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.     

Ionic liquid functionalized graphene oxide for enhancement of styrene‐butadiene rubber nanocomposites

Ionic liquid 1‐allyl‐3‐methyl‐imidazolium chloride (AMICl) is used to fine‐tune the surface properties of graphene oxide (GO) sheets for fabricating ionic liquid functionalized GO (GO‐IL)/styrene‐butadiene rubber (SBR) nanocomposites. The morphology and structure of GO‐IL are characterized using atomic force microscope, X‐ray diffraction, differential scanning calorimetry, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV‐vis spectra and Raman spectra. The interaction between GO and AMICl molecules as well as the effects of GO‐IL on the mechanical properties, thermal conductivity and solvent resistance of SBR are thoroughly studied. It is found that AMICl molecules can interact with GO via the combination of hydrogen bond and cation–π interaction. GO‐IL can be well‐dispersed in the SBR matrix, as confirmed by X‐ray diffraction and scanning electron microscope. Therefore, the SBR nanocomposites incorporating GO‐IL exhibit greatly enhanced performance. The tensile strength, tear strength, thermal conductivity and solvent resistance of GO‐IL/SBR nanocomposite with 5 parts per hundred rubber GO‐IL are increased by 505, 362, 34 and 31%, respectively, compared with neat SBR. This method provides a new insight into the fabrication of multifunctional GO‐based rubber composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermogravimetric study of rubber waste-polyurethane composites

Granulated rubber obtained from used tyres, below 1.5 mm granularity (fine rubber) and polyurethane prepolymers (Chemolan M, Chemolan M50 and Chemolan B3) were used for the synthesis of rubber waste-polyurethane composites, containing 90, 85, 80, 75 and 70% w/w of fine rubber. The influence of the kind of polyurethane resin on hardness, elasticity, glass transition temperature and thermal stability of composites was studied. Kinetic parameters of the thermal degradation process of composites were calculated from thermogravimetric analysis (TG) data.This work has been financially supported by the State Committee for Scientific Research, Poland (research project-grant no. 3 T09B 043 19).     

Dichlorocarbene modified butadiene rubber (DCBR): Preparation,kinetic study,and its properties in natural rubber/DCBR blend vulcanizates

Dichlorocarbene modified butadiene rubber (DCBR) was prepared via the addition of the dichlorocarbene group in the presence of 2 phase transfer agents (cetyltrimethylammonium bromide and tetraethylammonium chloride). The effects of the reaction temperature and time, amount of dichlorocarbene precursor, and the type and amount of phase transfer agent on the chlorine content were investigated. The highest chlorine content (30%) in DCBR was obtained using 0.062 mol chloroform and 0.003 mol cetyltrimethylammonium bromide at room temperature for 19 hours although 27.9% was obtained after 12 hours. The kinetics of this dichlorocarbene modification was best described by the pseudo–first order rate law with 2 rate constants. For practical applications, the DCBR with chlorine contents of 10%, 20%, or 30% were blended with natural rubber (NR) and then vulcanized using the sulfur‐curing system. Although the polarity of DCBR was increased, a good compatibility between NR and DCBR still existed, resulting in improved mechanical properties. The oil resistance, flame retardant, and ozone resistance properties of the NR/DCBR blend vulcanizates were enhanced compared to those of a NR/butadiene rubber blend vulcanizate, which was related to the amount of chlorine incorporated into the DCBR.     

Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber

The effects of functionalized graphene sheets (FGSs) on the mechanical properties and strain‐induced crystallization of natural rubber (NR) are investigated. FGSs are predominantly single sheets of graphene with a lateral size of several hundreds of nanometers and a thickness of 1.5 nm. The effect of FGS and that of carbon black (CB) on the strain‐induced crystallization of NR is compared by coupled tensile tests and X‐ray diffraction experiments. Synchrotron X‐ray scattering enables simultaneous measurements of stress and crystallization of NR in real time during sample stretching. The onset of crystallization occurs at significantly lower strains for FGS‐filled NR samples compared with CB‐filled NR, even at low loadings. Neat‐NR exhibits strain‐induced crystallization around a strain of 2.25, while incorporation of 1 and 4 wt % FGS shifts the crystallization to strains of 1.25 and 0.75, respectively. In contrast, loadings of 16 wt % CB do not significantly shift the critical strain for crystallization. Two‐dimensional (2D) wide angle X‐ray scattering patterns show minor polymer chain alignment during stretching, in accord with previous results for NR. Small angle X‐ray scattering shows that FGS is aligned in the stretching direction, whereas CB does not show alignment or anisotropy. The mechanical properties of filled NR samples are investigated using cyclic tensile and dynamic mechanical measurements above and below the glass transition of NR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Mechanical and thermal properties of green polylactide composites with natural fillers

Green composites of PLA with micropowders derived from agricultural by-products such as oat husks, cocoa shells, and apple solids that remain after pressing have been prepared by melt mixing. The thermal and mechanical properties of the composites, including the effect of matrix crystallization and plasticization with poly(propylene glycol), have been studied. All fillers nucleated PLA crystallization and decreased the cold-crystallization temperature. They also affected the mechanical properties of the compositions, increasing the modulus of elasticity but decreasing the elongation at break and tensile impact strength although with few exceptions. Plasticization of the PLA matrix improved the ductility of the composites.     

A facile and green preparation of nanosilica-supported antioxidant and its reinforcement and antioxidation effect on styrene-butadiene rubber

A novel solid-phase method has been proposed to prepare a nanosilica-supported antioxidant by the reaction of nanosilica with 2-mercaptobenzimidazole (MB) and silane coupling agent γ-chloropropyltriethoxysilane. Fourier transform-infrared spectroscopy and other characterization methods confirmed that MB was chemically bonded onto the surface of nanosilica. Silica-s-MB was homogeneously dispersed in a styrene-butadiene rubber (SBR) matrix with strong filler-rubber interaction, leading to enhanced mechanical performance of SBR/silica-s-MB composites compared with SBR/m-silica composites. Based on the results of thermo-oxidation testing of SBR/silica-s-MB and SBR/m-silica/MB composites containing equivalent antioxidant component, silica-s-MB showed better antioxidative efficiency than the corresponding low-molecular-weight MB owing to its lower migration and volatility at high temperature.     

Enhanced thermal conductivity and mechanical properties of polymeric composites through formation of covalent bonds between boron nitride and rubber chains

Hexagonal boron nitride (BN) platelets, also known as white graphite, are often used to improve the thermal conductivities of polymeric matrices. Due to the poor interfacial compatibility between BN platelets and polymeric matrices, in this study, polyrhodanine (PRd) was used to modify BN platelets and prepared functionalized BN-PRd platelets, thereby enhancing the interfacial interaction between the thermal conductive filler and polymeric matrix. Then, BN-PRd platelets were dispersed into the nitrile butadiene rubber (NBR) matrix to yield high thermally conductive composites. The presence of N? C═S groups in PRd allowed the combination of PRd and NBR chains containing stable covalent bonds via vulcanization reaction. The thermal conductivity of the as-prepared 30 vol% BN-PRd/NBR composite reached 0.40 W/mK, representing an increment of 135% over pure NBR (0.17 W/mK). In addition, the largest tensile strength of NBR composite containing 30 vol% BN-PRd platelets was 880% times of pure NBR. The 30 vol% BN-PRd/NBR composite also displayed a relatively high dielectric constant (9.35 at 100 Hz) and a low dielectric loss tangent value (0.07 at 100 Hz), indicating their usefulness as dielectric flexible materials of microelectronics. In sum, the simplicity and good efficiency of formation of covalent bonds between boron nitride and rubber chains look very promising for large-scale industrial production of high thermally conductive composites.     

Investigation of the dielectric,mechanical, and thermal properties of noncovalent functionalized MWCNTs/polyvinylidene fluoride (PVDF) composites

To improve the dispersion of multi‐walled walled carbon nanotubes (MWCNTs) and investigate the effect of dispersant for MWCNTs functionalization on the dielectric, mechanical, and thermal properties of Polyvinylidene fluoride (PVDF) composites, two different dispersants (Chitosan and TritonX‐100) with different dispersion capability and dielectric properties were used to noncovalently functionalize MWCNTs and prepare PVDF composites via solution blending. Fourier transform infrared, X‐Ray diffraction, and Raman spectroscopy indicated that TritonX‐100 and Chitosan were noncovalent functionalized successfully on the surface of MWCNTs. With the functionalization of Chitosan and TritonX‐100, the dispersion of MWCNTs changed in different extent, which was investigated by dynamic light scattering and confocal laser scan microscopy. The dielectric, mechanical, and thermal properties of PVDF composites were also improved. Meanwhile, it was also found that the dielectric properties of PVDF composites are closely related to the dielectric properties of dispersant. High dielectric constant of dispersant contributes to the grant dielectric constant of PVDF composites. The mechanical and thermal properties of MWCNTs/PVDF composites largely depend on the dispersion of MWCNTs in PVDF, interfacial interactions and the residual solvent. Copyright © 2016 John Wiley & Sons, Ltd.     

The improvement of thermal stability and adhesion of silicone rubber composites modified by phenolic epoxy resin

The phenolic epoxy resin (F51) was siliconized by KH550 and the product was named as FKS. A hydroxyl-terminated polydimethylsiloxane (HTPDMS) which was modified with FKS was prepared. The siliconization reaction ensured a segment of siloxane on the side chain of F51. FT-IR and ¹H-NMR were employed to confirm the chemical structure of FKS. Morphology observations revealed that the enhancement of mechanical properties of the silicone rubber systems can be attributed to good compatibility between FKS and silicone rubber matrix. Thermogravimetric analysis showed that the residual yield at 800?°C of silicone rubber composites increased significantly when compared with that of neat HTPDMS. The mechanical properties demonstrated that tensile strength and elongation at break of silicone rubber system increased distinctly after modification, especially when 30 phr siliconized F51 were added to the silicone rubber. Shear strength was improved gradually with the addition of FKS. These above observations emphasize the vital effect of FKS on the behavior of modified HTPDMS.     

POSS nanoparticles as a potential compatibilizer for natural rubber/butadiene rubber blends

In this study, it was aimed to investigate octavinyl‐polyhedral oligomeric silsesquioxane (OV‐POSS) incorporation into natural rubber (NR)/butadiene rubber (BR) elastomer blends as a potential compatibilizer. The effects of OV‐POSS loading levels on the thermal, mechanical, morphological, and dynamic‐mechanical properties of elastomer blends were explored. Fourier‐Transform Infrared Spectrometer (FTIR), Temperature Scanning Stress Relaxation (TSSR), and Differential Scanning Calorimetry (DSC) results revealed the conceivable effect of OV‐POSS nanoparticles in the vulcanization through reacting with sulfur and/or elastomers. Scanning Electron Microscope (SEM), X‐Ray Diffraction (XRD), and tensile test measurements supported the improvement of mechanical properties due to homogeneous dispersion at low loading levels. On the other hand, high amount of OV‐POSS incorporation (7 and 10 phr) resulted in a decrease in mechanical properties, owing to the agglomeration of nanoparticles. According to contact angle and Dynamic mechanical analysis (DMA) results, it could be concluded that OV‐POSS nanoparticles were localized at the interface of the elastomers and enabled the compatibilization of immiscible NR/BR blends.     

The effects of a silane coupling agent on curing characteristics and mechanical properties of bamboo fibre filled natural rubber composites

The effects of a silane coupling agent on curing characteristics and mechanical properties of bamboo fibre filled natural rubber composites were studied. Scorch time, t₂ and cure time, t₉₀ of the composites decrease with increasing filler loading and with the presence of a silane coupling agent, Si69. Mooney viscosity also increases with increasing filler loading but at a similar filler loading shows lower value with the presence of Si69. The mechanical properties of composites viz tensile strength, tear strength, hardness and tensile modulus were also improved with the addition of Si69.     

Styrene butadiene rubber/carbon black composites modified by imidazole derivatives

In this study, the imidazole derivatives such as 2-undecylimidazole (UI) and 2-mercapto-1-methylimidazole (MMI) are utilized to work as novel additives for modifying styrene butadiene rubber (SBR)/carbon black (CB) composites. The imidazole groups on UI and MMI can be hydrogen-bonded with oxygen-containing groups on the surface of CB, and the undecyl or thiol groups can be reacted with the SBR chains via physical entanglement or thiol-ene chemistry. The results demonstrate that the static and dynamic mechanical performances of SBR/UI and SBR/MMI composites are significantly improved over those of the SBR composite. Compared with blank SBR composite, the tensile strength, modulus at 300% elongation, and tear strength of SBR/MMI-1.0 are greatly improved by 30, 42, and 18%, respectively. The rolling resistance of SBR/MMI-1.0 is reduced by 10.4%, and the wet grip property is increased by 4.0%. The superiority of appropriate MMI content (1.0 phr in our work) in the enhancement for the overall performance of SBR composites is attributed to the promotion of a good dispersion of CB throughout the SBR matrix and the enhanced interfacial interactions between CB and the SBR matrix. This work may enlarge the potential applications of modified CB to fabricate high-performance rubber composites.     

Synergistic effects of functionalized graphene and functionalized multi-walled carbon nanotubes on the electrical and mechanical properties of poly(ether sulfone) composites

Mixed fillers composed of functionalized graphene (f-G) and functionalized multi-walled carbon nanotubes (f-CNTs) (f-G-f-CNTs) were prepared and their synergistic effects in terms of enhancing the electrical conductivity and tensile modulus of poly(ether sulfone) (PES) composites were investigated. The results indicate that the electrical conductivity of the 5 wt% f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite was 2.2 times higher than that of the 5 wt% f-G/PES composite and 8.9 times higher than that of the 5 wt% f-CNTs/PES composite. Moreover, the tensile modulus of the 5 wt% f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite relative to that of the 5 wt% f-G/PES composite and 5 wt% f-CNTs/PES composite increased by 16.5% and 50.6%, respectively. Additionally, enhancements in the electrical conductivity and tensile modulus of the PES composite depended on the weight ratio of f-G and f-CNTs in the mixed fillers. The electrical conductivity and tensile modulus exhibited maximum values when the weight ratios of f-G and f-CNTs were 1:3 and 1:1, respectively. When the weight ratio of f-G and f-CNTs was fixed at 1:1, the f-G-f-CNTs(W_f-G/W_f-CNTs = 1:1)/PES composite showed a percolation threshold of 0.22 vol%, much lower than that of the f-G/PES composite.     

New PP/PLA/cellulose composites: effect of cellulose functionalization on accelerated weathering behavior (accelerated weathering behavior of new PP/PLA/cellulose composites)

Polylactic acid (PLA) was used as partial replacement for conventional thermoplastic matrix, new composites comprising cellulose, polypropylene (PP), and PLA being realized. In order to obtain a compatible interface between cellulosic pulp and polymeric matrix, two chemical modifications of cellulose with stearoyl chloride and toluene di‐isocyanate (TDI) were performed, structural changes being evidenced by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The composite materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, dynamic scanning calorimetry, impact, tensile and melt rheological tests, surface tension, and dynamic vapor sorption. Because promising results for impact strength and Young modulus were recorded when replacing 15% of PP with PLA in blends of PP with the same cellulosic pulp load, the aim of our study was to assess the behavior to accelerate weathering of composites comprising PP, cellulosic pulp, and PLA. Although the slight decrease in the mechanical properties was recorded after accelerated weathering, the use of functionalized cellulose successfully prevented the deterioration of surface materials, especially for composite comprising stearoyl chloride treated cellulose pulp. Copyright © 2015 John Wiley & Sons, Ltd.     

湿法改性石墨烯在制备橡胶复合材料中的应用

橡胶由于其高弹性、良好的生物相容性、耐化学腐蚀及长期使用的稳定性等优点,在众多领域已有一百多年的应用历史。一般来说,在生胶硫化之前需要加入增强填料、润滑剂、偶联剂和促进剂等各类添加剂,以达到使用要求的性能。其中增强填料起到提高橡胶强度、提高橡胶耐磨耐热性、延长橡胶使用寿命的作用。相比于炭黑或者二氧化硅这些传统增强填料,新兴纳米材料石墨烯由于其优异的性能,只需极少量便可使橡胶的性能显著增强。然而,石墨烯片层之间的范德华力严重的阻碍了其在高分子机体内的分散,其在橡胶基体的分散性直接决定了石墨烯对于橡胶材料的增强效果。近年来,越来越多的研究开始关注通过在溶液中的湿法改性,包括物理或化学的方法来改性石墨烯,促进它与橡胶二者界面的相互作用,提高石墨烯在橡胶基体中的分散效果。本文总结了近几年湿法改性石墨烯在制备石墨烯/橡胶复合材料方面的研究进展。     

Influence of heat treatment on electromagnetic properties of polyimide/carbon black composites

A kind of absorbing materials was prepared by hot pressing method using polyimide as matrix and carbon black (CB) as filler. The mechanical properties, the electromagnetic properties, and the thermal stability of polyimide/CB composites were studied. The results showed that the complex permittivity increased from 6.82 + 1.38i to 18.69 + 9.47i, whereas the flexural strength decreased from 108 MPa to 77 MPa, respectively, when the CB content increased from 2 wt% to 8 wt%. The reflection loss curves shifted to low frequency with increase of the thickness at the same content. The reflection loss below ?10 dB could be obtained in the X band with 6 wt% CB content and did not display significant difference before and after the heat treatment at 400°C for 5 h. When the content of CB was 8 wt%, the decomposition temperature (at 5% weight loss) increased approximately 42°C compared with pure polyimide matrix. Copyright © 2014 John Wiley & Sons, Ltd.     

石墨烯/天然橡胶复合材料结构与性能研究

采用乳液共混、机械共混及两者并用制备了石墨烯(GNs)/天然橡胶(NR)复合材料,采用扫描电镜(SEM)、X-射线衍射(XRD)仪、高阻仪、动态热机械分析(DMA)仪、万能拉力试验机、热重分析(TG)仪对材料微观结构与宏观性能的相关性进行研究。研究表明:相比于机械共混,乳液共混有助于GNs的均匀分散和导电网络的形成,GNs/NR复合材料表现出较优的机械和导电性能,定伸应力和导电率分别是机械共混法的3倍和100倍;乳液共混后的机械共混则破坏了原有的导电网络,复合材料导电率下降;随后的机械共混打乱了原有的网络结构,并促使了GNs片层的卷曲化,降低了GNs与NR的接触面积,复合材料的综合性能下降。     

New double negative and positive temperature coefficients of conductive EPDM rubber TiC ceramic composites

In this paper, we have successfully prepared ethylene-propylene-diene monomer (EPDM)/TiC composites as thermistors, with new double negative and positive temperature coefficients of conductivity (NTCC/PTCC). EPDM composites loaded with 50 phr HAF carbon black and different concentrations of TiC were prepared. This study focuses on the effect of TiC content on the vulcanization process, the network structure and the electrical and thermal properties of EPDM/TiC composites. The effect of TiC on the network structure was evaluated e.g. the curing process, the characteristic time constant during vulcanization, the volume fraction of rubber, gel fraction, interparticle distance between conductive particles, the extent of TiC reinforcement in the rubber matrix and molecular weight between cross-linking through experimental and affine-phantom models. The effects of TiC content on the percolation theory, electrical conductivity, conducting mechanism of conductivity, conducting hysteresis and I-V characteristics were also studied, as well as its TiC on the (NTCC/PTCC), thermoelectric power, dielectric constant and thermal conductivity. Stability and reproducibility of the thermal cycles for heating element applications was tested. Specific heat and the amount of heat transfer by radiation and convection as a function of TiC content was calculated using both the calorimetric technique and a theoretical model. It was proved that TiC improves the network structure, electrical and thermal properties of EPDM composites for practical applications.