Filler Size Research Articles

Efficient Construction of SiO2 Colloidal Nanoparticle Clusters as Novel Fillers by a Spray-Drying Process for Dental Composites

The size and structure of inorganic fillers have a significant effect on the mechanical properties of dental resin composites. In this work, we report the use of spray-drying for the efficient cons...

Mechanical Characterization of the Natural Fiber Reinforced Polystyrene Composite

In the present work, polystyrene composites using wheat husk, rice husk and mustard husk as fillers are synthesized using in-situ polymerisation technique. Three different filler loading (5%, 10% and 15 %) and three different filler sizes (250-355 µ, 355-500 µ, 500-710 µ) were utilized for the studying the effect of these compositions on different mechanical properties of the synthesized composites. The results have shown that the filler size 250-355 µ and 5 % loading give the maximum values for tensile strength, flexural strength and hardness for all the three types of fillers. While in case of water absorptivity lower the size/loading, lesser would be the water absorbed. The SEM analysis is done to study the fractured surface of the specimen.

An investigation on effective thermal conductivity of hybrid-filler polymer composites under effects of random particle distribution, particle size and thermal contact resistance

The thermal conductivity (TC) of polymer composites with randomly distributed hybrid fillers is investigated numerically and theoretically. The effective thermal conductivity (ETC) of such composites is examined under various effects, such as the TC ratios, volume fraction (VF), and particle distribution, particle size, and particularly thermal contact resistance (TCR). The contribution of particle distribution to the ETC were explained comprehensively, which is as a function of projected area and effective length of hybrid fillers. Results indicated that the optimal ETC was affected significantly by particle distribution and particle size at high VF, high TC, low TCR, and largely total particle size of hybrid fillers. However, particle distribution and particle size show not to affect considerably to the value of the optimal TC ratio between two fillers. Particularly, it was confirmed that the TC is generally enhanced when more particles are stacked and concentrated along the thermal flow direction regardless of the effects of TCR. In addition, modified Hashin-Shtrikman model by Ngo's study again shows a good TC prediction even with the TCR effect. These results are very good in practical optimization process to achieve the maximum ETC of composites, thus total cost of composite synthesis can be reduced significantly.

A trade-off study toward highly thermally conductive and mechanically robust thermoplastic composites by injection moulding

In order to achieve high thermal conductivity (TC) for graphene-reinforced thermoplastic polymer composites, many efforts have been made to reduce the interfacial thermal resistance. However, good mechanical properties may be conflicting with thermal properties due to the poor interaction bonding between matrix and fillers. In this work, graphene sheets (GSs) filled thermoplastic polypropylene (PP) composite are prepared by three different moulding methods: i) melt extrusion with subsequent injection moulding, ii) single injection moulding and iii) hot-pressing. The relationship among processing methods, microstructures and properties are systematically demonstrated in detail. It is found that single injection moulding can be used to realize a random distribution of the filler with modest size to keep good mechanical properties, and an acceptable conductive network in the matrix to improve the thermal transfer ability of the composites. As a result, high TC of 2.07 Wm−1K−1 and tensile strength of 24 MPa are simultaneously achieved for 20 wt% GSs/PP composite, realizing a tradeoff between thermal and mechanical properties. Finite element simulation is also conducted to perceive the dependence of the thermal properties on the size and distribution of GSs filler. We think that this work provides an instructive route to design thermoplastic composites with overall consideration of thermal and mechanical properties and allows a considerable step to its industrial application.

Sound Absorption Coefficient and Water Content Responses in Acoustic Analysis Based on Renewable Polyurethane Foam Composites

In physiological health, negative effects are felt when unwanted noise is present. Given the negative effects of the unwanted noise, it become important to examine how environmentally-friendly and efficient sound absorbing materials could be developed. Some of the materials associated with acoustic absorption properties entail polymer foams. Particularly, the foams aid in controlling noise. The central purpose of this study was to examine renewable polymer (PU) foam composites’ aspects of moisture content and acoustical properties. Four major parameters that were evaluated included the thickness of the sample, the type of filler, the ratio of the fillers, and the nature of the monomer. A design of experiment (DoE) technique was employed. To prepare the PUs foams, 28 mm and 100 mm were selected as diameters for the cylindrical shapes on focus. Plotting the main effects was achieved through ANOVA, upon which variations in the role and performance of the selected input factors were discerned. From the findings, it was established that when bio-epoxy (B) was used in conjunction with renewable PU foams, the moisture content was greater than the case involving petroleum based PU foam synthesis. Hence, renewable PU foam composite is seen to be realized at 0.9, especially if the filler ratios and size are increased; with the experimental conditions set at 3 kHz. Overall, the study established that the renewable Pus’ state of sound absorption exhibits good agreement with the case of synthetic PU foam.

Effect of silica particle size on the microstructure and physical properties of microporous poly(L-lactic acid) produced by uniaxial stretching

Abstract The microporous poly( l -lactic acid) (PLLA) materials were prepared by uniaxial stretching PLLA/20 wt% silica (SiO2) composites. The SiO2 fillers with particle size of 15 nm, 200 nm, 500 nm, 1 μm, 2 μm, and 5 μm were selected to investigate the effect of particle size of fillers on the microstructures and physical properties of the microporous PLLA materials. Micropores were formed due to the debonding at the interface between PLLA and SiO2. The composites with SiO2 particle size of 15 nm, 200 nm, 500 nm, 1 μm, 2 μm, and 5 μm began to debond at 1.4, 1.0, 1.0, 1.0, 0.9, and 0.7, respectively. With the increase of SiO2 particle size, the micropore diameter was enlarged at the same stretching ratio, while the particle number of SiO2 was decreased, however, the porosity was still increased. The mechanical properties, thermal insulation properties, and water vapor permeation properties of microporous PLLA samples were all improved compared with that of undrawn PLLA.

Application of bio-based modified kaolin clay engineered as papermaking additive for improving the properties of filled recycled papers

The present study was conducted to modify kaolin clay by coating cationic starches, maize and tapioca, aimed at effective incorporation into recycled pulp fibers. The modification process was examined by using zeta potential, filler size, filler retention, and scanning electron micrograph (SEM) observations. In addition, paper sheets (65 ± 5 g/m2 basis weight) filled with unmodified kaolin or kaolin–starch filler followed by an internal sizing were fabricated and analyzed. Based on the results of zeta potential, the charge reversal of kaolin–starch particles substantiated the coating of kaolin fillers by cationic starches. Additionally, the kaolin–starch filler revealed a higher tendency to form clusters 3.5–7.5 times larger than the unmodified kaolin filler. Consistently, SEM images showed well–distributed kaolin–starch fillers, aggregated together and jointed to the fibers. Consequently, the paper filled with kaolin–starch fillers exhibited higher brightness and mechanical strengths indices compared to the unfilled papers, as well as the papers filled with unmodified kaolin. Interestingly, the results of water resistance and dynamic contact angle (DCA) indicated stable hydrophobic performance of kaolin–starch filled papers.

Experimental study on the effect of filler size on the denitrification of SBBR process in low temperature

In order to study the effect of filler size on the treatment of low temperature wastewater by SBBR process, three groups of SBBR reactors were established. They used cubic sponges with side lengths of 1, 1.5 and 2cm as filling fillers, respectively. The denitrification effect of the three fillers was compared under the conditions of stable water temperature of (10±1)°C, HRT of 10h and reactor filling rate of 16%. The results showed that the removal of NH4+-N and TN in the reactor with the filling size of 1cm was the best, and the removal rates were 96% and 80%. The NH4+-N and TN removal rates of the reactors filled with the other two sizes of fillers were all below 80% and 70%. The membrane biomass measurement of the reactor showed that the smaller size of the filler has a larger specific surface area, which was beneficial to mass transfer and microbial growth and enrichment, thereby promoting the denitrification of low temperature wastewater.

Structural Properties and Thermoelectric Performance of the Double-Filled Skutterudite (Sm,Gd)y(FexNi1-x)4Sb12.

The structural and thermoelectric properties of the filled skutterudite (Sm,Gd)y(FexNi1-x)4Sb12 were investigated and critically compared to the ones in the Sm-containing system with the aim of unravelling the effect of double filling on filling fraction and thermal conductivity. Several samples (x = 0.50–0.90 and y = 0.15–0.48) were prepared by melting-sintering, and two of them were densified by spark plasma sintering in order to study their thermoelectric features. The crystallographic study enables the recognition of the role of the filler size in ruling the filling fraction and the compositional location of the p/n crossover: It has been found that the former lowers and the latter moves toward lower x values with the reduction of the filler ionic size, as a consequence of the progressively weaker interaction of the filler with the Sb12 cavity. The analysis of thermoelectric properties indicates that, despite the Sm3+/Gd3+ small mass difference, the contemporary presence of these ions in the 2a site significantly affects the thermal conductivity of both p- and n-compositions. This occurs by reducing its value with respect to the Sm-filled compound at each temperature considered, and making the overall thermoelectric performance of the system comparable to several multi-filled (Fe, Ni)-based skutterudites described in the literature.

Numerical analysis of 3D mass diffusion in random (nano) composite systems: Effects of polydispersity and intercalation on barrier properties

Nanocomposite systems show promise as barrier materials for a wide range of applications. However, the enhancement of barrier properties requires a better understanding of the relationship between the system structure and the desired properties. The aim of the present study is to discuss first the effect of fillers size polydispersity on gas barrier properties through a step-by-step approach based on three-dimensional finite element modeling (FEM). Secondly, dispersions of monodisperse and polydisperse stacks are investigated coupled with a sensitive study of interplatelet diffusion effect on the overall diffusivity considering a wide range of diffusion coefficient values in the interplatelet area. The specificity of the developed model is its ability to account for interplatelet diffusion for a large range of fillers dimensions.

Thermal, fire, and mechanical properties of solvent‐free processed BN/boehmite‐filled prepregs

Within the scope of this research, platelet‐shaped hexagonal Boron Nitride (h‐BN) with a size of 2 and 12 μm, and oval‐shaped Boehmite (BT) with a size of 2 μm were incorporated in a glass fiber‐reinforced epoxy novolac matrix cured with a diamine‐based hardener. The effects of the platelet size (BN 2 and 12 μm) and filler nature (BT vs. BN) were correlated with the final thermal and fire‐related properties. The incorporation of the fillers shows that not only the thermal conductivity (σ) was increased from approximately 0.2 up to 1.04 W/mK (through‐plane) but also the flame retardancy was improved by using a hybrid combination. The time to ignition (tig) was increased by 48 s and the FIGRA value was decreased from 6.5 to 3.3 indicating a much lower fire hazard for the material. scanning electron microscopic micrographs of the laminate cross sections show that the fillers are distributed and oriented randomly in the fiber‐reinforced matrix, and also highlight the fiber wetting. Furthermore, the results show that the resulting 3D filler network and infiltration of the intratow regions is strongly dependent on lateral filler size and filler combination. With increasing the filler aspect ratio, the effect on thermal properties and filtration is more evident. Moreover, the hybrid combination of BN and Boehmite fillers has a strong effect on the network formation during processing, resulting in enhanced thermal and mechanical properties. A synergy was observed when using BN 12 μm in combination with Boehmite 2 μm as the larger platelets tend to assemble themselves in the intertow region (resin‐rich region) and the smaller particles infiltrate into the intratow regions. This leads to a formation of a thermal pathway throughout the glass fabric barrier. Considering the cost factor, the through‐plane (z‐direction) heat dissipation and the flame retardancy can be tailored by optimizing the size, aspect ratio/geometry, and nature of the fillers. POLYM. ENG. SCI., 59:1840–1852, 2019. © 2019 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.

Surface roughness and filler particles characterization of resin-based composites.

The purpose of this study was to evaluate the surface roughness (Ra), and the morphology and composition of filler particles of different composites submitted to toothbrushing and water storage. Disc-shaped specimens (15 mm × 2 mm) were made from five composites: two conventional (Z100™, and Filtek™ Supreme Ultra Universal, 3M), one "quick-cure" (Estelite ∑ Quick, Tokuyama), one fluoride-releasing (Beautiful II, Shofu), and one self-adhering (Vertise Flow, Kerr) composite. Samples were finished/polished using aluminum oxide discs (Sof-Lex, 3M), and their surfaces were analyzed by profilometry (n = 5) and scanning electron microscopy (SEM; n = 3) at 1 week and after 30,000 toothbrushing cycles and 6-month water storage. Ra data were analyzed by two-way analysis of variance and Tukey's test (α = 0.05). Filler particles morphology and composition were analyzed by SEM and X-ray dispersive energy spectroscopy, respectively. Finishing/polishing resulted in similar Ra for all the composites, while toothbrushing and water storage increased the Ra of all the tested materials, also changing their surface morphology. Beautifil II and Vertise Flow presented the highest Ra after toothbrushing and water storage. Filler particles were mainly composed of silicon, zirconium, aluminum, barium, and ytterbium. Size and morphology of fillers, and composition of the tested composites influenced their Ra when samples were submitted to toothbrushing and water storage.

Optimizing filler network formation in poly(hexahydrotriazine) for realizing high thermal conductivity and low oxygen permeation

Shape, size, and orientation of fillers within polymer matrix are important factors for realizing various composite functionalities. Here, we describe an industrially scalable approach to preparing composites bearing highly aligned model hexagonal boron nitride filler (hBN) by simple melt-pressing. This outcome is achieved by using a malleable but thermal stiffening polymer matrix. The matrix maintains or even increases its stiffness during processing at elevated temperatures, producing the composites with highly aligned hBN and consequently a high thermal conductivity (28 W/mK). Furthermore, the composite bearing aligned hBN exhibits a 62% reduction in oxygen permeation with only 2.7 vol% of hBN. Since the matrix can be chemically depolymerized with an aid of acid, it is also possible to recover the hBN from the composite without physical/chemical denaturation of the filler, thus the recovered filler can be re-used in the future.

The infl uence of glass fi ller size on the durability of polystyrene

Using the example of polystyrene fi lling with spherical granules of inorganic glass, it was shown that inorganic glass, when interacting with a polymer, manifests itself as an adhesively active reinforcing material. This is confi rmed by the study of the eff ect of dispersion of inorganic glass granules on the performance of the fi lled polymer, fi rst of all, on the change of its thermalfl uctuation constants, from the standpoint of the thermofl uctuation concept of destruction.

Effect of Tungsten Carbide Reinforcement on the Aluminum 6061 Alloy

Abstract Aluminum matrix composites are often preferred in automotive, aerospace, and ship building owing to their enhanced properties over conventional engineering aluminum alloys. In this article, the results of the investigations on the mechanical properties and sliding wear behavior of aluminum–tungsten carbide (WC) composites are presented and discussed. Metal matrix composites of Al6061 containing different percentages of WC were prepared by powder metallurgy techniques. All testing was conducted according to ASTM standards. The dry sliding wear tests were conducted at a constant velocity and load varying from 10 to 40 N. The composite density was found to increase with greater filler contents and is further in agreement with the values of theoretical density. The Brinell hardness and ultimate tensile strength of the composites increased with a greater ceramic phase and decreased filler size, with a decrease of percentage elongation. The dry sliding wear of the composites with WC reinforcement displayed the greater resistance to wear.

On specifics of hardening mechanisms in metallic matrix composition"

Introduction. Functional properties of diamond powders are determined by a large-scale structural factor since it affects the formation of structurally sensitive mechanical properties — stress limit and yield value. Considering the qualitative correlation between yield value and hardness, it is possible to predict an increase in hardness including highly rigid materials. Materials and Methods . Physical characteristics of the basic types of fillers that make up the reinforcers are considered, systematized and tabulated. M2-01 tin bronze (20 wt. % tin, 80% copper) was used as a bond. Ultradisperse natural diamond (UDND, 0.5-4 wt. %) was added to it, as well as powders of natural diamond (3/2 pm fraction, 7/5 pm, -40 pm) obtained through processing diamonds at the enterprise of “Sakha Daimond” JSC. The above materials were made on the crushing and screening equipment and shaking tables. The stages of obtaining powders were recorded using the raster electron microscopy. Vibroscreens were applied for the grain-size classification of diamond powders. Physical and mechanical characteristics of the produced samples were tested by standard methods. VLTE-500 electronic fourth-class laboratory balance was used for weighing. Density was determined by MK 0-25 mm micrometer according to GOST 6507-78. Research Results. Porosity was calculated through the actual and theoretical density. It was found that with a decrease in the filler size, an improvement in the physicomechanical properties of the binder modified with a diamond powder is observed. The best performance was observed in the samples with the UDND filler. Discussion and Conclusions . As a result of the study, it was recorded that the calculated data differ from the experimental data since they show an increase in the material hardening pro rata to the amount of the diamond particles introduced into the volume. An assumption has been made that the considered hardening model (Orowan model) does not take into account the formation of carbon and the agglomeration of diamonds into larger objects in the matrix volume under an increase in the number of input diamonds. If the UDND particle volume reaches 3%, the carbon con tent in the material increases. As a result, the filler particles are not fully oxidized, thus increasing the number of pores in the material.

The use of high content of fine crumb rubber in asphalt mixes using dry process

The two traditional methods to incorporate crumb rubber into asphalt mixes are the dry process and wet process. Although dry process has greater advantages including more crumb rubber usage, conservation of natural resources, and so on, there is less desire to apply dry process compared to wet process because of its poor performance. This study aims to evaluate the usage of high contents of crumb rubber powder (CRP) as filler in asphalt mixes and provide further development in the dry process method by considering the curing process effect, different CRP contents and micro-scale size of CRP filler. The conventional filler of mixes was replaced with 20, 40 and 60% CRP by weight of filler and the mechanical properties of modified mixes, including moisture susceptibility, stiffness modulus, rutting performance and fatigue life were evaluated. The results indicated that simultaneously applying curing process and very fine CRP in the asphalt mix, enhanced considerably the resistance of asphalt mixes against failures. In addition, the performance of mixes with high contents of CRP was weakened, which could be improved by curing process.

Influence of particle size and particle loading on mechanical properties of silicon carbide–reinforced epoxy composites

In this study, the effect of particle size and particle content of silicon carbide fillers in epoxy matrix on the mechanical properties and microstructure of the developed composites was investigated. Silicon carbide fillers sized to < 45 μm and 90–45 μm were incorporated to epoxy composites to obtain volume fractions of 2, 4, 6 and 8 wt% of SiC. Mechanical properties including flexural strength, compressive strength and hardness tests of the composite samples were performed according to ASTM D790-03 (2003), ASTM D695-15 (2015) and EN 1534 standards. Surface morphology, crack propagation and particulate dispersion were observed using scanning electron microscopes (SEM). The results of the mechanical properties obtained were examined statistically and the results that a strong negative correlation between hardness and flexural strength but the individual correlation between hardness and flexural modulus, compressive stress and compressive modulus were positive. Results also showed that the inclusion of small particulate silicon carbide (< 45 μm) displayed superior mechanical properties in term of flexural, compressive and hardness characterizations at a given volume fraction. Flexural properties of the composite samples decrease with increase in filler concentrations while the compressive strength and hardness increase as particulate loading increase. In terms of microstructure, uniform dispersion of silicon carbide particulates was observed within epoxy matrix with linear crack propagation.

Tribological behavior of unsaturated polyester hybrid composites containing wood flour and carbon nanotubes

The dry-wear behavior of hybrid composites comprising of multi-walled carbon nanotubes (MWCNTs) and wood flour (oil palm kernel shell powder) within an unsaturated polyester matrix was investigated in this paper. The results revealed that the incorporation of wood flour -even at little as 10 wt% filler content- significantly improved the tribological behavior of the composite. This improvement in tribological behavior was attributed to the transfer of a soft layer of wood flour on the worn area during the wear process, which acted as a self-lubricating material. Investigation of the effect of filler size revealed that composites containing smaller filler sizes exhibited higher values of friction coefficient (µ) and specific wear rate (Ws). This reduction attributed to the creation of a surface with a lower surface roughness (Ra) at the worn area which resulted in a larger number of contacts between counterpart surfaces. In addition, increasing in the normal load resulted in a considerable increment in the values of µ and Ws. Filler treatment with hot alkali solution (1 to 9 wt% concentration) showed that both µ and Ws reached their minimum values at 5 wt% alkali concentration due to improved interfacial bonding between the filler and matrix. Finally, a relatively small amount (0.2 wt%) of well-dispersed MWCNTs within the wood flour polyester composite was found to be capable of improving the tribological behavior of such hybrid composites.

Effect of Filler Concentration on Tracking Resistance of ATH-Filled Silicone Rubber Nanocomposites

It is necessary for polymeric materials to have superior tracking resistance against various stress conditions for outdoor applications. In this study, the effect of nano-sized alumina tri-hydrate (ATH) particles on the tracking resistance of silicone rubber (SiR) is studied. Specimens with filler loadings of 1, 3, 5, 10, and 20 wt % are used for performance characterization. From the inclined plane test (IPT) results, apparent improvement in tracking resistance was achieved by mixing 3 wt % of nano-sized fillers, compared to unfilled specimens. ATH/SiR nanocomposites with 5 wt % loading showed comparable tracking performance to SiO2/SiR microcomposites with 20 wt % loading. For detailed analysis, measurements of surface contact angle (SCA) and surface leakage current, and thermo-gravimetric analysis (TGA) were performed. As the nano-ATH filler concentration increased, both thermal stability and leakage current characteristics were improved. Such results agreed with the tracking resistance performance by showing that thermal decomposition and surface charge transport is inhibited in ATH/SiR nanocomposites. Furthermore, performance improvement in nanocomposites was achieved, even at low filler loadings, compared to microcomposites. Meanwhile, the change in SCA was found to be rather limited, regardless of filler loading and filler size.