Hybrid Filler System Research Articles

Effect of halloysite nanotubes and organically modified bentonite clay hybrid filler system on the properties of natural rubber

The versatility and potential have framed natural rubber (NR) nanocomposites as the focal point in the polymer research field and industry. Currently, NR nanocomposites filled with hybrid nanostructures is an interesting area than single filler or conventional filler systems. Halloysite nanotube (HNT) and bentonite clay are well-studied potential fillers of polymers. This work is an attempt to study the effect of hybrid filler system of HNT and organically modified bentonite nanoclay (NC) in the properties of NR. NR/HNT-NC systems with varied filler concentrations were prepared in a two-roll mixing mill. Properties such as cure characteristics, morphology, mechanical, thermal, and transport behavior were analyzed in detail. The prepared composites had better wear properties than gum vulcanizates. Improvement in physical properties was observed due to the increased contact surface area between the filler and the matrix. The nanocomposite with 2 wt% hybrid filler shows a 31% decrease in abrasion loss compared to neat NR composite. Apparently, 4 wt% of hybrid filler could improve modulus at 300% strain and tear by approximately 57% and 14%, respectively. The ability to withstand high strain was evident from the improved crack growth resistance as observed in micrographs. Lorenz–Park plots were employed to analyze the rubber–filler interaction. The activation energy of thermal degradation was calculated using Coats–Redfern equation.

Enhancement of thermal conductivity of carbon fiber-reinforced polymer composite with copper and boron nitride particles

A hybrid filler system, which combines hexagonal boron nitride (hBN) and copper particles, was applied on the surface of continuous carbon fiber tapes by utilizing electrophoretic deposition to maximize the thermal conductivity of carbon fiber-reinforced polymer (CFRP) composite in this study. The results show that as the deposition time increased, the thermal conductivity increased. The annealing treatment made the copper particles connect with adjacent particles, which highly enhanced the thermal conductivity. The CFRP made of annealed carbon fiber tapes with hBN/Cu coating performed the best thermal conductivity and largest enhancement efficiency in this work for as high as 2.16 W/m·K and 217% in through-plane direction, and 6.14 W/m·K, and 47% in in-plane direction.

Synergistic Effects of Various Ceramic Fillers on Thermally Conductive Polyimide Composite Films and Their Model Predictions.

In this study, thermally conductive composite films were fabricated using an anisotropic boron nitride (BN) and hybrid filler system mixed with spherical aluminum nitride (AlN) or aluminum oxide (Al2O3) particles in a polyimide matrix. The hybrid system yielded a decrease in the through-plane thermal conductivity, however an increase in the in-plane thermal conductivity of the BN composite, resulting from the horizontal alignment and anisotropy of BN. The behavior of the in-plane thermal conductivity was theoretically treated using the Lewis–Nielsen and modified Lewis–Nielsen theoretical prediction models. A single-filler system using BN exhibited a relatively good fit with the theoretical model. Moreover, a hybrid system was developed based on two-population approaches, the additive and multiplicative. This development represented the first ever implementation of two different ceramic conducting fillers. The multiplicative-approach model yielded overestimated thermal conductivity values, whereas the additive approach exhibited better agreement for the prediction of the thermal conductivity of a binary-filler system.

Role of CNT/clay hybrid on the mechanical, electrical and transport properties of NBR/NR blends

Hybrid fillers are making a remarkable improvement in the properties of polymeric systems. In the present study, the influence of hybrid of multiwalled carbon nanotube (MWCNT) and nanoclay on the mechanical, electrical and transport properties of nitrile rubber (NBR)/natural rubber (NR) blends has been investigated. Attempts were made to prepare NBR/NR/CNT/nanoclay composites on a two-roll mill and to study various mechanical properties such as tensile strength, tear resistance, abrasion loss and compression set percent. Transport, thermal and electrical properties were also investigated. By virtue of the synergism between MWCNT and nanoclay, the composites exhibited enhancement in the mechanical properties by the immobilization of rubber chains via coupling action between the filler surface and the rubber molecules. The fine and uniform dispersion of both CNT and clay in composite samples supported the observation. The hybrid filler system had a great impact on the thermal and electrical properties of the composites.

Synergistic effect of hybrid stainless steel fiber and carbon nanotube on mechanical properties and electromagnetic interference shielding of polypropylene nanocomposites

This study provides critical insight into the design of nanocomposites and presents both enhanced mechanical and electromagnetic interference (EMI) shielding performance. Polypropylene nanocomposites reinforced with carbon nanotube (CNT) alone, stainless steel fiber (SSF) alone, and a hybrid filler system of SSF and CNT, with 50/50 filler volume ratio but different total filler loadings, were developed via melt-mixing. It was revealed that the hybrid nanocomposites depicted simultaneous enhanced EMI shielding and mechanical performance over single filler composites. The enhanced mechanical and EMI shielding performance of the hybrid nanocomposite was attributed to the bridging of rigid SSFs with flexible CNTs, leading to a robust conductive hierarchical filler network. To characterize and assess the network, standard morphological analysis was performed.

Study on epoxy resin-based thermal adhesive filled with hybrid expanded graphite and graphene nanoplatelet

Reinforced epoxy composite adhesives of expanded graphite (EG) and graphene nanoplatelet (GNPs) were prepared by hand layup and mechanical mixing method. Disk-shaped epoxy composite samples with EG and GNP mixtures in varying ratios were prepared to measure the thermal conductivity (TC) enhancement. Thermal characterization testing data showed high thermal conductivity enhancement with three different hybrid filler concentrations of 10, 25, and 35 wt%, respectively. The highest thermal conductivity of 3.6 W/m K was obtained for an epoxy adhesive composite having 30 wt.% EG and 5 wt.% GNP which was tested by guarded heat flow meter technique. This significant improvement in thermal conductivity can be attributed to the lowering of overall thermal interface resistance due to small amounts of nanofiller (GNP) improving the thermal contact between the primary microfillers (graphite). The synergistic effect of this hybrid filler system is lost at higher loadings of the GNP relative to expanded graphite. The structure of the graphite flake, GNP/epoxy, EG/epoxy and hybrid EG/GNP/epoxy composites was investigated by XRD. The EG prepared by acid intercalation and abrupt thermal expansion showed good compatibility with GNP and the epoxy resin. From scanning electron microscopy photographs, the formation of conducting network observed through the expanded graphite and GNPs in a low conducting epoxy matrix. The thermal decomposition temperature of the composite increased to 450 and 615 °C with the addition of 10 and 35 wt% of hybrid EG/GNP inside epoxy matrix, respectively. LAP shear strength of single and hybrid filled epoxy adhesive decreased at 35 wt.% loading than neat epoxy.

Cork-wood hybrid filler system for polypropylene and poly(lactic acid) based injection molded composites. Structure evaluation and mechanical performance

Presented work discusses comparative studies of the use of a hybrid filler system on the properties of polypropylene and poly(lactic acid) composites. Wood flour have been added to improve the initially poor material performance of cork based composites. The hybrid cork/wood filler system used during this study was introduced to polymer system by two step extrusion/injection molding process in the amount of 10, 20 and 30 wt%. Samples were subjected to detailed thermo-mechanical and structural analysis. The investigated hybridization method was successfully implemented, leading to the enhancement of mechanical characteristics comparing to pure cork composites. Density analysis in combination with structural observations, confirmed significant changes in the morphology of cork, including the loss of the cellular structure, due to high shearing of the injection molding process. The favorable results of water absorbency tests indicate the potential use of cork filler to improve the dimensional stability of composites.

Influence of cell size on out of plane stiffness and in-plane compliance character of the sandwich beam made with tunable PCTPE nylon honeycomb core and hybrid polymer nanocomposite skin

Sandwich structures with honeycomb core find specific application in impact resistance and energy absorption applications. However, such studies were limited to cores with metallic honeycomb, which had limited energy absorption abilities apart from extrinsic weight. The current work aims to fabricate hybrid sandwich beams made with PCTPE (Plasticized Co-polyamide Thermoplastic Elastomer) nylon using Fused Filament Fabrication (FFF). The cell size was varied from 10 to36 mm with a variation of longest diagonal. The face sheets were prepared with High-density polyethylene (HDPE) matrix with equal loading of Graphite nanoplatelet and Nano-diamond hybrid filler system. The face sheets were joined to honeycomb core to prepare sandwich panel with tailored made adhesive. It was observed that during out of the plane test, for 10 mm cell the SEA (specific energy absorption) was 1.15 kJ/kg, which decreased upto and 69% for 36 mm respectively. During the in-plane flexural test, the minimum flexural modulus showed by 36 mm longest diagonal cell was 31 MPa, which had increased further by 24, 50, 62, 67 and 76% for 27, 21, 15, 12 and 10 mm respectively, indicating elastic nature and damping ability of sandwich beam. The free vibration analysis was performed on by taking cantilever configuration. The experimentally obtained results were then validated using Ansys-14 simulation. It was concluded that PCTPE nylon core exhibited dual properties of stiffness and compliance for the period of out-plane testing and in-plane respectively, with a threshold limit of 36 mm cell size.

Polycarbonate biocomposites reinforced with a hybrid filler system of recycled carbon fiber and biocarbon: Preparation and thermomechanical characterization

ABSTRACTIn this article, we present the investigation of the use of a partly biobased hybrid reinforcement system to improve the mechanical properties of polycarbonate (PC). To minimize the amount of recycled carbon fibers (rCFs) used in this study, their initial quantity of 20% was reduced and replaced by pyrolyzed biocarbon (BC) particles in amounts of 5%, 10%, 15%, and 20%. The materials were prepared during an extrusion‐/injection‐molding processing procedure. In addition to basic mechanical tests (tensile, flexural, and Izod tests), the samples were also subjected to detailed dynamic mechanical analysis to determine the thermomechanical relationships, such as the C factor, entanglement density, adhesion factor, and reinforcing efficiency. The results confirm the positive effect of hybridization, especially for the samples with low BC contents. In relation to the 20% pure BC composites, the hybrid samples containing the same amount of mixed filler (10%; rCF10–BC10) achieved an almost triple (270%) increase in the tensile strength and a 35% increase in the modulus. The impact resistance was also increased by 170%. Differential scanning calorimetry analysis showed significant changes in the glass‐transition temperatures for the BC‐rich samples; this was due to the sensitivity of the PC matrix to the processing degradation. The application of a small quantity of epoxy‐based chain extender proved to be effective in reducing this unfavorable phenomenon. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46449.

The capability of graphene on improving the electrical conductivity and anti-corrosion properties of Polyurethane coatings

Graphite and graphene particles were used to reinforce the electrical conductivity and anti-corrosion properties of polyurethane (PU) coatings. The effect of graphite and graphene were compared. Hybrid filler using carbon nanotube was adopted as well and the performance in electrical conductivity was much superior to single filler system. At the same filler loading, the electrical conductivity of hybrid filler system was significantly higher than single filler system (0.77S/m at 5wt% while single filler system was not conductive). The conductive mechanism was revealed. In terms of anti-corrosion properties, the coatings with low filler loading had better anti-corrosion properties. The resistance values obtained from EIS (Electrochemical Impedance Spectroscopy) and four point probe method were compared and discussed.

Enhanced thermal and mechanical properties of epoxy composites filled with hybrid filler system of aluminium nitride and boron nitride

The study aims to enhance the thermal and mechanical properties of epoxy composite materials. This is done based on combination of micron sized aluminium nitride (AlN) and hexagonal boron nitride (hBN) particles. A set of AlN/BN hybrid epoxy composites with filler content ranging from 35, 40, and 42 wt% was prepared by conventional casting method. The use of these hybrid fillers was found to be very effective in increasing the composite thermal conductivity due to synergetic connectivity offered by the fillers with different geometries; polyhedral AlN and hBN platelets. Maximum thermal conductivity of 0.57 W mK−1 was achieved for the formulation of AlN:BN = 2:1 at 42 wt% filler loading. Glass transition (Tg), coefficient of thermal expansion (CTE), and modulus of the composites were measured experimentally. The integrated properties of AlN/BN epoxy composites are expected to enhance the heat dissipating capabilities in microelectronic industry. POLYM. COMPOS., 39:E1372–E1380, 2018. © 2016 Society of Plastics Engineers

Effect Hybrid Filler on the Properties of Epoxy Resin

Composites are materials which are widely used in aerospace industry for its high strength to weight ratio, where most of the alloys add weight as penalty. These composites are made up of two phases namely matrix phase and reinforcement phase. Matrix is the most important phase as it has to hold the reinforcement and to distribute the loads to the reinforcement i.e., the matrix should be adhesive and as well strong enough to resist de-bonding of reinforcement due to load acting on it. To improve certain properties of the matrix system fillers are added to it. Some filler may improve certain properties, while others reduce certain properties and improve some other properties. Combination of two or more fillers (hybrid filler system) can also be added to the matrix in certain proportion to improve its property. This work mainly concentrates on the effects addition of 1% by weight of hybrid fillers on the properties of the matrix system. Two selected filler system is mixed in the predefined proportion and added to the matrix system to prepare specimen. These specimens were tested for its flexural properties and compared with the neat matrix system.

Study on Mechanical Properties of Natural Rubber Filled with Molasses Black/Carbon Black Hybrid Filler System

Molasses is an inexpensive byproduct made during the extraction of sugars from sugarcane. Viscous molasses was converted to powder form under heating process. Molasses black (MB), mainly consisting of carbon, was finally obtained. As a result of elemental analyzer, it is evident that MB containing 56.13 % of carbon. Additionally, Fourier Transform Infrared Spectrophotometer (FTIR) result confirmed that function groups of MB were comparable with carbon black (CB). Nevertheless, the large particle size and low specific surface area of MB was less effective for reinforcement. Therefore, in this research, a feasibility study was carried out on the utilization of MB together with carbon black as hybrid filler in natural rubber (NR). Reinforcement of NR with MB/CB hybrid filler at various ratios was studied. The total hybrid filler content was 30 parts per hundred of rubber (phr). The mechanical properties were determined. The results revealed that the NR vulcanizates containing hybrid filler exhibited the better reinforcement than that filled with single MB filler.

Reduction of filler networking in silica based elastomeric nanocomposites with exfoliated organo-montmorillonite

Montmorillonite with dimethyl di(hydrogenatedtalloyl) ammonium as the compensating cation was added to a silica based elastomeric composite and the hybrid filler system led to reduction of filler networking phenomenon, better stability of elastic modulus with temperature, enhancement of stresses at all elongations, improvement of ultimate properties. This composite was based on a blend of natural rubber, poly(1,4-cis-isoprene) and poly(styrene-co-butadiene) from anionic polymerization and contained 70 parts per hundred rubber (phr) of silica. The organically modified clay (OC) was below the threshold required to establish an hybrid OC-silica filler network. Such threshold (about 7phr) was estimated by preparing silica based nanocomposites containing various amounts of OC and determining shear storage and loss moduli as a function of strain amplitude. This work demonstrates that exfoliated OC favour lower dissipation of energy of silica based elastomeric composites under dynamic mechanical stresses and paves the way for further large scale applications.

Thermal and mechanical properties of epoxy composite filled with binary particle system of polygonal aluminum oxide and boron nitride platelets

The increased heat generated in high-density electronics has intensified the search for advanced thermal management solutions. This urge has prompted fundamental studies on various filler-filled polymer composites with enhanced thermal performance. This research is intended to attain better understanding on the effect of particle sizes and geometry of fillers with different ratios of composition on the thermal and mechanical properties of hybrid composite system. It investigates the effect of combining polygonal aluminum oxide (Al2O3) and boron nitride (BN) platelets to enhance the thermal conductivity of epoxy composite. The surface of the two fillers was functionalized with aminopropyltriethoxysilane (KH550), thereby reducing the thermal interfacial resistance between filler and matrix. It was observed that there is no significant difference in the thermal and mechanical performance between BN1µm and BN5µm filler-filled composites. However, at filler loading of 30 wt%, the Al2O3 and BN1µm hybrid filler system (ratio 5:5) provided significant enhancement of maximum thermal conductivity of 0.57 Wm−1 K−1 compared to 0.17 Wm−1 K−1 that of neat epoxy. This synergistic effect results from the bridging of BN platelets between the Al2O3 particles facilitating the formation of effective thermal conductance network within the epoxy matrix.

Thermally conductive polyamide 6/carbon filler composites based on a hybrid filler system

We explored the use of a hybrid filler consisting of graphite nanoplatelets (GNPs) and single walled carbon nanotubes (SWCNTs) in a polyamide 6 (PA 6) matrix. The composites containing PA 6, powdered GNP, and SWCNT were melt-processed and the effect of filler content in the single filler and hybrid filler systems on the thermal conductivity of the composites was examined. The thermal diffusivities of the composites were measured by the standard laser flash method. Composites containing the hybrid filler system showed enhanced thermal conductivity with values as high as 8.8 W (m · K)−1, which is a 35-fold increase compared to the thermal conductivity of pure PA 6. Thermographic images of heat conduction and heat release behaviors were consistent with the thermal conductivity results, and showed rapid temperature jumps and drops, respectively, for the composites. A composite model based on the Lewis–Nielsen theory was developed to treat GNP and SWCNT as two separate types of fillers. Two approaches, the additive and multiplicative approaches, give rather good quantitative agreement between the predicted values of thermal conductivity and those measured experimentally.

Synergistic reinforcement ofNBRby hybrid filler system including organoclay and nano‐CaCO3

ABSTRACTRubber nanocomposites containing one type of nanofiller are common and are widely established in the research field. In this study, nitrile rubber (NBR) based ternary nanocomposites containing modified silicate (Cloisite 30B) and also nano‐calcium carbonate (nano‐CaCO3) were prepared using a laboratory internal mixer (simple melt mixing). Effects of the hybrid filler system (filler phase have two kind of fillers) on the cure rheometry, morphology, swelling, and mechanical and dynamic–mechanical properties of the NBR were investigated. Concentration of nano‐CaCO3[0, 5, 10, and 15 parts per one hundred parts of rubber by weight (phr)] and organoclay (0, 3, and 6 phr) in NBR was varied. The microstructure and homogeneity of the compounds were confirmed by studying the dispersion of nanoparticles in NBR via X‐ray diffraction and field emission scanning electron microscopy. Based on the results of morphology and mechanical properties, the dual‐filler phase nanocomposites (hybrid nanocomposite) have higher performance in comparison with single‐filler phase nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 42744.

Improving flexural and dielectric properties of MWCNT/epoxy nanocomposites by introducing advanced hybrid filler system

In this study, the authors attempted to enhance the flexural and dielectric properties of epoxy resin using advanced carbon nanotube–alumina (CNT–Al2O3) hybrid filler system that was chemically synthesised via chemical vapor deposition (CVD). The hybrid CNT–Al2O3 filled epoxy composite was compared to the physically mixed CNT–Al2O3 filled epoxy composites. The assessment showed that the CNT–Al2O3 hybrid filler produced more homogeneous dispersion in the epoxy matrix with higher flexural and dielectric properties as compared to the physically mixed CNT–Al2O3 filler. The flexural strength, flexural modulus and dielectric constant of CNT–Al2O3 hybrid epoxy composites improved significantly up to 30%, 35% and 20%, respectively, compared to the neat epoxy.

Graphite–graphene hybrid filler system for high thermal conductivity of epoxy composites

Abstract

Effect of nanostructures of modified clay–carbon black on physico‐mechanical, electrical, and acoustic properties of elastomer‐based composites

Elastomeric composites based on nitrile rubber (NBR), carbon black (CB), and organically modified nanoclay (NC) were prepared using a laboratory two‐roll mixing mill. Influences of the hybrid filler system (CB+NC) on various properties of NBR compound were analyzed. It was found that the addition of hybrid filler (CB+NC) over only carbon black enhances various properties. It was also found that the addition of nanoclay to the rubber matrix effectively improved key properties. Acoustics and electrical properties were modified with reduced water absorption because of layered clay platelets. The lower volume resistivity of NBR composites reflected better electrical conductivity attributed to the presence of nanoclay leading to effective filler connectivity. X‐ray diffraction and transmission electron microscopy measurements revealed that nanoclays were mostly intercalated and were uniformly dispersed. Use of calcium stearate facilitated dispersion of nanoclay in the rubber matrix which was observed through the formation of nanostructures including “nano” and “halo” units. Time temperature superposition in dynamic mechanical analysis test of the composites indicated lower mechanical loss in the frequency range of interest. The advantages accruing due to overall property enhancement, including lower water absorption, and better electrical and excellent acoustic properties of NBR composites make it suitable as underwater acoustic transparent materials for transducer encapsulation application. POLYM. COMPOS., 37:1786–1796, 2016. © 2014 Society of Plastics Engineers