Self-assembled fabrication and flame-retardant properties of reduced graphene oxide/waterborne polyurethane nanocomposites

The graphite oxide (GO) was prepared from expandable graphite by the pressurized oxidation method, and samples were characterized using XRD, UV–Vis, and TEM. GO is reduced in situ emulsion using hydrazine to achieve reduced graphene oxide/waterborne polyurethane (rGO/WPU) nanocomposites. The effect of rGO content on the stability, fracture morphologies, mechanical performance, thermal degradation, and flame-retardant properties of rGO/WPU composites was investigated by zeta potential analyzer, TEM, SEM, universal testing machine, TG, and Cone Calorimeter. The results of zeta potential, TEM, and SEM analysis indicate that rGO has a good stability and dispersibility in rGO/WPU nanocomposites. The results of mechanical tests showed that the mechanical properties of rGO/WPU nanocomposites increased consistently with increasing rGO content up to 2 mass%, and TG showed that the thermostability of rGO/WPU nanocomposites decreased slightly compared to pure WPU, but carbon residue increased from 0.99 to 1.99 % when the mass fraction of rGO in WPU is 2 %. Cone Calorimeter test indicated that the flame-retardant and smoke suppression properties of rGO/WPU composites showed significant improvement compared to the WPU alone. When the mass fraction of rGO is 1 %, the total smoke release and smoke factor decreased by 25 and 38 %, respectively, compared to those of pure WPU.     

Click coupled graphene for fabrication of high‐performance polymer nanocomposites

An effective technique of using click coupled graphene to obtain high‐performance polymer nanocomposites is presented. Poly(ε‐caprolactone) (PCL)‐click coupled graphene sheet (GS) reinforcing fillers are synthesized by the covalent functionalization of graphene oxide with PCL, and subsequently the PCL‐GS as a reinforcing filler was incorporated into a shape memory polyurethane matrix by solution casting. The PCL‐click coupled GS has shown excellent interaction with the polyurethane matrix, and as a consequence, the mechanical properties, thermal stability, thermal conductivity, and thermo‐responsive shape memory properties of the resulting nanocomposite films could be enhanced remarkably. In particular, for polyurethane nanocomposites incorporated with 2% PCL‐GS, the breaking stress, Young's modulus, elongation‐at‐break, and thermal stability have been improved by 109%, 158%, 28%, and 71 °C, respectively. This click coupling protocol offers the possibility to fully combine the extraordinary performance of GSs with the properties of polyurethane. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Preparation and Characterization of Microwave-absorption of Sarulla North Sumatra Zeolite and Ferric Oxide-filled Polyurethane Nanocomposites

Microwave-absorptive polymeric composite materials are becoming important to protect interference of any communication systems due to the increase in the use of microwave-inducing devices. In this work, the microwave-absorptive polyurethane composites are prepared using natural zeolites of Sarulla North Sumatra and commercial ferric-oxide as fillers. Weight ratio of the natural zeolite to ferric oxide were varied (18:2; 16:4; 14:6; 12:8 and 10:10) by weight. The fillers are prepared using ball milling technique and characterized using Particle Size Analyzer for particle size distribution. The nanocomposites, prepared using in-situ reaction of polyethylene glycol and toluene diisocyanate, is characterized for physical and mechanical properties using tensile strength, thermal properties with TGA techniques, as well as morphological and chemical properties using scanning electron microscopy. Composition and loading of the nanofillers against polyurethane matrices is 20% by weight. Microwave-absorption properties of the nanocomposites is characterized using 8-12 GHz frequency. Tensile strengths of the natural zeolite-ferric oxides polyurethane nanocomposites shows higher values when matrices filled with lower ferric-oxide, which could be due to the nanozeolites have functioned as reinforcement for the polyurethane matrix through polar-polar interaction between the filler surfaces with the matrices. The microwave absorption properties, which investigated by Vector Network Analyzer, of the nanocomposites filled in polyurethane with the ratio of nanozeolite to ferric oxide filler of 12:8 shows reflection loss of – 13.2 dB. This condition was observed at 11.1 GHz.     

Comparison of photocatalytic and antibacterial activities of allotropes of graphene doped Sm2O3 nanocomposites: Optical,thermal, and structural studies

This study mainly focuses on the synthesis of two allotropes of graphene, graphene oxide (GO) and reduced graphene oxide (rGO), by the modified Hummers' method and chemical reduction method, respectively. Sm₂O₃/GO and Sm₂O₃/rGO nanocomposites were further synthesized in the presence of the cationic surfactant CTAB via the sol–gel method followed by the reflux method. Synthesized nanocomposites were subjected to characterization by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and UV–Visible spectroscopy to explore structural, thermal, optical, and photocatalytic properties. Characteristic FTIR peaks were observed in nanocomposites, and the bond length of the Sm-O bond was calculated. The Coats-Redfern method was employed to calculate the kinetics and thermodynamic parameters. Hexagonal crystallite shapes of Sm₂O₃/GO and Sm₂O₃/rGO nanocomposites with 11.8 and 13.13 nm crystallite sizes and 3.9 and 2.5 eV optical band gaps were observed. The photocatalytic efficiency of Sm₂O₃/GO and Sm₂O₃/rGO nanocomposites was assessed against the degradation of methylene blue in the presence of sunlight, and its degradation was confirmed through FTIR. The antimicrobial activities were also performed against the bacterial strains Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus.     

高介电常数石墨烯/聚酰亚胺复合材料的制备与性能

在原位聚合制备氧化石墨烯/聚酰亚胺复合材料的过程中,加入季铵盐表面活性剂,抑制氧化石墨烯在高温亚胺化时的聚集,同时将氧化石墨烯原位还原,获得高介电常数的石墨烯/聚酰亚胺复合材料.结果表明,采用四丁基溴化铵和四丁基碘化铵作为还原剂,利用原位化学还原方法所制备的石墨烯/聚酰亚胺复合材料的介电常数超过聚酰亚胺薄膜40倍以上,复合材料的热稳定性和机械性能也优于聚酰亚胺薄膜.热重分析结果表明,在复合材料高温亚胺化过程中,季铵盐发生热分解,未残留在复合材料中.     

微波调控石墨烯-碳纳米管协同增强聚氨酯损伤自修复研究

首先采用溶液共混法制备出石墨烯-碳纳米管(G-CNT)/聚氨酯(TPU)复合材料,然后通过拉伸实验及扫描电子显微镜(SEM)表征来考察该材料的拉伸强度和微波自修复特性,并从力学及材料与微波之间的相互作用等角度对其拉伸强度增强和微波修复机理进行研究.结果表明:在拉伸强度方面,与单一的石墨烯或CNT增强TPU相比,G-CNT之间形成的协同效应使TPU拉伸强度得到进一步提高,当石墨烯和CNT的质量比为3∶1时,G-CNT/TPU抗拉强度较纯TPU提高了67%,较G/TPU提高了18%,较CNT/TPU提高了25%;在材料裂纹的微波修复方面,石墨烯和CNT之间的协同效应使TPU材料自修复效果得到有效提高,当石墨烯和CNT的质量比为3∶1时,G-CNT/TPU修复效果达到最高值117%.     

Preparation of waterborne polyurethane nanocomposites: Polymerization from functionalized hydroxyapatite

We report the preparation and characterization of waterborne polyurethane (WBPU)/hydroxyapatite (HAp) nanocomposites through in situ polymerization from functionalized HAp. The HAp nanoparticles (HAp NPs) were urethanated with 3-isocyanatemethyl-3,5,5-trimethyl-cyclohexylisocyanate (isophorone diisocyanate) to obtain grafted HAp NPs containing isocyanate groups (HAp-g-NCO) as crosslinkers and then the HAp-g-NCO is further polymerized with WBPU monomers to form the WBPU/HAp nanocomposites. The HAp NPs were homogeneously dispersed in the polyurethane matrix at low loading levels (?2.0 wt%), thus the mechanical strength and the elongation at break of the WBPU/HAp nanocomposites were significantly improved. Thermal stability and water resistance of the WBPU/HAp nanocomposites are also enhanced. These results suggest that the WBPU/HAp nanocomposites prepared by in situ polymerization hold the potential as new materials with improved mechanical properties, thermal stability and water resistance.     

Polymer brushes grafted from graphene via bioinspired polydopamine chemistry and activators regenerated by electron transfer atom transfer radical polymerization

Polymer brushes decorated reduced GO (rGO) with advanced applications have been prepared by bioinspired polydopamine (PDA) chemistry integrated with activators regenerated by electron transfer atom transfer radical polymerization (ARGET‐ATRP) technique. First, rGO/PDA was obtained by the process for graphene oxide (GO) coated with a homogeneous bio‐adhesive PDA layer. Then the initiator 2‐bromoisobutyryl bromide (BIBB) was immobilized on the surface of PDA functionalized rGO. Finally, rGO/PDA‐Br was polymerized with N, N‐diethylaminoethyl methacrylate (DEAEMA) and glycidyl methacrylate (GMA) to obtain rGO/PDA‐g‐polymer brushes by ARGET‐ATRP process. The prepared rGO/PDA‐g‐PGMA brush would be subjected to further functionalization with ethylenediamine (EDA), which would impart the obtained products (rGO/PDA‐g‐PGMA‐NH₂) with good adsorption ability toward cationic dyes. The chemical structures and morphologies of the functionalized GO products have been characterized in detail by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermal gravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope(TEM), and atomic force microscopy (AFM). The distinctive pH‐responsive character of rGO/PDA‐g‐PDEAEMA and adsorption ability of rGO/PDA‐g‐PGMA‐NH₂ for cationic dyes have been explored by UV–vis spectrophotometer. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 689–698     

Preparations and properties of waterborne polyurethane/allyl isocyanated-modified graphene oxide nanocomposites

We synthesized waterborne polyurethane (WPU)/allyl isocyanate modified graphene oxide (iGO) nanocomposites by UV curing, and the effects of iGO on the mechanical, dynamic mechanical, and thermal properties of the nanocomposites were systematically investigated. It was shown that the iGO chemically incorporated into the WPU chains by covalent bonding acts as a multifunctional cross-linking agent as well as reinforcing filler. Consequently, the tensile strength, glassy and rubbery state moduli, glass transition temperature, and thermal stability of the WPU were significantly increased up to an iGO content of 1%, beyond which most of the above properties showed a decrease, due probably to the auto-inhibition of the allyl compounds.     

Functionalization of graphene oxide with different diisocyanates and their use as a reinforcement in waterborne polyurethane composites

Abstract

To examine the reinforcing effects of isocyanated graphene oxide (NCO-GO) on a waterborne polyurethane matrix, the surface of GO was respectively modified by isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) and toluene diisocyanates (TDI) and then confirmed by FT-IR, Raman, TGA, XRD, TEM, AFM and SEM-EDS. The dispersity behavior between different NCO-GO and polymer was evaluated by FESEM and XRD. The nanocomposites’ chemical structure, emulsion morphology, hydrophobicity, thermal and mechanical properties were investigated by FT-IR, TEM, TGA, tensile testing machine and water contact angle test, respectively. It was shown that these properties of nanocomposites including tensile strength, initial thermal degradation and hydrophobicity were increased by the incorporation of NCO-GO, in which, particularly, the tensile stress and initial degradation temperature were respectively increased from 13.32 to 18.80?Mpa and 249 to 288?°C after the addition of TDI-GO. These superior reinforcing effects were attributed to the two-dimensional structure of NCO-GO as well as the good interfacial adhesion between the NCO-GO and WPU matrix.     

Reactive copolymer functionalized graphene sheet for enhanced mechanical and thermal properties of epoxy composites

Uniform dispersion of graphene nanosheets (GNS) in a polymer matrix with strong filler–matrix interfacial interaction, preserving intrinsic material properties of GNS, is the critical factor for application of GNS in polymer composites. In this work, a novel reactive copolymer VCz–GMA containing carbazole and epoxide group was designed, synthesized and employed to noncovalently functionalize GNS for preparing epoxy nanocomposites with enhanced mechanical properties. The presence of carbazole groups in VCz–GMA enables the tight absorption of copolymer on to graphene surface via π–π stacking interaction, as evidenced by Raman and fluorescence spectroscopy, whereas the epoxide segments chemically reacts with the epoxy matrix, improving the compatibility and interaction of graphene with epoxy matrix. As a result, the VCz–GMA–GNS/epoxy composite showed a remarkable enhancement in both mechanical and thermal property than either the pure epoxy or the graphene/epoxy composites. The incorporation of 0.35 wt % VCz–GMA–GNS yields a tensile strength of 55.72 MPa and elongation at break of 3.45, which are 42 and 191% higher than the value of pure epoxy, respectively. Increased glass transition temperature and thermal stability of the epoxy composites were also observed. In addition, a significant enhancement in thermal conductivity was achieved with only 1 wt % VCz–GMA–GNS loading. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2776–2785     

Waterborne polyurethane nanocomposites having shape memory effects

UV curable waterborne polyurethane/silica nanocomposites were designed and synthesized with functionalized silicas, where the functionalization was made with allyl isocyanate. The incorporated silica particles gave triple effects of multifunctional chemical cross‐links, reinforcing fillers, and stress relaxation retarders. Consequently, functionalized silica incorporated into the polymer chains showed significantly improved mechanical and thermal properties than the simple addition of unmodified silica. Notably, over 99% shape fixity and shape recovery with minimum cyclic hysteresis were obtained for the repeated cycles at 1% loading of the modified silica. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Thermal kinetics and thermo‐mechanical properties of graphene integrated fluoroelastomer

In this work, the thermal properties of a fluoroelastomer enhanced by graphene were systematically investigated. Although graphene oxide (GO) is the most popular and cheapest source for graphene, its chemical and thermal properties were quite different from reduced graphene oxide (RGO). By comparing their influences on the thermal properties of elastomer, the effects from chemical structures and morphologies of graphene were analyzed. As the vulcanization and decomposition determine the properties of the elastomer proved by significantly different thermo‐mechanical properties of the fluoroelastomer reinforced by GO and RGO presented, this work provides a method to ultimate utilize graphene to reinforce elastomer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1691–1700     

Functionalized graphene/thermoplastic polyester elastomer nanocomposites by reactive extrusion‐based masterbatch: preparation and properties reinforcement

A reactive extrusion process was developed to fabricate polymer/graphene nanocomposites with good dispersion of graphene sheets in the polymer matrix. The functionalized graphene nanosheet (f‐GNS) activated by diphenylmethane diisocyanate was incorporated in thermoplastic polyester elastomer (TPEE) by reactive extrusion process to produce the TPEE/f‐GNS masterbatch. And then, the TPEE/f‐GNS nanocomposites in different ratios were prepared by masterbatch‐based melt blending. The structure and morphology of functionalized graphene were characterized by Fourier transform infrared, X‐ray photoelectron spectroscopy, X‐ray diffraction and transmission electron microscopy (TEM). The incorporation of f‐GNS significantly improved the mechanical, thermal and crystallization properties of TPEE. With the incorporation of only 0.1 wt% f‐GNS, the tensile strength and elongation at break of nanocomposites were increased by 47.6% and 30.8%, respectively, compared with those of pristine TPEE. Moreover, the degradation temperature for 10 wt% mass loss, storage modulus at ?70°C and crystallization peak temperature (T_cp) of TPEE nanocomposites were consistently improved by 17°C, 7.5% and 36°C. The remarkable reinforcements in mechanical and thermal properties were attributed to the homogeneous dispersion and strong interfacial adhesion of f‐GNS in the TPEE matrix. The functionalization of graphene was beneficial to the improvement of mechanical properties because of the relatively well dispersion of graphene sheets in TPEE matrix, as suggested in the TEM images. This simple and effective approach consisting of chemical functionalization of graphene, reactive extrusion and masterbatch‐based melt blending process is believed to offer possibilities for broadening the graphene applications in the field of polymer processing. Copyright © 2014 John Wiley & Sons, Ltd.     

Reduced graphene oxide-porous In2O3 nanocubes hybrid nanocomposites for room-temperature NH3 sensing

Metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted great attention for room-temperature gas sensing applications. The development of novel sensing materials is the key issue for the effective detection of ammoniagas at room temperature. In the present work, the novel reduced graphene oxide (rGO)-In₂O₃ nanocubes hybrid materials have been prepared via a simple electrostatic self-assembly strategy. Characterization results exhibit that the intimate interfacial contact between In₂O₃ nanocubes and the rGO sheets are achieved. Particularly, the as-prepared rGO/In₂O₃ nanocomposites displayed high sensitivity, fast response and excellent selectivity towards ammonia (NH₃) at room-temperature, which clearly uncovers the merit of structural design and rational integration with rGO sheets. The superior gas sensing performance of the rGO/In₂O₃ nanocomposites can be attributed to the synergetic effects of rGO sheets and porous In₂O₃ nanocubes. The reported synthesis offers a general approach to rGO/MOS-based semiconductor composites for room-temperature gas sensing applications.     

Fabrication of graphene‐silver/polyurethane nanofibrous scaffolds for cardiac tissue engineering

The graphene‐based nanocomposites are considered as great candidates for enhancing electrical and mechanical properties of nonconductive scaffolds in cardiac tissue engineering. In this study, reduced graphene oxide‐silver (rGO‐Ag) nanocomposites (1 and 2 wt%) were synthesized and incorporated into polyurethane (PU) nanofibers via electrospinning technique. Next, the human cardiac progenitor cells (hCPCs) were seed on these scaffolds for in vitro studies. The rGO‐Ag nanocomposites were studied by X‐ray diffraction (XRD), Raman spectroscopy, and transmission electron microscope (TEM). After incorporation of rGO‐Ag into PU nanofibers, the related characterizations were carried out including scanning electron microscope (SEM), TEM, water contact angle, and mechanical properties. Furthermore, PU and PU/nanocomposites scaffolds were used for in vitro studies, wherein hCPCs showed good cytocompatibility via 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay and considerable attachment on the scaffold using SEM studies. Real‐time polymerase chain reaction (PCR) and immunostaining studies confirmed the upregulation of cardiac specific genes including GATA‐4, T‐box 18 (TBX 18), cardiac troponin T (cTnT), and alpha‐myosin heavy chain (α‐MHC) in the PU/rGO‐Ag scaffolds in comparison with neat PU ones. Therefore, these nanofibrous rGO‐Ag–reinforced PU scaffolds can be considered as suitable candidates in cardiac tissue engineering.     

Effect of surface modification of colloidal silica nanoparticles on the rigid amorphous fraction and mechanical properties of amorphous polyurethane–urea–silica nanocomposites

Colloidal silica nanoparticles (NPs) modified with eight different silane coupling agents were incorporated into an amorphous poly(tetramethylene oxide)‐based polyurethane–urea copolymer matrix at a concentration of 10 wt % (4.4 vol %) in order to investigate the effect of their surface chemistry on the structure–property behavior of the resulting nanocomposites. The rigid amorphous fraction (RAF) of the nanocomposite matrix as determined by differential scanning calorimetry and dynamic mechanical analysis was confirmed to vary significantly with the surface chemistry of the NPs and to be strongly correlated with the bulk mechanical properties in simple tension. Hence, nanocomposites with an RAF of about 30 wt % showed a 120% increase in Young's modulus, a 25% increase in tensile strength, a 15% decrease in elongation at break with respect to the neat matrix, which had no detectable RAF, whereas nanocomposites with an RAF of less than 5% showed a 60% increase in Young's modulus, a 10% increase in tensile strength and a 5% decrease in the elongation at break. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2543–2556     

Multifunctional nanocomposites based on tetraethylenepentamine-modified graphene oxide/epoxy

Composites based on epoxy/graphene were investigated for thermal-mechanical performance. Initially, few-layer graphene oxide (GO) was modified with tetraethylenepentamine (GO-TEPA) in a reaction assisted by microwave radiation. GO and GO-TEPA samples were characterized for their structure and morphology. Composites containing 0.1, 0.3 and 0.5 wt.% of GO and GO-TEPA were prepared, and the effect of fillers on the morphology of cryofractured regions of epoxy matrix was observed through electron microscopy images. Dynamic mechanical thermal analysis (DMA) tests revealed increases of approximately 20 °C in glass transition. Moreover, when compared to neat polymer, composites containing 0.5 wt.% of GO-TEPA gained up to 103% in thermal conductivity (obtained by flash laser). Finally, nanoindentation analyses showed increases of 72% in Young's modulus and 143% in hardness for the same sample. The system is characterized as multifunctional nanocomposites because of the simultaneous gains in thermal and mechanical properties. The best results of the multifunctional composites were strongly associated with the chemical modification of the GO by TEPA.     

Preparation of Polyethylene/Graphene Nanocomposites with Octadecylamine‐Modified Graphene Oxide‐MgCl‐Supported Ziegler–Natta Catalyst

In this work, an octadecylamine‐modified graphene oxide (ODA‐GO)‐MgCl‐supported Ziegler–Natta catalyst was synthesized by reacting ODA‐GO with a Grignard reagent, followed by anchoring TiCl₄ to the structure. The effect of the ODA‐GO on the catalyst morphology and ethylene polymerization behavior was examined. The resultant polyethylene (PE)/ODA‐GO nanocomposites directly mirrored the catalyst morphology by forming a layered morphology, and the ODA‐GO fillers were well dispersed in the PE matrix and showed strong interfacial adhesion with it. The resultant PE/ODA‐GO nanocomposites exhibited better thermal stability and mechanical properties than neat PE, even with a small amount of ODA‐GO added. Thus, this work provides a facile approach to the production of high‐performance PE. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 855–860     

Nanocomposites of Sulfonic Polyaniline Nanoarrays on Graphene Nanosheets with an Improved Supercapacitor Performance

A new nanocomposite, poly(aniline‐co‐diphenylamine‐4‐sulfonic acid)/graphene (PANISP/rGO), was prepared by means of an in situ oxidation copolymerization of aniline (ANI) with diphenylamine‐4‐sulfonic acid (SP) in the presence of graphene oxide, followed by the chemical reduction of graphene oxide using hydrazine hydrate as a reductant. The morphology and structure of PANISP/rGO were characterized by field‐emission (FE) SEM, TEM, X‐ray photoelectron spectroscopy (XPS), Raman, FTIR, and UV/Vis spectra. The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The PANISP/rGO nanocomposite showed a nanosized structure, with sulfonic polyaniline nanoarrays coated homogeneously on the surface of graphene nanosheets. This special structure of the nanocomposite also facilitates the enhancement of the electrochemical performance of the electrodes. The PANISP/rGO nanocomposite exhibits a specific supercapacitance up to 1170 F g^?1 at the current density of 0.5 A g^?1. The as‐prepared electrodes show excellent supercapacitive performance because of the synergistic effects between graphene and the sulfonic polyaniline copolymer chains.