A morphological study on the migration and selective localization of graphene in the PLA/PMMA blends

Nano‐filled polymer blends offer the opportunity to obtain materials with fine‐tuned properties. In this work, the dispersion and localization behavior of graphene nanoplate (GNP) and graphene oxide (GO) in solution mixed blends of polylactic acid (PLA) and polymethyl methacrylate (PMMA) were investigated. The blends were prepared by using different mixing sequences to investigate the effect of kinetics parameters and surface chemistry of filler as well as thermodynamics affinity on the localization of fillers. Field Emission Scanning Electron Microscopy (FESEM) and Rheometric Mechanical Spectroscopy (RMS) were employed. In addition, graphene materials were compared by Fourier transform infrared and Raman spectroscopy as well as elemental analysis characterization. Results showed that depending on the mixing sequence, the GNPs were localized in the both phases and interface through migration to reach thermodynamics equilibrium. However, GO localization was significantly affected by the mixing sequence due to better interaction with the polymer phases. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43799.     

Synthesis of polypropylene‐grafted graphene and its compatibilization effect on polypropylene/polystyrene blends

Polypropylene‐graft‐reduced graphene oxide (PP‐g‐rGO) was synthesized and used as a novel compatibilizer for PP/polystyrene (PP/PS) immiscible polymer blends. SEM observation revealed an obvious reduction of the average diameter for the dispersed PS phase with the addition of PP‐g‐rGO into a PP/PS (70/30, w/w) blend. The compatibilization effect of PP‐g‐rGO will subsequently lead to the enhancement of the tensile strength and elongation at break of the PP/PS blends. The compatibilizing mechanism should be ascribed to the fact that PP‐g‐rGO can not only adsorb PS chains on their basal planes through π‐π stacking but also exhibit intermolecular interactions with PP through the grafted PP chains. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40455.     

Strategies for interfacial localization of graphene/polyethylene-based cocontinuous blends for electrical percolation

We have investigated melt blending approaches to interfacial localization of few-layer graphene in cocontinuous polymer blends with polyethylene as one of the components. When linear low-density polyethylene (LLDPE)/polypropylene (PP) or high-density polyethylene (HDPE)/polylactic acid (PLA) and graphene were mixed all together, graphene preferred polyethylene over PP or PLA. When PP and graphene were premixed and blended with polyethylene, some graphene was trapped at the blend interface but not enough to cover the large interfacial area. In contrast, an ultralow electrical percolation was achieved (< 0.1 vol%) in HDPE/PLA blend due to smaller interfacial area. In another approach, polystyrene was added as a tertiary minor component to HDPE/PLA blends. This continuous interfacial layer containing graphene led to a low electrical percolation threshold (< 0.2 vol%). From these investigations, we suggest general ways to reduce a percolation threshold by kinetic control of the morphology of cocontinuous polymer blends.     

Morphological properties,rheological behaviors,and phase interaction of nylon 11/polypropylene blends by in situ reactive compatibilization and dispersion through polyhydroxybutyrate

The current research discusses the reactive compatibilization of nylon 11 (PA11) and polypropylene (PP) using maleic anhydride grafted PP (PP-g-MA) through an extruder. PP phase is dispersed in PA11 by coalescence and droplet break-up mechanism by using polyhydroxybutyrate (PHB) as a dispersion agent that induces uniform interaction between the blend components. The reactive compatibilization ensures the mixing of polymers, and the consistent interaction of phases is controlled by dispersion. All of the blends were processed through melt processing at different compositions using a twin-screw extruder. Scanning electron microscopy was used to determine the morphologies of the binary and ternary blends. Surface tension and interfacial tension of the homopolymer characterizes the interaction of the polymers at interphase. The interaction of PHB/PA11 appeared preferable than that of PHB/PP, elaborating on the efficient dispersion and droplet formation of the PP phase. The compatibilizer maleic anhydride grafted PP (PP-g-MA) imparts a drastic effect on the compatibility of PA11-PP and PA11-PHB-PP blends and reduces PP phase particle size, which indicates the affinity of PHB and PP. The encapsulation of PP by PHB was seen in the expectation of minimum free energy models. The rheological measurements were used to understand the phase separation within blends. These measurements were also applied to understand the interaction between PA11-PP-PHB phases. The modulus values and viscosity ratio of the blends were measured to follow the chain relaxation in the melt. In the Cole–Cole plot, it was found that the reduction in PP phase size influences the relaxation of chains of blends.     

The effects of surface-modified graphene nanoplatelets on the sliding wear properties of basalt fibers-reinforced epoxy composites

Possessing unique designs and properties absent in conventional materials, nanocomposites have made a remarkable imprint in science and technology. This is particularly true regarding the polymer matrix composites when they are further reinforced with nanoparticles. In this study, the effects of different weight percentages (0, 0.1, 0.2, 0.3, 0.4, and 0.5) of surface-modified graphene nanoplatelets (GNPs) on the microhardness and wear properties of basalt fibers/epoxy composites were investigated. The GNPs were surface modified by silane, and the composites were made by the hand lay-up method. The wear tests were conducted under two different loads of 20 and 40 N. The best wear properties were achieved at 0.3 wt % GNPs as a result of the GNPs' self-lubrication property and the formation of a stable transfer/lubricating film at the pin and disk interface. Moreover, the friction coefficient was lower at the higher normal load of 40 N. The microscopic studies by FESEM and SEM showed that the presence of GNPs up to 0.3 wt % led to the stability of the transfer/lubricating film by enhancing the adhesion of the basalt fibers to the epoxy resin. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47986.     

Effect of montmorillonite modification on the behaviour of polyamide/polystyrene blends

BACKGROUND: In nanocomposites with multiphase matrices, the addition of layered silicate not only has a reinforcing effect, but also changes significantly the morphology, namely the size and the structure of the dispersed phase. In this paper, we focus on systems with polyamide 6 (PA6)/polystyrene (PS) matrices. The effect of clay was studied over the whole composition range together with the simultaneous variation of basic parameters influencing the structure and mechanical behaviour, i.e. the clay treatment type and mixing protocol. RESULTS: At all compositions, remarkable refinements of both particulate and co‐continuous structures by clay were found. This effect and a significant shift of the glass transition temperature of blend components were more pronounced for clay with less polar treatment as a result of distinct localization of clay in the interfacial area (due to its lower affinity for PA6 phase). An increase in modulus was found at all compositions, whereas strength and toughness were enhanced at low PS contents only, as a consequence of small particle size and enhanced interfacial bonding. CONCLUSIONS: The results presented indicate that nanosilicates can effectively influence the structure and properties of PA6/PS blends. Copyright © 2008 Society of Chemical Industry     

Structure development via reaction-induced phase separation in tetrafunctional epoxy/polysulfone blends

For the cure process of tetrafunctional epoxy resin/polysulfone(EP/PSF) blends, we investigated the effect of cure temperature and blend composition on the phase separation behavior by light scattering and the structure development during cure by an optical microscope. The EP/PSF blend without the curing agent was shown to exhibit an LCST-type phase behavior (LCST = 241°C). At the early stage of curing, the EP/PSF blend was homogeneous at the cure temperature. As the cure reaction proceeded, the blend was thrust into a two-phase regime by the LCST depression caused by the increase in a molecular weight of the epoxy-rich phase, and the phase separation took place via a spinodal decomposition (SD) or nucleation and growth (NG) mode, depending on the blend composition and the cure temperature. When cured isothermally at 220°C, the blend exhibited a sea-island morphology formed via the NG mode below 5 wt % PSF content, while the SD mode prevailed above 20 wt % PSF content. At the intermediate composition range, combined morphology with both sea-island and cocontinuous structure was observed. On the other hand, by lowering the cure temperature and/or increasing the content of PSF component, a two-phase structure with a shorter periodic distance was obtained. It seems that the rate of the phase separation is considerable reduced, while that of the cure reaction is not as much. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2233–2242, 1997     

Dielectric behavior of PVDF/POMA blends that have a low doped POMA content

The real (ε′) and imaginary (ε″) components of the complex permittivity of blends of PVDF [poly(vinylidene fluoride)] with POMA [poly(o‐methoxyaniline)] doped with toluenosulfonic acid (TSA) containing 1, 2.5, and 5 wt % POMA–TSA were determined in the frequency interval between 10² and 3 × 10⁶ Hz and in the temperature range from ?120 up to 120°C. It was observed that the values of ε′ and ε″ had a greater increase with the POMA–TSA content and with a temperature in the region of frequencies below 10 kHz. This effect decreased with frequency and it was attributed to interfacial polarization. This polarization was caused by the blend heterogeneity, formed by conductive POMA–TSA agglomerates dispersed in an insulating matrix of PVDF. The equation of Maxwell–Garnett, modified by Cohen, was used to evaluate the permittivity and conductivity behavior of POMA–TSA in the blends. A strong decrease was observed in POMA–TSA conductivity in the blend, which was bigger the lower the POMA–TSA content in the blend. This decrease could have been caused either by the POMA dedoping during the blend preparation process or by its dispersion into the insulating matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 752–758, 2003     

Electromagnetic interference shielding behavior of chemically and thermally reduced graphene based multifunctional polyurethane nanocomposites: A comparative study

This article presents the effect of exfoliation, dispersion, and electrical conductivity of graphene sheets onto the electrical, electromagnetic interference (EMI) shielding, and gas barrier properties of thermoplastic polyurethane (TPU) based nanocomposite films. The chemically reduced graphene (CRG) and thermally reduced/annealed graphene (TRG) having Brunauer–Emmett–Teller surface areas of 18.2 and 159.6 m²/g, respectively, when solution blended with TPU matrix using N,N-dimethylformamide as a solvent. Graphene sheets based TPU nanocomposites have been evaluated and compared for EMI shielding in Ku band, electrical conductivity, and gas barrier property. TRG/TPU nanocomposite films showed excellent gas barrier against N₂ gas as compared to CRG/TPU. The EMI shielding effectiveness for neat CRG and TRG graphene sheets is found to be −80, −45 dB, respectively, at 2 mm thickness. The EMI shielding data revealed that TRG/TPU nanocomposites showed better shielding at lower concentration (10 wt %), while CRG displayed better attenuation at higher concentrations. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47666.     

Mechanical properties and morphology of LCP/ABS blends compatibilized with a styrene–maleic anhydride copolymer

A co‐polyester liquid crystalline polymer (LCP) was melt blended with an acrylonitrile–butadiene–styrene copolymer (ABS). LCP fibrils are formed and a distinct skin/core morphology is observed in the injection moulded samples. At higher LCP concentration (50 wt%), phase inversion occurs, where the dispersed LCP phase becomes a co‐continuous phase. While the tensile strength and Young's modulus remain unchanged with increasing LCP content up to 30 wt% LCP, a significant enhancement of the modulus at 50 wt% LCP is observed due to the formation of co‐continuous morphology. The blend modulus is lower than the values predicted by the rule of mixtures, suggesting a poor interface between the LCP droplets and ABS matrix. A copolymer of styrene and maleic anhydride (SMA) was added in the LCP/ABS blends during melt blending. It is observed that SMA has a compatibilizing effect on the blend system and an optimum SMA content exists for mechanical properties enhancement. SMA improves the interfacial adhesion, whereas excess of SMA reduces the LCP fibrillation. Copyright © 2003 Society of Chemical Industry     

Effects of olefin‐based compatibilizers on the morphology,thermal and mechanical properties of ABS/polyamide‐6 blends

In this study, commercially available epoxidized and maleated olefinic copolymers, EMA‐GMA (ethylene‐methyl acrylate‐glycidyl methacrylate) and EnBACO‐MAH (ethylene‐n butyl acrylate‐carbon monoxide‐maleic anhydride), were used at 0, 5, and 10% by weight to compatibilize the blend composed of ABS (acrylonitrile‐butadiene‐styrene) terpolymer and PA6 (polyamide 6). Compatibilizing performance of these two olefinic polymers was investigated from blend morphologies, thermal and mechanical properties as a function of blend composition, and compatibilizer loading level. Scanning electron microscopy (SEM) studies showed that incorporation of compatibilizer resulted in a fine morphology with reduced dispersed particle diameter at the presence of 5% compatibilizer. The crystallization behavior of PA6 phase in the blends was explored for selected blend compositions by differential scanning calorimetry (DSC). At high compatibilizer level a decrease in the degree of crystallization was observed. In 10% compatibilizer containing blends, formation of γ‐crystals was observed contrary to other compatibilizer compositions. The behavior of the compatibilized blend system in tensile testing showed the negative effect of using excess compatibilizer. Different trends in yield strengths and strain at break values were observed depending on compatibilizer type, loading level, and blend composition. With 5% EnBACO‐MAH, the blend toughness was observed to be the highest at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 926–935, 2007     

Compatibilization of immiscible nylon 6/poly(vinylidene fluoride) blends using graphene oxides

A new strategy to compatibilize immiscible blends is proposed, using graphene oxide (GO) nanosheets taking advantage of their unique amphiphilic structures. When 0.5 or 1 wt% GOs were incorporated in immiscible nylon 6/poly(vinylidene fluoride) (PVDF) (90/10 wt%) blends, the dimension of PVDF dispersed particles was markedly reduced and became more uniform, revealing a well‐defined compatibilization effect of GOs on the immiscible blends. Correspondingly, the ductility of the compatibilized blends increased several times compared with uncompatibilized immiscible blends. In order to explore the underlying compatibilization mechanism, Fourier transform infrared and Raman spectra were applied to suggest that the edge polar groups of GOs can form hydrogen bonds with nylon 6 while the basal plane of GOs can interact with electron‐withdrawing fluorine on PVDF chains leading to the so‐called charge‐transfer C–F bonding. In this case, GOs exhibit favorable interactions with both nylon 6 and PVDF phase, therefore stabilizing the interface during GO migrations from PVDF/GO masterbatch to nylon 6 phase, which can minimize the interfacial tension and finally lead to compatibilization effects. Obviously, this work may open a broad prospect for GOs to be widely applied as a new compatibilizer in industrial fields. © 2012 Society of Chemical Industry     

Piezoresistive behavior of graphene nanoplatelets/carbon black/silicone rubber nanocomposite

Silicon rubber (SR) filled with carbon black (CB) and carbon black (CB)/graphene nanoplatelets (GNPs) hybrid fillers are synthesized via a liquid mixing method. The effects of filler type on the electrical properties and piezoresistive properties (near the region of the percolation) of the conductive SR composites are studied. It is suggested that the conductivity of the composite filled with CB/GNPs hybrid fillers in the mass ratio of 2 : 4 is much higher than that in other ratio. Percolation threshold for CB/GNPs/SR is found to be 0.18 volume fractions lower than CB/SR. Moreover, force rang and linearity of GNPs/CB/SR is higher than CB alone filling system. And the repeatability of the GNPs/CB/SR composites is better than CB/SR. Not repetitive index () of them is 0.1 and 0.18, respectively. The results suggest that the GNPs/CB/SR composites provide a new route toward fabrication of flexible piezoresistive sensors with high performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39778.     

Use of oxazoline functionalized polyolefins and elastomers as compatibilizers for thermoplastic blends

Oxazoline functionalized polypropylene, polyethylene, ethylene propylene copolymer (E/P), and styrene ethylene/butylene styrene copolymer (SEBS) were studied as compatibilizers in blends of polyolefins with polyesters and polyamides. The blends investigated were polypropylene/polyamide 6, polypropylene/polybutylene terephtalate, and polyethylene/polyamide 6, with engineering thermoplastic contents of 30 wt %. The blends were prepared in a twin-screw midiextruder, and injection molded with a mini-injection molding machine. The effect of compatibilizing on the morphology and mechanical properties of the blends was of interest. Compatibilization substantially improved the toughness of all tested blends. Their strength and stiffness remained at the level of the binary blends when polypropylene or polyethylene based compatibilizers were used, but slightly decreased with other compatibilizers. Morphological studies showed that the particle size was reduced, and the adhesion of the dispersed phase to the matrix improved by compatibilization. The effect of unfunctionalized polyethylene, polypropylene, E/P, and SEBS was also studied to compare the compatibilizers with them. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1923–1930, 1998     

Reduced graphene oxide reinforced PET/PBT nanocomposites: Compatibilization and characterization

This research work focused on the effects of different compatibilizers on the properties of reduced graphene oxide (rGO) reinforced poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) nanocomposites. The samples were prepared via melt compounding and injection molding methods. The Joncryl and glycidyl isooctyl polyhedral oligomeric silsesquioxane (GPOSS) were used as compatibilizers at different loading levels (0.5%-4%). The structural, thermal, mechanical, morphological, and electrical properties of the nanocomposites were investigated. The Fourier transform infrared analysis results revealed that no significant interaction was observed when GPOSS was added. On the other hand, there were more obvious changes in the peaks of the nanocomposite containing Joncryl. The thermal results showed that the compatibilizer addition caused small changes while rGO addition did not considerably affect the thermal stability of blend. The glass transition temperature of the nanocomposite significantly decreased with the addition of GPOSS. The tensile test indicated that compatibilizers improved the mechanical performance of PET/PBT/rGO nanocomposite.     

Engineering investigation for the size effect of graphene oxide derived from graphene nanoplatelets in polyurethane composites

In this study, commercial polyurethane (PU) and graphene nanoplatelets (GnP) and their derivative graphene oxide (GO) were used to fabricate PU composites. The size effect of fillers on mechanical properties and anti-corrosion performance of as-prepared composites was thoroughly investigated. It was found that GO was more uniformly dispersed in the PU matrix than GnP due to its compatibility with PU. Furthermore, GO led to the higher mechanical properties and anti-corrosion performance than PU/GnP composites, and the properties were strongly dependant on the size of the GO. Specifically, incorporating large sized GO (GO-M25) in 0.5 wt% indicated the highest average synergetic tensile modulus up to 53% from the neat PU and the lowest corrosion rate of 0.001 MPY (1 MPY = 0.547 g · m⁻² · d⁻¹). This phenomenon was attributed to the fact that the larger size of GO is not only uniformly dispersed within the PU matrix but also enables interaction between PU and GO. Conversely, PU composites incorporated with the small sized GO (GO-C750) did not show elastic behaviour from 0.1 to 0.5 wt% of the filler. This is due to the fact that the high surface area and hydrophilic functionalities of GO-C750 resulted in hard-segment content reduction in PU. This research can help in the design of a PU coating that is physically improved and that has a superior anti-corrosive capacity, particularly for pipelines in the oil-sands transportation industry.     

Effect of a styrene–butadiene copolymer on the phase structure and impact strength of polyethylene/high‐impact polystyrene blends

The effect of a styrene–butadiene block copolymer on the phase structure and impact strength of high‐density and low‐density polyethylene/high‐impact polystyrene blends with various compositions was studied. For both the blends, the type of the phase structure was not affected by addition of a styrene–butadiene compatibilizer. The localization and structure of the compatibilizer in the blends were dependent on their composition. Addition of the compatibilizer improved impact strength of the blends in the whole concentration range. The improvement was the largest for blends with a low amount of the minor phase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 570–580, 2001     

石墨烯的制备及石墨烯/PVDF合材料介电性能的研究

通过Staudenmaier法制备了完全氧化的氧化石墨(GO),并通过高温热膨胀制备了单层石墨烯(graphene).用FT-IR、TG和XRD对GO的氧化程度、含氧官能团进行了表征;Graphene的XRD测试结果证明了单层石墨的存在.利用超声共混法制备了graphene/PV DF介电纳米复合材料.介电性能的测试表...     

Enhancing the mechanical,morphological, and rheological behavior of polyethylene/polypropylene blends with maleic anhydride-grafted polyethylene

This is the first study to showcase the use of maleic anhydride-grafted polyethylene (MAPE) to compatibilize polyethylene (PE)-rich blends, where polypropylene (PP) represents the minor phase. By first mixing PP with MAPE, and then adding PE, MAPE was assumed to be localized at the PE/PP interface. Microscopy analysis confirmed that MAPE led to a remarkably fine PE/PP/MAPE morphology, with PP being uniformly dispersed into PE and having an average diameter 267% smaller than that in the PE/PP blend. According to mechanical and rheological tests, this translated into a 14%, 20%, and 14% enhancement of tensile strength, tensile modulus, and tensile toughness, respectively, as well as a 10% and 20% drop in PE/PP viscosity mismatch and interfacial tension, respectively. Finally, PE/PP/MAPE tensile toughness and elongation at break were greater than those of virgin PP, while PE/PP/MAPE strength and stiffness were similar to the ones of neat PP. Therefore, this study provides industries with the possibility to utilize products rich in PE instead of those made of more expensive PP, while still keeping the level of performance high; hence, creating a paradigm shift in the development of advanced lightweight polyolefin materials with tuned functionalities.