structure on microhardness of carbon black-polymer composites

The microhardness, H, of carbon black–polycarbonate and carbon black–low-density polyethylene composites was investigated. Two types of microadditives with different average particle sizes were employed. It has been shown that the morphology of the polymeric matrix conspicuously influences the hardness dependence of the composites with volume concentration of filler, ϕ. The microhardness of the carbon black–polycarbonate composites shows a steplike behavior with respect to carbon black content, while the H value of the carbon black–low-density polyethylene composite linearly increases with increasing ϕ. The influence of filler structure on the microhardness of the carbon black–polymer composites is also discussed. Results favor the concept that a smaller carbon black particle size (smaller aggregate diameters and interaggregate distances) enhances the microhardness of the composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 90–95, 2001

Generalized rheological characteristic of plastic disperse systems with polymeric and low-molecular dispersion media (matrices)

Analysis of literature data on the flow of polymeric and oligomeric compositions as well as on systems of low viscous dispersion media containing a high-disperse filler (carbon black, silica, high-disperse chalk) has been carried out. As the basic idea, a proposal is made that their viscosity anomaly is due not to the matrix viscosity anomaly, but to the gradual breakdown of the filler structural skeleton with increasing shear stressτ and shear rate\(\dot \gamma\). The viscosity anomaly of those compositions is determined by the zeroshear but not by the apparent matrix viscosity. A general relationship has been found to describe the flow of such systems depending on the zero-shear matrix viscosity values,η0, their yield stress,τy, and filler volume concentration\(\varphi :\tau = \tau _y + K\varphi \eta _o^n \dot \gamma ^n\), whereK=4.9 andn=0.69 are constants.

Flow behaviour and physical chemistry of bouncing putties and related polymers in view of tectonic laboratory applications

The initiation of analogue studies of rock flow is stimulated by improving our knowledge of suitable model materials. Bouncing Putties and “Plasticines” are the most frequently used model materials in analogue studies of flow instabilities in deforming rocks. Polydimethyl-siloxane (PDMS) and polyborondimethylsiloxane (PBDMS), both substrates of Bouncing Putty, are introduced as convenient geological model materials. The chemistry of PDMS, PBDMS, Bouncing Putties and “Plasticines” is reviewed. A comprehensive set of instructions and graphs is provided for the manipulation of these model materials. In particular, a high viscosity PDMS produced as an intermediate compound under the code name SGM36 by Dow Corning (Great Britain) opens exciting possibilities for analogue studies of rock flow, because it is perfectly transparent. This allows continuous observation of three-dimensional strain markers during an experiment. The polymeric flow mechanisms are compared with the flow behaviour and crystal plasticity theory of rocks. The flow of natural rocks is taken to be of Reiner-Rivlin type with powers n varying between 1 and 10. Flow curves have been constructed for Bouncing Putties, Plastilinas (cf. Plasticines) and SGM36 (cf. PDMS). These original curves are supplemented with extensive data on similar materials compiled from the literature. The combined data reveal a consistent flow curve pattern for each group of model materials considered. Strain-rate softening of commercially available Bouncing Putties and “Plasticines” at low strain rates can be attributed to the solid filler concentration. The power n, which describes the departure from Newtonian flow, appears to be dependent on the angular filler volume concentration c and is governed by the preliminary equation n = 1−11 c + 48 c 2. This finding provides a technique for manipulating liquid polymers to simulate natural rock flow with various powers of n. The ( T, P) dependence of the viscosity and thermal properties of PDMS are outlined to stimulate modelling which includes natural ( T, P) gradients.

Electrical resistivity behavior of solution‐cast metal‐filled composites

AbstractSolvent‐cast metal‐filled composites made of polymethyl methacrylate and aluminum or copper exhibited electrical resistance behavior as is predicted by the percolation and tunneling mechanisms. A precipitous change in volume resistivity of about 1010 ohm‐cm was found to be thermally dependent at volume concentration of filler in the range from 17 to 19.5 percent. Materials with compositions at the conductive‐non‐conductive threshold showed semi‐conductor behavior and exhibited memory switching.

The production of powder-filled/metal composites in space

The physics of composites made of a metal matrix with a glass microsphere filler is worthy of study since at a sufficiently high volume concentration of filler the electron mean free path in the metal is controlled by the separation of the glass spheres. Studies of electron dynamics can therefore be made in specimens for which the electron mean free path is very well defined. For good experiments a random distribution of the glass spheres is desirable and this can best be done in a low gravity environment. The preparation of such specimens should also be very interesting to the metallurgist concerned with the production of new materials, since they would give information about the degree of uniformity of dispersion which can be achieved by the preparation of composites in space.

Bound rubber in elastomers: Analysis of elastomer‐filler interaction and its effect on viscosity and modulus of composite systems

AbstractBound rubber measurement may be very misleading as a measure of elastomer–carbon black interaction because sometimes only part of the apparently bound rubber is truly adsorbed on the carbon black surface. A theory is proposed which utilizes bound rubber measurements, but separates truly adsorbed rubber from other insoluble gel and enables calculation of the adsorbed elastomer layer thickness, a numerical value of interaction. Measurements of interaction were obtained for many different rubbers, including polybutadienes, styrene–butadienes, EPDMs, and butyl, with several different furnace blacks. An equation for viscosity of a rubber–carbon black composite is proposed, based on the degree of interaction obtained from the theory and the possible varying degree of orientation of the composite as the rate of shear is changed. This has been applied experimentally both to soluble elastomers and to an elastomer containing a nonrigid gel. The modulus of a vulcanized composite is shown to be related to the effective volume fraction of filler, which is equivalent to the volume fraction of filler plus adsorbed rubber, at temperatures above the glass transition temperature, regardless of the type of rigid filler. Below the glass transition temperature, the modulus depends only on the filler volume concentration.

Elastic Modulus and Swelling of Butyl Vulcanizates. Influence of Fillers

Abstract The reinforcing of elastomeric vulcanizates by filler particles has been studied with Butyl rubber, a polymer of limited unsaturation. This limited unsaturation enables a comparison to be made of filler reinforcement in materials having a constant concentration of chemical cross-links, because excess curing agents can be added without increasing the state of cure byond a certain limit. Under such conditions differences in the adsorptive powers of fillers do not result in variations in the ultimate state of vulcanization. Reinforcement in this paper was defined as the ability of a pigment to enhance the elastic or equilibrium stress (at constant elongation) of a vulcanized specimen. Equilibrium stress at 50 per cent elongation was determined on a triple-beam balance, and the internal energy and entropy components of stress were determined. The entropy component of stress was found to conform more closely to the classical viscosity analog equation for reinforcement, where only the volume concentration of filler and not the surface area is the controlling factor. It was observed that carbon blacks, especially those of finer particle size, produced a greater internal energy contribution to stress than did mineral fillers, which appeared as a function of the total pigment surface added. The increase in stress observed with mineral fillers was due largely to entropy contributions. Another manifestation of reinforcement was shown to be the restriction of volume swelling of a network (in a good solvent) in the presence of pigments. Carbon blacks showed the greatest restriction of swelling capacity, and in distinction to stress behavior, this restriction was solely a function of the total surface area of carbon black present, regardless of type. With mineral fillers, far less restriction was observed, and in one case an increase in swelling was noted. This can be attributed to poor bonding, which results in voids. The photomicrograph of clay particles in a thin stretched section of Butyl shows this effect in Figure 21. The role of surface forces in the case of carbon blacks has been further demonstrated through measurements of the elastic properties of swollen rubber. The reinforcing nature of carbon black is maintained in a swollen network, while the weak bonds between the polymer and a mineral filler are destroyed when the chains are separated by the imbibed solvent, and the stress then approaches that of an unloaded compound.