Dispersion State Of Particles Research Articles

Morphology and properties of highly filled iPP/TiO2 nanocomposites

Nanocomposites based on isotactic polypropylene (iPP) and titanium dioxide (TiO2) nanoparticle containing 1–15 vol% (4.6–45.5 wt%) of the nanoparticle were prepared by the melt blending process. The effect of an anhydride‐modified polypropylene as a compatibilizer on dispersion of TiO2 nanoparticles was assessed using SEM. TGA and DSC analysis were performed to study the thermal properties of the nanocomposites. Crystalline structures of iPP in the presence of TiO2 were analyzed by XRD. Mechanical properties of the nanoparticles were measured and a micromechanical analysis was applied to quantify interface interaction between the polymer and particle. SEM results revealed improvement of TiO2 particle dispersion by adding the compatibilizer. It was shown that the thermal stability and crystalline structure of the nanocomposite are significantly affected by the state of particle dispersion. TiO2 nanoparticles were shown to be strong β‐nucleating agents for iPP, especially at concentrations less than 5 vol%. Presence of the β‐structure crystals reduced the elastic modulus and yield strength of the nanocomposites. Micromechanical analysis showed enhanced interaction between organic and inorganic phases of the compatibilized nanocomposites. POLYM. ENG. SCI., 54:874–886, 2014. © 2013 Society of Plastics Engineers

Preparation of water-soluble nanographite and its application in water-based cutting fluid

Water-soluble nanographite was prepared by in situ emulsion polymerization using methacrylate as polymeric monomer. The dispersion stability and dispersion state of graphite particles were evaluated by UV-visible spectrophotometry and scanning electron microscopy, respectively. The water-soluble nanographite was then added into the water-based cutting fluid as lubricant additive. The lubrication performance of water-based cutting fluid with the nanographite additive was studied on four-ball friction tester and surface tensiometer. Results indicate that the modification method of in situ emulsion polymerization realizes the uniform and stabilized dispersion of nanographite in aqueous environment. The optimal polymerization condition is 70°C (polymerization temperature) and 5 h (polymerization time). The addition of nanographite decreases the friction coefficient and wear scar diameter by 44% and 49%. Meanwhile, the maximum non-seizure load (PB) increases from 784 to 883 N, and the value of surface tension (32.76 × 10−3 N/m) is at low level. Nanographite additive improves apparently the lubrication performance of water-based cutting fluid.

Unsaturated polyester-based hybrid nanocomposite: fracture behavior and tensile properties

In this study, unsaturated polyester (UP) resin was reinforced by using an organically-modified montmorillonite (OMMT) and toughened with poly(n-butyl acrylate)/poly(vinyl acetate-co-methyl methacrylate) core-shell rubber (CSR) particles. The effects of OMMT and CSR levels on the fracture behavior and tensile properties of UP were investigated. The results showed that the incorporation of OMMT of up to 3 wt.% increased the UP fracture toughness (KIC) to some extent, while further addition caused the fracture toughness to reach a constant level. Furthermore, the dispersion state of OMMT platelets and CSR particles inside the UP matrix was studied by means of transmission electron microscopy (TEM). TEM micrographs showed a good dispersion of organoclay tactoids with an intercalated structure or partial exfoliation for the UP reinforced by 1 and 3 wt.% OMMT. On the other hand, addition of 5 and 10 wt.% CSR particles to the UP increased the fracture toughness much more than the OMMT. Locally clustered but globally good CSR particle dispersion inside the UP matrix was observed in toughened UP specimens. Interestingly, a synergistic effect in fracture toughness was only observed for the UP hybrid composite containing 1 wt.% OMMT and 10 wt.% CSR particles, when compared with other reinforced, toughened, and hybrid specimens. In this case, the OMMT platelets were found to act as bridges between the small rubber-particle agglomerates, which may cause alternating clay debonding/CSR particle cavitation and improve plastic deformation inside the UP matrix. The incorporation of OMMT increased Young’s modulus and also decreased the tensile strength of the neat and CSR-toughened UP specimens with increasing the amount of OMMT.

Sulfonated SBA-15 mesoporous silica-incorporated sulfonated poly(phenylsulfone) composite membranes for low-humidity proton exchange membrane fuel cells: Anomalous behavior of humidity-dependent proton conductivity

Sulfonated SBA-15 mesoporous silica (SM-SiO2)-incorporated sulfonated poly(phenylsulfone) (SPPSU) composite membranes are fabricated for potential application in low-humidity proton exchange membrane fuel cells (PEMFCs). The SM-SiO2 particles are synthesized using tetraethoxy silane (TEOS) as a mechanical framework precursor, Pluronic 123 triblock copolymer as a mesopore-forming template, and mercaptopropyl trimethoxysilane (MPTMS) as a sulfonation agent. A distinctive feature of the SM-SiO2 particles is the long-range ordered 1-D skeleton of hexagonally aligned mesoporous cylindrical channels bearing sulfonic acid groups. Based on a comprehensive characterization of the SM-SiO2 particles, the effect of SM-SiO2 (as a functional filler) addition on the proton conductivity of the SPPSU composite membrane is examined as a function of temperature and relative humidity. An intriguing finding is that the proton conductivity of the SPPSU composite membrane exhibits a strong dependence on the relative humidity of measurement conditions. This anomalous behavior is further discussed with an in-depth consideration of the characteristics and dispersion state of SM-SiO2 particles, which affect the tortuous path for proton movement, water uptake, and state of water. Notably, at low-humidity conditions, the SM-SiO2 particles in the SPPSU composite membrane serve as an effective water reservoir to tightly retain water molecules and also as a supplementary proton conductor, whereas they behave as a barrier to proton transport at fully hydrated conditions.

Rubber modification of unsaturated polyester resin with core–shell rubber particles: Effect of shell composition

AbstractPoly(butyl acrylate)/poly(vinyl acetate‐co‐methyl methacrylate) PBA/P(VAc‐co‐MMA) core–shell rubber particles with various shell compositions, i.e., VAc/MMA weight ratios, were used to toughen unsaturated polyester. The morphology and surface‐free energy of the rubber particles were determined by transmission electron microscopy (TEM) and contact angle measurements, respectively. The effect of shell structure on the dispersion state of rubber particles inside the unsaturated polyester resin was studied by scanning electron microscopy and TEM. Increasing MMA units in the shell changed the particle dispersion state from small agglomerates or globally well‐dispersed particles to large aggregates in the cured‐resin matrix. For the blends that contain 5 wt% rubber, the highest un‐notched impact toughness, stress‐intensity factor (KIC), and fracture energy (GIC) were observed for the blend containing PVAc shell particles. The results showed that by increasing the particle level from 5 to 10 wt%, the highest KIC and GIC values were obtained for the blend containing rubber particles with VAc/MMA (80/20 wt/wt) copolymer shell. The crack‐tip damage zone in the neat and rubber‐modified unsaturated polyester resins was observed by means of transmission optical microscopy. In addition, using PVAc shell particles exhibited a minimum reduction in the volume shrinkage and tensile properties of the rubber‐modified resin. POLYM. ENG. SCI., 52:1928–1937, 2012. © 2012 Society of Plastics Engineers

Hydrostatic pressure measurement for evaluation of particle dispersion and flocculation in slurries containing temperature responsive polymers

The state of particle dispersion and flocculation was evaluated through hydrostatic pressure measurements in aqueous slurries of alumina with neutral and charged temperature responsive co-polymers of poly (N-isopropylacrylamide) (PNIPAM). Slurries were prepared and poured into test tubes at room temperature, and then heated in a hot water bath to a controlled temperature. The slurries were then cooled down to room temperature. The hydrostatic pressure at the bottom of the slurry was continuously measured. The effect of the fraction of charge on the polymer on the particle dispersion state was investigated by changing the ratio of acrylic acid (AA) to PNIPAM in the synthesized co-polymers. It was shown that the hydrostatic pressure of the slurry with 15% AA–PNIPAM co-polymer decreased the fastest at temperature above the polymer lower critical solution temperature (LCST), indicating that the largest flocs were formed due to a strong attractive force. However, the hydrostatic pressure of the 15% charged polymer did not recover (increase) after reducing the temperature below the LCST, revealing that the formed flocs did not re-disperse. On the other hand, the hydrostatic pressures of the slurries with 1% and 5% AA–PNIPAM co-polymer showed relatively quick decrease at temperature above the LCST and clearly recovered (increased) after changing the temperature to below LCST. The particles in these slurries can be changed from the dispersed to the flocculated state by temperature control. The hydrostatic pressure measurement has been shown to be a very useful tool to monitor how the particle dispersion and flocculation state are changed by changing the surrounding temperature for slurries with temperature responsive polymer.

Comparison of Particle Size and Dispersion State among Commercial Cyclosporine Formulations and Their Effects on Pharmacokinetics in Rats

Generic versions of Neoral, a microemulsion capsule formulation of cyclosporine, have been approved worldwide. However, there are concerns about the quality and efficacy of the generics due to the formulation specificity and differences in inactive ingredients among products. In this study, we measured the physicochemical properties of both the innovator and the generic formulations, and compared their bioavailability in rats. When the capsule contents were dispersed in water, the absorbance (600 nm wavelength) of generic products was higher than that of the innovator. Whereas the dispersion solution of the innovator in Fed State Simulated Intestinal Fluid was nearly clear, that of all the generics became white and turbid. The mean diameter of the microemulsion (or emulsion) formed in water by the generics was 39.7, 57.7, 64.5, and 74.8 nm, all of which were larger than that of the innovator (26.4 nm). Although the T(max) of the generics tended to be long relative to that of the innovator, there were no significant differences between the innovator and generics with regard to maximum blood concentration (C(max)) or area under the curve (AUC). These results suggest that the physicochemical differences between the innovator and the generics will not have a significant effect on C(max) or AUC, which is necessary to ensure bioequivalence.

Super- and sub-Einstein intrinsic viscosities of spherical nanoparticles in concentrated low molecular weight polymer solutions

We explore the intrinsic viscosity of 40 nm silica particles in concentrated solutions of low molecular weight hydroxyl terminated polyethylene glycol (PEG), polyethylene glycol dimethyl ether (PEGDME) and polytetrahydrofuran (PTHF). Our goal is to develop a correlation between the intrinsic viscosity and the strength of the polymer segment-surface attractions, εpc. We show when the particles are large compared to the polymer radius of gyration and the polymer molecular weight is below the entanglement molecular weight, the intrinsic viscosity can be larger or smaller than the Einstein value of 2.5 expected for spheres with hard surfaces experiencing no-slip boundary conditions at the fluid/particle interface. Extensive small angle X-ray scattering studies are undertaken to extract εpc and establish the thermodynamic state of particle dispersion. We demonstrate a monotonic dependence of intrinsic viscosity on εpc with weaker polymer segment-particle surface interactions leading to sub-Einstein intrinsic viscosities. When interpreted in terms of a continuum model, our results suggest that the variations in intrinsic viscosity can be understood in terms of adsorbed layers which can have different viscosities from that of bulk fluid and which can slip at the particle surface. Increased layer viscosities are encouraged by large εpc while slip and or low viscosities are encouraged by low εpc.

Preparation of poly(styrene‐co‐butyl acrylate)/montmorillonite nanocomposite by emulsion polymerization: Characterization and nanoscratch behavior

AbstractOrganic–inorganic hybrid poly(styrene‐co‐butyl acrylate)/organically modified montmorillonite (PSBA/organo‐MMT) latex particles have been prepared by in situ emulsion polymerization. The effects of modifier variety and the level of organo‐MMT have been investigated on the basis of the characteristics and mechanical properties of the resulting hybrid emulsion polymers. Although the more hydrophilic intercalated organic modifiers increased the latex particle size, the hydrophobic ones decreased the particle size. A more heterogeneous copolymer chain intercalation was seen by widespread XRD reflection as the organo‐MMT (organoclay) level increases. The tapping mode atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to determine the dispersion state of organoclay particles inside the nanocomposite copolymer films. Dynamic mechanical thermal analysis (DMTA) showed that adding the organoclay to the copolymer decreased the maximum loss tangent (tanδ) value and caused the shift to a lower temperature. Interestingly, the incorporation of organoclay decreased the glass storage modulus of the copolymer, while increased the rubbery storage modulus to some extent. In addition, a standard indenter for the nanoscratching of copolymer nanocomposite films was used under low applied loads of 150 and 250 μN. The nanoscratch results showed that incorporation of a 3 wt % hydrophobic organoclay, e.g., Closite15A, in the copolymer matrix enhanced considerably the near‐surface hardness and grooving resistance of the nanocomposite film at room temperature. In fact, copolymer nanocomposite films with higher near‐surface hardness and tanδ curve broadening exhibited more nanoscratch resistance through a specific variety of viscoelastic deformation, which did not create a bigger groove. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Dispersion state and rheology of hectorite particles in water over a broad range of salt and particle concentrations

The relationship between the rheological properties of deionized aqueous suspensions of hectorite particles and the dispersion states of the particles has been studied with a broad range of salt and particle concentrations. The shear viscosity of the hectorite suspensions decreases drastically after exhaustively deionizing the suspensions with ion-exchange resins. By means of DLS measurements, it is clarified that the average size of the flocs of hectorite particles decreases and reaches the Stokes diameter of the individual particle as the degree of deionization advances. This fact strongly supports the idea that the electrical double layer around the hectorite particles expands significantly in the exhaustively deionized state and the particles are well-dispersed individually and do not form a three-dimensional network structure composed of particles, whereas such a network structure forms in the presence of a large amount of salt. In the case of exhaustively deionized state, the suspension forms a glassy state, at high particle fractions. The results show the importance of the electrical double layer that causes a strong repulsive force among the particles on the particle dispersion state, especially in the exhaustive deionization area below 10 − 4 M, and on the rheological properties; the hectorite suspension can be considered a Newtonian liquid in the deionized state, but it becomes elastic-solid in the presence of salt above a certain concentration confirmed by normal stress measurements.

Effect of boron oxide/carbon arrangement of precursor derived from condensed polymer-boric acid product on low-temperature synthesis of boron carbide powder

The effect of the boron oxide (B2O3)/carbon arrangement of the precursor on the low-temperature synthesis of boron carbide (B4C) powder was investigated in this study. The precursor was prepared by low-temperature heat treatment without thermal decomposition and subsequent pyrolysis in air of the condensed product formed from poly(vinyl alcohol) (PVA) and boric acid. The dispersion state of B2O3 particles in the carbon matrix of the precursor significantly affected the acceleration of the synthesis reaction. Crystalline B4C powder with little free carbon was obtained by heat treatment at 1100°C, which was also the critical formation temperature, for 20 h in an Ar flow starting from a precursor with a B2O3/carbon structure homogeneously arranged at the nanometer scale.

A novel approach for producing polymer nanocomposites by in-situ dispersion of clay particles via friction stir processing

A novel method based on friction stir processing was developed for fabrication of polymer/clay nanocomposites to enhance the dispersion state of nanoclay particles and surface mechanical properties. X-ray diffraction, transmission electron microscopy, microhardness and rheological analysis were employed to investigate the effect of processing parameters on morphology and surface mechanical properties. An attempt was made to establish correlations between the significantly enhanced microhardness values and FSP-induced dispersion of nanoclay.

Octadecylammonium montmorillonite/natural rubber/cis-1,4-polybutadiene nanocomposites

Octadecylammonium montmorillonite/natural rubber/cis-1,4-polybutadiene (OMMT/NR/BR) nanocomposites were prepared by direct mechanical blending. The structure of these nanocomposites and the dispersion state of OMMT particles were evaluated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The cure characteristics, static mechanical properties, dynamic mechanical properties, and thermal stability were also determined. TEM confirmed that the majority of the OMMT particles was dispersed uniformly in the NR matrix. The XRD patterns revealed that the clay mineral particles were completely exfoliated when the OMMT content was < 6 mass%. The addition of OMMT decreased the scorch time ( Ts) of the NR/BR blends and led to synchronic vulcanization of NR and BR. Nanocomposites containing 6 mass% OMMT showed a tensile strength of 19.6 MPa, an increase by 90.3% compared to the pure NR/BR hybrids. Dynamic mechanical analysis indicated that the peak loss factor (tan δ) was lower than that of NR/BR and shifted to higher temperatures, especially for the NR phase. OMMT/NR/BR nanocomposites had exactly the same onset decomposition temperature and lower thermal degradation rate as the NR/BR blends.

Effect of particle size on the phase behavior of block copolymer/nanoparticle composites

Effect of particle size on the self-assembly of thiol-terminated polystyrene-stabilized Pd nanoparticles in microphase-separated block copolymers composed of poly(styrene- b-2 vinyl pyridine) (PS-PVP) was investigated using transmission electron microscopy and differential scanning calorimetry. We observe that the state of particle dispersion depends strongly on the relative size between the particle diameter ( d) and PS domain spacing ( D). As d/ D ∼ 0.3, the self-assembly of nanoparticles in the PS domains causes swelling and increases the interfacial curvature that induces order–order transitions. At intermediate d/ D, the introduction of nanoparticles in the PS domains causes polymer stretching, resulting in the reduction of the conformational entropy. This behavior leads to the particle aggregation, which induces the macrophase separation. Additionally, these particle aggregates increase in size with increasing particle loading, and eventually they create conditions to induce disorder in the polymer morphology. As d is compatible to D, packing constraints prevent particles from assembling in the PS domains, and particles aggregate at low particle loading. This study provides valuable experimental results on the recent emerging field of nanostructured polymer nanocomposites. Our results will enable to gain better insight into the physical properties of these functional materials and will serve to validate the simulation studies of block copolymer/nanoparticle mixtures.

Nanocomposites: Structure, Phase Behavior, and Properties

It is well recognized that nanocomposites formed by adding nanoparticles to polymers can have significantly enhanced properties relative to the native polymer. This review focuses on three aspects that are central to the outstanding problem of realizing these promised property improvements. First, we ask if there exist general strategies to control nanoparticle spatial distribution. This is an important question because it is commonly accepted that the nanoparticle dispersion state crucially affects property improvements. Because ideas on macroscale composites suggest that optimizing different properties requires different dispersion states, we next ask if we can predict a priori the particle dispersion and organization state that can optimize one (or more) properties of the resulting nanocomposite. Finally, we examine the role that particle shape plays in affecting dispersion and hence property control. This review focuses on recent advances concerning these underpinning points and how they affect measurable properties relevant to engineering applications.

Intermediate temperature solid oxide electrolysis cell using LaGaO3 based perovskite electrolyte

The application of a LaGaO3 based electrolyte for steam electrolysis was studied and it was found that the H2 formation rate obeys the Faraday's law suggesting unity of oxide ion conductivity in LaGaO3 perovskite oxide under an electrolysis condition up to 2.0 V applied potential. Among the examined metal catalysts, nickel shows the smallest cathodic overpotential and the addition of Fe to Ni is highly effective for increasing the H2 formation rate in the steam electrolysis at 873 K. The highest H2 formation rate is obtained at the composition of Ni : Fe = 9 : 1. The improved cathodic performance results from the high dispersion state of Ni particles. Impedance measurement suggests that the diffusion resistance is the dominant overpotential in cathodic reaction of the steam electrolysis. Comparing the cathodic operation mode in a fuel cell, gas and surface chemical diffusion in the electrode catalyst tends to be the rate-determining step in the cathodic operation mode in steam electrolysis because of a large molecular size, chemical stability, and molecular weight of water. Comparing the cathodic operation mode in a fuel cell, gas diffusion in the electrode catalyst tends to be the rate-determining step because of a large molecular size and molecular weight of water. Increasing the steam partial pressure is effective for increasing H2 formation rate because of the improved gas diffusion. Decreasing the thickness of a LaGaO3 based electrolyte is also effective for increasing the H2 formation rate. The H2 formation rate reached a value as high as 180 μmol cm−2 min at 0.2 mm thickness and 873 K.

Microstructures and properties of direct laser sintered tungsten carbide (WC) particle reinforced Cu matrix composites with RE–Si–Fe addition: A comparative study

The poor wettability between ceramics and metals is a main obstacle in obtaining high-performance metal-matrix composites (MMCs) parts using direct metal laser sintering (DMLS). Rare earth (RE) elements, due to their unique physical and chemical properties, have high potential for improving laser processability of MMCs. In this work, a comparative study was performed to investigate the influence of RE–Si–Fe addition on microstructural features and mechanical properties of DMLS processed tungsten carbide (WC) particle reinforced Cu MMCs parts. It showed that by adding 3 wt% RE–Si–Fe, the WC reinforcing particles were refined, the particle dispersion state was homogenized, and the particle/matrix interfacial compatibility was enhanced. The RE–Si–Fe-containing WC/Cu MMCs parts possessed significantly elevated mechanical properties, i.e., densification level of 95.7%, microhardness of 417.6 HV, fracture strength of 201.8 MPa, and friction coefficient of 0.8. The metallurgical functions of the RE–Si–Fe additive for the improvement of DMLS quality of MMCs parts were discussed.

Synthesis of sub‐micrometer core–shell rubber particles with 1,2‐azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditions

AbstractBACKGROUND: Sub‐micrometer core‐shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2‐azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB‐g‐PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core‐shell rubber particles and deformation mechanisms under various conditions were investigated.RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ‘cluster’ dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge‐like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests.CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ‘cluster’ state leads to better impact resistance. The deformation mechanism in impact tests was multi‐crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright © 2009 Society of Chemical Industry

Effect of acrylic core–shell rubber particles on the particulate flow and toughening of PVC

AbstractDifferent types of acrylic core–shell rubber particles with a poly(butyl acrylate) (PBA) core and a grafted poly(methyl methacrylate) (PMMA) shell were synthesized. The average size of acrylic core–shell latex particles ranged from 100 to 170 nm in diameter, having the core gel content in the range of 35–80%. The melt blending behavior of the poly(vinyl chloride) (PVC) and the acrylic core–shell rubber materials having different average particle sizes and gel contents was investigated in a batch mixing process. Although the torque curves showed that the particulate flow of the PVC in the blends was dominant, some differences were observed when the size and gel content of the particles varied. This behavior can be attributed to differences in the plasticizing effect and dispersion state of various types of core–shell rubber particles, which can vary the gelatin process of the PVC in the mixing tool. On the other hand, the highest toughening efficiency was obtained using core–shell rubber particles with the smallest particle size (i.e., 100 nm). The results showed that increasing the gel content of the core–shell impact modifiers with the same particle size improved the particle dispersion state in the PVC matrix. The toughening efficiency decreased for the blends containing 100 and 170 nm rubber particles as the gel content increased. Nevertheless, unexpected behavior was observed for the blends containing 140 nm rubber particles. It was found that a high level of toughness could be achieved if the acrylic core–shell rubber particles as small as 100 nm had a lower gel content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Thermal, electrical, and mechanical properties of Si3N4 filled LLDPE composite

AbstractSilicon nitride (Si3N4) filled linear low‐density polyethylene (LLDPE) composite was prepared. The effects of Si3N4 filler content, dispersion, and LLDPE particle size on the thermal conductivity, and Si3N4 filled content on the mechanical and electrical properties of Si3N4 reinforced LLDPE composites prepared using powder mixing were investigated. The results indicate that there existed a unique dispersion state of Si3N4 particles in LLDPE, shell‐kernel structure, in which Si3N4 particles surrounded LLDPE matrix particles. With increasing filler content and LLDPE particles size, thermal conductivity increased, and reached 1.42 W/m K at 30 vol% of filler, seven times as that of unfilled LLDPE. Furthermore, the examinations of Agari model demonstrate that larger size LLDPE particles form thermal conductive networks easily compared with smaller ones. The values predicted by theoretical model underestimate the thermal conductivity of Si3N4/LLDPE composites. In addition, the composites still possessed rather higher electrical resistivity and dielectric properties, but the mechanical properties decreased. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers