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.     

Synthesis and properties of silanized waterborne polyurethane/graphene nanocomposites

A series of silanized waterborne polyurethane (WPU)/graphene oxide (GO) chemical hybrids were synthesized from polycaprolactone diol, isophorone diisocyanate, dimethylol butanoic acid, and (3-aminopropyl) triethoxysilane with GO as multifunctional crosslink as well as reinforcing filler. With the addition of GO, dispersion size greatly decreased due to the increased water phase viscosity, while it increased after chain extension reaction due to the migration of GO into the PU particles. The GO covalently bonded to WPU via the sol–gel type reaction augmented contact angle, glass transition temperature (Tg), hardness, and Young’s modulus of the cast film up to 1 %. However, the effects were less pronounced at high content (1.5 %) due to the agglomeration of GO particles.     

Morphology and properties of waterborne polyurethane/clay nanocomposites

Aqueous emulsion of polyurethane ionomers, based on poly(tetramethylene glycol) or poly(butylene adipate) as soft segment, isophorone diisocyanate as diisocyanate, 1,4-butandiol as chain extender, dimethyl propionic acid as potential ionic center, triethylene tetramine as crosslinker, and triethyl amine as neutralizer, were reinforced with organoclay to give nanocomposites. The particle size of emulsion was measured and the morphology of these nanocomposites was observed by transmission electron microscope, where the effectively intercalated or exfoliated organoclay was observed. The reinforcing effects of organoclay in mechanical properties of these nanocomposites were examined by dynamic mechanical and tensile tests, and the Shore A hardness was measured. Enhanced thermal and water resistance and marginal reduction in transparency of these nanocomposites were observed compared with pristine polymer.     

Preparation and characterization of waterborne polyurethane/attapulgite nanocomposites

In this paper, waterbrone polyurethane (WPU)/attapulgite (AT) nanocomposites have been prepared by direct emulsion blending. The WPU was synthesized from poly(tetramethylene glycol), 4,4-diphenylmethane diisocyanate, dimethylol butanic acid, and neutralized by triethylamine. SEM examination of fractured surfaces showed that AT particles were irregularly dispersed in the WPU matrix. FTIR analysis suggested no major chemical structural changed in the presence of a small amount of AT. DMA results showed that the storage modulus of WPU/AT nanocomposites was increased and the glass transition temperatures of both soft and hard segments shifted to higher temperature compared to the pristine WPU. Thermal resistance of the samples measured by TGA was improved with the addition of AT. The mechanical properties of the nanocomposites, examined by tensile tests, showed higher tensile strength and elongation at break than that of the pristine WPU.     

Physical and mechanical properties of graphene oxide/polyethersulfone nanocomposites

The aim of this study was to investigate physical and mechanical properties of graphene oxide (GO)/polyethersulfone (PES) nanocomposite films. The films were produced by solution casting method. The mechanical properties of composite films were evaluated by tensile test. A significant enhancement in the mechanical properties of neat PES films was obtained incorporating a small amount of GO loading (0.05–1 wt.%). The highest tensile strength was observed at 1 wt.% of GO. Comparisons were made between experimental data and the Halpin–Tsai model predictions for the tensile strength and modulus of GO/PES composites. The effect of an orientation factor on model predictions was also acquired. The hydrophilicity of the nanocomposite was evaluated by assessing contact angle and enhanced wet ability of the films was obtained with increasing the amount of GO up to 1%. The morphology of the nanocomposites was investigated using scanning electron microscopy and transmission electron microscopy and the results revealed a good dispersion of GO in the PES matrix. The thermal behavior of the composite was also studied. Thermal stability of composites was increased by adding the GO. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and properties of near IR induced self-healable polyurethane/graphene nanocomposites

A series of self-healable polyurethane (SHPU)/modified graphene (MG) nanocomposites were synthesized from poly(tetramethylene glycol) (PTMG) and 4,4′-methylene diphenyl diisocyanate (MDI) with minute amounts (0–1 wt%) of MG which was chemically modified graphene oxide (GO) with phenyl isocyanate and reduced in the presence of phenylhydrazine.     

Hydrogen bonding,mechanical properties,and surface morphology of clay/waterborne polyurethane nanocomposites

A novel clay/waterborne polyurethane (WPU) nanocomposite was synthesized from polyurethane and saponite organoclay. The clay was organically modified with various swelling agents, the effect of which has been investigated. Hydrogen bonding between organic and inorganic materials was characterized with Fourier transform infrared (FTIR) spectroscopy. The results implied that hydrogen bonding increased when organoclay was added. Mechanical and wear property studies revealed that introducing clay into waterborne polyurethane will enhance the Young's modulus (from 56 to 126 MPa), the maximum stress (from 3.9 to 7.6 MPa), and the elongation at break (from 27.7 to 58.7%) of the nanocomposite by a factor of two, whereas the wear loss will be only one third of the neat waterborne polyurethane. Atomic force microscopy (AFM) was used to analyze the surface morphology of the nanocomposite. An AFM microphotograph showed that the surface of the clay/waterborne polyurethane nanocomposite was smoother when clay was added in waterborne polyurethane. The average roughness (R_a) decreased from 1.00 to 0.12. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1–12, 2005     

Preparation of quaternarized N-halamine-grafted graphene oxide nanocomposites and synergetic antibacterial properties

At present, frequent outbreaks of bacteria and viruses have seriously affected people's normal lives. Therefore, the study of broad-spectrum antibacterial nanocomposites is very promising. However, most antibacterial materials have some disadvantages, such as single bactericidal mechanisms and unrepeatable use. Based on the current situation, a kind of nanocomposite with three structures of graphene oxide (GO), quaternary ammonium salt (QAs) and N-halamine was prepared, which showed synergistic effect to improve antibacterial activity and combined with a variety of sterilization mechanisms. Meanwhile, GO can provide richer ways of sterilization and high specific surface area, which is conducive to the grafting of quaternarized N-halamine. The advantages of physical sterilization of GO, charge adsorption of QAs, reuse of N-halamine and efficient sterilization are fully utilized. The results showed that the quaternarized N-halamine-grafted GO was obtained successfully. GO grafted with quaternarized N-halamine polymer showed strong speedy bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (99%). It had good storage and regeneration properties.     

Preparation and physicochemical properties of hydroxyapatite/polyurethane nanocomposites

In this study, nanohydroxyapatite/polyurethane （nHA/PU） composites with various contents of methoxy- poly（ethylene glycol） modified nHA （0 wt%, 10 wt%, 20 wt% and 30 wt%） were prepared by solution blending process. The physicochemical properties of the composite membranes were investigated by Fourier transform infrared spectroscopy （FTIR）, X-ray diffraction （XRD）, Transmission electronic microscopy （TEM）, Differential scanning calorimetry （DSC）, Thermo gravimetric analysis （TGA） and tensile tests. TEM photos of the nanocomposites showed that the nHA was uniformly dispersed in the polymer matrix. The membrane with 10 wt% nHA showed the highest tensile strength which was about 75% higher than that of the pure PU membrane. However, the tensile strength decreased when high content （above 20 wt%） fillers were added, which was still higher than that of pure PU. TGA measurements suggested that the thermal stability of the membranes was improved owing to nHA fillers. XRD and DSC results illustrated that the crystallinity of PU soft segments decreased with the increasing content of nanoparticles in the composites.     

纳米SiO_2/氧化石墨烯复合物的制备及其应用

综述了纳米二氧化硅(SiO_2)和氧化石墨烯(GO)纳米片的优缺点以及二者在应用中的协同效应.介绍了纳米SiO_2/氧化石墨烯复合物(SiO_2/GO)的制备方法,综述了该复合物在聚合物改性及其他领域中的应用.     

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.     

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.     

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.     

Synthesis and thermal properties of antimony doped tin oxide/waterborne polyurethane nanocomposite films as heat insulating materials

The waterborne polyurethane (WPU) was synthesized from the polycondensation between isophorone diisocyanate (IPDI) and polyoxypropylene glycol (N‐210) and then dispersed into water. Subsequently, the WPU emulsion was modified with antimony doped tin oxide (ATO) nanoparticle by ultrasonic dispersion. The ATO/WPU emulsion was cast onto Teflon molds. After being dried, ATO/WPU films were prepared. TEM indicated that the ATO nanoparticles were homogeneously dispersed in the polymer matrix at the nanometer scale. DSC showed that the ATO/WPU nanocomposites displayed increased glass transition temperatures compared to the control WPU. The mechanical properties of the films were characterized by dynamic‐mechanical analysis (DMA). The higher glass transition temperature and storage modulus indicates the superior mechanical properties of WPU modified by ATO nanoparticles over the conventional unmodified WPU. The thermal behaviors of the films were evaluated by thermogravimetric analysis (TGA). It could be found that the incorporation of ATO into WPU can improve the thermal stability dramatically. The results from UV–visible–near infrared spectra indicated that the ATO/WPU films could decrease the infrared transmission effectively. The heat‐insulation measurements showed that glass coated with ATO/WPU films possessed better heat‐insulating effect than empty glass. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and physical properties of layered silicates/polyurethane nanocomposites

Samples of polyurethane nanocomposites were synthesized using diphenylmethane diisocyanate, poly(ε‐caprolactone) diol, di(ethylene glycol), and a clay functionalized by hydroxyl groups. The inorganic content in the hybrids was 2 wt %, 4 wt %, and 8 wt %. The X‐ray analysis showed that exfoliation occurred for clay content equal to 2% (w/w), whereas for higher contents, the inorganic phase rearranges in an intercalated structure. FTIR analysis suggested that the degree of hydrogen bonding in the hard segments was greatly reduced because of the amount of silicate layers and their dispersion. The dynamic‐mechanical analysis showed that the presence of clay lamellae extends very much the temperature range before the hard domain transition, causing the loss of mechanical consistency of the samples. It is less than 100 °C for the pure polymer, and increases up to 200 °C for the nanocomposites. The permeability of water vapor decreases linearly with inorganic content up to 4% of inorganic phase, and levels off at higher concentrations. The permeability behavior, at low activities, is largely dominated by the diffusion phenomenon. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2454–2467, 2005     

Morphology and properties of cyanate ester/liquid polyurethane/silica nanocomposites

The high‐speed homogeneous shearing method was applied to prepare nanocomposites of cyanate ester (CE) with liquid polyurethane elastomer (PUR) and silica. To investigate the influence of various components on the morphology and properties of the ternary composites, the binary composites of CE/PUR and CE/silica were also involved in this article. The morphology of the cured materials of binary and ternary systems was investigated by transmission electron microscopy (TEM), and the results show that silica nanoparticles were uniformly distributed in the ternary and binary matrix. Phase separation of elastomer in composites was not observed by TEM. FTIR test and dynamic mechanical analysis (DMA) proved that chemical linking was existent between PUR and CE. Scanning electron microscopy examinations and mechanical properties tests were carried out. The results show that ternary composites displayed higher fracture toughness and impact strength compared with most of the binary systems. This suggests that the addition of PUR and nanosilica can synergistically improve the toughness of CE. DMA studies confirmed that the incorporation of silica can increase the storage modulus and T_g for CE and CE/PUR system, since there are a good adhesion and a strong hydrogen bonding between silica and polymers. The thermal property of ternary composites increases with the increase of silica nanoparticle loading. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1243–1251, 2008     

Preparation and characterization of functionalized graphene oxide/carbon fiber/epoxy nanocomposites

Graphene oxide (GO) was functionalized using three different diamines, namely ethylenediamine (EDA), 4,4′-diaminodiphenyl sulfone (DDS) and p-phenylenediamine (PPD) to reinforce an epoxy adhesive, with the aim of improving the bonding strength of carbon fiber/epoxy composite. The chemical structure of the functionalized GO (FGO) nanosheets was characterized by elemental analysis, FT-IR and XRD. Hand lay-up, as a simple method, was applied for 3-ply composite fabrication. In the sample preparation, the fiber-to-resin ratio of 40:60 (w:w) and fiber orientations of 0°, 90°, and 0° were used. The GO and FGO nanoparticles were first dispersed in the epoxy resin, and then the GO and FGO reinforced epoxy (GO- or FGO-epoxy) were directly introduced into the carbon fiber layers to improve the mechanical properties. The GO and FGO contents varied in the range of 0.1–0.5 wt%. Results showed that the mechanical properties, in terms of tensile and flexural properties, were mainly dependent on the type of GO functionalization followed by the percentage of modified GO. As a result, both the tensile and flexural strengths are effectively enhanced by the FGOs addition. The tensile and flexural moduli are also increased by the FGO filling in the epoxy resin due to the excellent elastic modulus of FGO. The optimal FGO content for effectively improving the overall composite mechanical performance was found to be 0.3 wt%. Scanning electron microscopy (SEM) revealed that the failure mechanism of carbon fibers pulled out from the epoxy matrix contributed to the enhancement of the mechanical performance of the epoxy. These results show that diamine FGOs can strengthen the interfacial bonding between the carbon fibers and the epoxy adhesive.