Filler Particle Size Research Articles

Effect of particle size of mineral fillers on polymer-matrix composite shielding materials against ionizing electromagnetic radiation

Filler particle size is an important particle that effects radiation attenuation performance of a composite shielding material but the effects of it have not been exploited so far. In this study, two mineral (hematite–ilmenite) with different particle sizes were used as fillers in a polymer-matrix composite and effects of particle size on shielding performance was investigated within a widerange of radiation energy (0–2000 keV). The thermal and structural properties of the composites were also examined. The results showed that as the filler particle size decreased the shielding performance increased. The highest shielding performance reached was 23% with particle sizes being between <7 and <74 µm.

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 filler particles morphology of resin-composites on cavity packing force for repeated condensation.

Effect of variation in morphology and size of filler particles, temperature and increase in condensation speed on packability of resincomposites was investigated. Eight experimental light-cured resin-composites (RZDn series) were tested. Each material was placed in a cylindrical mould at 26 or 32ºC. A flat-ended stainless-steel probe (φ=6 mm) was mechanically lowered with two different speeds 2 and 8 mm/s onto and into at the surface of the unset sample until a compressive force of 1 N was reached. This was repeated for five cycles, and from each cycle Fp was calculated. All spherical and irregular filler particle resin-composites showed a decrease in Fp with increase in number of compressions. Increase in temperature also decreased Fp, but this effect was not very prominent in the case of irregular filler resin-composites. Filler particle morphology, increase in temperature and compression cycle speed has a prominent effect on packability of resin-composites.

Organic Solvents Transport Through Alkali-Treated Agro-waste Microfibre Incorporated with Low Density Polyethylene Composites

We report the transport behaviour of low density polyethylene composites containing both untreated and alkali-treated agro-waste microfibre in three aromatic organic solvents (benzene, toluene, and xylene) at 40, 60 and 80°C by the conventional weight-gain method. The effects of fibre content, alkali treatment, and filler particle size on solvent sorption were analysed. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated in terms of microfibre content, particle size, nature of the solvent, and temperature. It was observed that all the systems follow the Fickian mode of transport on increasing temperature. The van’t Hoff’s relationship was used to determine the thermodynamic parameters and was found that the estimated free energies of sorption were all positive, indicating non-spontaneity of the solubility of micro fibre/LDPE composites. The first order kinetic rate constant and swelling parameters were also evaluated.

Characterization of partial discharge performance of die attach adhesives

In this paper, the suitability of two types of die attach (DA) material within an isolating system is compared: non-conductive and antistatic epoxy adhesives, respectively. The electrical conductivity of second material has been adjusted by density, size, and shape of carbon filler particles incorporated into the resin matrix.The study shows that micro-voids inside die attach layers of a semiconductor package can lead to partial discharges (PD). Such discharges are reduced by a design-in of carbon filled glues into the device. The experimental verification of the simulation shows increased partial discharge immunity, improved by conductivity tuning of the adhesive materials.

Microstructural and rheological analysis of fillers and asphalt mastics

Pavements are made of different grades of mineral aggregates and organic binder. The aggregates are sorted in different sizes and different amount which are mixed together with bitumen. The finest mineral fraction (d<0.063 mm) is called filler. This component has an important role in asphalt mixture - it fills the gaps between the aggregates and if mixed with bitumen (which is called asphalt mastics) it sticks the larger particles together. Particle size, microstructure and surface properties of fillers highly affect the cohesion with bitumen, therefore the aim of our research was to investigate the microstructure of mineral fillers (limestone, dolomite) which are used in Hungarian road constructions with the use of different techniques (particle size distribution, scanning electronmicroscopy tests, mercury intrusion porosimetry, BET specific surface tests, determination of hydrophobicity). After the tests of fillers, asphalt mastics were prepared and rheological examinations were obtained. These examinations served to observe the interaction and the effect of fillers. The stiffening effect of fillers and the causes of rutting were also investigated. Based on our results, it can be stated that particle size, hydrophobic properties and the amount of fillers highly affect the rheological properties of mastics.

Evaluation of polymerization shrinkage, polymerization shrinkage stress, wear resistance, and compressive strength of a silorane-based composite: A finite element analysis study.

Understanding the mechanical properties is important in predicting the clinical behavior of composites. Finite element analysis (FEA) evaluates properties of materials replicating clinical scenario. This study evaluated polymerization shrinkage and stress, wear resistance (WR), and compressive strength (CS) of silorane in comparison with two methacrylate resins. This study design was a numerical study using FEA. Three-dimensional (3D) models of maxillary premolar with Class I cavities (2 mm depth, 4 mm length, and 2.5 mm width) created and restored with silorane, nanohybrid, and microhybrid; Groups I, II, and III, respectively. Loads of 200-600 N were applied. Polymerization shrinkage was first determined by displacement produced in the X, Y, and Z planes. Maximum stress distribution due to shrinkage was calculated using AN SYS software. 3D cube models of composite resins were simulated with varying filler particle size. Similar loads were applied. WR and compressive stress were calculated: K W L/H and load/cross-sectional area, respectively. Statistical analysis done using one-way ANOVA, Kruskal-Wallis, and Tukey's honestly significant difference test (P < 0.05). Polymerization shrinkage (0.99%) and shrinkage stress (233.21 Mpa) of silorane were less compared to microhybrid (2.14% and 472.43 Mpa) and nanohybrid (2.32% and 464.88 Mpa). Silorane (7.92×/1011 μm/mm3) and nanohybrid (7.79×/1011) showed superior WR than microhybrid (1.113×/1017). There was no significant difference in compressive stress among the groups. Silorane exhibited less polymerization shrinkage and shrinkage stress compared to methacrylates. Silorane and nanohybrid showed greater WR compared to microhybrid. CS of all groups was similar.

Effect of different impression materials on the marginal fit of frameworks: An in-vitro study

Objectives: The objective of this study was to compare the accuracy of three different impression materials with evaluating the marginal fits of metal frameworks using replica technique. Materials and Methods: A phantom premolar tooth was prepared with a 1 mm circumferential chamfer preparation. Four impression materials: two vinyl polysiloxane (VPS) (Affinis Precious, (Group A); Elite HD, (Group E)), one polyether (Impregum Penta Soft, (Group P)) and one vinyl siloxanether (Identium, (Group I)) were used for producing stone casts of this master model. Twelve measurements per replica were carried out using a light microscope X40 magnification by Leica software, to assess the vertical marginal gap (VMG). Data were analyzed using the analysis of variance followed by Tukey’s test ( p =0.05). Results: Specimens of the Group A and I showed significantly lower VMG values than those of Group E and Group P ( p 0.05). Conclusions: All impression materials were clinically acceptable. As well as composition of the impression materials, size of filler particles and fluid mechanics of flow into very small spaces can be effective on accuracy of the materials.

Mechanical behaviour of self-compacting concrete made with recovery filler from hot-mix asphalt plants

The aim of this paper is to assess the feasibility of the use of a fine grain waste generated in hot-mix asphalt plants (HMA), namely recovery filler (RF), as filler materials in self-compacting concrete (SCC) production. A comparative study of two types of SCC was performed. The first concrete type was made incorporating recovery filler (SCC-RF) of a dolomitic nature and the second was made with commercial siliceous filler (SCC-SF), the latter used as reference. Good results of self-compatibility were obtained using RF. The thermogravimetric study showed that in SCC-SF the higher loss weight occurs in the dehydration zone (0–400°C) and in SCC-RF it occurs in the decarbonation area (550–735°C). The aging mechanism of both concrete types (SCC-SF and SCC-RF) was different. In the SCC-SF mixes, portlandite undergoes carbonation processes and pozzolanic reactions and in the SCC-RF mixes it only undergoes carbonation processes. The experimental results (splitting tensile strength, flexural strength and static modulus of elasticity) show the validity of using EHE-08, initially proposed for NVC (Normally Vibrated Concrete), in SCC. The ultrasonic pulse velocity values for SCC-SF was greater than for SCC-RF, which can be attributed to compacity and compressive strength. The shrinkage behaviour was better in SCC-RF than SCC-SF, mainly due to the greater particle size of recovery filler (RF), although the SCC-RF mixes showed lower density and mechanical strength than SCC-SF. In short, the SCC manufactured with recovery filler from plants manufacturing hot-mix asphalt (HMA) – SCC-RF – is expected to have better features than SCC-SF in relation to shrinkage and early appearance of cracks.

Rheology of plastisol formulations for coating applications

A plastisol is a suspension of PVC particles and mineral fillers in a liquid phase composed of plasticizer and adjuvants. Plastisol formulations are commonly used in coating processes for flooring application. In the knife-over-roll process, they are subjected to a wide range of shear rates (0–105 s−1). They are adjusted in order to fulfil the target end-use properties but their processability depends on their rheology. Plastisol based on three PVC resins with or without mineral filler have been investigated using a Couette device and a capillary rheometer. Results show a high impact of PVC particle content, particle sizes and distribution on rheology: a polydisperse formulation displays a shear-thinning behavior in the whole shear rates range and exhibits yield stress; a monodisperse formulation shows a shear thinning behavior at low shear rate, followed by a Newtonian plateau, then a more or less pronounced dilatancy peak depending on plasticizer rate and finally another shear-thinning behavior; a bidisperse resin stands in between. Filler content also impacts the rheology: shear thickening effects at intermediate shear rates decrease or even disappear; however, the viscosity increase is important for low shear rates and depends on the filler particle size and particle size distribution. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

The magnetic inorganic-organic hybrid membranes based on polyimide matrices for gas separation

Abstract Various magnetic inorganic-organic hybrid membranes based on linear or hyperbranched polyimide matrix and magnetic microparticles were prepared and characterized. It was stated that the magnetic membrane's gas transport parameters ( D , P, S and α) were improved with the rise of membrane's saturation magnetization, remanence, magnetic particle content and coercivity, associated with the decrease in magnetic powder particle size. The hybrid membranes had much higher gas permeability and diffusivity, while their permselectivity and solubility coefficient values slightly increased. The mechanical and rheological parameters of the tested membranes were improved by the increase of the magnetic filler addition, decrease of its granulation and selection of appropriate type of polymer matrix. The best resistance to elastic deformation had the hybrid PI membranes with high filler addition and small granulation, while their resistance to viscous flow increased with filler particle size rise. The investigated membranes showed the excellent thermooxidative stability.

The Effect of Foaming on the Electrical Conductivity of Thermoplastic/Carbon Composites Containing Nano and Micro Carbon Fillers in Compression and Injection Molding

The effect of foaming on the electrical conductivity of polystyrene/carbon composites with emphasis on the particle size of conductive filler and molding method has been studied. Carbon black and expanded graphite, as nano carbon fillers, and natural flake graphite, as a micro carbon filler, were used as conductive fillers. Compression and injection molding were employed to investigate the impact of molding method while foaming the composites. Polystyrene and the carbon fillers were mixed in a batch melt mixer and subsequently molded to rectangular sheets either by injection or compression molding. The electrical conductivity of the foam and solid composites were measured by two or four probe methods. The microstructure of the samples was studied by scanning electron microscopy and optical microscopy. The optical images showed a good dispersion and distribution of the filler particles in polystyrene with some degree of agglomeration. The results of electrical conductivity measurements showed that foaming can considerably enhance the electrical conductivity of the composites containing nano carbon fillers i.e. carbon black and expanded graphite but reduced that of the composites containing micro carbon fillers i.e. graphite. The enhancement was more significant in injection molding than compression molding. In the nanocomposites, the nano particles must have been re-localized, redistributed, reoriented or restructured via foaming to increase the electrical conductivity. Such phenomena are not likely to happen for large micro fillers so that the electrical conductivity of polystyrene/graphite composites reduced with foaming due to excluded volume of the cells.

The influence of particle size and surface treatment of filler on the properties of oyster shell powder filled polypropylene composites

In this study, properties of oyster shell powder filled polypropylene (OSP/PP) composites were improved by enhancing particle distribution and filler‐matrix interfaces in the composites. The OSP enhances thermal stability and fire retardant properties of polymer composites but it decreases the mechanical strength due to poor interaction with the polymer matrix. OSP is an amorphous powder which agglomerates during distribution. Polyvinyl alcohol (PVA) was used to enhance the interfacial bonding between OSP and PP, while distribution of the OSP particles in composites was improved by varying the particle size of the filler. The effects of particle size and PVA treatment on mechanical properties of composites were studied through experimental tests and finite element analysis. Experimental results and finite element analysis agree to each other, it was observed that small size particles and PVA incorporation resulted in improving properties of OSP/PP composites. Mechanical properties were improved while thermal stability and fire retardancy were further enhanced. Fourier transform infrared spectroscopy revealed a physical interaction between the composite constituents in the presence of PVA. POLYM. COMPOS., 39:2420–2430, 2018. © 2016 Society of Plastics Engineers

Effect of nanoclay on the mechanical behavior of epoxy composites

Abstract The present study investigated the mechanical characteristics of epoxy strips reinforced with Cloisite 30B nanoclay. Epoxy materials were reinforced with different particulate fractions of chosen nanoclay and the specimens were investigated regarding mechanical properties such as tensile, impact and flexural strengths. The nanoclay content was varied from 2 to10 wt.-% of the total matrix in the matrices. The results showed that the mechanical properties of the composites mainly depended on the dispersion condition of the filler particles, particle size and aggregate structure. Improved tensile modulus, flexural modulus and impact strength in bending properties with less nanoclay content were observed and were found to decrease with increased filler content.

Investigation on Mechanical and Physical Properties of GFRP-Egg Shell Powder Hybrid Composites

Objectives: In this paper, various physical and mechanical properties of egg shell powder filled hybrid composites have been found. Methods/Analysis: Different types of composites have been fabricated using 5 wt% egg shell powder and 10 wt% egg shell powder with 50 wt% fiber, rest matrix material. The composites were fabricated by hand-layup process. Specimens were cut and tested according to ASTM standards. Findings: All composite with filler material exhibited better tensile strength than unfilled composites. Adding filler material might have resulted in restriction of propagation of crack and delamination. The shape and size of egg shell powder was the fine-tuning factor. The rate of burning of the composites at any given filler particle size decreased with increase in filler contents. Novelty/Improvement: The cost of egg shell powder fillers is less than that of the polyester matrix. The use of egg shell powder as fillers for the plastic industry will not only provide a renewable source of filler for the plastic industry but also generate a non - food source of economic development for the famers in the rural areas.

Designing and analyzing a mixture experiment to optimize the mixing proportions of polyvinyl chloride composites

ABSTRACTPolyvinyl chloride (PVC) products are typically complex composites, whose quality characteristics vary widely depending on the types and proportions of their components, as well as other processing factors. It is often required to optimize PVC production for specific applications at the highest cost efficiency. This study describes the design and analysis of a statistical experiment to investigate the effects of different parameters over the mechanical properties of PVC intended for use in electrical wire insulation. Four commonly used mixture components, namely, virgin PVC, recycled PVC, calcium carbonate, and a plasticizer, and two process variables, type of plasticizer and filler particle size, were examined. Statistical tools were utilized to analyze and optimize the mixture while simultaneously finding the proper process parameters. The mix was optimized to achieve required strength and ductility, as per ASTM D6096 while minimizing cost. The paper demonstrates how statistical models can help tailor complex polymeric composites in the presence of variations created by process variables.

Preparation and properties of metal-containing polyamide hybrid composites via reactive microencapsulation

Polyamide 6 microcapsules (PAMC) loaded with 2–8 wt% of Cu, Zn, or Fe and up to 30 wt% of Al particles are synthesized via activated anionic polymerization (AAP) of e-caprolactam in suspension performed in the presence of the respective micro- or nanosized loads. The high-molecular weight porous PAMC are with typical diameters of 10–90 µm depending on the size of the metal filler particles. The latter are entrapped in the core of PAMC as proven by microscopy methods. The melt processing of the loaded microcapsules produced PA6/metal hybrid thermoplastic composites with homogeneous distribution of the loads without any functionalization. The crystalline structure of all PAMC and molded composites is studied by thermal and microfocus X-ray diffraction methods suggesting polymorph changes during the transition from PAMC to molded plates. Mechanical tests in tension showed that transforming Al-loaded PAMC into composites produces polyamide hybrids with higher modulus and strength at break. Measuring the conductivity and dielectric properties of the composites in linear and cyclic modes showed that 30 wt% of Al can change significantly the permittivity of the hybrid composites without increasing the conductivity of the PA6 matrix.

The mechanical performance of sugar palm fibres (ijuk) reinforced phenolic composites

Sugar palm fibres are one of the natural fibres which have many features and need further study to understand their properties. The aim of this work is to investigate the flexural, compressive and impact properties of sugar palm fibres reinforced phenolic composites. Sugar palm fibres were used as a filler (particle size 150 μm) and with loading of 0, 10, 20, 30, and 40 vol.%. The fibres were treated by sea water and then fabricated into composites by hot press technique. Flexural, compressive, and impact tests were carried out as per ASTM D790, ASTM D695-08a, and ASTM D256 standards, respectively. Scanning electron microscopy (SEM) was used to investigate the morphology and the interfacial bonding of the fibres-matrix in composites. The results show that the mechanical properties of the composites improve with the incorporation of fibres. The composite of 30 vol.% particle loading exhibit optimum values which are 32.23 MPa, 61.66 MPa, and 4.12 kJ/m2 for flexural, compressive, and impact strength, respectively. This was because good compatibility of fibre-matrix bonding. Consequently, sugar palm fibre is one of the prospective fibres and could be used as a potential resource to reinforcement polymer composite.

Effect of particle size and volume fraction of BaTiO3 powders on the functional properties of BaTiO3/poly(ε-caprolactone) composites

A systematic study concerning the effect of particle size and volume fraction of BaTiO3 filler on the functional properties of composite materials with poly-(ε-caprolactone) polymer matrix obtained by solvent casting method was performed. Two series of xBT-(1-x)PCL composites prepared by using BaTiO3 powders with two different particles size (60 nm and 400 nm) in different amounts (x = 2; 5; 10 and 20 vol %) were investigated. The X-ray diffraction analysis indicated a particle size dependence of phase symmetry for BT filler powders (cubic phase for ultrafine particles and tetragonal phase for larger particles size) and the formation of pure composites consisting of orthorhombic PCL and cubic or tetragonal BT with no chemical reactions between them. The micrographs of the composites revealed the formation of homogeneous composites with two distinct phases, a good dispersion of ferroelectric phase into the polymer matrix and a low content of air pores. Dielectric investigations at room temperature showed the increases of permittivity with increasing the particle volume fraction of ferroelectric filler as result of the “sum property” of the effective permittivity in composites. For a given concentration, the permittivity of composites increases with particle size, as result of a size effect of BT powder. The composites with low BT addition presents stable dielectric properties at bending cycles. The polarization-field dependences also show a BT-induced size dependence, i.e. at a given value of field, polarization is higher for the composites with coarser BT particles. The composition x = 0.05 with coarse particles can be considered as an optimum among these series for the stored energy density.

Leveraging comprehensive baseline datasets to quantify property variability in nuclear-grade graphites

The full characterization of the physical and mechanical properties of candidate nuclear-grade graphites is highly dependent upon an understanding of the distribution of values that are inherent to graphite. Not only do the material properties of graphites vary considerably between grades owing to the raw materials sources, filler particle type and size, methods of compaction, and production process parameters, but variability is observed between billets of the same grade from a single batch and even across spatial positions within a single billet. Properly enveloping the expected properties of interest requires both a substantial amount of data to statistically capture this variability and a representative distribution capable of accurately describing the range of values. A two-parameter Weibull distribution is confirmed to be representative of the distribution of physical (density, modulus) and mechanical (compressive, flexure, and tensile strength) values in five different nuclear-grades of graphite. The fine-grained isomolded grades tend toward higher Weibull modulus and characteristic strength values, while the extruded grade being examined exhibits relatively large distributions in property values. With the number of candidate graphite specimens that can undergo full irradiation exposure and subsequent testing having limited feasibility with regard to economics and timely evaluations, a proper capture of the raw material variability in an unirradiated state can provide crucial supplementary resolution to the limited amount of available data on irradiated candidate grades.