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.     

Thermal behavior of thermoplastic polymer nanocomposites containing graphene nanoplatelets

Polypropylene (PP), acrylonitrile butadiene styrene (ABS), and thermoplastic polyurethane (TPU) nanocomposites filled with 5 wt % of two different kinds of commercially available graphene nanoplatelets (GNPs) were prepared. Composites materials were characterized in terms of thermal properties (thermal conductivity and thermal stability) in order to study the effect of different fillers within different thermoplastic matrices. The exfoliation process and the mechanical properties were also investigated. We chose three different thermoplastic polymers (polyolefin, copolymer and elastomer) to cover a wide range of thermoplastic materials and identify a guideline in the use of GNPs for nanocomposite materials. No drastic differences were observed in terms of mechanical properties when the same matrices were filled with different GNPs. Concerning thermal conductivity, it was observed that the GNPs plane dimensions play a crucial role in the increase of conductive properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44814.     

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.     

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     

Mechanical,thermal, and morphological properties of graphene reinforced polycarbonate/acrylonitrile butadiene styrene nanocomposites

Nanocomposites of polycarbonate/acrylonitrile butadiene styrene (PC/ABS) with (70/30) composition containing different amounts of graphene nanoplates (GNPs) (1, 3, and 5 wt%) were prepared by melt‐blending in a twin‐screw extruder. The structural, morphological, mechanical, and thermal properties of the nanocomposites were investigated. The Young's modulus and flexural modulus of the nanocomposites were increased by 30 and 54%, respectively, when 3 wt% GNPs was added. The flexural strength and tensile strength of the PC/ABS/GNPs nanocomposites increased up to a loading of 3 wt% GNPs. The incorporation of GNPs enhanced the thermal stability and char yield of the nanocomposites. X‐ray diffraction and field emission scanning electron microscopy showed uniform dispersion and alignment of GNPs in PC/ABS matrix. The interaction between the GNPs and the PC/ABS matrix were confirmed by Fourier transform infrared spectra. Therefore, the PC/ABS/GNP nanocomposites with improved flexural and tensile properties, without loss of extensibility and good thermal properties may have promising applications in automotive, electric tools, household, communication, and safety appliances. POLYM. COMPOS., 37:1633–1640, 2016. © 2014 Society of Plastics Engineers     

Effect of lattice structure evolution on the thermal and mechanical properties of Cu–Al2O3/GNPs nanocomposites

In this study, high-energy ball milling accompanied by compaction and sintering were employed for manufacturing Cu-based hybrid nanocomposite reinforced by Al₂O₃ and GNPs. This hybrid nanocomposite is proposed to meet the specification of heat sink applications, where excellent mechanical and thermal performance is demanding. Different processing parameters were experimentally considered such as sintering temperature and weight percentage of GNPs, 0, 0.25, 0.50, 0.75, and 1 wt %. The weight percentage of Al₂O₃ was fixed at 10%. The results demonstrated that the mechanical and thermal performance of the fabricated nanocomposites were superior for nanocomposite containing 0.5% GNPs and sintered at 1000 °C. The hardness, the thermal conductivity and the coefficient of thermal expansion (CTE) were improved by 21%, 16.7%, and 55.2%, respectively, compared to composite without GNPs addition. The improved mechanical and thermal properties were attributed to the low stacking fault energy, small crystallite size, high dislocation density, and low lattice strain of the composite prepared at this composition. Moreover, the better dispersion of the nano-particles of GNPs and Al₂O₃ inside the matrix helped for the strength and thermal conductivity improvement while maintaining low CTE.     

The effect of different GNPs addition on the electrical conductivities and percolation thresholds of the SiAlON matrix composites

Insulating SiAlON ceramics may become electrically conductive with the addition of a conductive phase such as GNPs and can be used more widely. However, the differences in the properties of the used GNPs significantly affect the amount of electrical conductivity that they provide to the matrix. In this study, four different GNPs with different properties such as lateral dimension, thickness and aspect ratio were added to SiAlON in the amount of 1.5, 2, 3 and 4 wt. % and the effects of different properties on the conductivity of composites were investigated. The thinnest GNPs with largest dimension and aspect ratio among the used GNPs provided the highest electrical conductivity and lowest percolation thresholds to SiAlON. The decrease in dimension, aspect ratios and the increase in thickness decreased the electrical conductivity of GNPs. Composites exhibited anisotropic behavior with better conductivity and percolation threshold values in the in-plane direction than through-plane direction.     

Effects of facile amine‐functionalization on the physical properties of epoxy/graphene nanoplatelets nanocomposites

Graphene nanoplatelets (GNPs) have excellent thermal, electrical, and mechanical properties. The incorporation of GNPs into a polymer can remarkably enhance the thermal and mechanical properties of the polymer especially when GNPs are well dispersed in the polymer matrix with strong interfacial bonding. Therefore, in this study, GNPs were amine‐functionalized by covalently bonding 4,4′‐methylene dianiline onto their surfaces via a facile synthetic route. The amine‐functionalization was confirmed by FTIR spectroscopy and TGA. Epoxy/GNPs nanocomposites were prepared and their curing behavior, thermomechanical properties and impact strength were investigated. The amine‐functionalization increased curing rate, storage modulus, thermal dimensional stability, and impact strength of the nanocomposites. The SEM images for the fracture surface of the nanocomposite with amine‐functionalized GNPs showed a smooth and ductile failure‐like surface, resulted from the improved interfacial bonding between GNPs and the epoxy matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42269.     

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分布在PA6中;当GNPs先加入PP中复合,再与PA6共混时,GNPs从PP相向界面处迁移,有利于GNPs在界面上搭建较多的导热网络,从而提高复合材料的导热性能;GNPs的含量为7 %时,其热导率最高可达0.83 W/（m·K）;SEBS的加入改善了PP和PA6之间的相容性,消除了两相间部分界面空隙。     

Investigation of rheological,mechanical, and thermal properties of nanocomposites based on nitrile rubber-phenolic resin reinforced with nanographene

In this study, nanocomposites of acrylonitrile butadiene rubber (NBR)/phenolic resin/graphene nanoparticles (GNPs) were prepared using a two-roll mill. According to the results, the addition of GNPs increased the scorch time, vulcanization time, and viscosity of the blends. By adding phenolic resin and in the presence of a higher percentage of acrylonitrile, the modulus and tensile strength increased and the elongation at break decreased. The mechanical properties of the nanocomposites improved with increasing the amount of nanoparticles. The addition of 1.5 phr GNP to the blends containing NBR with 33% and 45% acrylonitrile increased the tensile modulus by 56% and 49%, respectively. The tensile properties of the nanocomposites were also investigated at 50, 25, and 75°C. It was observed that with increasing the amount of nanoparticles, the deterioration of the mechanical properties at elevated temperatures was reduced. Also, thermal stability increased with increasing the amount of nanoparticles in all the samples.     

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.     

Experimental investigation on the mechanical,structural and thermal properties of Cu–ZrO2 nanocomposites hybridized by graphene nanoplatelets

Hybrid Cu–ZrO₂/GNPs nanocomposites were successfully produced using powder metallurgy technique. The effect of GNPs mass fraction, 0, 0.5, 1 and 1.5%, on the mechanical and electrical properties of the produced hybrid nanocomposite was investigated while maintaining ZrO₂ mass fraction constant at 5%. High-energy ball milling was applied for mixing powders followed by compaction and sintering. The morphological analysis of the produced powder showed acceleration of Cu particles fracture during ball milling with the addition of GNPs up to 0.5% with noticeable reduction of agglomeration size. Moreover, the crystallite size of Cu–5%ZrO₂/0.5%GNPs hybrid nanocomposites revealed smaller crystallite size, 142 nm, compared to 300 nm for Cu–5%ZrO₂ nanocomposite. Additionally, the hybrid nanocomposite with 0.5% GNPs shows homogeneous distribution of both reinforcement phases in the sintered samples. The compressive strength increased with the GNPs content and reached 504.6 MPa at 0.5%, 31% higher than the Cu-5%ZO₂. The thermal conductivity had the maximum value at 0.5 wt%GNPs and reached 345 W/m k. The results provide efficient manufacturing process for high strength and good conductivity hybrid nanocomposites, which is applicable in many structural applications such as heat exchange purposes.     

Effects of an aminosilane and a tetra‐functional epoxy on the physical properties of di‐functional epoxy/graphene nanoplatelets nanocomposites

The physical properties of difunctional epoxies would be improved by adding nanofillers and multifunctional epoxies. Therefore, in this study, a tetrafunctional epoxy was added to difunctional epoxy/GNPs nanocomposites. An aminosilane was used to improve the interfacial bonding between GNPs and the epoxy matrix. The physical properties of the epoxy/GNPs nanocomposites were investigated by DSC, TMA, DMA, and electrical resistivity test. The glass transition temperature and storage modulus of the nanocomposites increased with increasing GNPs content. Adding the aminosilane resulted in a marginal increase in the glass transition temperature of the nanocomposites. However, adding the tetrafunctional epoxy resulted in a considerable increase in the glass transition temperature, thermal dimensional stability, and storage modulus of the nanocomposites. SEM images of the fracture surfaces of the nanocomposites showed that the aminosilane improved the interfacial bonding. The aminosilane and tetrafunctional epoxy made the sheet resistance of the nanocomposites higher. The sheet resistance data showed electrical percolation at 1–2 phr of GNPs. POLYM. ENG. SCI., 54:969–976, 2014. © 2013 Society of Plastics Engineers     

Preparation and properties of polyurethane/multiwalled carbon nanotube nanocomposites by a spray drying process

A spray drying approach has been used to prepare polyurethane/multiwalled carbon nanotube (PU/MWCNT) composites. By using this method, the MWCNTs can be dispersed homogeneously in the PU matrix in an attempt to improve the mechanical properties of the nanocomposites. The morphology of the resulting PU/MWCNT composites was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM observations illustrate that the MWCNTs are dispersed finely and uniformly in the PU matrix. X‐ray diffraction results indicate that the microphase separation structure of the PU is slightly affected by the presence of the MWCNTs. The mechanical properties such as tensile strength, tensile modulus, elongation at break, and hardness of the nanocomposites were studied. The electrical and the thermal conductivity of the nanocomposites were also evaluated. The results show that both the electrical and the thermal conductivity increase with the increase of MWCNT loading. In addition, the percolation threshold value of the PU composites is significantly reduced to about 5 wt % because of the high aspect ratio of carbon nanotubes and exclusive effect of latex particles of PU emulsion in dispersion. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

外掺料对磷石膏基胶凝材料力学及导热性能的影响

将磷石膏应用于建筑业,可以解决磷化工副产物堆积的问题。采用单因素实验,通过改变水灰质量比、粉煤灰掺量、生石灰掺量等条件来研究各因素对磷石膏基胶凝材料力学性能及保温性能的影响,借助X射线衍射（XRD）、X射线荧光光谱（XRF）、扫描电镜（SEM）等手段来分析磷石膏基胶凝材料的物化性质和形貌结构。结果表明,磷石膏基胶凝材料的导热系数和抗压强度都与水灰质量比呈负相关,在水灰质量比为0.250时胶凝材料的抗压强度最大、水灰质量比为0.550时胶凝材料的导热系数最小;粉煤灰在磷石膏基胶凝体系中除了提供胶凝性能外,还会被生石灰激发出活性,增强胶凝体系的综合性能,粉煤灰掺量为50%（质量分数）时胶凝体系的综合性能最佳;生石灰在磷石膏基胶凝体系中对杂质的吸附效果明显,生石灰掺量超过7%（质量分数）以后对胶凝体系的保温性能和力学性能的增强效果明显。     

Mechanical,thermal and electrical properties of multi‐walled carbon nanotube/aluminium nitride/polyetherimide nanocomposites

A series of polyimide‐based nanocomposites containing polyimide‐grafted multi‐walled carbon nanotubes (PI‐g MWCNTs) and silane‐modified ceramic (aluminium nitride (AlN)) were prepared. The mechanical, thermal and electrical properties of hybrid PI‐g MWCNT/AlN/polyetherimide nanocomposites were investigated. After polyimide grafting modification, the PI‐g MWCNTs showed good dispersion and wettability in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The utilization of the hybrid filler was found to be effective in increasing the thermal conductivity of the composites due to the enhanced connectivity due to the high‐aspect‐ratio MWCNT filler. The use of spherical AlN filler and PI‐g MWCNT filler resulted in composite materials with enhanced thermal conductivity and low coefficient of thermal expansion. Results indicated that the hybrid PI‐g MWCNT and AlN fillers incorporated into the polyetherimide matrix enhanced significantly the thermal stability, thermal conductivity and mechanical properties of the matrix. Copyright © 2012 Society of Chemical Industry     

Impact of various oxidation degrees of graphene oxide on the performance of styrene–butadiene rubber nanocomposites

In this work, graphene oxide (GO) with various oxidation degrees were synthesized by adjusting the dosage of oxidation agent based on a modified Hummers' method, and were then used for the fabrication of the styrene–butadiene rubber (SBR)/GO nanocomposites through latex coagulation method, followed by a high‐temperature cure process. The vulcanization characteristics, thermal stability, mechanical properties, thermal conductivity as well as solvent resistance of SBR/GO nanocomposites were investigated. The results indicated that various surface structures of GO due to oxidation degrees may lead to different dispersion states of GO in the rubber matrix, and thus greatly influenced the cure rate, mechanical properties as well as thermal conductivity of SBR/GO nanocomposites. The optimal (moderate) oxidation degree of GO was achieved at the oxidation agent (KMnO₄)/graphite weight ratio 9/5, for which case the tensile strength, tear strength, and thermal conductivity of SBR/GO nanocomposites increased by 271.3%, 112.3%, and 28.6%, respectively, compared with those of neat SBR. In addition, the mentioned nanocomposites also showed the best solvent resistance in toluene. POLYM. ENG. SCI., 58:1409–1418, 2018. © 2017 Society of Plastics Engineers     

Effect of alkyl chain length grafted to graphene nanoplatelets on the characteristics of polypropylene nanocomposites

To improve the compatibility of graphene nanoplatelets (GNPs) to polypropylene (PP), alkyl chains were grafted to the GNPs’ surfaces by chemical reactions between alkyl amines and the corresponding functional groups of the GNPs. Hexylamine, dodecylamine, and octadecylamine were used respectively to prepare three different alkyl‐grafted GNPs (alkyl‐GNPs) with different alkyl chain lengths. Functional group analysis of the alkyl‐GNPs by Fourier transform infrared confirmed the alkyl‐grafting reaction. PP/alkyl‐GNP nanocomposites with 0.5 phr of hexyl‐, dodecyl‐, or octadecyl‐GNPs were prepared respectively by melt‐blending and compression molding and their mechanical and thermal properties and fracture surfaces morphology were investigated. With increasing alkyl chain length the flexural strength and melting temperature increased marginally but the flexural modulus, impact strength and storage modulus of the nanocomposites increased to a large extent. POLYM. ENG. SCI., 59:752–756, 2019. © 2018 Society of Plastics Engineers     

The aspect ratio of epoxy matrix nanocomposites reinforced with graphene stacks

The improvement of physical and mechanical properties of nanofilled matrices significantly depends on the average size of dispersed fillers. In particular, the aspect ratio of lamellar nanofillers, such as graphene stacks, results from a combination of both filler morphology and processing techniques. In this study, nanocomposites were obtained dispersing three different graphene precursors in an epoxy resin: expanded graphite, commercial graphene nanoplatelets, and natural graphite. Epoxy matrix nanocomposites reinforced with graphene stacks, ranging from 1 wt% to 3 wt% were prepared and characterized. The structural, mechanical, and thermal properties of expanded graphite‐based nanocomposites, as well as the rheological properties of liquid resin/filler suspensions, were studied and compared with those of the unfilled epoxy matrix and of the matrix filled with natural graphite and commercial nanoplatelets. The comparison of mechanical and rheological properties with simple mathematical models indicated that the aspect ratio of expanded graphite is in the order of 1000, i.e., a dispersion of nanoscale graphene stacks was obtained. This result suggests that the measurement of engineering properties of nanocomposites not only represents an objective but can also provide information about the average degree of dispersion. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Exceptional micromachining performance of silicon carbide ceramics by adding graphene nanoplatelets

The electrical discharge machining (EDM) performance of silicon carbide (SiC) ceramics containing graphene nanoplatelets (GNPs) is investigated for the first time. Under fine machining conditions, the material removal rate (MRR) dramatically increases up to 186% when 20 vol.% of GNPs are added to SiC ceramics, leading to reductions on the electrode wear rate of 132%. The EDMed nanocomposites exhibit surface roughness ≤ 0.8 μm. This outstanding EDM response of the graphene nanocomposites as compared to monolithic SiC is explained by their enhanced transport properties, establishing a direct dependence of MRR with the electrical conductivity. EDM performance of the nanocomposites also depends on the testing direction for materials with low GNPs connectivity (≤ 10 vol.%). Melting/evaporation are the main removal mechanisms, thermal spalling also operating for low thermal conducting materials. The employ of EDM on SiC/graphene nanocomposites allows machining microparts with a fine dimensional precision, opening new opportunities for SiC-based microcomponents.