Preparation of functional reduced graphene oxide and its influence on the properties of polyimide composites

Homogeneous dispersion and strong filler–matrix interfacial interactions were vital factors for graphene for enhancing the properties of polymer composites. To improve the dispersion of graphene in the polymer matrix and enhance the interfacial interactions, graphene oxide (GO), as an important precursor of graphene, was functionalized with amine‐terminated poly(ethylene glycol) (PEG–NH₂) to prepare GO–poly(ethylene glycol) (PEG). Then, GO–PEG was further reduced to prepare modified reduced graphene oxide (rGO)–PEG with N₂H₄·H₂O. The success of the modification was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and Raman spectroscopy. Different loadings of rGO–PEG were introduced into polyimide (PI) to produce composites via in situ polymerization and a thermal reduction process. The modification of PEG–NH₂ on the surface of rGO inhibited its reaggregation and improved the filler–matrix interfacial interactions. The properties of the composites were enhanced by the incorporation of rGO–PEG. With the addition of 1.0 wt % rGO–PEG, the tensile strength of PI increased by 81.5%, and the electrical conductivity increased by eight orders of magnitude. This significant improvement was attributed to the homogeneous dispersion of rGO–PEG and its strong filler–matrix interfacial interactions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45119.     

Solvothermally reduced graphene oxide/polyimide composites: Structures and thermal and mechanical properties

Solvothermally reduced graphene oxide (SRGO)/polyimide (PI) composites were prepared by in situ polymerization. The structures and components were carefully investigated by X-ray diffraction. Thermal properties were measured by thermogravimetry and dynamic thermomechanical analysis. Mechanical properties were carefully evaluated by tensile testing and scanning electron microscopy. The SRGO/PI composites exhibit extremely high tensile strength and elastic modulus, which is 30% higher than that of pure PI film. Meanwhile, the thermal stability of SRGO/PI composites also displays an obvious enhancement. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47164.     

Preparation of a functional reduced graphene oxide and carbon nanotube hybrid and its reinforcement effects on the properties of polyimide composites

The homogeneous dispersion and strong interfacial interactions of carbon nanomaterials are vital factors on enhancing the properties of polymer composites. Two‐dimensional reduced graphene oxide (rGO) and one‐dimensional carbon nanotubes (CNTs) were first grafted by 4,4′‐oxydianiline (ODA). The successful grafting of ODA onto the rGO and CNTs were confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and X‐ray photoelectron spectroscopy. The hybrid carbon nanomaterials of the functionalized CNTs and rGO with different ratios were prepared via a solution‐mixing method, and their dispersion state was investigated. The hybrid carbon nanomaterials with good stability were introduced to polyimide (PI) via in situ polymerization. The morphology and properties of the polymer composites were studied. The results show that much better mechanical and electrical properties of the composites could be achieved in comparison with those of the neat PI. An improvement of 100.7% on the tensile strength and eight orders for the electrical conductivity were achieved at only a 1.0 wt % hybrid content. A significant enhancement effect was attributed to the homogeneous dispersion of the filler, filler–matrix strong interfacial interactions, and unique structure of the hybrid carbon nanomaterials in the composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44575.     

Dielectric properties of graphene–iron oxide/polyimide films with oriented graphene

The preparation of high‐dielectric‐constant (k) materials is important in the field of electronics. However, how to effectively use the function of fillers to enhance k is still a challenge. In this study, anisotropic graphene (GNS)–iron oxide (Fe₃O₄)/polyimide (PI) nanocomposite films with oriented GNSs were prepared by the in situ polymerization of 4,4′‐oxydianiline and pyromellitic anhydride in the presence of GNS–Fe₃O₄. Films of the precursors were fabricated, and this was followed by stepwise imidization under a magnetic field at a higher temperature to orient the magnetic sheets. The orientation of GNS–Fe₃O₄ and the relationships of the GNS–Fe₃O₄ content and measurement frequency with the dielectric properties of the GNS–Fe₃O₄/PI films were studied in detail. The dielectric property differences of the GNS–Fe₃O₄/PIs with GNS–Fe₃O₄ parallel or perpendicular to the film surface were not obvious, when the content of GNS–Fe₃O₄ was lower than 5 wt %. However, at the percolation threshold, the k values of GNS–Fe₃O₄/PI films with horizontal GNS–Fe₃O₄ were much higher than those of the other two kinds of films at 10³ Hz; this was derived from the contribution of more effective microcapcitors parallel to the film surface. So, making the GNS–Fe₃O₄ parallel to the film surface greatly enhanced k of GNS–Fe₃O₄. However, switching the charges on the large lateral surface of the parallel GNSs with the electric field also caused a higher dielectric loss and the frequency dependence of k and the dielectric loss at low frequency. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43041.     

Tribological behavior of short‐fiber‐reinforced polyimide composites under dry‐sliding and water‐lubricated conditions

Polyimide composites reinforced with short‐cut fibers such as carbon, glass, and quartz fibers were fabricated by the polymerization of monomer reactants process. The mechanical properties of the composites with different fiber contents were evaluated. The friction and wear properties of the polyimide and its composites were investigated under dry‐sliding and water‐lubricated conditions. The results indicated that the short‐carbon‐fiber‐reinforced polyimide composites had better tensile and flexural strengths and improved tribological properties in comparison with glass‐fiber‐ and quartz‐fiber‐reinforced polyimide composites. The incorporation of short carbon fibers into the polyimide contributed to decreases in the friction coefficient and wear rate under both dry and water‐lubricated conditions and especially under water lubrication because of the boundary lubrication effect of water. The polyimide and its composites were characterized by plastic deformation, microcracking, and spalling under both dry and water‐lubricated conditions, which were significantly abated under the water‐lubricated condition. The glass and quartz fibers were easily abraded and broken; the broken fibers transferred to the mating metal surface and increased the surface roughness of mating stainless steel, which led to the wear rate increasing for the glass‐fiber‐ and quartz‐fiber‐reinforced polyimide composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and properties of polyimide/silica hybrid composites based on polymer‐modified colloidal silica

A new type of polyimide/silica (PI/SiO₂) hybrid composite films was prepared by blending polymer‐modified colloidal silica with the semiflexible polyimide. Polyimide was solution‐imidized at higher temperature than the glass transition temperature (T_g) using 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐diaminodiphenyl ether (ODA). The morphological observation on the prepared hybrid films by scanning electron microscopy (SEM) pointed to the existence of miscible organic–inorganic phase, which resulted in improved mechanical properties compared with pure PI. The incorporation of the silica structures in the PI matrix also increased both T_g and thermal stability of the resulting films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2053–2061, 2006     

Preparation and properties of octadecylamine modified graphene oxide/styrene‐butadiene rubber composites through an improved melt compounding method

Octadecylamine modified graphene oxide/styrene‐butadiene rubber (GO‐ODA/SBR) composites are prepared by a novel and environmental‐friendly method called “Improved melt compounding”. A GO‐ODA/ethanol paste mixture is prepared firstly, and then blended with SBR by melt compounding. GO‐ODA sheets are uniformly dispersed in SBR as confirmed by scanning electron microscope, transmission electron microscopy, and X‐ray diffraction. The interfacial interaction between GO‐ODA and SBR is weaker than that between GO and SBR, which is proved by equilibrium swelling test and dynamic mechanical analysis. GO‐ODA/SBR show more pronounced “Payne effect” than GO/SBR composites, indicating enhanced filler networks resulted from the modification of GO with ODA. GO‐ODA/SBR composite has higher tensile strength and elongation at break than SBR and GO/SBR composite. The tensile strength and elongation at break for the composite with 5 parts GO‐ODA per hundred parts of rubber increase by 208% and 172% versus neat SBR, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42907.     

Preparation and properties of APPSSQ‐like/polyimide hybrid composites

Hydrolysis and condensation proceeded to generate 3‐aminopropyl polysilsesquioxane‐like (APPSSQ‐like) particles from 3‐aminopropyl triethoxysilane. An APPSSQ‐like particle includes two domains: crosslinking Si? O? Si networks inside and 3‐aminopropyl groups outside the particle. The APPSSQ‐like/polyimide (APPSSQ‐like/PI) hybrid composites were prepared from a solution of poly(amic acid) (PAA, polyimide precursor) and APPSSQ‐like particles using N,N‐dimethylacetamide as a solvent. Scanning electron microscopy (SEM) showed that the APPSSQ particle sizes were about 100 nm, and there was no obvious phase separation between the APPSSQ‐like particles and the PI matrix in the fracture surfaces of the hybrid films. Owing to the highly crosslinked Si? O? Si networks inside the APPSSQ‐like particles, the APPSSQ‐like/PI hybrid composites possessed desired properties such as improved thermal resistance and reduced coefficients of thermal expansion (CTE). The presence of covalent bonds between the APPSSQ‐like particles and the PI molecules improved the compatibility between these two components. Thus, the tensile strength increased with the APPSSQ‐like content, and the elongation at break also slightly increased with the APPSSQ‐like content. The initial tensile and storage moduli of the APPSSQ‐like/PI hybrid composites increased with the APPSSQ‐like content, which indicates that the mechanical properties of these hybrid composites were enhanced by the incorporation of the APPSSQ‐like content in the PI matrix. Furthermore, the glass transition temperatures of these composites increased with the APPSSQ‐like content because the adhesion between the APPSSQ‐like particles and the PI molecules restricts the PI chains' mobility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2865–2874, 2003     

Epoxy/p‐phenylenediamine functionalized graphene oxide composites and evaluation of their fracture toughness and tensile properties

In an attempt to enhance the mechanical properties of epoxy/graphene‐based composites, the interface was engineered through the functionalization of graphene oxide (GO) sheets with p‐phenylenediamine; this resulted in p‐phenylenediamine functionalized graphene oxide (GO–pPDA). The morphology and chemical structure of the GO–pPDA sheets were studied by spectroscopic methods, thermal analysis, X‐ray diffraction, and transmission electron microscopy. The characterization results show the successful covalent functionalization of GO sheets through the formation of amide bonds. In addition, p‐phenylenediamine were polymerized on graphene sheets to form crystalline nanospheres; this resulted in a GO/poly(p‐phenylenediamine) hybrid. The mechanical properties of the epoxy/GO–pPDA composite were assessed. Although the Young's modulus showed improvement, more significant improvements were observed in the strength, fracture strain, and plane‐strain fracture toughness. These improvements were attributed to the unique microstructure and strong interface between GO–pPDA and the epoxy matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43821.     

Synergistic improvement of mechanical and thermal properties in epoxy composites via polyimide microspheres

Achieving synergetic improvements of mechanical strength, toughness, and thermal stability of epoxy resin has been a crucial but very challenging issue. Herein, to explore a new solution for circumventing this issue, polyimide microspheres were successfully prepared through the inverse nonaqueous emulsion process, and the structure, size distribution and morphologies of polyimide (PI) microspheres were comprehensively investigated. Then the PI microspheres were incorporated in epoxy resin matrix to systematically investigate the mechanical and thermal properties of obtained epoxy/PI microspheres composites. It was found that the PI microspheres can not only enhance the mechanical strength of epoxy resin, but also significantly improve the toughness. Specially, the epoxy-based composites containing 3 wt% PI microspheres exhibit a 47% increase in tensile strength, while the G_IC and Charpy impact strength increase by 106% and 200%, respectively. The toughing mechanism of epoxy/PI microspheres composites was discussed. Moreover, the PI microspheres can also endow the epoxy resin with excellent thermal stability and heat resistance. Thus, this work may open a new opportunity to synergistically enhance the mechanical and thermal properties of epoxy-based composites and may also give some valuable inspiration for the rational design of other high-performance thermosetting composites.     

Mechanical and thermal properties of hierarchical composites enhanced by pristine graphene and graphene oxide nanoinclusions

Epoxy resin nanocomposites incorporated with 0.5, 1, 2, and 4 wt % pristine graphene and modified graphene oxide (GO) nanoflakes were produced and used to fabricate carbon fiber‐reinforced and glass fiber‐reinforced composite panels via vacuum‐assisted resin transfer molding process. Mechanical and thermal properties of the composite panels—called hierarchical graphene composites—were determined according to ASTM standards. It was observed that the studied properties were improved consistently by increasing the amount of nanoinclusions. Particularly, in the presence of 4 wt % GO in the resin, tensile modulus, compressive strength, and flexural modulus of carbon fiber (glass fiber) composites were improved 15% (21%), 34% (84%), and 40% (68%), respectively. Likewise, with inclusion of 4 wt % pristine graphene in the resin, tensile modulus, compressive strength, and flexural modulus of carbon fiber (glass fiber) composites were improved 11% (7%), 30% (77%), and 34% (58%), respectively. Also, thermal conductivity of the carbon fiber (glass fiber) composites with 4% GO inclusion was improved 52% (89%). Similarly, thermal conductivity of the carbon fiber (glass fiber) composites with 4% pristine graphene inclusion was improved 45% (80%). The reported results indicate that both pristine graphene and modified GO nanoflakes are excellent options to enhance the mechanical and thermal properties of fiber‐reinforced polymeric composites and to make them viable replacement materials for metallic parts in different industries, such as wind energy, aerospace, marine, and automotive. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40826.     

Mechanical properties of graphene nanoplatelet/epoxy composites

Because of their high‐specific stiffness, carbon‐filled epoxy composites can be used in structural components in fixed‐wing aircraft. Graphene nanoplatelets (GNPs) are short stacks of individual layers of graphite that are a newly developed, lower cost material that often increases the composite tensile modulus. In this work, researchers fabricated neat epoxy (EPON 862 with Curing Agent W) and 1–6 wt % GNP in epoxy composites. The cure cycle used for this aerospace epoxy resin was 2 h at 121°C followed by 2 h at 177°C. These materials were tested for tensile properties using typical macroscopic measurements. Nanoindentation was also used to determine modulus and creep compliance. These macroscopic results showed that the tensile modulus increased from 2.72 GPa for the neat epoxy to 3.36 GPa for 6 wt % (3.7 vol %) GNP in epoxy composite. The modulus results from nanoindentation followed this same trend. For loadings from 10 to 45 mN, the creep compliance for the neat epoxy and GNP/epoxy composites was similar. The GNP aspect ratio in the composite samples was confirmed to be similar to that of the as‐received material by using the percolation threshold measured from electrical resistivity measurements. Using this GNP aspect ratio, the two‐dimensional randomly oriented filler Halpin–Tsai model adjusted for platelet filler shape predicts the tensile modulus well for the GNP/epoxy composites. Per the authors' knowledge, mechanical properties and modeling for this GNP/epoxy system have never been reported in the open literature. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

功能化石墨烯改性双马来酰亚胺复合材料的微观表征及性能

采用改进Hummers法制备氧化石墨烯（GO）,分别采用水合肼、壳聚糖、KOH还原得到了还原氧化石墨烯（rGO）并对三种还原方法做了对比,选择最佳方案;再通过离子液体（NH₂IL）对rGO功能化得到改性还原氧化石墨烯（NH₂IL-rGO）。以二烯丙基双酚A （BBA）和双酚A双烯丙基醚（BBE）为活性稀释剂,4,4'-二氨基二苯甲烷型双马来酰亚胺（MBMI）为反应单体,制备了MBMI-BBA-BBE （MBAE）树脂基体;同时以NH₂IL-rGO为增强体采用原位聚合法制备NH₂IL-rGO/MBAE复合材料。表征了石墨烯和复合材料的微观形貌并分析了石墨烯对复合材料性能的影响。结果表明：NH₂IL-rGO在树脂基体中以两相形式存在,结构完整,并赋予复合材料优异的性能。当NH₂IL-rGO含量为2%（质量）时,复合材料冲击强度和弯曲强度最大,分别为15.33 kJ/m²和142 MPa,热分解温度为435.73℃、当测试频率为100 Hz～10 kHz时介电常数发生突变达到84。     

Relationship between microstructure of lamellar graphene sheets and properties of polyimide/graphene nanocomposites film under different imidization stages

Herein, polyimide/graphene sheets (PI/GS) nanocomposite films with different GS distribution structures have been successfully obtained by controlling the imidization degrees, and the effect of the lamellar structure on the properties of PI film has been investigated. The results show that GS are gradually parallel to the surface of PI nanocomposite film with the increase of the imidization temperature, and 150 °C is the critical temperature, where the imidization rate is the fastest and the lamellar structure begins to form. Furthermore, with the drying temperature increasing, the corresponding thermal, electrical and mechanical properties of PI/GS nanocomposite films are significantly improved compared with that of pure PI films, which are ascribed to both the higher imidization degree and the lamellar GS structure. It is noteworthy that the formation process of the lamellar structure at different imidization stages can be directly observed by scanning electron microscope. Based on these results, a model has been proposed to explain the relationship between the lamellar structure and properties of PI composite film under different imidization stages, and the confinement of the thickness may be the most important factor for the formation of lamellar GS structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43575.     

Synthesis and characterization of polyimide/modified mCOC composites

Two types of monomers, 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride and 4,4′‐oxydianiline, were employed to synthesize poly(amic acid) (PAA) as a precursor of polyimide (PI). Through the addition of modified metallocene cyclic olefin copolymer (mCOC), PAA/mCOC composites were formed. PI/mCOC composites were obtained through a blade coating and multistep thermal curing process. The structure of the prepared PI/mCOC composites was characterized through Fourier transform infrared spectrometry. The results showed that the copolymerization of PAA and modified mCOC improved thethermal stability and hydrophobic and electrical properties of the PI/mCOC composites. The formation of a network structure between PI and modified mCOC considerably reduced the mobility of PI molecules, thereby improving the glass transition temperature and thermal properties of the composite. The thermal and hydrophobic properties were improved by increasing the mCOC grafting ratio. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44144.     

Mechanical properties and drug release of microcapsules containing quaternized‐chitosan‐modified reduced graphene oxide in the capsular wall

Reduced graphene oxide (rGO) sheets were first modified with 2‐hydroxypropyltrimethyl ammonium chloride chitosan (HACC), and these modified rGO sheets (named HACC–rGO) were used as reinforcement materials and introduced to the walls of chitosan (CS) microcapsules. All of the monodisperse microcapsules were conveniently generated by a gas–liquid microfluidic technique. The results of scanning electron microscopy, X‐ray diffraction, and thermogravimetric analysis all demonstrate that the HACC–rGO sheets existed and were dispersed in the capsular shell. The HACC–rGO‐reinforced CS microcapsules showed better mechanical strength and better chemical stability with an α‐cyclodextrin solution than the CS microcapsules without HACC–rGO. Importantly, the HACC–rGO‐reinforced CS microcapsules exhibited a slower drug‐release behavior and provide a method for the control of the release rate of drug‐loaded microcapsules. In an in vitro cytotoxicity evaluation by a 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2‐H‐tetrazolium bromide assay, the Schwann cells still showed good cell viability after they were treated by extracts of the CS/HACC–rGO microcapsules with concentrations ranging from 0.02 to 2000 μg/mL. Therefore, the HACC–rGO‐reinforced CS microcapsules are promising for applications in the fields of drug delivery and controlled release. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44549.     

Preparation and properties of nadic‐end‐capped cyclotriphosphazene‐containing polyimide/carbon fiber composites

New novel fire‐resistant and heat‐resistant cyclotriphosphazene‐containing polyimide resins were prepared in situ by the polymerization of (p‐aminophenoxy)(phenoxy)cyclotriphosphazenes with 3,3′,4,4′‐benzophenonetetracarboxylic acid or 3,3′,4,4′‐diphenylsulfonetetracarboxylic acid and a crosslink agent, 5‐norbornene‐2,3‐dicarboxylic acid and were used as polymer matrix compositing with a woven carbon fiber to prepare nadic‐end‐capped cyclotriphosphazene‐containing polyimide/carbon fiber composites. The thermal stability, flame retardance, morphology of the surface fracture, and some physical properties of the composites were investigated by thermogravimetric analysis, scanning electron microscopy, and a material testing system, respectively. The composites had good thermal stability, flame retardance, and mechanical properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 810–818, 2003     

Mechanical and thermal properties of polyimide/silica hybrids with imide‐modified silica network structures

A series of hybrid materials incorporating imide‐modified silica (IM‐silica) network structures into a polyimide (PI) matrix were produced with a sol–gel technique from solution mixtures of poly(amic acid) and tetraethoxysilane (TEOS) containing alkoxysilane‐terminated amic acids with various degrees of polymerization. The hybrid films, obtained by solvent evaporation, were heated successively to a maximum temperature of 300°C to carry out the imidization process and silica network formation in the PI matrix. The morphology and mechanical properties of these hybrids with IM‐silica networks were studied and compared with the properties of one in which reinforcement of the matrix was achieved with a pure silica network generated from TEOS. The introduction of longer imide spacer groups into the silica network led to a drastic decrease in the silica particle size. Improved tensile modulus was observed in such compatibilized hybrid systems. Comparative thermogravimetric measurements of these hybrids showed improved thermooxidative resistance. A PI hybrid with 30% IM‐silica had a thermal decomposition temperature nearly 260°C higher than that of the pure PI matrix. The high surface area of the interconnected silica domains and increased interfacial interaction were believed to restrict the segmental motion of the polymer and thus slow the diffusion of oxygen in the matrix, thereby slowing the oxidative decomposition of the polymer. The reinforcement of existing and new PIs by this method offers an opportunity for improving their thermooxidative stability without degrading their mechanical strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrical conductivity of silicon carbonitride‐reduced graphene oxide composites

Silicon carbonitride ceramics–reduced graphene oxide (SiCN–rGO) composites are synthesized using polyvinylsilazne (PVSZ) and GO as precursors and N‐dimethylformamide (DMF) as a solvent. We find that the electrical conductivity of SiCN–rGO composites exhibits nonmonotonic changes as a function of GO concentrations, in which the conductivity increases by six orders of magnitude from 7.41E‐09 (Ω/cm)^?1 to 4.35E‐03 (Ω/cm)^?1 after the integration of 0.2 wt% GO, followed by three orders of magnitude drop to 3.34E‐06 (Ω/cm)^?1 when 0.3 wt% GO is integrated. Based on the energy‐dispersive spectroscopy and Raman spectroscopy analysis, we conclude that the conductive behavior of SiCN–rGO composites is controlled by both the concentration and the distribution of “free‐carbon” in the composites.     

Multifunctional polyimide/graphene oxide composites via in situ polymerization

In this article, we detail an effective way to improve electrical, thermal, and gas barrier properties using a simple processing method for polymer composites. Graphene oxide (GO) prepared with graphite using a modified Hummers method was used as a nanofiller for r‐GO/PI composites by in situ polymerization. PI composites with different loadings of GO were prepared by the thermal imidization of polyamic acid (PAA)/GO. This method greatly improved the electrical properties of the r‐GO/PI composites compared with pure PI due to the electrical percolation networks of reduced graphene oxide within the films. The conductivity of r‐GO/PI composites (30:70 w/w) equaled 1.1 × 10¹ S m^?1, roughly 10¹⁴ times that of pure PI and the oxygen transmission rate (OTR, 30:70 w/w) was reduced by about 93%. The Young's modulus of the r‐GO/PI composite film containing 30 wt % GO increased to 4.2 GPa, which was an approximate improvement of 282% compared with pure PI film. The corresponding strength and the elongation at break decreased to 70.0 MPa and 2.2%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40177.