Dispersion of graphite nanosheets in polymer resins via masterbatch technique

The dispersion of graphite nanosheets (GNs) in polymer matrices via the masterbatch technique was investigated. Modifying resin was added to GNs to prepare blend which is designated as the masterbatch. Such masterbatches, containing 70–80 wt % of GN filler, were blended with target polymers via melt extrusion process to prepare polymer/GN nanocomposites. The extruded nanocomposites showed characteristic conducting percolation behaviors with the percolation thresholds mainly dependent on the miscibility of the modifying resin with polymer matrix. The percolation thresholds of AS (Acrylonitrile‐Styrene compolymer)/GN and high‐density polyethylene (HDPE)/GN nanocomposites prepared by this technique were about 9 and 14 wt % of GN, respectively. Scanning electron microscopy and other characterizations showed that the GNs were well dispersed in AS and HDPE resins. The extrusion process and compatibility of the modifying resin with target polymer proved to be important factors for the homogeneity of the nanodispersion. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3470–3475, 2007     

Fabrication of polyethylene/graphite nanocomposite from modified expanded graphite

A novel process was employed to fabricate a polymer/expanded graphite nanocomposite by modifying the conducting filler expanded graphite (EG) with unsaturated polyester resin (UPR). The modified expanded graphite (MEG) was prepared from EG in which the graphite nanosheets, already present in EG, were wrapped and isolated by the UPR during processing. The as‐prepared MEG was reduced to powder form to improve its dispersion in the matrix. MEG powders were embedded into a high‐density polyethylene (HDPE) matrix via melt‐extrusion in a single‐screw extruder to prepare the conducting composite. The as‐prepared HDPE/EG conducting composite exhibited a low percolation threshold of ～5.7 wt% due to the high aspect ratio of graphite nanosheets. Mechanical properties such as the tensile and impact strength were also studied. Scanning electron microscopy was used to characterize the microstructure of EG, MEG powder and the resulting nanocomposites. Copyright © 2006 Society of Chemical Industry     

Preparation of interfacially compatibilized PP‐EPDM thermoplastic vulcanizate/graphite nanocomposites: Effects of graphite microstructure upon morphology,electrical conductivity,and melt rheology

Electrically conductive PP/EPDM dynamically crosslinked thermoplastic vulcanizate (TPV)/expanded graphite (EG) has been successfully prepared via melt compounding of maleic anhydride grafted polypropylene (PP‐g‐MA)/EG masterbatch and a commercially available TPV material. Correlation between graphite microstructure, and electrical conductivity as well as melt rheological behavior has been studied. Natural graphite flake (NGF), graphite intercalated compound (GIC), and exfoliated graphite (EG) have been employed and compared. Scanning electron microscopy (SEM) showed the presence of 100–200 nm nanolayers in the structure of PP‐g/EG masterbatches, whereas thinner platelets (1.5–2.5 nm) were revealed by transmission electron microscopy (TEM). Better dispersion of the graphite nanolayers in the microstructure of TPV/PP‐g‐MA/EG composite was verified, as the 7.3 Å spacing between the aggregated graphite nanolayers could not be observed in the XRD pattern of this material. TPV/PP‐g/EG nanocomposites exhibited much lower conductivity percolation threshold (φ_c) with increased conductivity to 10^?5 S/cm at EG wt % of 10. Higher nonlinear and nonterminal melt rheological characteristics of dynamic elastic modulus (G′) at low frequency region was presented by the TPV/PP‐g/EG nanocomposites, indicating the formation of nanoscopic conducting multiple networks throughout the continuous TPV matrix. Maleated PP was found to be much more effective in separating EG nanolayers which is attributed to the higher interfacial interaction between PP‐g‐MAH and EG, synergized with its multiporous structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of high‐density polyethylene/expanded graphite conducting masterbatch

High level of expanded graphite (EG) was melt‐blended with high‐density polyethylene to prepare electrical conducting masterbatch. Some factors such as processing temperature, EG contents, treating time were discussed for the effect on electrical and mechanical properties of composites. Results showed that EG tends to reunite while the content of EG is higher than 60% because of the large aspect ratio and surface area of EG nanosheets. In addition, increasing processing temperature and mixing time appropriately could enhance the dispersion of EG, leading to improvement in electrical and mechanical properties. Scanning electron microscopy (SEM) measurements were used as an assistant analysis to study the microstructure of composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Alumina‐filled polystyrene micro‐ and nanocomposites prepared by melt mixing with and without latex precompounding: Structure and properties

Alumina fillers were incorporated in polystyrene (PS) in 4.5 wt % by melt blending with and without latex precompounding. Latex precompounding was used for the latex‐mediated predispersion of the alumina particles. The related masterbatch was produced by mixing PS latex with water dispersible boehmite alumina in various particle sizes followed by drying. The dispersion of the alumina in the PS was studied by transmission and scanning electron microscopy (TEM and SEM, respectively). The mechanical and thermomechanical properties of the PS composites were determined in uniaxial tensile, dynamic‐mechanical thermal analysis (DMTA), and short‐time creep tests performed at various temperatures. In addition, the melt flow of the composites was characterized in a plate/plate rheometer. It was found that direct melt mixing of the alumina with PS resulted in micro‐, whereas the masterbatch technique in nanocomposites. The stiffness and resistance to creep (summarized in master curves) of the nanocomposites were improved compared to those of the microcomposites. The properties of the composites were upgraded by decreasing nominal size of the water dispersible alumina. The preparation technique and the size of the alumina particles affected the tensile strength, melt viscosity, and heat distortion temperature in lesser extent than the stiffness and thus compliance data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Phase morphology evolution and compatibilization of immiscible polyamide 6/polystyrene blends using nano‐montmorillonite

Nanocomposites of organic nano‐montmorillonite (nano‐OMMT)‐filled immiscible polyamide 6 (PA6)/polystyrene (PS) blends were prepared by three different processing methods. Masterbatch M1 of OMMT/PA6 and masterbatch M2 of OMMT/PS were prepared as separate masterbatchs by melt mixing with PA6 or PS, and then either mixed together or each mixed individually with appropriate amounts of PS or PA6, respectively. The effects of nano‐OMMT content and processing method on the structure, phase morphology, and mechanical properties of the PA6/PS/OMMT nanocomposites were investigated by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and mechanical properties tests. The results showed that the nano‐OMMT by M1 and M2 masterbatches dispersed primarily as exfoliated platelets in the PA6 matrix in the final composites regardless of the method of preparation. A drastic decrease of dispersed PS phase size and a very homogeneous size distribution were observed with the addition of nano‐OMMT. The PA6/PS/OMMT nanocomposites prepared from the M2 displayed the smallest dispersed PS phase size and best distribution of OMMT. The improvement of the mechanical properties of the PA6/PS/OMMT nanocomposites was attributed to the enhanced compatibilization of the immiscible PA6/PS blends by using nano‐OMMT. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

丁腈橡胶/膨胀石墨导电纳米复合材料的制备和性能

采用熔融插层法制备了丁腈橡胶/膨胀石墨纳米复合材料。扫描电镜(SEM)研究表明,超声处理后的膨胀石墨薄片厚度为纳米级。透射电镜(TEM)研究证实,膨胀石墨确以纳米级尺寸分散在橡胶基体中。力学性能研究表明,填加5份膨胀石墨时,纳米复合材料的拉伸强度最大,为28·4MPa,是不含膨胀石墨的复合材料的1·8倍。导电性能研究显示,填加10份膨胀石墨时,纳米复合材料的表面电导率和体积电导率分别为1·1×10-9S/cm和1·2×10-9S/cm,是不含膨胀石墨的复合材料的100倍和43倍。     

Effects of direct melt compounding and masterbatch dilution on the structure and properties of nanoclay‐filled polyolefins

The differences that direct melt compounding and masterbatch dilution cause in the properties of melt compounded polypropylene (PP) and high density polyethylene‐based (PE‐HD) nanocomposites are presented. The results include comparison of properties and morphology of directly melt processed organoclay nanocomposites with similar compounds diluted from commercial and in‐house‐made masterbatches to clay concentrations of 1, 3, 6, and 8 wt%. The compounds were prepared with a co‐rotating Brabender twin‐screw extruder. The degree of exfoliation and the dispersion of the nanoclay were verified with transmission electron microscopy and X‐ray diffraction. Thermal stability of the materials was examined with thermogravimetric analysis and the mechanical properties of the compounded materials were also determined. The most promising results regarding mechanical behavior were achieved with the in‐house‐made masterbatch in the form of a notable increase in Young's modulus in both matrices. There was also a distinct increase in impact strength when masterbatch was used. Changes were more pronounced in case of PP. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Thermomorphological analysis of Al2O3/HDPE nanocomposites: One approach in function of the processing and vinyltrimethoxysilane (VTMS) content

The present study assesses the influence of processing and adding alumina (Al₂O₃) nanoparticles functionalized with vinyltrimethoxysilane (VTMS) on high‐density polyethylene (HDPE) matrix. The model proposed by Henk, Kortsen, and Kvarts is used to calculate the ideal alumina nanoparticle concentration, in order to provide a larger interface area with lower agglomeration. Two different processing techniques are used to add the alumina nanoparticles functionalized with VTMS to the HDPE: direct blending and masterbatches applying the same processing extrusion parameters'. The alumina's nanoparticle functionalization with VTMS is confirmed by Fourier transform infrared spectroscopy analysis. The MFI is measured and nanoparticles dispersion is evaluated by scanning electron microscopy and by energy dispersive spectroscopy. Thermal behavior is measured by thermogravimetric analysis and differential scanning calorimetry. The addition of Al₂O₃ nanoparticles increases the thermal stability of the nanocomposites. Functionalization with VTMS provides improve adhesion to the polymer matrix, while the masterbatch processing technique promotes better alumina nanoparticle dispersion in the HDPE matrix and produce high crystalline composites. © 2019 Society of Plastics Engineers POLYM. ENG. SCI., 59:1332–1343 2019. © 2019 Society of Plastics Engineers     

Synthesis and characterization of conducting gas barrier polyacrylonitrile/graphite nanocomposites

Graphite platelets were expanded by functionalization with inorganic acids followed by strong thermal treatment. The expanded graphite (EG) was exfoliated on the polyacrylonitrile (PAN) matrix through in situ emulsion sonication technique with different proportions of EG. The Ultraviolet‐visible (UV) spectroscopy revealed the interaction between EG and PAN matrix. In Fourier Transform Infrared spectroscopy (FTIR), the chemical interaction between EG and the cyanide group of PAN was evidenced to the formation of PAN/EG composites. The X‐ray diffraction pattern of raw graphite (RG), expanded graphite (EG), polyacrylonitrile (PAN), and PAN/EG nanocomposites were evidenced the dispersion of EG with the PAN matrix. The morphology of EG, PAN, and PAN/EG composites were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tensile strength of PAN/EG nanocomposite was measured and found to be increased with increase in EG concentrations. The conductivity and impedance of composites were measured as function of EG concentration. It was found that, conductivity of composites gradually increased with the increase in EG loading. Oxygen permeability of PAN/EG was reduced substantially with rise of EG proportion. To investigate the flame retardancy behavior of PAN/EG nanocomposites, the limiting oxygen indexes were calculated. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Nanoclay reinforced polyethylene composites: Effect of different melt compounding methods

Nanoclay (NC) reinforced high‐density polyethylene (HDPE) composites were prepared by different melt compounding methods using (1) a single screw extruder (SSE), (2) twin screw extruder (TSE), (3) a combination of SSE and extensional flow mixer (EFM), and (4) a bowl mixer masterbatch method (MB). PE‐grafted maleic anhydride (PE‐g‐MA) was used as a compatibilizer. EFM increased complex melt viscosity (η*) of the HDPE/NC composites as compared to the neat HDPE and also provided a better interaction between HDPE and NC to create slightly lower melt η* as compared to MB and PE‐g‐MA composites. The low viscosity melt behavior of the pure HDPE changes to more solid like melt behavior in the PE‐g‐MA HDPE/NC composites in the low frequency (ω) region. PE‐g‐MA + EFM method exhibited better impact strength compared to the other HDPE/NC composites. Using the PE‐g‐MA and masterbatch compounding methods had a beneficial role in improving mechanical properties. POLYM. ENG. SCI., 57:324–334, 2017. © 2016 Society of Plastics Engineers     

New generation layered nanocomposites derived from ethylene‐co‐vinyl acetate and naturally occurring graphite

New ethylene‐co‐vinyl acetate (EVA, with 60% vinyl acetate content) based nanocomposites were prepared with graphites modified by various techniques and a commercially available expanded graphite (EG). The infrared spectra and the surface energy measurements indicated better oxidation and higher surface energy of the graphite modified by mixed acids followed by high temperature treatment (GO). Interlayer space and surface area were increased as a result. EG possessed higher surface area. GO was found to distribute in finer tactoids of average thickness of 25 nm in the matrix, as compared with the unmodified graphite (UG), having average tactoid thickness more than 40 nm along with aggregation. EG also showed finer dispersion in the EVA matrix with some network formation. The dynamic mechanical and the mechanical properties were superior at the 2 wt % concentration of the GO, beyond which the improvement was less, possibly because of aggregation of GO. Greater EVA‐GO interaction at 2 wt % concentration was also supported from the swelling analysis, thermal conductivity, and the thermo‐oxidative degradation data of the hybrid composites. The melt viscosity was lower at 2 wt % GO concentration. EG based nanocomposites registered similar properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrical and mechanical properties of expanded graphite‐reinforced high‐density polyethylene

High‐density polyethylene (HDPE) was reinforced with expanded and untreated graphite in a melt‐compounding process. Viscosity increased upon addition of graphite phase, with the expanded graphite (EG) showing more dramatic rise than the untreated graphite (UG) in viscosity. The increase in viscosity was attributed to the increased surface‐to‐volume ratio for the EG filler after acid treatment. Electrical conductivity also increased from that pertaining to an insulator to one characteristic of a semiconductor. The EG system showed a lower percolation threshold for transition in conductivity compared to that in the UG system. DSC results indicated that the fillers acted as a nucleating agent in inducing the crystallization of HDPE in the composites. However, the overall degree of crystallinity and melting temperature of HDPE decreased with the addition of EG and UG. Mechanical properties improved as a function of filler content but the overall enhancement was not impressive. It was conjectured that the filler–matrix interface was not optimized in the melt‐mixing process. However, the role of EG as a reinforcement phase for both electrical and mechanical properties was unambiguously established. The EG composites demonstrated potentially useful attributes for antistatic, barrier, mechanical, electrical, and cost‐effective applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:2781–2788, 2004     

Polystyrene–fluorohectorite nanocomposites prepared by melt mixing with and without latex precompounding: Structure and mechanical properties

Sodium fluorohectorite (FH) was dispersed in polystyrene (PS) by direct melt blending with and without a master batch composed of PS and FH and produced by latex compounding. FH was not intercalated by PS when it was prepared by direct melt compounding. In contrast, FH was well dispersed (mostly intercalated) in PS via the PS‐latex‐mediated predispersion of FH following the master‐batch route. The dispersion of FH was studied with transmission and scanning electron microscopy and X‐ray diffraction techniques and discussed. The nanocomposites produced by the master‐batch technique outperformed the directly melt‐compounded microcomposites with respect to stiffness, strength, and ductility according to dynamic mechanical analysis and static tensile tests. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

In situ dynamic vulcanization process in preparation of electrically conductive PP/EPDM thermoplastic vulcanizate/expanded graphite nanocomposites: Effects of state of cure

In situ melt dynamic vulcanization process has been employed to prepare electrically conductive polypropylene (PP)/ethylene–propylene–diene rubber (EPDM) (40/60 wt %) thermoplastic vulcanizates (TPVs) incorporated by expanded graphite (EG) as a conductive filler. Maleic anhydride grafted PP (PP‐g‐MAH) was used as compatibilizer and a sulfur curing system was designed and incorporated to vulcanize the EPDM phase during mixing process. Developed microstructures were characterized using scanning electron microscopy (SEM), melt rheomechanical spectroscopy (RMS), X‐ray diffraction (XRD), and transmission electron microscopy (TEM) and were correlated with electrical conductivity behavior. For comparison, another class of TPV/EG nanocomposites was fabricated using a commercially available PP/EPDM‐based TPV via both direct and masterbatch melt mixing process. Conductivity of the nanocomposites prepared by in situ showed no significant change during dynamic vulcanization till the mixing torque reached to the stationary level where micro‐morphology of the cured rubber droplets was fully developed, and conductivity abrupt was observed. In situ cured nanocomposites showed higher insulator to conductor transition threshold (3.15 vol % EG) than those based on commercially available TPV. All electrically conductive in situ prepared TPV nanocomposites exhibited reinforced melt elasticity with pseudosolid‐like behavior within low frequency region in dynamic melt rheometry indicating formation of physical networks by both EG nanolayers and crosslinked EPDM droplets. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

High‐performance antistatic ethylene–vinyl acetate copolymer/high‐density polyethylene composites with graphene nanoplatelets coated by polyaniline

Graphene nanoplatelets coated by polyaniline (GNP@PANI) and ethylene–vinyl acetate (EVA) copolymer–high‐density polyethylene (HDPE) were used for the first time to prepare high‐performance antistatic composites through an effective method that combined solution mixing and melt blending. GNP@PANI nanocomposites were fabricated by in situ polymerization to improve the dispersion of graphene nanoplatelets (GNPs) in the EVA–HDPE matrix and the compatibility between the GNPs and the EVA–HDPE matrix. The GNP@PANI nanocomposites and EVA were first prepared as a premix through solution mixing, and then, the premix and HDPE were prepared as highly antistatic composites through melt blending. The dispersion of the GNPs in the EVA–HDPE matrix and the compatibility between the GNPs and the EVA–HDPE matrix were confirmed by field emission scanning electron microscopy and transmission electron microscopy observations. The GNP@PANI–EVA–HDPE composites met the requirements for antistatic materials when the content of the GNP@PANI nanocomposites was 5 wt % with only about 1 wt % GNPs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45303.     

Effects of crystallization on dispersion of carbon nanofibers and electrical properties of polymer nanocomposites

Polymer nanocomposites filled with low volume fractions of carbon nanofibers (CNFs) were prepared by melt‐compounding. Three types of polymers with different crystallization behavior, i.e., weakly‐crystallized low density polyethylene (LDPE), strongly crystallized high density polyethylene (HDPE) and amorphous polystyrene (PS), were selected as matrices for the nanocomposites. The effects of polymer crystallization on the dispersion of CNFs were examined. Optical and electron microscopic examinations revealed that the dispersion of CNFs in the nanocomposite matrices was strongly depended on the crystallization behavior of polymer matrices. The CNFs were found to disperse uniformly in weakly crystallized LDPE and amorphous PS matrices, but agglomerated in HDPE due to its strong crystallization tendency. Such a distinct dispersion behavior of CNFs in polymers had a profound effect on the electrical properties of the nanocomposites investigated. The PS/CNF nanocomposites exhibited the lowest percolation threshold. The HDPE/CNF nanocomposites showed the largest percolation threshold due to the CNF agglomeration within the amorphous phase of HDPE. POLYM. ENG. SCI., 48:177–183, 2008. © 2007 Society of Plastics Engineers     

Influence of twin-screw extrusion conditions on the dispersion of multi-walled carbon nanotubes in a poly(lactic acid) matrix

Twin-screw extrusion using a co-rotating Berstorff ZE25 extruder was applied to disperse multi-walled carbon nanotubes (MWNT) in poly(lactic acid) (PLA). The masterbatch dilution technique was used whereas four different masterbatches were produced under variation of MWNT content, screw profile, temperature profile, and rotation speed which then were diluted to composites with 0.75 wt% MWNT under varied process conditions. The state of dispersion was investigated by light microscopy from which a dispersion index was quantified. Transmission electron microscopy was performed to observe the MWNT dispersion and network formation in the sub-micron scale.The state of MWNT dispersion within the diluted composites was predominated by the state of filler dispersion in the masterbatches. High rotation speed (500 rpm) that still ensures a certain residence time of the melt combined with a screw profile containing mainly mixing elements were found to be highly convenient to disperse and distribute the MWNT in the PLA matrix as well during masterbatch production as the dilution step. The temperature profile showed less influence, however, an increasing profile resulted in slightly better nanotube dispersions. By means of these processing conditions a percolation set was performed indicating an electrical percolation threshold below 0.5 wt% MWNT content as measured on compression molded samples.     

Mechanical and functional properties of composites based on graphite and carboxylated acrylonitrile butadiene rubber

In this study, carboxylated acrylonitrile butadiene rubber (xNBR)/expanded graphite (EG) nanocomposites were prepared with a latex compounding technique by ultrasonic stirring. The dispersion of EG in the xNBR matrix was investigated with transmission electron microscopy, scanning electron microscopy, and X‐ray diffraction analysis. EG could be exfoliated into lots of nanosheets dispersing in the xNBR matrix. More EG loading resulted in the presence of a few incompletely exfoliated agglomerates. The mechanical properties (hardness, tensile modulus, and tensile strength) of the xNBR/EG composites were determined. Dynamic mechanical thermal analysis was also performed, and it showed that the nanosheets of EG somewhat immobilized the motion of rubber macromolecular chains and led to the shifting and broadening of the tan δ peak toward higher temperatures. Many other functional properties of EG‐filled xNBR composites were studied, and it was established that the composites had excellent electrical conductivity as well as gas‐barrier and wear properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010