Mechanical,thermal, and conductivity performances of novel thermoplastic natural rubber/graphene nanoplates/polyaniline composites

Conventional polymer blending has a shortcoming in conductivity characteristic. This research addresses the preparation of conductive thermoplastic natural rubber (TPNR) blends with graphene nanoplates (GNPs)/polyaniline (PANI) through melt blending using an internal mixer. The effect of PANI content (10, 20, 30, and 40 wt %) on the mechanical and thermal properties, thermal and electrical conductivities, and morphology observation of the TPNR/GNPs/PANI nanocomposites was investigated. The results showed that the tensile and impact properties as well as thermal conductivity of nanocomposite had improved with the incorporation of 3 wt % of GNPs and 20 wt % of PANI as compared to neat TPNR and reduced with further increase of the PANI content. It was observed that the GNPs and PANI acted as a critical component to improve the thermal stability and electrical conductivity of the TPNR/GNPs/PANI nanocomposites. The most improved conductivity of 5.22 E-5 S/cm was observed at 3 wt % GNPs and 40 wt % PANI. Variable-pressure scanning electron microscopy micrograph revealed the good interaction and distribution of GNPs and PANI within TPNR matrix at PANI loadings lower than 30 wt %. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48873.     

Enhanced thermal conductivity of PLA‐based nanocomposites by incorporation of graphite nanoplatelets functionalized by tannic acid

Enhancing thermal conductivity of polymeric nanocomposites remains a great challenge because of the poor compatibility between nanofillers and the polymeric matrix and the aggregation effect of nanofillers. We report the enhanced thermal conductivity of poly(lactic acid) (PLA)‐based nanocomposites by incorporation of graphite nanoplatelets functionalized by tannic acid. Graphite nanoplatelets (GNPs) were noncovalently functionalized with tannic acid (TA) by van der Waals forces and π–π interaction without perturbing the conjugated sp² network, thus preserving the high thermal conductivity of GNPs. PLA‐based nanocomposites with different contents of TA‐functionalized GNPs (TA‐GNPs) were prepared and characterized, and the influences of TA‐GNPs content on the morphologies, mechanical properties, and thermal properties of the composites were investigated in detail. TA‐GNPs remarkably improved the thermal conductivity of PLA up to 0.77 W/(m K), showing its high potential as a thermally conductive filler for polymer‐based nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46397.     

Processing–morphology–property relationships of polypropylene–graphene nanoplatelets nanocomposites

Polypropylene (PP) nanocomposites reinforced with graphene nanoplatelets (GNPs) were prepared via melt extrusion. A special sheet die containing with two shunt plates was designed. The relationships among the flow field of the special die, exfoliation, and dispersion morphology of the GNPs in PP and the macroscopic properties of the nanocomposites were analyzed. Flow field simulation results show that the die with shunt plates provided a high shear stress, high pressure, and high velocity. The differential scanning calorimetry, X‐ray scattering, and electron microscopy results reveal that the nanocomposites prepared by the die with the shunt plates had higher crystallinity values and higher exfoliation degrees of GNPs. The orientation of the GNPs parallel with the extrusion direction was also observed. The nanocomposites prepared by the die with shunt plates showed a higher electrical volume conductivity, thermal conductivity, and tensile properties. This indicated that the high shear stress exfoliated the GNPs effectively to a thinner layer and then enhanced the electrical, thermal, and mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44486.     

Toward a better understanding of multifunctional cement-based materials: The impact of graphite nanoplatelets (GNPs)

The impact of graphite nanoplatelets (GNPs) on the physical and mechanical properties of cementitious nanocomposites was investigated. A market-available premixed mortar was modified with 0.01% by weight of cement of commercial GNPs characterized by two distinctively different aspect ratios.The rheological behavior of the GNP-modified fresh admixtures was thoroughly evaluated. Hardened cementitious nanocomposites were investigated in terms of density, microstructure (Scanning Electron Microscopy, SEM and micro–Computed Tomography, μ-CT), mechanical properties (three-point bending and compression tests), and physical properties (electrochemical impedance spectroscopy, EIS and thermal conductivity measurements). At 28 days, all GNP-modified mortars showed about 12% increased density. Mortars reinforced with high aspect ratio GNPs exhibited the highest compressive and flexural strength: about 14% and 4% improvements compared to control sample, respectively. Conversely, low aspect ratio GNPs led to cementitious nanocomposites characterized by 36% decreased electrical resistivity combined with 60% increased thermal conductivity with respect to the control sample.     

Synergistic thermal conductivity enhancement of PC/ABS composites containing alumina/magnesia/graphene nanoplatelets

Graphene nanoplatelets (GNPs) have attracted considerable attention in the field of thermal management materials due to their unique structure and exceptional thermal conductive properties. In this work, we demonstrate a significant synergistic effect of GNPs, alumina (Al₂O₃), and magnesia (MgO) in improving the thermal conductivity of polycarbonate/acrylonitrile‐butadiene‐styrene polymer alloy (PC/ABS) composites. The thermal conductivity of the composites prepared through partial replacement of Al₂O₃ and MgO with GNPs could increase dramatically compared with that without GNPs. The maximum thermal conductivity of the composite is 3.11 W mK⁻¹ at total mass fraction of 70% with 0.5 wt% GNPs loading. It increases 60% compared with that without GNPs (1.95 W mK⁻¹). The synergistic effect results from the compact packing structure formed by Al₂O₃/MgO and the bridging of GNPs with Al₂O₃/MgO, thus promoting the formation of effective thermal conduction pathways within PC/ABS matrix. More importantly, together with the intrinsically high thermal conductivity of GNPs, boosted and effective pathways for phonon transport can be created, thus decrease the thermal resistance at the interface between fillers and PC/ABS matrix and increase the thermal conductivity of composites. POLYM. COMPOS., 38:2221–2227, 2017. © 2015 Society of Plastics Engineers     

Tailoring the properties of spark plasma sintered SiAlON containing graphene nanoplatelets by using different exfoliation and size reduction techniques: Anisotropic mechanical and thermal properties

SiAlON ceramics are intensively used in different areas but still there is a need to improve the mechanical and thermal properties as well as ease of machinability and reduce the weight. In this study, the effect of graphene nanoplatelets (GNPs) exfoliation and dispersion techniques on the microstructure and properties of SiAlON ceramics were investigated. For this purpose, 2, 4 and 8 wt% GNPs were dispersed by using traditional sonication and newly proposed microfluidization techniques. Then, composites were densified in spark plasma sintering (SPS) furnace. Scanning electron microscope (SEM), x-ray diffraction analyses (XRD) and property measurements were performed in through-plane and in-plane directions. The microfluidization technique found to be more effective than sonication for the exfoliation, size reduction and homogenization of GNPs. Addition of GNPs prepared by both techniques increased the fracture toughness and in-plane direction thermal conductivity whereas decreased the hardness and through-plane direction thermal conductivity of the SiAlON.     

Thermal and mechanical properties of wood‐plastic composites filled with multiwalled carbon nanotubes

Wood plastic composites (WPCs) are a new generation of green composites which can come mostly from recycled materials. This study focuses on the thermal conductivity and mechanical properties of WPCs filled multiwalled carbon nanotubes (MWCNTs). The thermal conductivity increases with increasing amount of MWCNTs and decreases with increasing temperature. By comparing the temperature changes of specimens during heating and cooling processes, WPCs with higher MWCNTs contents presents higher average temperature when heated until equilibrium temperature. From differential scanning calorimeter test, the melting temperatures of MWNTs reinforced WPCs change slightly, but the crystallinity is reduced with the increasing amount of MWCNTs. Based on a series of laboratory experiments carried out to investigate the mechanical performance, it can be concluded that the addition of the MWCNTs decreases the mechanical properties of WPCs due to the decohesion between thermoplastic matrix and MWCNTs particles under stress. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46308.     

Influence of filler type and content on thermal conductivity and mechanical properties of thermoplastic compounds

Combining thermal conductivity with electrical isolation is a very interesting topic for electronic applications in order to transfer the generated heat. Typical approaches combine thermally conductive fillers with a thermoplastic matrix. The aim of this work was to investigate the influence of different fillers and matrices on the thermal conductivity of the polymer matrix composites. In this study, various inorganic fillers, including aluminum oxide (Al₂O₃), zinc oxide (ZnO), and boron nitride (BN) with different shapes and sizes, were used in matrix polymers, such as polyamide 6 (PA6), polypropylene (PP), polycarbonate (PC), thermoplastic polyurethane (TPU), and polysulfone (PSU), to produce thermally conductive polymer matrix composites by compounding and injection molding. Using simple mathematical models (e.g., Agari model, Lewis–Nielson model), a first attempt was made to predict thermal conductivity from constituent properties. The materials were characterized by tensile testing, density measurement, and thermal conductivity measurement. Contact angle measurements and the calculated surface energy can be used to evaluate the wetting behavior, which correlates directly with the elastic modulus. Based on the aforementioned evaluations, we found that besides the volume fraction, the particle shape in combination with the intrinsic thermal conductivity of the filler has the greatest influence on the thermal conductivity of the composite.     

Thermal conductivity and lap shear strength of GNP/epoxy nanocomposites adhesives

The addition of graphene nanoplatelets (GNPs) into the epoxy adhesives has been studied in order to increase their thermal conductivity. Thermally conductive adhesives are often used as thermal interface materials (TIMs). The incorporation of 8 and 10 wt% GNPs reinforcement caused a thermal conductivity enhancement of ~206 and ~306%, respectively. The wettability seems to decrease with low GNPs content (2–3 wt%) in comparison with the neat epoxy adhesive but the contact angle remains constant for higher GNPs contents. Lap shear strength remains constant for neat adhesives and resins doped with GNPs. The lack of enhancement of adhesive properties of doped resins is due to a weak interface reinforcement-matrix. In fact, the joint failure is in the adhesive except for high GNPs content (10 wt%) where a cohesive failure mode is observed.     

Thermal and mechanical properties of polyamide 12/graphene nanoplatelets nanocomposites and parts fabricated by fused deposition modeling

The printable polyamide 12 (PA12) nanocomposite filaments with 6 wt % graphene nanoplatelets (GNPs) for fused deposition modeling (FDM) were prepared by melting compounding and smoothly printed via a commercial FDM three‐dimensional (3D) printer. The thermal conductivity (λ) and elastic modulus (E) of 3D printed PA12/GNPs parts along to the printing direction had an increase by 51.4% and 7% than that of compression molded parts, which is due to the GNPs preferentially aligning along to the printing direction. Along with these improved properties, ultimate tensile strength of 3D printed PA12/GNPs parts was well maintained. These results indicate that FDM is a new way to achieve PA12/GNPs parts with enhanced λ over compression moulding, which could contribute to realize efficient and flexible heat management for a wide range of applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45332.     

High performance thermoplastic composites: Study on the mechanical,thermal, and electrical resistivity properties of carbon fiber‐reinforced polyetheretherketone and polyethersulphone

High temperature processing thermoplastic polymers, polyetheretherketone (PEEK) and polyethersulphone (PES), were melt blended with carbon fibers (CFs) to make composites. These composites were investigated for their mechanical, thermal, and electrical properties. Mechanical properties that are expressed in terms of storage modulus, loss, and damping were enhanced with the addition of CFs. Thermal properties were determined by DSC and TGA. These methods help to understand the effects of fiber content and fiber–matrix adhesion in the composites. Composites were also tested for their electrical and thermal conductivity because CFs leave the composites thermally and electrically conductive. CFs enhanced the crystallinity of the PEEK appreciably that in turn influenced thermal conductivity, electrical resistivity, and the stiffness of PEEK/CF (composites of PEEK with CFs). PES/CF (composites of PES with CF) shows a different behavior due to the amorphous nature of PES. The work involves one filler and two different matrices, and so it provides an interesting comparison of how matrix morphology can influence the properties of composites. POLYM. COMPOS. 28:785–796, 2007. © 2007 Society of Plastics Engineers.     

Highly compatible wood thermoplastic composites from lignocellulosic material modified in ionic liquids: Preparation and thermal properties

A study of converting chemically modified wood into thermoplastic materials was undertaken to develop a new technology platform for the effective utilization of wood‐based lignocellulosic materials. Highly substituted benzoylated spruce thermomechanical pulp (TMP) and lauroylated spruce TMP were used as components for thermoplastic composites of poly(styrene) and poly(propylene). Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) were used to characterize the interfacial morphology and thermal properties of the resultant composite filaments. The coupling of the interfacial morphology effort and that of torque analysis applied during processing indicated that the thorough modification of wood fibers by benzoylation and/or lauroylation reactions can improve the compatibility between the wood‐based lignocellulosic materials and poly(styrene) and poly(propylene). Thermal analysis showed that, with the addition of wood derivatives into poly(styrene) and poly(propylene) matrices, a slight decrease in their T_gs was observed. Furthermore, all of the prepared composites showed improved thermal stability, as revealed by TGA. The resultant thermoplastic wood composites exhibited good melting properties and were readily extruded into filaments or sheets. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Noncovalent functionalization of boron nitride and its effect on the thermal conductivity of polycarbonate composites

Polycarbonate (PC) is an engineering thermoplastic with excellent insulation and mechanical properties. However, the low thermal conductivity restricted its application in electronic devices. Hexagonal boron nitride (h ‐BN) microparticle, a promising material with high thermal conductivity, was functionalized with cationic polyacrylamide (CPAM) and introduced into PC matrix to improve the thermal conductivity. SEM and XRD analysis showed that the modified BN (CBN) particles oriented and formed thermal conductive pathways within PC matrix. The formation of large‐area oriented CBN significantly improved the thermal conductivity and thermal stability of composites. At 20 wt % CBN loading, the thermal conductivity of 0.7341 Wm^?1 K^?1 and the temperature for 5% weight loss (T ₅) of 498.6 °C were obtained, which was 3.1 times and 77 °C higher than that of pure PC, respectively. Furthermore, outstanding electrical insulation property of matrix was retained in the composites. These results revealed that PC/CBN composite was a promising material for thermal management and electrical enclosure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44978.     

Recent advances in bio‐sourced polymeric carbohydrate/nanotube composites

Nanotubes (NTs), especially carbon nanotubes (CNTs), have attracted much attention in recent years because of their large specific surface area, and their outstanding mechanical, thermal, and electrical properties. In this review we emphasize the development of fascinating properties of polymeric carbohydrate/CNT composites, particularly in terms of their mechanical and conductivity properties and potential applications. Many methods used to modify CNTs during preparation of polymeric carbohydrate/CNT composites are presented. Moreover, we also discuss the enhanced mechanical and electrical effectiveness when hybrid CNTs or halloysite nanotubes were incorporated into different carbohydrate polymer matrices. Finally, we give a future outlook for the development of polymeric carbohydrate/CNT composites as potential alternative materials for various applications including sensors, electroactive paper, electrodes, sorbents for environmental remediation, packaging film, specialty textile, and biomedical devices. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40359.     

Effects of ultrasound vibration on the structure and properties of polypropylene/graphene nanoplatelets composites

An ultrasound‐assisted extrusion system was added to melt extrusion process to prepare polypropylene (PP) nanocomposites reinforced with graphene nanoplatelets (GNPs). The relationships among the ultrasound vibration, exfoliation, and dispersion morphology of GNPs in PP matrix, the crystallinity, and the macroscopic properties of nanocomposites were investigated. The properties measurement results showed that the present of ultrasound vibrations increased the conductive properties, decreased the apparent viscosity and crystallinity of PP/GNPs nanocomposites. FESEM results revealed that the ultrasound vibration increased the exfoliation and dispersion of GNPs in PP matrix. This morphology was benefit for forming electrical and thermal network, therefore the electrical conductivity and thermal conductivity of PP/GNP nanocomposites were increased. But the powerful vibration that provided by 300 W ultrasound power would reduce the diameter of GNPs, then reduce its conductive properties. FTIR and TGA results showed that ultrasound vibration had less effect on the chemical bond and the degradation of PP/GNPs nanocomposites. POLYM. ENG. SCI., 58:377–386, 2018. © 2017 Society of Plastics Engineers     

共混顺序对石墨烯微片在PP/PA6/SEBS共混物中的选择性分布和迁移的影响

研究了聚丙烯(PP)/聚酰胺6(PA6)/氢化苯乙烯-丁二烯嵌段共聚物(SEBS)/石墨烯微片(GNPs)纳米复合材料在不同共混顺序下的微观形貌、导电及导热性能,分析了GNPs在复合体系中的选择性分布和迁移及其对复合材料性能的影响.结果表明,在PP/PA6/SEBS/GNPs共混体系中,GNPs在界面张力的作用下趋向于...     

Valorization of waste thermoset material as a filler in thermoplastic: Mechanical properties of phenolic molding compound waste‐filled PP composites

As most thermoset material, phenolic molding compound (PMC) wastes are an environmental problem. Very few recycling solutions have been proposed so far for this type of material. A mechanical recycling method to valorize these materials is proposed in this work. It relies on the use of phenolic waste as filler in thermoplastic. Such phenolic filler can increase mechanical properties (tensile, flexural) of the matrix, and be used in substitution of traditional particulate fillers such as calcium carbonate or talc. In this study, several morphological parameters influencing the final mechanical properties of a PMC‐filled polypropylene (PP) micro‐composite are studied, such as filler loading rate, particles size distribution of the filler, and interfacial adhesion between the filler and the matrix. Some structural parameters are also studied and linked with mechanical properties, such as dispersion of the filler and crystallinity of the matrix. Finally, the properties of PMC‐filled PP are compared with CaCO₃‐ and talc‐filled PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45849.     

Electrical conductivity and mechanical properties of carbon black modified polyolefinic blends influenced by phase inversion

Electrically conductive polymer composites (CPCs) containing a carbonaceous filler and a polymeric matrix have been widely researched and utilized. Immiscible polymers are often used as the matrix of CPCs, which leads to segregated structures, hence low percolation threshold and good conductivity of a material. Polymeric blends often show low mechanical properties due to the lack of affinity of the resins. A way to improve toughness of a CPC and maintain good electrical properties is mixing two immiscible yet compatible resins. In our case one of them was polyethylene and the other was an olefinic conductive thermoplastic elastomer. In this study, a correlation between conductivity, mechanical properties, and morphology of conductive blends was analyzed. Results of tensile test, conductivity measurements, and differential scanning calorimetry were juxtaposed with information of phase morphology of the blends. A relationship of drastic changes of different properties of the blends and phase inversion point was found. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45512.     

Enhanced properties of polyvinyl chloride modified by graphene reinforced thermoplastic polyurethane

Graphene sheets with a range of unusual properties and thermoplastic polyurethane (TPU ) were combined to modify polyvinyl chloride (PVC ), and the enhanced properties such as flexibility, thermal stability and mechanical properties of the PVC were investigated. In order to avoid the C ? Cl bonds in PVC being weakened, graphene was incorporated into TPU in the melting state first and then this TPU was employed as a modifier to enhance and plasticize PVC in another melt blending step. In comparison with the ternary blending method, this step‐by‐step melt blending method was more efficient and convenient. The distribution of graphene sheets in the polymer matrix is uniform and no C ? Cl bond weakened effect can be observed. Due to the similar polarity, TPU showed good compatibility with PVC and its plasticizing effect allowed a broader range of low temperature flexibility of the modified PVC matrix. Moreover, other properties of the resultant PVC matrix (PTG ‐x ) including mechanical properties, thermal stability and plasticizer migration resistance were all found to be improved. With innovative applications in mind, the development of new graphene‐based materials will certainly lead to many future advances in science and technology. © 2017 Society of Chemical Industry     

Characterisation of graphite nanoplatelets and the physical properties of graphite nanoplatelet/silicone composites for thermal interface applications

Thermally conducting and highly compliant composites were developed by dispersing graphite nanoplatelets (GNPs) into a silicone matrix by mechanical mixing. X-ray diffraction (XRD) indicates that the average thickness of the GNPs decreased from 60 to 35 nm during mechanical mixing. XRD-texture analysis demonstrated that GNP/silicone composites at 8 wt.% GNPs have a higher degree of basal plane alignment than at 20 wt.%. Differential scanning calorimetry showed that GNPs raised the curing temperature of silicone with no significant effect on the glass transition temperature. The thermal conductivity of the 20 wt.% composites reached 1.909 W/m.K, an 11-fold increase over silicone suggesting an improved dispersion compared to similar composites prepared by dual asymmetric centrifuge mixing. The percolation threshold for electrical conductivity of the composites was at ∼15 wt.%. The compressive modulus of the composite increased to twice that of silicone at 20 wt.%. The corresponding strength decreased by a factor of two compared to silicone and this can be attributed to the weak bonding at the GNP-silicone interface. Overall, these GNP/silicone composites, with a high thermal conductivity, low electrical conductivity and compliant nature are promising materials for use as thermal pads for thick gap filling thermal interface applications.