Co-reporter:Jinrong Wu;Lingping Zeng;Xiaopeng Huang;Lijuan Zhao;Guangsu Huang
Journal of Materials Chemistry A 2017 vol. 5(Issue 29) pp:15048-15055
Publication Date(Web):2017/07/25
DOI:10.1039/C7TA02686B
Super-insulating aerogels are promising materials to improve the energy efficiency of buildings. However, fabricating super-insulating yet mechanically robust and shape-memory aerogels remains challenging. Here, we integrate graphene oxide and a block copolymer to fabricate hybrid aerogels with triple networks and systematically study their mechanical and thermal properties. We show that the first network serves as sacrificial bonds and dissipates energy upon deformation, enabling the aerogels to have a high mechanical performance. The second network allows the aerogels to memorize the original permanent shape, and the third network is able to store strain energy and fix the aerogels in a temporary shape by vitrification. Remarkably, the strong phonon-scattering effect generated by the enormous interfaces between the three networks yields an ultra-low solid thermal conductivity of ∼8 mW m−1 K−1. The multi-functionality makes this class of hybrid aerogels particularly suitable for super-insulation applications on complex surfaces and in small spaces of buildings, industry and spacecrafts.
Co-reporter:Wang Xing, Hengyi Li, Guangsu Huang, Li-Heng Cai, Jinrong Wu
Composites Science and Technology 2017 Volume 144(Volume 144) pp:
Publication Date(Web):26 May 2017
DOI:10.1016/j.compscitech.2017.03.006
Conventional elastomer processing requires crosslinking elastomer using specific chemical reagents and reinforcing it using filler particles. Here we report a method to simultaneously crosslink and reinforce styrene-butadiene rubber (SBR) using graphene oxide (GO). We find that GO not only acts as an effective reinforcing filler, but also is capable of generating free radicals upon heating, enabling covalent crosslinking of SBR. Moreover, the interaction between GO surface and SBR polymers results in an interfacial layer in which the density of crosslinks increases towards to the GO surface, thus interfacial layer shows much slower relaxation dynamics than the bulk rubber. The unique role of GO allows GO/SBR nanocomposites to have better mechanical properties than SBR crosslinked with conventional sulfur or dicumyl peroxide. The concept of using GO as both a filler and crosslinking agent may enable the discovery of polymeric nanocomposites with exceeding mechanical properties.Graphene oxide simultaneously crosslinks and reinforces rubbers, thus acting dual roles of crosslinking agent and filler particles.Download high-res image (352KB)Download full-size image
Co-reporter:Zheng-Tian Xie, Xuan Fu, Lai-Yun Wei, Ming-Chao Luo, Yu-Hang Liu, Fang-Wei Ling, Cheng Huang, Guangsu Huang, Jinrong Wu
Polymer 2017 Volume 118(Volume 118) pp:
Publication Date(Web):2 June 2017
DOI:10.1016/j.polymer.2017.04.056
•Interfacial interaction of IR/SGE composite was significantly enhanced by modifying GE with BTESPT.•The thicker bound rubber of IR/SGE composite was observed by Raman mapping.•IR/SGE shows slower chain dynamics and strain-induced crystallization rate than IR/GE.•More efficient load transfer leads to superior mechanical properties of IR/SGE composite.Interfacial interaction is of crucial importance for polymer nanocomposites. To improve interfacial interaction between graphene (GE) and isoprene rubber (IR), we grafted a silane coupling reagent, (bis-[γ-(triethoxysilyl) propyl]-etrasulfide), onto graphene oxide (GO). The modified GO was mixed with IR by solution blending and then reduced in situ to prepare IR/surface modified GE nanocomposites (IR/SGE). Raman mapping illustrates that the bound rubber on SGE is much thicker than that on unmodified GE, suggesting a strong interfacial interaction between SGE and IR. As a result, IR/SGE shows slower chain dynamics and lower strain-induced crystallinity than IR/GE. However, on-line Raman measurements show that the G band of IR/SGE shifts more noticeably during uniaxial tensile deformation than that of IR/GE; this suggests more efficient load transfer between SGE and IR. Consequently IR/SGE has better mechanical properties than IR/GE.Download high-res image (234KB)Download full-size image
Co-reporter:Ming-Chao Luo, Jian Zeng, Zheng-Tian Xie, Lai-Yun Wei, Guangsu Huang, Jinrong Wu
Polymer 2016 Volume 105() pp:221-226
Publication Date(Web):22 November 2016
DOI:10.1016/j.polymer.2016.10.042
•A new relaxation process in supramolecular elastomer.•Quadruple hydrogen bonds disassociation during tensile process.•Re-association of quadruple hydrogen bonds.Here our special consideration is devoted to the relationship between dynamics and mechanical behaviours of supramolecular elastomer (SE) based on 2-ureido-4[1H]-pyrimidinone (UPy) groups. We find that SE exhibits a new relaxation mode (α′ relaxation) which differs from segmental relaxation mode (α relaxation) and normal relaxation mode (NM). Calculated by Arrhenius model, supramolecular interactions are much lower than the bonds energy of covalent bonds; this enables high energy dissipation as the elastomer is subjected to deformation. Moreover, unlike covalent bonds, the hydrogen bonds of UPy groups are dynamic and longer waiting time leads to better re-association efficiency, as evidenced by recovery of hysteresis loop during cyclic tensile tests. This work on the relationship between dynamics and mechanical properties will not only improve the understanding of reversible bonds relaxation, but also provide an idea on preparing mechanically robust SE for us.
Co-reporter:Ming-Chao Luo, Jian Zeng, Xuan Fu, Guangsu Huang, Jinrong Wu
Polymer 2016 Volume 106() pp:21-28
Publication Date(Web):5 December 2016
DOI:10.1016/j.polymer.2016.10.056
•The increase of toughness by incorporation of strong hydrogen bonds interactions.•Quadruple hydrogen bonds disassociation during relaxation behavior and tensile process.•Re-association behavior of quadruple hydrogen bonds.Introducing reversible hydrogen bonds as sacrificial bonds is an emerging strategy to improve the toughness of elastomers. However, binary hydrogen bonds are not strong enough and highly dynamic, and thus have only a moderate toughening effect. Here we demonstrate that quadruple hydrogen bonds have a remarkable toughening effect for diene elastomers. To fabricate the quadruple hydrogen bonds toughened elastomer, we graft 2-ureido-4[1H]-pyrimidinone (UPy) groups onto the backbone of polyisoprene (PI). The UPy groups dimerize to form strong hydrogen bonds which have higher bond energy than binary hydrogen bonds. Compared with weak hydrogen bonds with the same mole fraction, the strong hydrogen bonds lead to higher reversible crosslinking density and slower chain mobility of the elastomer; this enables higher energy dissipation as the elastomer is subjected to deformation. As a result, the introduction of UPy significantly increases both the toughness and the tensile strength of the elastomer. Moreover, unlike covalent sacrificial bonds, the hydrogen bonds of UPy are dynamic and show the re-association of sacrificial bonds at room temperature, as evidenced by recovery of hysteresis loop during cyclic tensile tests. This work will not only greatly extend our understanding on the different toughening effects of weak and strong hydrogen bonds, but also help us to rationally design tougher elastomers.Ashby plot in terms of toughness versus tensile strength, which includes PB-Urazole, Elastomer-Amide and hydroxyl, SBR-Zinc diacrylate, and PI-UPy.
Co-reporter:Maozhu Tang, Wang Xing, Jinrong Wu, Guangsu Huang, Kewei Xiang, Lili Guo and Guangxuan Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 11) pp:5942-5948
Publication Date(Web):04 Feb 2015
DOI:10.1039/C4TA06991A
Diolefin elastomers are particularly susceptible to thermal oxidative ageing, due to the instability of double bonds and allylic hydrogens when exposed to heat or oxygen. Here we demonstrate that graphene (GE) is a prominent antioxidant for preventing styrene-butadiene rubber (SBR) from thermal oxidation. The antioxidant effect is attributed to its free-radical scavenging and gas barrier abilities, which significantly reduces the free-radical concentration and oxygen permeability of the SBR/GE nanocomposites. Thus, incorporation of graphene strongly suppresses the formation of oxygenic groups and additional crosslinking points, at the same time prolongs the oxidative induction time of the nanocomposites. As a result, the nanocomposites show a lower increase in stiffness and glass transition temperature, and a higher retention ratio of tensile strain and strength, compared to the unfilled and the carbon black filled SBR.
Co-reporter:Hengyi Li, Lei Yang, Gengsheng Weng, Wang Xing, Jinrong Wu and Guangsu Huang
Journal of Materials Chemistry A 2015 vol. 3(Issue 44) pp:22385-22392
Publication Date(Web):09 Oct 2015
DOI:10.1039/C5TA05836H
Unfilled rubbers usually show poor mechanical properties. Here, we demonstrate toughening natural rubber (NR) by designing a compact hybrid filler network composed of graphene (GE) and carbon nanotubes (CNTs). The physical interactions in this network have a bond energy lower than covalent bonds; and thus they preferentially break upon deformation and serve as sacrificial bonds that dissipate energy before failure of the materials. The high energy dissipation of the hybrid filler network not only increases the fracture toughness and tensile strength, but also suppresses the crack growth of the NR/GE/CNT nanocomposites. These properties will provide the nanocomposites with better sustainability during practical applications.
Co-reporter:Siduo Wu, Guangsu Huang, Jinrong Wu, Feng Tian and Hui Li
RSC Advances 2015 vol. 5(Issue 42) pp:32909-32919
Publication Date(Web):13 Mar 2015
DOI:10.1039/C5RA02942B
A regulated morphology of Multi-walled Carbon Nanotube Bundles (CNTBs) in an Olefin Block Copolymer (OBC) matrix is achieved via solution blending after short-time strong sonication which breaks the CNTBs into smaller bundles. Inside the CNTBs which consist of several to dozens of nanotubes, the nanotubes exhibit a well aligned structure. A hybrid shish-kebab (HSK) superstructure is observed where the nanotubes in the CNTBs act like a central stem and OBC crystals periodically locate perpendicular to the axis of the nanotubes. With 2 wt% incorporation of the CNTBs, dramatic mechanical reinforcement is achieved with both tripled tensile strength and Young's modulus. The reinforcement might result from an efficient load-transfer brought about by the HSK superstructure as well as the unique bundle morphology of the CNTBs with high robustness. In situ small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques were carried out to investigate the structural evolution of the OBC and nanocomposites upon uniaxial deformation. With a considerable proportion of OBC crystals attached onto the surface of the CNTBs, the scattered lamellaes in the nanocomposites are of lower density. With the contribution from the larger long period of the HSK superstructure and increased space between adjacent lamellaes, the long period of the nanocomposites is remarkably increased. Upon stretching, the decrease of the long period of the neat matrix is dominated by the density of the lamellaes, which increases upon the fragmentation of the lamellaes. Inversely, the increase in the long period of the nanocomposites is dominated by the stretching process, which leads to the increased separation of crystal lamellaes that are of lower density. The HSK superstructures in the nanocomposites act as much larger but fewer hybrid crystal junctions, thus the OBC chains in the nanocomposites are involved in even fewer physical junctions, indicating a less effective network structure than that of the neat matrix. Thus the Hermans' orientation factor of both the orthorhombic crystal and amorphous phases of the nanocomposites are lower than that of the neat matrix. With high incorporation of CNTBs and the prominent stereo hindrance brought about by the rigid CNTB network, the orientation behavior of the nanocomposites doesn't comply to the slip-link theory.
Co-reporter:Siduo Wu;Guangsu Huang;Hui Li
Journal of Applied Polymer Science 2015 Volume 132( Issue 31) pp:
Publication Date(Web):
DOI:10.1002/app.42368
ABSTRACT
In this paper, we report interfacial crystallization in olefin block copolymer (OBC) with low crystallinity incorporated by multi-walled carbon nanotubes (MWCNTs). A hybrid shish-kebab (HSK) superstructure in nanocomposites is observed that MWCNTs act as central shish and OBC crystals grow perpendicular to the nanotubes axis. The mechanical properties of nanocomposites are significantly improved with incorporation of MWCNTs. The most ideal reinforcing and toughening effect is both observed in nanocomposites with MWCNTs content of 1 wt % that can increase tensile strength by 122% as well as elongation at break by 36%. Efficient load transfer are confirmed with in-situ Raman spectra that G’ band of MWCNTs in OBC matrix exhibit a downshifting trend and symmetric broadening of line shape which reveals additional macroscale strain from axial extension of MWCNTs in nanocomposites, thus suggesting a certain load is carried by HSK superstructure. The structural evolution of OBC and nanocomposites are investigated by in-situ wide-angle X-Ray Diffraction (WAXD). The Herman's orientation factor of nanocomposites with 2 wt % MWCNTs incorporation is lower than that of neat matrix at mall and intermediate strains, indicating a heterogeneous stress distribution and low compliance of HSK superstructure, which is consistent with in-situ Raman results. Moreover, the nanocomposites presents significantly enhanced thermal stability. The onset decomposition temperature of nanocomposites with 3 wt % MWCNTs can be 60.2°C higher than that of neat OBC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42368.
Co-reporter:Lijuan Zhao, Xijing Sun, Zhouyue Lei, Jinghong Zhao, Jinrong Wu, Quan Li, Aiping Zhang
Composites Part B: Engineering 2015 Volume 83() pp:317-322
Publication Date(Web):15 December 2015
DOI:10.1016/j.compositesb.2015.08.063
In this work, we presented that the Seebeck coefficient and electrical conductivity can be increased simultaneously in aerogels based on graphene and multi-walled carbon nanotube (graphene-MWCNT) nanocomposites, and at the same time the thermal conductivity is depressed due to 3D porous skeleton structure. As a result, graphene-MWCNT aerogels possess ultra-low thermal conductivities (∼0.056 W m−1 K−1) and apparent density (∼24 kg m−3), thereafter the figure of merit (ZT) of ∼0.001 is achieved. Although the ZT value is too low for practical application as a thermoelectric (TE) material, the unique structure in this project provides a potential way to overcome the challenge in bulk semiconductors that increasing electrical conductivity generally leads to decreased Seebeck coefficient and enhanced thermal conductivity.
Co-reporter:Siduo Wu;Guangsu Huang;Hui Li
Macromolecular Research 2015 Volume 23( Issue 6) pp:537-544
Publication Date(Web):2015 June
DOI:10.1007/s13233-015-3071-8
Co-reporter:Wang Xing;Guangsu Huang;Hui Li;Maozhu Tang ;Xuan Fu
Polymer International 2014 Volume 63( Issue 9) pp:1674-1681
Publication Date(Web):
DOI:10.1002/pi.4689
Graphene/natural rubber (GE/NR) nanocomposites were prepared by a modified latex mixing method combined with in situ chemical reduction. It was found that the GE nanosheets are well dispersed and have strong interfacial interaction with NR. Thus, adding a low content of GE can remarkably increase the tensile strength and the initial tensile modulus of NR. With incorporation of as low as 0.5 phr of GE, a 48% increase in the tensile strength and an 80% increase in the initial tensile modulus are achieved without sacrificing the ultimate strain. But further increasing the GE loading degrades the tensile strength and the ultimate strain. Dynamic mechanical measurement indicates that the storage modulus of the nanocomposites is greatly enhanced with addition of GE, while the loss tangent peak is depressed due to the reduced mobility of the rubber molecules. The reinforcement effect of GE on NR is interpreted as a change in the strain induced crystallization and network structure of the nanocomposites, based on the analysis of Mooney − Rivlin plots and the tube model.© 2013 Society of Chemical Industry
Co-reporter:Hui Li;Siduo Wu;Guangsu Huang
Journal of Polymer Research 2014 Volume 21( Issue 5) pp:
Publication Date(Web):2014 May
DOI:10.1007/s10965-014-0456-x
Styrene-butadiene-styrene tri-block copolymer/graphene (SBS/GE) nanocomposites were prepared by solution mixing and in situ reduction of graphene oxide using hydrazine hydrate. The dispersion state of graphene was examined by XRD and optical examination, which indicates that the graphene nanosheets are well exfoliated and dispersed in the SBS matrix. The interfacial interaction between graphene and SBS was investigated by sedimentation experiment in toluene. After dissolving of the SBS/GE nanocomposite, the graphene nanosheets do not separate from the solution, moreover, even after prolonged ultracentrifugation, a dark-colored supernatant with graphene suspension is still retained, suggesting that the graphene nanosheets are stabilized in the solution with the attached SBS molecules due to the existence of strong interfacial interaction. The well dispersion of graphene and the enhanced interfacial interaction lead to a remarkable improvement in the electrical conductivity and mechanical properties. A percolation threshold as low as 0.12 vol.% of graphene has been achieved because of the formation of a three dimensional conductive network. Meanwhile, with the incorporation of as low as 0.5 wt% of graphene, the tensile strength of the nanocomposite has already displayed a two-fold increase compared with that of pure SBS.
Co-reporter:Mao-zhu Tang;Wang Xing;Jin-rong Wu 吴锦荣
Chinese Journal of Polymer Science 2014 Volume 32( Issue 5) pp:658-666
Publication Date(Web):2014 May
DOI:10.1007/s10118-014-1427-8
This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber (SBR) with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.
Co-reporter:Jinrong Wu, Wang Xing, Guangsu Huang, Hui Li, Maozhu Tang, Siduo Wu, Yufeng Liu
Polymer 2013 Volume 54(Issue 13) pp:3314-3323
Publication Date(Web):7 June 2013
DOI:10.1016/j.polymer.2013.04.044
In the present work, the influence of graphene (GE) on the vulcanization kinetics of natural rubber (NR) with sulfur curing system was investigated in detail for the first time. It is found that on adding graphene the induction period of the vulcanization process is remarkably depressed, whereas the vulcanization rate is enhanced at low graphene loading and then suppressed. As a result, the optimum cure time decreases dramatically at first and subsequently shows a slight increase with increasing graphene loading. At the same time, the crosslinking density of NR increases monotonically, because graphene takes part in the vulcanization process. The exothermal peak of the vulcanization reactions is split into two peaks on adding ≥0.5 phr graphene. It is interpreted in terms of two reaction stages, i.e., chemical reaction controlling stage and diffusion controlling stage. The activation energy of the former stage decreases with increasing graphene loading, while that of the latter stage is higher than the former one and increases with graphene loading. A possible mechanism was proposed to interpret the accelerating effect of graphene and the enhanced crosslinking density of NR.
Co-reporter:Hui Li;Siduo Wu;Guangsu Huang
Colloid and Polymer Science 2013 Volume 291( Issue 10) pp:2279-2287
Publication Date(Web):2013 October
DOI:10.1007/s00396-013-2959-0
Graphene-based polystyrene (PS) nanocomposites were prepared by latex mixing, co-coagulation, and in situ reduction process. In the process, aqueous dispersion of graphene oxide (GO) was mixed with PS latex, which was then co-coagulated with sodium chloride to form stabilized particle suspension; subsequently, hydrazine hydrate was added to reduce GO in situ. This process could avoid the use of additional surfactant or ultrasonic power to stabilize graphene during reduction, thus is facile and energy saving. The preparation process and the resulting nanocomposites were characterized in detail. The results show that, after co-coagulation, GO nanosheets are isolated by PS nanospheres through π–π interaction, which prevents the restacking of graphene in the subsequent reduction process. Thus, a molecular-level dispersion of the graphene nanosheets in the PS matrix is achieved, which greatly improves the electrical conductivity and the mechanical properties of the nanocomposites.
Co-reporter:Xiaoan Wang, Xiaojun He, Guangsu Huang, Jinrong Wu
Polymer 2012 Volume 53(Issue 2) pp:665-672
Publication Date(Web):24 January 2012
DOI:10.1016/j.polymer.2011.11.059
In the present paper, dynamic mechanical properties of poly(n-alkyl acrylates) (PnAA) and poly(n-alkyl methacrylates) (PnAMA) with different alkyl side chain length were studied. The results show that with the increase of alkyl side chain length, the storage modulus changes more steadily, and the loss modulus peak and the tanδ peak become broader for PnAA and PnAMA. At the same time, the tanδ peak is more and more apart from the loss modulus peak and the point where the storage modulus begins to drop. For quantitative discussion, three variables, the steepness index (S), the transition wideness (W) of storage modulus and the integration area (A) of tanδ were defined to investigate the potential correlation between the dynamic mechanical properties and alkyl side chain length. It can be observed that S decreases while W and A increase with increasing alkyl side chain length. Moreover, the relaxation spectra of the two series of polymers are calculated from the corresponding mechanical spectra. The shapes of the relaxation spectra are broader and broader with the increase of the alkyl side chain length. These phenomena are interpreted by the perspective of fragility, molecular packing efficiency and intermolecular coupling.
Co-reporter:Jinrong Wu, Lingping Zeng, Xiaopeng Huang, Lijuan Zhao and Guangsu Huang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 29) pp:NaN15055-15055
Publication Date(Web):2017/06/12
DOI:10.1039/C7TA02686B
Super-insulating aerogels are promising materials to improve the energy efficiency of buildings. However, fabricating super-insulating yet mechanically robust and shape-memory aerogels remains challenging. Here, we integrate graphene oxide and a block copolymer to fabricate hybrid aerogels with triple networks and systematically study their mechanical and thermal properties. We show that the first network serves as sacrificial bonds and dissipates energy upon deformation, enabling the aerogels to have a high mechanical performance. The second network allows the aerogels to memorize the original permanent shape, and the third network is able to store strain energy and fix the aerogels in a temporary shape by vitrification. Remarkably, the strong phonon-scattering effect generated by the enormous interfaces between the three networks yields an ultra-low solid thermal conductivity of ∼8 mW m−1 K−1. The multi-functionality makes this class of hybrid aerogels particularly suitable for super-insulation applications on complex surfaces and in small spaces of buildings, industry and spacecrafts.
Co-reporter:Maozhu Tang, Wang Xing, Jinrong Wu, Guangsu Huang, Kewei Xiang, Lili Guo and Guangxuan Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 11) pp:NaN5948-5948
Publication Date(Web):2015/02/04
DOI:10.1039/C4TA06991A
Diolefin elastomers are particularly susceptible to thermal oxidative ageing, due to the instability of double bonds and allylic hydrogens when exposed to heat or oxygen. Here we demonstrate that graphene (GE) is a prominent antioxidant for preventing styrene-butadiene rubber (SBR) from thermal oxidation. The antioxidant effect is attributed to its free-radical scavenging and gas barrier abilities, which significantly reduces the free-radical concentration and oxygen permeability of the SBR/GE nanocomposites. Thus, incorporation of graphene strongly suppresses the formation of oxygenic groups and additional crosslinking points, at the same time prolongs the oxidative induction time of the nanocomposites. As a result, the nanocomposites show a lower increase in stiffness and glass transition temperature, and a higher retention ratio of tensile strain and strength, compared to the unfilled and the carbon black filled SBR.
Co-reporter:Hengyi Li, Lei Yang, Gengsheng Weng, Wang Xing, Jinrong Wu and Guangsu Huang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 44) pp:NaN22392-22392
Publication Date(Web):2015/10/09
DOI:10.1039/C5TA05836H
Unfilled rubbers usually show poor mechanical properties. Here, we demonstrate toughening natural rubber (NR) by designing a compact hybrid filler network composed of graphene (GE) and carbon nanotubes (CNTs). The physical interactions in this network have a bond energy lower than covalent bonds; and thus they preferentially break upon deformation and serve as sacrificial bonds that dissipate energy before failure of the materials. The high energy dissipation of the hybrid filler network not only increases the fracture toughness and tensile strength, but also suppresses the crack growth of the NR/GE/CNT nanocomposites. These properties will provide the nanocomposites with better sustainability during practical applications.
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