Influence of graphene-based compounds on the mechanical toughness and thermal stability of polypropylene

A study of the improvement of the mechanical and thermal properties of nanocomposites prepared with polypropylene (PP) and different graphene samples [graphene oxide (GO), reduced GO (RGO), and commercial graphene (G)] is presented. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy characterization were applied to the graphene samples. The nanocomposites were characterized by thermogravimetric analysis, XRD, differential scanning calorimetry, transmission electron microscopy (TEM), tensile, and impact resistance tests. PP/RGO nanocomposites showed significant improvement in mechanical and thermal properties. Sample PP/RGO-0.75 resulted in an increment in Young's modulus (51%), tensile strength (24%), and elongation at break (15%). This is attributed to a good dispersion state, a higher crystallinity percentage, and a good interfacial adhesion between PP and RGO. Sample PP/RGO-0.50 exhibited an increase of 197 °C in the temperature at which a loss in weight of 5% occurred, compared to that for pure PP. The height of stacked layers calculated by XRD measurements was similar to the value observed by TEM. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48258.     

Reduced graphene oxide-reinforced unsaturated polyester resin nanocomposites with improved thermal stability,mechanical modulus,and electromagnetic interference shielding performance

This article aims to investigate the impact of reduced graphene oxide (RGO) nanofillers on the curing kinetics, thermal stability, mechanical modulus, electrical conductivity, and EMI shielding effectiveness of unsaturated polyester resin (UPR). The curing rates of UPR/styrene (60/40 by wt%) mixtures with small amounts of RGO (0.1–0.3 wt%) exhibit slight delays owing to the barrier and scavenger roles of 2-dimensional RGO sheets. Nonetheless, it is observed that within the cured nanocomposites, RGOs are effectively dispersed and firmly bonded to the UPR matrix at interfaces through hydrogen bonding and π-π interactions. Consequently, the nanocomposites display heightened thermal decomposition temperatures and increased residue at 800°C with higher RGO loading content. The addition of RGO notably improves the elastic storage modulus and increases the temperature associated with glass transition-related relaxation. The electrical percolation threshold is attained at a specific RGO loading between 0.2 and 0.3 wt%. Thus, the nanocomposite with 0.3 wt% RGO is characterized to have an electrical conductivity of 1.9 × 10⁻⁶ S/cm and an EMI shielding effectiveness of ~9 dB at 8 GHz, for a thickness of 1 mm.     

Preparation and characterization of graphene‐agar and graphene oxide‐agar composites

Biodegradable counterparts of petro plastics for packaging applications are highly desired due to environmental considerations. Agar can be a potential material due to its availability and biodegradability. However, moderate mechanical strength and thermal stability, in addition to poor resistance against water, needs to be addressed before agar can be commercially implemented as packaging material. As a step toward this objective, graphene oxide (GO) and reduced GO (RGO) were incorporated in agar and were solution casted in the form of films. The tensile strength was increased by 118.4% and 69.4% at 2% GO and 2% RGO loading, respectively. Higher interfacial bonding between GO and agar compared to that of RGO and agar was attributed for the observed mechanical properties. Resistance to swelling and hydrophobicity (contact angle) of the composite were improved as well when compared to pure agar. The tensile strength and the contact angle values were however, decreased after the addition of 2% GO and 2% RGO. The morphological investigation showed that the formation of pores at higher concentration of reinforcement was the contributing factor for the decrease in tensile strength. No significant change in thermal properties was observed. The transmittance value was reduced to 0% after the incorporation of GO and RGO. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45085.     

Interpenetrating polymer network/functionalized-reduced graphene oxide nanocomposite: As an advanced functional material

In this report, smart polyurethane-polystyrene interpenetrating polymer network (IPN)-based nanocomposites were fabricated using simultaneous polymerization technique with different doses of functionalized reduced graphene oxide (f-RGO). RGO was functionalized with monoglyceride of sunflower oil in the presence of toluene diisocyanate. Successful functionalization of RGO was supported by Fourier-transform infrared spectroscopy, X-Ray diffraction, and transmission electron microscopy analyses. Most interestingly, the fabricated IPN-based nanocomposites showed significant enhancements in mechanical (tensile strength: 165%; elongation at break: 198%; toughness: 340%) and thermal (thermally stable up to 262°C) properties upon incorporation of 1 weight% of f-RGO. Moreover, the fabricated nanocomposites exhibited outstanding chemical resistance, self-cleaning behavior through surface hydrophobicity (static contact angle: 125.6–136.5°), multi-stimuli responsive shape memory effect (100% recovery within 33–44 s by microwave and 265–308 s by sunlight) and thermally actuated artificial muscle-like behavior. Therefore, the studied smart nanocomposites with the aforementioned properties hold significant potential for possible advanced applications.     

Morphology,thermal and mechanical behavior of polypropylene nanocomposites toughened with poly(ethylene‐co‐octene)

Rubber‐toughened polypropylene (PP) nanocomposites containing organophilic layered silicates were prepared by means of melt extrusion at 230 °C using a co‐rotating twin‐screw extruder in order to examine the influence of the organoclay and the addition of PP grafted with maleic anhydride (PPgMAH) as a compatibilizer on the morphological, mechanical and thermal properties. The mechanical properties of rubber‐toughened polypropylene nanocomposites (RTPPNCs) were studied through tensile, flexural and impact tests. Scanning electron microscopy (SEM) was used for investigation of the phase morphology and rubber particles size. X‐ray diffraction (XRD) was employed to characterize the formation of nanocomposites. The thermal properties were investigated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The dynamic mechanical properties were examined by using dynamic mechanical analysis (DMA). From the tensile and flexural tests, the optimum loading of organoclay in RTPP was found to be 6 wt%. The optimum loading of PPgMAH, based on the tensile and flexural properties, was also 6 wt%. The increase in the organoclay and PPgMAH content resulted in a severe embrittlement, manifested by a drop in the impact strength and tensile elongation at break. XRD studies revealed that intercalated RTPPNCs had been successfully prepared where the macromolecular PP segments were intercalated into the interlayer space of the organoclay. In addition, the organoclay was dispersed more evenly in the RTPPNC as the PPgMAH content increased. TGA results revealed that the thermal stability of the RTPPNC improved significantly with the addition of a small amount of organoclay. Copyright © 2006 Society of Chemical Industry     

Synthesis and properties of fluorinated graphene oxide bisphenol a epoxy nanocomposites

This study thoroughly studied the implements of fluorosilane modified graphene oxide (GO) on the mechanical, thermal, and water absorption properties of the epoxy composites built up by specific content of modified GO. Fluorosilane graphene oxide (GOSiF) was analyzed using Fourier transform infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray diffractometer. The epoxy composites tensile and bending modulus were increased by 11.46% and 62.25% with 0.1 and 0.5 wt% GOSiF loading, respectively. The good interfacial interaction was observed between epoxy matrix and GOSiF nanosheets under scanning electron microscopy. The thermal stability increases with GOSiF loading. Epoxy composite with 0.3 wt% GOSiF shows 5 °C increases in the T_10%. The residual weight raised by 58.67% with 0.3 wt% GOSiF content. The water absorption study revealed small water uptake was obtained for all GOSiF composites. With 0.3 wt% loading of GOSiF, the maximum water content drops from 4.97% for neat epoxy to 1.98%. POLYM. ENG. SCI., 59:1250–1257 2019. © 2019 Society of Plastics Engineers     

Morphology,thermal, mechanical,and barrier properties of graphene oxide/poly(lactic acid) nanocomposite films

To improve the physical and gas barrier properties of biodegradable poly(lactic acid) (PLA) film, two graphene nanosheets of highly functionalized graphene oxide (0.3 wt% to 0.7 wt%) and low-functionalized graphene oxide (0.5 wt%) were incorporated into PLA resin via solution blending method. Subsequently, we investigated the effects of material parameters such as loading level and degree of functionalization for the graphene nanosheets on the morphology and properties of the resultant nanocomposites. The highly functionalized graphene oxide (GO) caused more exfoliation and homogeneous dispersion in PLA matrix as well as more sustainable suspensions in THF, compared to low-functionalized graphene oxide (LFGO). When loaded with GO from 0.3 wt% to 0.7 wt%, the glass transition temperature, degree of crystallinity, tensile strength and modulus increased steadily. The GO gave rise to more pronounced effect in the thermal and mechanical reinforcement, relative to LFGO. In addition, the preparation of fairly transparent PLA-based nanocomposite film with noticeably improved barrier performance achieved only when incorporated with GO up to 0.7wt%. As a result, GO may be more compatible with hydrophilic PLA resin, compared to LFGO, resulting in more prominent enhancement of nanocomposites properties.     

Improving the mechanical,thermal and electrical properties of polyurethane- graphene oxide nanocomposites synthesized by in-situ polymerization of ester-based polyol with hexamethylene diisocyanate

Many polyols or diols have been used for the synthesis of polyurethanes (PU), however, to the best of our knowledge, PU-graphene oxide (GO) nanocomposites synthesized with ester-based polyols have been rarely studied. In this work ester-based polyol synthesized by the reaction of adipic acid and 1,4 butane diol, was in-situ polymerized with hexamethylene diisocyanate (HDI) and GO to prepare PU-GO nanocomposites. The content of GO was changed from 1 to 2.5 wt% and its effect on the mechanical, thermal and electrical properties of the samples were examined. The presence of GO more than 1.5% in the nanocomposites resulted in brittle samples and reduced the tensile strength, however, the Young’s modulus of the samples containing 1 and 1.5% was increased to 11 and 12.08-fold (275 and 302 MPa) compared to the neat PU (25 MPa), respectively. The shore A hardness of the samples was increased from 86 for PU to 96 for PUGO-1.5. The abrasion resistance of the samples was decreased by increasing the GO content. Results of the thermogravimetric analysis showed that higher amounts of GO increase the thermal stability of the samples. The chemical and physical interactions between the surface of GO nanolayers and the PU chains were confirmed by FTIR spectroscopy. The dynamic mechanical analysis of the samples showed that GO nanolayers decreased the molecular motions of the PU chains in the nanocomposites which were noticed by shifting the glass transition to the higher temperatures.     

Effect of Organomodified Ni-Al Layered Double Hydroxide (OLDH) on the Properties of Polypropylene (PP)/LDH Nanocomposites

This work addresses the effect of organomodified layer double hydroxide (OLDH) on the properties of PP/LDH nanocomposites prepared by melt intercalation method using a single screw extruder with maleic anhydride grafted polypropylene (PP-g-MA) as a compatibilizer. For this, Ni-Al LDH was first prepared by the co-precipitation method at constant pH using their nitrate salts. The above synthesized pristine LDH was organically modified using sodium dodecyl sulphate (SDS) by the regeneration method. The structural and thermal properties of LDH and PP nanocomposites were performed by X-ray diffraction (XRD), FTIR spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The influence of LDH loading on the mechanical and thermal properties of the nanocomposite was also investigated. The XRD results confirmed the formation of exfoliated PP/LDH nanocomposites. PP/LDH nanocomposites exhibited enhanced thermal stability relative to the pure PP. When 10% weight loss was selected as a point of comparison, the decomposition temperature of PP/LDH (5 wt%) nanocomposite was 15.3°C higher than that of pure PP. The DSC result indicated an increase in crystallization and melting temperature of the PP/LDH nanocomposites compared to pure PP. Overall, the mechanical properties of the PP/LDH nanocomposites increased with an increase in the LDH content. The maximum improvement of tensile strength, Young's modulus, flexural strength, and flexural modulus for the PP/LDH nanocomposite was found to be 11, 22.5, 28, and 22%, respectively, over neat PP. For comparison purposes, a nanocomposite with 5 wt% modified bentonite (PP/B5) was also prepared under the same operating condition and there was no significant improvement in mechanical properties (tensile strength and modulus).     

Enhanced thermal conductivity and dimensional stability of flexible polyimide nanocomposite film by addition of functionalized graphene oxide

Polyimide (PI) nanocomposites with both enhanced thermal conductivity and dimensional stability were achieved by incorporating glycidyl methacrylate‐grafted graphene oxide (g‐GO) in the PI matrix. The PI/g‐GO nanocomposites exhibited linear enhancement in thermal conductivity when the amount of incorporated g‐GO was less than 10 wt%. With the addition of 10 wt% of g‐GO to PI (PI/g‐GO‐10), the thermal conductivity increased to 0.81 W m^?1 K^?1 compared to 0.13 W m^?1 K^?1 for pure PI. Moreover, the PI/g‐GO‐10 composite exhibited a low coefficient of thermal expansion (CTE) of 29 ppm °C^?1. The values of CTE and thermal conductivity continuously decreased and increased, respectively, as the g‐GO content increased to 20 wt%. Combined with excellent thermal stability and high mechanical strength, the highly thermally conducting PI/g‐GO‐10 nanocomposite is a potential substrate material for modern flexible printed circuits requiring efficient heat transfer capability.     

硅烷偶联剂改性氧化石墨烯/水性聚氨酯复合物的合成与性能

采用改进的Hummers方法制得氧化石墨烯(GO),利用硅烷偶联剂改性氧化石墨烯后经氨水还原得到硅烷化还原氧化石墨烯(KRGO),再与水性聚氨酯(WPU)预聚体复合得到KRGO/WPU复合物。采用FTIR、XRD、SEM、TEM、TGA和电子万用机对复合物的结构和性能进行表征。结果表明,KRGO/WPU复合物热稳定性较纯WPU有所提高,KRGO/WPU-1质量损失为5%时的温度(T5%)比WPU大约高20℃;随着KRGO质量分数的增加,复合材料的拉伸强度先增大后减小,当KRGO质量分数为0.5%时,KRGO/WPU复合物的拉伸强度达到最大值(20.2 MPa),较纯WPU(10.8 MPa)提高了187.1%;另外,KRGO/WPU复合材料疏水性能较纯WPU也有明显改善。     

In situ polymerisation and characteristic properties of the waterborne graphene oxide/poly(siloxane-urethane)s nanocomposites

In this study, waterborne graphene oxide/poly(siloxane-urethane)s (GO/SWPUs) nanocomposites were in situ synthesised. Therein, siloxane units facilitated the crosslinking of polyurethanes, and GO imparted the nanocomposites with special functions. With increasing GO content, the average particle size, viscosity, and ionic conductivity of the GO/SWPU dispersion increased, but the absolute value of the zeta potential decreased; this was due to ionic interactions between the COO^?NH⁺(C₂H₅)₃ ions of the SWPU and COO^?H⁺ ions of the GO. The surface roughness of the GO/SWPU film was larger as GO content was higher, which was due to a strong interaction between the GO and SWPU phases. Increasing the GO content improved the thermal resistance, dynamic glass transition temperature, and tensile strength of the GO/SWPU film, but adding more than 0.1 wt% GO yielded unfavourable results. Thus, adding GO improved the thermal and mechanical properties of the GO/SWPU nanocomposites, but this improvement was observed only up to a certain GO concentration, possibly because of the agglutination of GO in SWPU. In addition, the surface and volumetric electrical resistivities of the GO/SWPU nanocomposites decreased when the GO content were increased.     

Improvement of heat resistance and mechanical properties of epoxy resin with nano-Cu-Ni supported RGO

This study reports the synthesis and characterization of epoxy resin/redox graphene/nano-copper-nickel (EP/RGO/Cu-Ni) composites. The RGO/Cu-Ni was characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Using dynamic thermodynamic analysis (DMA), the glass transition temperature (Tg) of the modified epoxy resin was increased by 21°C compared to EP. The addition of 1.3 wt% RGO/Cu-Ni to the epoxy matrix resulted in an increase of 79.6% and 161.3% respectively in the tensile strength and impact strength of the new material. Finally, the excellent mechanical properties of EP/RGO/Cu-Ni nanocomposites contribute to the research and development of new high-performance polymer materials.     

Characterization and performance of dodecyl amine functionalized graphene oxide and dodecyl amine functionalized graphene/high‐density polyethylene nanocomposites: A comparative study

Dodecyl amine (DA) functionalized graphene oxide(DA‐GO) and dodecyl amine functionalized reduced graphene oxide (DA‐RGO) were produced by using amidation reaction and chemical reduction, then two kinds of well dispersed DA‐GO/high‐density polyethylene (HDPE) and DA‐RGO/HDPE nanocomposites were prepared by solution mixing method and hot‐pressing process. Thermogravimetric, X‐ray photoelectron spectroscopy, Fourier transforms infrared spectroscopy, X‐ray diffractions, and Raman spectroscopy analyses showed that DA was successfully grafted onto the graphene oxide surface by uncleophilic substitution and the amidation reaction, which increased the intragallery spacing of graphite oxide, resulting in the uniform dispersion of DA‐GO and DA‐RGO in the nonpolar xylene solvent. Morphological analysis of nanocomposites showed that both DA‐GO and DA‐RGO were homogeneously dispersed in HDPE matrix and formed strong interfacial interaction. Although the crystallinity, dynamic mechanical, gas barrier, and thermal stability properties of HDPE were significantly improved by addition of small amount of DA‐GO or DA‐RGO, the performance comparison of DA‐GO/HDPE and DA‐RGO/HDPE nanocomposites indicated that the reduction of DA‐GO was not necessary because the interfacial adhesion and aspect ratio of graphene sheets had hardly changed after reduction, which resulting in almost the same properties between DA‐GO/HDPE and DA‐RGO/HDPE nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39803.     

Ultrasound–assisted synthesis and characterization of polymethyl methacrylate/reduced graphene oxide nanocomposites

This article reports ultrasound–assisted synthesis of polymethyl methacrylate (PMMA)/reduced graphene oxide (RGO) nanocomposites by in situ emulsion polymerization coupled with in situ reduction of graphene oxide. The thermal degradation kinetics of the nanocomposites was also assessed with Criado and Coats‐Redfern methods. Intense microconvection generated by ultrasound and cavitation results in uniform dispersion of RGO in the polymer matrix, which imparts markedly higher physical properties to resulting nanocomposites at low (≤1.0 wt %) RGO loadings, as compared to nanocomposites synthesized with mechanical stirring. Some important properties of the PMMA/RGO nanocomposites synthesized with sonication (with various RGO loadings) are: glass transition temperature (0.4 wt %) = 124.5°C, tensile strength (0.4 wt %) = 40.4 MPa, electrical conductivity (1.0 wt %) = 2 × 10^?7 S/cm, electromagnetic interference shielding effectiveness (1.0 wt %) = 3.3 dB. Predominant thermal degradation mechanism of nanocomposites (1.0 wt % RGO) is 1D diffusion with activation energy of 111.3 kJ/mol. © 2017 American Institute of Chemical Engineers AIChE J, 64: 673–687, 2018     

Morphology,thermal and mechanical properties of epoxy adhesives containing well-dispersed graphene oxide

Graphene oxide (GO) is prepared and introduced into epoxy resins through a wet-transfer migration technique using a three-roll mill. The results of TEM, XRD and digital microscope observation show that good dispersion of GO is achieved without using any additives. The mechanical and thermal properties of GO/epoxy (GO/EP) adhesives are enhanced with GO incorporated. A 10.2% increase in Young's modulus and a 56.3% increase in elevated-temperature (120 °C) lap shear strength (LSS) was observed on addition of 1.0 wt% GO, compared to the neat epoxy adhesive. Increased glass transition temperature and improved thermal stability of the GO/EP adhesives are also observed in the DMA and TG analysis. Moreover, the toughness of the GO/EP adhesives is improved and much rougher fracture surface can be observed compared with the neat epoxy adhesive. No GO agglomeration can be observed in the SEM images of GO/EP adhesive with 1.0 wt% loading.     

Synthesis of cellulose/reduced graphene oxide/polyaniline nanocomposite and its properties

A series of conductive nanocomposites cellulose/reduced graphene oxide/polyaniline (cellulose/RGO/PANi) were synthesized via in situ oxidative polymerization of aniline on cellulose/RGO with different RGO loading to study the effect of RGO on the properties of nanocomposites. The results showed that when RGO is inserted into cellulose/PANi structure, its thermal stability and conductivity are increased. So that adding of only 0.3 wt% RGO into the cellulose/PANi structure, its conductivity is increased from 1.1 × 1 10^?1 to 5.2 × 110^?1 S/cm. Scanning electron microscopy results showed that the PANi nanoparticles are formed a continuous spherical shape over the cellulose/RGO template; this increases the thermal stability of nanocomposite.     

Study of thermomechanical,structural and antibacterial properties of poly(lactic acid) reinforced with graphene oxide nanoparticles via melt mixing

Addition of graphene oxide (GO) to poly(l ‐lactic acid) (PLLA) offers an alternative approach for tuning its crystallinity, improving its mechanical properties and transfusing an antibacterial behavior. GO/PLLA nanocomposites were prepared by melt extrusion, thus avoiding the potentially toxic, for biomedical applications, residue of organic solvents. Fourier transform infrared spectroscopy verified the formation of intermolecular hydrogen bonds. Using differential scanning calorimetry experiments concerning the isothermal crystallization of PLLA and PLLA containing 0.4 wt% GO, a two‐dimensional disc‐like geometry of crystal growth was determined, whereas at 125 and 130 °C the nanocomposite developed three‐dimensional spherulitic growth. Higher crystallization rate constant values suggest that the incorporation of 0.4 wt% GO accelerated the crystallization of PLLA. The lowest crystallization half‐time for PLLA was observed at 115 °C, while at 110 °C GO caused its highest decrease, accompanied by the highest increase in melting enthalpy (ΔH_m), as compared to that of PLLA, after completion of isothermal crystallization. Their ΔH_m values increased with T_ic, whereas multiple melting peaks transited to a single one with increasing T_ic. GO improved the PLLA thermal stability, tensile strength and Young's modulus. Incorporation of 0.8 wt% GO endowed PLLA with another potential application as a biomaterial since the derived composite presented good thermomechanical properties and effective prohibition of Escherichia coli bacteria attachment and proliferation. This effect was more prominent under simulated sunlight exposure than in the dark. The preparation method did not compromise the intrinsic properties of GO. © 2020 Society of Chemical Industry     

In situ Synthesis and mechanical,thermal properties of polyimide nanocomposite film by addition of functionalized graphene oxide

Polyimide (PI) and chemical modified graphene oxide nanocomposite films are prepared by in situ polymerization from solutions of pyromellitic dianhydride and 4,4′‐oxydianiline with various amount (0.5–2 wt%) of 3‐aminopropyltriethoxysilane (APTS) functionalized graphene oxide (GO) sheets in dimethylacetamide. The APTS functionalized GO (GO‐APTS) is a versatile platform for polymer grafting, improving excellent dispersion of GO in the PI matrix, and forming strong interaction with the PI matrix. The GO‐APTS/PI nanocomposites exhibited improvement in mechanical and thermal properties by addition of a small amount of GO‐APTS. With the addition of a small amount of GO‐APTS (1.5 wt%) to PI matrix, mechanical properties with the tensile strength and Young's modulus improved by 45% and 15%, respectively. The thermal analysis showed that the thermal stability of PI was slightly enhanced by the incorporation of GO‐APTS (1.5 wt%). This approach provides a strategy for developing high performance functionalized GO‐polymer composite materials. POLYM. COMPOS., 37:907–914, 2016. © 2014 Society of Plastics Engineers     

Bio-based Sulfonated Epoxy/Hyperbranched Polyurea-modified MMT Nanocomposites

Hyperbranched polyurea modified nanoclay was used for the preparation of vegetable oil modified sulfone epoxy nanocomposites at different loadings (1–5 wt%) for the first time. The bio-based nanocomposites were characterized by XRD, SEM, TEM, and FTIR techniques. These nanocomposites showed an enhancement of thermal stability up to 48°C as revealed by thermo-gravimetric analysis. The nanocomposites with 5 wt% of nanoclay exhibited more than 300 percent improvement in tensile strength, though the elongation at break decreases with the increase of nanoclay loading. Thus the studied nanocomposites possess better performance over the pristine system.