Effect Of Filler Particle Size Research Articles

Influence of carbon black particle size on fatigue life of rubber compound by varying strain and temperature

AbstractFatigue failure is one of the most critical failure modes in engineering structures. The fracture process proceeds through two major phases: crack nucleation and subsequent crack propagation leading to the ultimate failure. With special reference to rubber products especially tyre, the fatigue crack growth characteristics have been well understood with good approximation by many researchers. But the experimental research on crack nucleation is in the nascent stage. In the present study, we have focused on the role of filler particle size, temperature and strain on crack nucleation and fracture surface morphology of unfilled and carbon black (CB)‐filled natural rubber (NR) compounds. Three different kinds of ASTM grade carbon blacks, namely, N134, N234 and N339 have been used to determine the effect of filler particle size on crack initiation. All compounds have been tested at room temperature (i.e., RT 25°C), 70°C and 100°C with different strain amplitudes (50%, 75%, 100%, and 125%) to understand its effect on damage mechanics. It is observed that at a given strain and temperature, compound with N134 has better fatigue life in comparison to the N234 and N339. It is also found that with increasing temperature, fatigue life is being reduced for all the compounds. Optical microscope and field emission scanning electron microscope (FESEM) along with micro computational tomography (CT) have been utilized to understand the failure mechanism which reveal the presence of initial flaws as filler protrusions that creates micro cracks during fatigue loading and thus leads to crack nucleation.

Isolated effect of filler particle size on surface properties of experimental resin composites before and after toothbrush abrasion.

This study aimed to isolate the relationship between filler size and the surface properties of roughness and gloss before and after toothbrush abrasion for experimental resin-based composites (RBCs) containing uniform spherical fillers. Five experimental light-cured RBCs with different spherical filler sizes and three commercial RBCs were studied. Forty specimens were polished using silicon carbide papers. Gloss was measured after 0, 90, 180, and 360 min of simulated toothbrushing, and surface roughness was measured before and after 360 min of toothbrushing. Two-way ANOVA/Tukey's multiple comparison tests were used to compare the RBCs, and the correlation between particle size and surface roughness or gloss was also determined. After polishing and toothbrushing, RBCs with smaller fillers exhibited significantly higher gloss and lower surface roughness, and RBCs with larger fillers exhibited lower gloss and higher surface roughness. A significant correlation was found between filler particle size and gloss and surface roughness both before and after toothbrush abrasion. Gloss of RBCs containing fillers with larger particle sizes was significantly reduced. After toothbrushing abrasion, the surface roughness increased for all RBCs, except those containing the finest-sized fillers. The particle size of the filler is a critical determinant of the surface roughness and gloss of RBCs, after polishing and after toothbrushing. Increased surface roughness caused by toothbrush abrasion reduces the gloss of resin-based composites. Resin-based composites containing finer fillers best maintain glossiness after routine tooth brushing.

Itaconic Anhydride as a Green Compatibilizer in Composites Prepared by the Reinforcement of a Tung Oil-Based Thermosetting Resin with Miscanthus, Pine Wood, or Algae Biomass

Unsaturated vegetable oils with conjugated carbon–carbon double bonds, such as tung oil, can undergo free-radical polymerization, originating alternatives to petroleum-based materials. The introduction of fillers to vegetable oil-based polymer matrices results in composites with improved mechanical properties. In this work, thermosets were synthesized by the free-radical polymerization of a mixture of tung oil, divinylbenzene, and n-butyl methacrylate, and reinforced with bio-based fillers, namely Miscanthus, Pinus taeda (also known as southern pine), and algae (Microspora and Oedogonium) biomass. The effect of filler particle size on the composites’ properties was evaluated. Additionally, to develop a better interaction between the hydrophobic resin and the hydrophilic reinforcements, and improve the mechanical properties of the composites prepared, itaconic anhydride, a bio-based molecule derived from itaconic acid, was added to the resin. Thermogravimetric analysis (TGA) showed that the presence of itaconic anhydride improved the overall thermal stability of the composites. The storage modulus of the composites at room temperature, assessed by dynamic mechanical analysis (DMA), was increased by approximately 32% and 68%, for Miscanthus and southern pine composites, respectively, when itaconic acid was added to the resin. It was also observed that the glass transition temperatures were not significantly affected by the presence of itaconic acid. Scanning electron microscope (SEM) images indicated better matrix-reinforcement adhesion in the presence of itaconic anhydride.

Performance Enhancement of Flexible and Self-Powered PVDF-ZnO Based Tactile Sensors

Flexible, self-powered, and intelligent tactile sensors are essential for accurate sensing in prosthetic devices. This paper explores piezoelectric polyvinylidene difluoride - zinc oxide (PVDF-ZnO) nanocomposite layer-based sandwich assembly as tactile sensor. ZnO nanoparticle addition as filler can overcome the challenges associated with PVDF-based tactile sensors. The effect of filler particle size on the enhancement of sensing performance of PVDF-ZnO-based tactile sensors is investigated. Structural, morphological, piezoelectric and thermal studies were performed on the PVDF-ZnO composite layers using SEM, EDS, DC-EFM and Raman Spectroscopy. A comparative investigation of the potential developed across the sensor samples with different filler particle sizes was performed for touch and bending actions. The obtained results showed a remarkable improvement in performance due to particle size reduction of the ZnO fillers. The nanocomposite sensor with less filler particle size generated more voltage on the same applied force. The experimental analysis demonstrates that the filler size reduction can improve the piezo-voltage response up to 123 mV/N for dynamic touch events. The self-powered sensor also has excellent potential in detecting finger bending action with a response of 29 mv/°. The results demonstrate the promising application of the polymer nanocomposite-based sensor in the prosthetic application.

Effect of Filler Particle Size on the Recyclability of Fly Ash Filled HDPE Composites.

Fly ash polymer composites are innovative high-performance materials that reduce the environmental worries and disposal complications of heavy industry produced fly ash. This study developed and characterized such composites of high-density polyethylene (HDPE) matrices and found that the use of small (50–90 µm) particles of fly ash could give rise to the tensile modulus (~95%) and tensile strength (~7%) of their reinforced composites when compared to neat HDPE materials. While these results themselves convey a strong message of how fly ash can be effectively utilized, this was not the key aim of the current study. The study was extended to examine the effect of fly ash particle size on the recyclability of relevant HDPE composites. The extrusion-based multiple recycling of composites gave slightly lower mechanical properties, primarily due to filler/matrix delamination when large fly ash particles were used. Compared to freshly made fly ash-filled HDPE composites, although using small (50–90 µm) fly ash particles reduced the tensile modulus and tensile strength of recycled composites, the values were still far above those from neat HDPE materials. This novel insight directs the effective utilization of fly ash and provides long-term sustainable and economical solutions for their practical applicability.

Effects of mesoporous silica particle size and pore structure on the performance of polymer-mesoporous silica mixed matrix membranes.

The fabrication of mixed matrix membranes (MMMs) has been regarded as an effective and economic approach to enhance the gas permeability and selectivity properties of conventional polymeric membranes for gas separation applications. However, the poor compatibility between polymeric matrix and inorganic filler in MMMs could lead to the generation of interfacial defects resulting in reduced gas selectivity. In this work, with the aim of studying the effect of particle size and pore structure of the filler on the performance of the resultant MMMs, nano/micro sized spherical mesoporous silicas with 2D/3D pore structure (MCM-41 and MCM-48) were synthesized and selected as fillers for the preparation of polydimethylsiloxane (PDMS)-based MMMs. The separation properties of the membranes prepared were characterized by permeability measurements for nitrogen and organic vapors (C3H6 and n-C4H10). Compared with microsized particles, nanosized fillers have better dispersion in the polymer matrix which could minimize the formation of non-selective microvoids around the particles, leading to higher vapor/N2 ideal selectivities of the MMMs, even at the high loading (15 wt%). Moreover, due to the conventional random packing orientation of the particles in the polymer, vapor permeation was severely hindered in the MMMs fabricated from mesoporous silica with 2D pore channels. The interface morphologies and gas diffusion paths in the MMMs have also been proposed. With an optimum loading of nanosized MCM-48 (3D pore structure), the vapor permeabilities and vapor/N2 ideal selectivities of the MMMs were shown to increase simultaneously, compared with the neat polymer membrane.

Effects of filler particle size and ageing on the fatigue behaviour of bituminous mastics

Fatigue cracking is caused by repeated traffic loads and environmental conditions (temperature, ageing, etc.); it predominantly initiates within the mastic phase in the form of micro-cracks. In this sense, bituminous mastics (comprised of a binder, filler and entrapped air) play a significant role in the anti-fatigue performance of asphalt mixes. In this paper, the effects of filler particle size and ageing on the fatigue behaviour of bituminous mastics were evaluated. Prior to this, the rheological properties of the studied samples were evaluated using physical tests and frequency sweep tests. Moreover, the mastic morphology and filler distribution inside a bituminous matrix were characterized by Scan Electronic Microscope (SEM). The results revealed that ageing had a greater effect than filler particle size on the rheological behaviour of SBS-modified bituminous mastics, especially for mastics containing coarse filler particles. According to the ageing responses derived from log-log fatigue law plots, aged mastics containing coarse filler particles had higher slopes (represented by coefficient B) and lower intercepts (identified by coefficient A) than un-aged mastics. However, opposite fatigue behaviour was observed with fine filler granules, where coefficient B slightly decreased while coefficient A slightly increased after ageing. In addition, mastic morphology and filler dispersion inside a bituminous matrix were characterized by SEM, providing insight to possible relationships between morphological characteristics and fatigue performance.

Study the effects of filler particle size and filler/asphalt ratio on the high and low temperature performance of asphalt mastics

In this study, the conventional and rheological analysis methods are employed to evaluate the effects of filler particle size and filler/bitumen (F/B) ratio on the high and low temperature performance of asphalt mastics. It is found that the addition of mineral fillers can significantly improve the high temperature rutting resistance of asphalt mastics. Meanwhile, it is detrimental to thermal cracking behavior. As the increase of particle size, the percent recovery R, creep stiffness S and m-value increase, while non recoverable creep compliance Jnr decrease. In addition, scanning electron microscope (SEM) imaging analysis shows that the dispersion degree and the morphology of asphalt mastics with various particle sizes have the great differences.

Effect of an organotin catalyst on the physicochemical properties and biocompatibility of castor oil-based polyurethane/cellulose composites

Abstract

Preparation of Pinewood Residues/Recycled HDPE Composites with Potential to Substitute Medium-density Fiberboards

This work reports on the preparation of pinewood residues/recycled high-density polyethylene (HDPE) composites to evaluate their performance under flexion, extraction of nails and screws, and moisture absorption (MA) to assess their potential to replace medium-density fiberboards (MDFs). The effect of filler particle size (PS) was evaluated, and scanning electron microscopy (SEM) was conducted to elucidate the state of the interphase. The effect of UV-light accelerated weathering (AW) on samples with and without a UV stabilizer (UVS) was assessed. A dynamic mechanical analysis (DMA) was also conducted. The composites had better flexural performance, MA, and screw extraction resistance than the MDFs. However, AW affected the composites, mostly affecting those without UVS. Scanning electron microscopy showed the appearance of cracks on the surfaces with less UVS. The DMA results suggested that the composites with the largest PS showed a better resistance to creep.

Effects of chicken eggshell filler size on the processing, mechanical and thermal properties of PVC matrix composite

ABSTRACTThe effects of filler particle size of poly(vinyl chloride)/chicken eggshell powder (PVC/ESP) composites on the processing, tensile properties, morphology and thermal degradation were investigated. The mixing of composites was done using Rheomix internal mixer. The processing torque of PVC/ESP composite at a particle of 0.2 μm exhibits lower processing torque compared to that at a particle size of 7 μm due to the dispersive resistance from larger ESP filler particles. Good interfacial adhesion exists between the filler and matrix in composites prepared via a filler particle size of 0.2 μm, which has improved the tensile strength and modulus of PVC/ESP composite compared to a filler particle size of 7 μm as justified from FESEM images on the tensile fracture surface of the composites. Thermogravimetric analysis results show that the filler particle size of 0.2 μm composite exhibits higher thermal stability compared to the filler particle size of 7 μm composite.

Effect of silica particle size on chain dynamics and frictional properties of styrene butadiene rubber nano and micro composites

Size and curvature of filler particles affect dynamics of polymer chains in composites. In this work, effects of filler particle size, in two scales of nano- and micro-meters, on dynamics of rubbery chains and frictional properties of composites were studied. Surface modification of nano- and micro-fumed silica by grafting low molecular weight hydroxyl-terminated polybutadiene (HTPB) guaranteed similar surface energy for fillers as measured by their surface tension. Nano- and micro-composites of styrene butadiene rubber were prepared by solvent assisted mixing and progressively increasing volume fraction of fillers. Achievement of nano and micro-composites was confirmed by the scanning electron microscopy. Effect of silica aggregate size on the dynamics of rubber chains was measured by dynamic-mechanical-thermal analyzer and compared through calculation of the activation energy for mobilization of slow-dynamic chains in the rubbery region. It was shown that nano-silica immobilizes the rubber chains more than micro-silica even at equal total interfacial area between filler aggregates and rubber matrix, especially above the percolation limit. Similar trend was seen for the coefficient of friction of composites against rough surfaces, showing the strong effect of chain dynamics on friction properties of rubber vulcanizates.

Rigorous calculations of permeation in mixed-matrix membranes: Evaluation of interfacial equilibrium effects and permeability-based models

We present rigorous calculations of single-component permeation in mixed-matrix membranes (MMMs), and show their importance in developing a more reliable understanding of MMM permeation behavior. We first develop methods for the construction of detailed and large-scale 3D mixed-matrix membrane (MMM) models, which are then solved by finite-element methods. Our models explicitly account for the effects of matrix-filler interfacial equilibrium in addition to the differences in Fickian diffusivity between the two phases. Analytical equations (e.g., Maxwell model) can only predict the MMM permeability under an implicit assumption that the interfacial equilibrium constant K and the diffusivity ratio of the filler and the matrix (Df/Dm) can be lumped into a single parameter, the permeability ratio Pf/Pm=KDf/Dm. It is shown here that the individual values of K and Df/Dm, and not the combined permeability ratio Pf/Pm, determine the MMM permeability. Our simulations also indicate that an ideal MMM shows no significant direct effect of filler particle size. We fit our computational data to an empirical correlation that can be easily and accurately used to calculate ideal MMM permeabilities, given equilibrium and diffusion data for the matrix and filler. We also examine some current issues regarding interpretation of MMM permeation behavior. For example, CO2 solubilities and diffusivities in representative MOF filler and polymer matrix materials are used to rigorously compare the ‘exact’ predictions with permeability-based models. The rigorous calculations show non-monotonic behavior of the MMM permeability as a function of the matrix permeability, which cannot be predicted by permeability-based models. Also, the ‘apparent’ CO2 permeability of ZIF-8 fillers extracted with Maxwell and Lewis–Nielsen models from the computational MMM permeation data, varies by 3 orders of magnitude depending upon the matrix polymer. Though the ZIF-8 filler maintains a constant permeability of ~3000 Barrer, the permeability models would require postulation of (spurious) non-idealities such as matrix-dependent filler behavior or interfacial rigidification to explain the results. Overall, this work provides a method for more reliable use of models to understand and design MMMs, as well as to better interpret the large and growing body of experimental data on these membranes.

Anisotropic Thermal Diffusivity of Hexagonal Boron Nitride-Filled Polyimide Films: Effects of Filler Particle Size, Aggregation, Orientation, and Polymer Chain Rigidity

A series of inorganic/organic composite films exhibiting high thermal stability and high thermal diffusivity was prepared from five different grades of flake-shaped hexagonal boron nitride (hBN) and aromatic polyimides (PIs). Thermal diffusivities along the out-of-plane (D(perpendicular)) and in-plane (D//) directions of hBN/PI films were separately measured and analyzed in terms of particle size, shape, concentration, and orientation, as well as molecular structures of rigid and flexible PI matrices. hBN/PI films filled with large flake-shaped particles exhibited a large anisotropy in D(perpendicular) and D// due to the strong in-plane orientation of heat-conducting basal plane of hBN, while smaller anisotropy was observed in composites with small flakes and aggregates which tend to orient less in the in-plane direction during film processing. The anisotropic thermal diffusion property observed in hBN/PI films exhibited strong correlation with the orientation of hBN particles estimated using scanning electron micrographs (SEM) and wide-angle X-ray diffraction. Moreover, composites of hBN with a rigid-rod PI matrix exhibited much larger anisotropy in D(perpendicular) and D// than flexible PI-composites, reflecting the effect of the rigid and densely packed PI chains preferentially orienting parallel to the film plane. The thermal conductivities of the hBN/rigid-rod PI films were estimated as 5.4 and 17.5 W/m·K along the out-of-plane and in-plane directions, respectively, which is one of the largest values ever reported.

Fabrication of Composite Tiles from Poly(Ethylene Terephthalate) (Pet) and Micro-Marble Particles Reinforced with Glass Fiber Mats: Comparison of Recycled and Commercial Resin

Polyester composite tiles (PCT) are synthesized from PET and fabricated by compression molding using micro-marble clusters as filler. Identical PCTs are also fabricated by using commercially available polyester resin to compare properties. Three batches of marble clusters with different size distributions are used to assess the effect of filler particle size on mechanical properties. Tiles prepared using finer marble grades yield consistently higher flexural strength and stiffness values regardless of the synthesized or commercial polyester resin. However, the flexural strength and stiffness of the tiles prepared with commercial polyester are observed to be on average 1.8 and 2.5 fold higher, respectively. Prospects of improving mechanical properties are explored by reinforcing PC tiles with randomly oriented, discontinuous glass fibers. This is achieved by placing a single layer of glass fiber mat on the top and bottom tile surface. Presence of fiber mats leads to the formation of a graded particle size distribution across the mat thickness when the coarse grade marble dust is used. This distribution resulted in significant improvements in flexural strength, stiffness and overall toughness of the tiles. The improvements observed in PCTs prepared with synthesized polyester resin surpassed the improvements in their counterparts prepared with commercial polyester. In fact, the flexural strength of the glass fiber mat reinforced PCTs prepared with synthesized and commercial polyester resin are observed to be statistically identical.

Investigation on a Novel Fly Ash Based Calcium Silicate Filler: Effect of Particle Size on Paper Properties

Value-added utilization of fly ash has recently gained a strong interest. As a solid waste, fly ash can be used as a paper filler, and the recent innovation on the production of high-brightness fly ash products further facilitated such applications. This work reports the results on using the novel fly ash based fillers in the paper making process, with a focus on the effect of filler particle size. In comparison with ground calcium carbonate (GCC) commonly used as paper fillers, the original fly ash based calcium silicate filler (FACS) has a larger particle size (27.6 μm), a much lower true density (1.3–1.4 g/cm3), a higher specific surface area (121 m2/g), and a similar brightness (91% ISO). FACS exhibits porous, aggregated, and needle-like morphologies based on the results of scanning electron microscope image analysis. Ball milling decreased the particle size, broadened the particle size distribution, and improved the brightness while changing its morphology. The paper bulk increased dramatically when ...

Effect of resin-composite filler particle size and shape on shrinkage-stress

ObjectivesThe aim of this study was to investigate the effect of variations in filler particle size and shape on the polymerization shrinkage-stress kinetics of resin-composites. MethodsA model series of 12 VLC resin-composites were studied. The particulate dispersed phase volume fraction was 56.7%: these filler particles were systematically graded in size, and further were either spherical or irregular. A Bioman instrument (cantilever beam method) was employed to determine the shrinkage-stress kinetics following 40s irradiation (600mW/cm2) at 23°C (n=3). All data were captured for 60min and the final shrinkage-stress calculated. ResultsShrinkage-stress varied between 3.86MPa (SD 0.14) for S3 (spherical filler particles of 500nm) and 8.44MPa (SD 0.41) for I1 (irregular filler particles of 450nm). The shrinkage-stress values were generally lower for those composites with spherical filler particles than those with irregular filler particles. The differences in shrinkage-stress with filler particle size and shape were statistically significant (p<0.001). SignificanceComposites with spherical filler particles exhibit lower shrinkage-stress values compared to those with irregular filler particles. Shrinkage-stress and shrinkage-stress rate vary in a complex manner with variations in the size of the dispersed phase particles: a hypothesized explanation for the effect of filler particle size and shape is presented.

Kinetic energy density and agglomerate abrasion rate during blending of agglomerates into powders

Problems related to the blending of a cohesive powder with a free flowing bulk powder are frequently encountered in the pharmaceutical industry. The cohesive powder often forms lumps or agglomerates which are not dispersed during the mixing process and are therefore detrimental to blend uniformity. Achieving sufficient blend uniformity requires that the blending conditions are able to break up agglomerates, which is often an abrasion process. This study was based on the assumption that the abrasion rate of agglomerates determines the required blending time. It is shown that the kinetic energy density of the moving powder bed is a relevant parameter which correlates with the abrasion rate of agglomerates. However, aspects related to the strength of agglomerates should also be considered. For this reason the Stokes abrasion number ( St Abr ) has been defined. This parameter describes the ratio between the kinetic energy density of the moving powder bed and the work of fracture of the agglomerate. The St Abr number is shown to predict the abrasion potential of agglomerates in the dry-mixing process. It appeared possible to include effects of filler particle size and impeller rotational rate into this concept. A clear relationship between abrasion rate of agglomerates and the value of St Abr was demonstrated.

Computational study of dielectric composites with core-shell filler particles

Phase field modeling and computer simulation is employed to study dielectric composites with core-shell filler particles for high-energy-density applications. The model solves electrostatic equations in terms of polarization vector field in reciprocal space using fast Fourier transform technique and parallel computing algorithm. Composites composed of linear constituent phases (matrix, core, and shell materials) of different dielectric constants are considered. Inter-phase boundary conditions are automatically taken into account without explicitly tracking inter-phase interfaces in the composites. The core-shell structures of filler particles are systematically investigated in terms of shell thickness and dielectric constant with respect to core size and matrix dielectric constant, respectively. The effects of filler particle size, shape, and orientation are considered. It is found that core-shell structures of filler particles provide effective means to mitigate local electric field concentration in dielectric composites, improving dielectric breakdown strength and energy density of the composites. Optimal design of core-shell filler particles requires low shell dielectric constant and thick shell coating as compared to core material and core size, respectively.

Elongational and shear flow behavior of calcium carbonate filled low density polyethylene: Effect of filler particle size, content, and surface treatment

AbstractIn this article, calcium carbonate filled low density polyethylene (LDPE) was prepared and the influence of filler content, particle size, and surface treatment with stearic acid on the strain hardening and viscoelastic properties of the composites were investigated. Both elongational and shear rheological measurements were conducted on the different formulations and completed by microscopical observations and by differential scanning thermal analysis. The obtained results indicate that the effect of filler content and particle size are negligible on strain hardening behavior. Also the filler surface treatment has a less important effect on the nonlinear elongational tests in comparison with low frequency range measurements. However in shear rheology, we noted the absence of yield stress and network structure at different filler contents, and the presence of shear thinning behavior. Scanning electron microscopy (SEM) observations showed the enhancement of dispersion for surface treated samples, while differential scanning calorimetry (DSC) experiments have shown that the content of crystallinity of LDPE matrix is slightly affected by the presence of filler. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011