Co-reporter:Zenghui Yang;Tingmei Wang
Journal of Materials Chemistry A 2017 vol. 5(Issue 26) pp:13823-13833
Publication Date(Web):2017/07/04
DOI:10.1039/C7TA02842C
The combination of shape memory with other new-fashioned functions will facilitate great potential in the development of shape memory materials. Demonstrated here is a multifunctional polymer based on hyperbranched polyimides (HBPIs) that integrates shape memory into a gas capture membrane. The new kind of shape memory gas capture HBPIs were prepared by branching conventional thermoplastic polyimides via a two-step method with 2,4,6-triaminopyrimidine (TAP) as the branched center. The optimized HBPIs exhibit good shape-memory properties with shape fixity above 98% and recovery values above 82%. Moreover, they show large Brunauer–Emmett–Teller (BET) surface areas (218–387 m2 g−1), mesoporous characteristics (3–5 nm) and narrow pore size distribution, which endow them with preferable CO2 capture (up to 36.93 cm3 g−1) and selectivity (up to 66.3). The comprehensive properties, especially the shape recovery ratio and CO2 uptake, of the HBPIs can be effectively controlled by adjusting the degree of branching (DB) or the content of the rigid heterocyclic diamine, 5-amino-2-(4-aminobenzene) benzoxazole (BOA). Our multifunctional shape memory polymer (SMP) may expand the application field of shape memory and accelerate the development of SMPs.
Co-reporter:Ding Zhang, Huimin Qi, Fuyan Zhao, Ga Zhang, Tingmei Wang, Qihua Wang
Tribology International 2017 Volume 115(Volume 115) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.triboint.2017.05.040
•Hexagonal nanoparticles improve sliding performance of PPS composite in diesel.•Presence of only limited quantity diesel results in best tribological performance.•Tribo-chemical reactions of PPS with steel and AlN nanoparticles were identified.The roles of various fillers, i.e. short carbon fibers (SCF), graphite, hexagonal structured tungsten disulfide (WS2) and aluminium nitride (AlN) nanoparticles, on the tribologial performance of polyphenylene sulphid (PPS) were explored with low-sulfur diesel as lubricant. It was demonstrated that the nanoparticles, especially AlN, remarkably improved the tribologial performance of PPS composites under diesel lubrication conditions. Moreover, presence of only very limited quantity of diesel results in the best tribological performance. It was manifested that the tribological performance was closely dependent on the tribofilm formed on steel counterface. Tribo-chemical reactions of PPS with both the steel counterpart and AlN nanoparticles were identified, as deemed important for generation of a robust tribofilm.
Co-reporter:Chuanping Gao, Guofan Guo, Ga Zhang, Qihua Wang, Tingmei Wang, Honggang Wang
Materials & Design 2017 Volume 115(Volume 115) pp:
Publication Date(Web):5 February 2017
DOI:10.1016/j.matdes.2016.11.016
•The hydration of h-BN nanoparticles plays an important role to form a stable boundary film on the sliding contact surfaces.•H3BO3 and B2O3 molecules are arrayed in a closely packed outmost layer of the boundary film.•The basal planes of H3BO3 and B2O3 are aligned parallel to the sliding direction.•The aligned H3BO3 and B2O3 basal planes are crucial for the high tribological performance of the POM nanocomposite.Development of high-performance polymer composites exposed to water lubrication conditions is of increasing interests for numerous applications, where high durability and reliability are demanded. However, formation of a protective boundary reaction layer on the rubbing surfaces can be problematic with the presence of water. The roles of hexagonal boron nitride (h-BN) nanoparticles on the tribological performance of polyoxymethylene (POM) and POM composite reinforced with short carbon fibers were investigated. It is identified that the addition of low loading h-BN greatly improves the tribological performance, e.g. wear resistance of POM is enhanced by one order of magnitude. Moreover, h-BN and carbon fibers play a synergetic role in enhancing the wear resistance. Tribo-chemistry and nanostructures of the boundary film were comprehensively investigated. It is revealed that H3BO3 and B2O3 generated as products of tribo-chemical reactions are arrayed in a closely packed outmost layer of the boundary film and exert an important influence on the tribological performance. Our work gives the evidence that the basal planes of H3BO3 and B2O3 are aligned parallel to the sliding direction, leading to low friction and wear.Download high-res image (334KB)Download full-size image
Co-reporter:Zenghui Yang, Qihua Wang, and Tingmei Wang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 33) pp:21691
Publication Date(Web):July 27, 2016
DOI:10.1021/acsami.6b07403
Conventional thermoset shape memory polymers can maintain a stable permanent shape, but the intrinsically chemical cross-linking leads to shape that cannot be altered. In this paper, we prepared shape memory graphene-vitrimer composites whose shape can be randomly changed via dynamic covalent transesterification reaction. Consecutive shape memory cycles indicate stable shape memory with undetected strain shift and constant shape fixity and recovery values (Rf > 99%, Rr > 98%). Quantitative characterization of shape reconfiguration by dynamic mechanical thermal analysis (DMA) shows prime reconfigurable behavior with shape retention ratio of 100%. Thus, the arbitrary 2D or 3D newly permanent shape can be easily obtained from a simple plain sample by facile thermal treatment at 200 °C above transesterification temperature (Tv). Besides, it is found that graphene-vitrimers show a ductile fracture in tensile test with a large breaking strain and classical yield phenomenon because of the well-dispersed graphene sheets in the vitrimer that endow effective stress transfer. As the graphene loading increases from 0% to 1%, the yield strength and breaking stain increase from 12.0 MPa and 6% to 22.9 MPa and 44%, respectively. In addition, graphene also serves as energy convertor to convert near-infrared (NIR) irradiation into thermal energy to induce a helix shape sample that is recovered totally within 80 s sequent NIR irradiation. These dual-triggered and reconfigurable shape memory graphene-vitrimers are expected to significantly simplify processing of complex shape and broaden the applications of shape memory polymers.Keywords: graphene; reconfiguration; shape memory polymer; stimulus; vitrimer
Co-reporter:Fuzhi Song, Qihua Wang, Tingmei Wang
Composites Science and Technology 2016 Volume 134() pp:251-257
Publication Date(Web):6 October 2016
DOI:10.1016/j.compscitech.2016.08.011
In the present work, the effects of nano-SiO2 and solid lubricants (SLs) such as PTFE and WS2 on friction and wear behavior of polyimide (PI) composites reinforced by carbon fibers were investigated in extremely wide PV (the product of velocity and pressure) factors. The results showed that the nano-SiO2 particles can reduce friction coefficient significantly under all conditions. Under low PV conditions, from the perspective of anti-wear property, the wear rate of SiO2/SLs/SCF/PI is remarkably reduced by the synergistic effect of nanoparticles and solid lubricants. Under PV value higher than 59.26 MPa m/s, however, it performs poor anti-wear property, which mainly due to the deteriorated mechanical properties by incorporating solid lubricants and thermal instability of solid lubricants. However, the nanoparticles improve the wear resistance of SiO2/SCF/PI considerably especially under high PV conditions and the PV limit is got at 152.37 MPa m/s. The protection of fiber-matrix interface by nanoparticles, the higher mechanical properties and high thermal stability of SiO2 are responsible for the improvement of PV limit.
Co-reporter:Chuanping Gao, Ga Zhang, Tingmei Wang and Qihua Wang
RSC Advances 2016 vol. 6(Issue 56) pp:51247-51256
Publication Date(Web):19 May 2016
DOI:10.1039/C6RA06904E
The formation of a tribo-film on the counterface plays an important role on the tribological performances of polymer subjected to mixed and boundary lubrication conditions. However, when freshwater is used as a lubricant, the formation of a tribo-film usually is hindered. In order to overcome this disadvantage, PEEK/α-FeOOH nanocomposites were developed and their tribological performances were studied under water lubrication conditions in the present work. It was demonstrated that the inclusion of α-FeOOH nanoparticles (NPs) into the PEEK matrix improves significantly the tribological performance of the matrix. The nanostructures and properties of the tribo-films formed on the steel counterface were comprehensively studied. It was identified that the addition of α-FeOOH NPs promotes the formation of a lubricating tribo-film which covers the entire counterface. Based on the investigations on tribo-films, we deem that the α-FeOOH NPs act as precursors for the dehydration reaction promoting the formation of a tribo-film which consists of α-Fe2O3 and transferred PEEK. It is assumed that the enhanced tribological performance is related to the possibly high load-bearing capability and “easy-to-shear” characteristic of the tribo-film.
Co-reporter:Jingfeng Yang, Qihua Wang, Tingmei Wang and Yongmin Liang
RSC Advances 2016 vol. 6(Issue 31) pp:26271-26279
Publication Date(Web):03 Mar 2016
DOI:10.1039/C5RA28053B
In this study, we developed a new and rapid preparation method of alumina aerogels based on the sol–gel method and supercritical drying technique. In the developed method, the prepared wet gels were sealed to directly conduct supercritical drying without aging or solvent exchange which is required in conventional supercritical drying and ambient pressure drying techniques, which greatly shortened the preparation process. Lanthanum doped alumina aerogels with a high specific surface area (SSA) were prepared firstly according to the developed method and then its structure and thermal stability at high temperature were investigated. Investigation results proved that the incorporation of lanthanum resulted in the formation of LaAl11O18 on the surface of alumina particles, which distinctly delayed the transformation of the α-phase, and improved the thermal stability. Under the optimum atomic ratio of La/Al = 0.05, lanthanum doped alumina aerogels possessed high SSA and pore volume, while excessive lanthanum would result in the decreases in SSA and pore volume. Lanthanum doped alumina aerogels still had a high SSA and pore volume at 1000 °C and was not transformed into α-phase until the temperature rose to 1300 °C, exhibiting the excellent thermal stability. However, its SSA drastically decreased due to the collapse of pore structure.
Co-reporter:Zenghui Yang;Tingmei Wang
Macromolecular Chemistry and Physics 2016 Volume 217( Issue 11) pp:1305-1313
Publication Date(Web):
DOI:10.1002/macp.201500539
Co-reporter:Fuzhi Song, Qihua Wang, Tingmei Wang
Tribology International 2016 Volume 104() pp:392-401
Publication Date(Web):December 2016
DOI:10.1016/j.triboint.2016.01.015
•MoS2 has better reinforcement in improving wear resistance than glass fibers at 1 m/s. But composite C shows high wear rate at 3 m/s.•Glass fibers show poor reinforcement in improving anti-wear property of composite D. However, the glass fibers provide a tough transfer film with good interfacial compatibility and the lowest friction coefficient.•The synergistic effect of MoS2 and glass fibers has great effect on improving tribological behaviors and PV limit of composite E.In this work, tribological behaviors and PV limit of chopped carbon fiber, glass fibers and MoS2 reinforced PTFE composites were investigated. The experiment results revealed that single incorporation of MoS2 could improve anti-wear property significantly under low velocity but shown a failure at 3 m/s. However, glass fibers deteriorated the wear resistance of the PTFE composite drastically as single filler. A synergistic effect was found for the combination of MoS2 and glass fibers, which lead to the best tribological properties with the highest PV limits of 9.5 MPa m/s at 1 m/s and 15 MPa m/s at 2 m/s.
Co-reporter:Fuyan Zhao, Guitao Li, Werner Österle, Ines Häusler, Ga Zhang, Tingmei Wang, Qihua Wang
Tribology International 2016 Volume 103() pp:208-217
Publication Date(Web):November 2016
DOI:10.1016/j.triboint.2016.07.002
•Tribological behaviors of short glass fibers (SGF) reinforced epoxy (EP) composites when lubricated with base oil were investigated.•SGF significantly reduces both the friction coefficient and the wear rate of EP under oil lubrication conditions.•The formation of a tribofilm on the metallic counterface and the transfer of materials between composite and counterpart play an important role on the tribological performance.The tribological performance of short glass fibers (SGF), solid lubricants and silica nanoparticles filled epoxy (EP) composites was investigated under oil lubrication conditions. It is demonstrated that the addition of SGF greatly reduces the friction and wear of EP. However, further addition of solid lubricants and silica nanoparticles does not change obviously the friction and wear. It is identified that the high tribological performance of SGF reinforced EP is related to the high load carrying capacity and abrasion resistance of SGF. The nanostructure of the tribofilm was comprehensively characterized. It is deemed that the tribofilm plays an important role in the tribological performance by avoiding the direct rubbing of the sliding pairs exposed to boundary and mixed lubrication conditions.
Co-reporter:Fuzhi Song, Qihua Wang, Tingmei Wang
Tribology International 2016 Volume 93(Part A) pp:1-10
Publication Date(Web):January 2016
DOI:10.1016/j.triboint.2015.09.017
•Higher mechanical and thermal properties, lower friction coefficient and higher LPV value were obtained with the increasing of crystallinity.•The wear resistance of PTFE was enhanced with the increase of crystallinity in rubbery state, since larger energy was needed to break the links between crystallites.•Higher velocity was beneficial for improving LPV of PTFE, while excessively high velocity was supposed to be adverse for the large generation of frictional heating.In this work, the effects of crystallinity on the LPV (short for the limiting PV) value and tribological behaviors were investigated under different surface roughness and velocities. The experiment results revealed that the one which had a higher degree of crystallinity exhibited higher mechanical and thermal properties, lower friction coefficient and higher LPV value. The wear resistance was enhanced with the increase of crystallinity in rubbery state, since larger energy was needed to break the links between crystallites. In the present study, LPV value of PTFE reached to 2.5 Mpa m/s under 2 m/s. Surface roughness of 0.5 µm was the very profile in this work, which exhibited the best performance with the lowest friction coefficient and highest LPV value under 1 m/s.
Co-reporter:C.P. Gao, G.F. Guo, F.Y. Zhao, T.M. Wang, B. Jim, B. Wetzel, G. Zhang, Q.H. Wang
Tribology International 2016 Volume 95() pp:333-341
Publication Date(Web):March 2016
DOI:10.1016/j.triboint.2015.11.041
•Short carbon and glass fibers enhance greatly wear resistance of epoxy.•Graphite reduces friction but increases wear of carbon fiber reinforced epoxy.•Silica nanoparticles improve tribological properties of epoxy composite.•Tribological behavior is closely related to tribofilm formation.The aim of this work is to investigate the tribological behaviors of epoxy (EP)composites under water lubrication conditions at both varying and constant sliding speeds. In particular, the roles of reinforcing fillers, i.e. carbon and glass fibers, solid lubricants and SiO2 nanoparticles, on the friction and wear properties of EP were investigated. It is demonstrated that both the reinforcing fibers significantly enhance the wear resistance of EP. Under mixed and boundary lubrication conditions, the addition of SiO2 nanoparticles into EP conventional composite filled with carbon fibers and graphite reduces the friction and wear. It is revealed that the tribological performance of the fiber-reinforced EP composites is mainly attributed to the high abrasion resistance of the fibers and the tribofilm formation.
Co-reporter:Zenghui Yang, Yu Chen, Qihua Wang, Tingmei Wang
Polymer 2016 Volume 88() pp:19-28
Publication Date(Web):6 April 2016
DOI:10.1016/j.polymer.2016.02.001
•Poly(benzoxazole-co-imide)s films with tunable physical properties are prepared.•High temperature multiple-shape memory behaviors of poly(benzoxazole-co-imide)s are demonstrated.•Potential mechanism of multiple-shape memory effects is suggested.High temperature triggered multiple-shape memory poly(benzoxazole-co-imide)s with adjustable properties were prepared via facile random copolymerization 3,3′,4,4′-biphenyltetracarbolylic dianhydride (BPDA) with two different diamine of 4,4′-oxydianiline (ODA) and 5-amino-2-(4-aminobenzene) benzoxazole (BOA). The effect of polybenzoxazole on the molecular packing, physical properties and shape memory behaviors of poly(benzoxazole-co-imide)s was investigated systematically. The incorporation of polybenzoxazole into polyimides endows better mechanical properties, higher chain packing, broad glass transition temperature and excellent tunable dual-shape memory behaviors with shape fixity above 98% and shape recovery up to 98%. Besides, multiple-shape memory effects with high switching temperature are first achieved in poly(benzoxazole-co-imide)s, and the multiple-shape memory could be adjusted by choosing the two different switching temperatures. Lastly, the potential mechanism of multiple-shape memory behaviors of poly(benzoxazole-co-imide)s are suggested.
Co-reporter:Yu Chen, Qihua Wang and Tingmei Wang
Nanoscale 2015 vol. 7(Issue 39) pp:16442-16450
Publication Date(Web):07 Sep 2015
DOI:10.1039/C5NR04123F
The core–shell structured mesoporous silica nanomaterials (MSNs) are experiencing rapid development in many applications such as heterogeneous catalysis, bio-imaging and drug delivery wherein a large pore volume is desirable. We develop a one-pot method for large-scale synthesis of brain-like mesoporous silica nanocomposites based on the reasonable change of the intrinsic nature of the –Si–O–Si– framework of silica nanoparticles together with a selective etching strategy. The as-synthesized products show good monodispersion and a large pore volume of 1.0 cm3 g−1. The novelty of this approach lies in the use of an inorganic–organic hybrid layer to assist the creation of large-pore morphology on the outermost shell thereby promoting efficient mass transfer or storage. Importantly, the method is reliable and grams of products can be easily prepared. The morphology on the outermost silica shell can be controlled by simply adjusting the VTES-to-TEOS molar ratio (VTES: triethoxyvinylsilane, TEOS: tetraethyl orthosilicate) as well as the etching time. The as-synthesized products exhibit fluorescence performance by incorporating rhodamine B isothiocyanate (RITC) covalently into the inner silica walls, which provide potential application in bioimaging. We also demonstrate the applications of as-synthesized large-pore structured nanocomposites in drug delivery systems and stimuli-responsive nanoreactors for heterogeneous catalysis.
Co-reporter:Yu Chen, Qihua Wang and Tingmei Wang
Dalton Transactions 2015 vol. 44(Issue 19) pp:8867-8875
Publication Date(Web):27 Mar 2015
DOI:10.1039/C5DT00925A
We demonstrate the fabrication of yolk–shell catalysts consisting of a single M (M = Ag, Au) nanoparticle encapsulated within a hollow mesoporous organosilica shell via an organosilane-assisted strategy. The advantages of our method lie in its good controllability of the void space as well as the thickness of the mesoporous shell. The M@CTAB/SiO2 synthesized through a modified Stöber method can transform to yolk–shell structures after adding (3-aminopropyl)trimethoxysilane (APTMS)/TEOS or (3-aminopropyl)triethoxysilane (APTES)/TEOS into the synthetic medium. We give unambiguous evidence that the middle CTAB/SiO2 layer transforms into a less dense APTMS-rich organic–inorganic layer which was selectively removed in alkaline aqueous solution, while the amino-functionalized hybrid shells remain intact. Moreover, we discuss the role of alkylamino groups in the shell in the transformation from Ag@SiO2 nanorattles to hollow structures when impregnating the as-synthesized Ag@SiO2 nanorattles in HAuCl4 aqueous solution. The nanorattles also exhibit high catalytic activity for the catalytic reduction of p-nitrophenol.
Co-reporter:Mei Lv, Yanming Wang, Qihua Wang, Tingmei Wang and Yongmin Liang
RSC Advances 2015 vol. 5(Issue 101) pp:83065-83073
Publication Date(Web):16 Sep 2015
DOI:10.1039/C5RA15441C
The changes in the surface structure and the tribological performance of polyetheretherketone (PEEK) induced by individual and sequential irradiations with atomic oxygen (AO) and protons (Prs) were investigated in a space environment simulation facility. The experimental results showed that Pr irradiation induced the surface carbonization of PEEK which induced the greatest degree of decrease in the surface roughness from 29.61 nm to 16.15 nm, surface energy from 49.16 mJ m−2 to 46.96 mJ m−2, friction coefficient from 0.28 to 0.08 and wear rate from 10.28 × 10−5 mm3 N−1 m−1 to 5.45 × 10−5 mm3 N−1 m−1. The AO irradiation induced the surface oxidation of PEEK, and then increased the surface roughness from 29.61 nm to 58.77 nm, surface energy from 49.16 mJ m−2 to 73.75 mJ m−2, friction coefficient from 0.28 to 0.35 and wear rate from 10.28 × 10−5 mm3 N−1 m−1 to 18.22 × 10−5 mm3 N−1 m−1. The surface structural variations and tribological performance of PEEK induced by the sequential Pr–AO and AO–Pr irradiations were respectively similar to the results of the individual AO and Pr irradiations, and the final form of irradiation has a bigger effect on the changes in the surface structure and tribological performance during the sequential irradiation tests. The erosion stacking effect of the sequential irradiations was observed, and the AO–Pr irradiations caused the biggest changes in infrared spectra and the surface composition of C and O elements in X-ray photoelectron spectroscopy. The Pr–AO irradiations gave the biggest increment in the surface energy from 49.16 mJ m−2 to 74.03 mJ m−2 and wear rate from 10.28 × 10−5 mm3 N−1 m−1 to 24.07 × 10−5 mm3 N−1 m−1.
Co-reporter:Zenghui Yang, Qihua Wang, Yongkang Bai and Tingmei Wang
RSC Advances 2015 vol. 5(Issue 89) pp:72971-72980
Publication Date(Web):24 Aug 2015
DOI:10.1039/C5RA12293G
Shape memory polyimide/silica (PI/silica) composites with atomic oxygen resistance, good thermal stability and mechanical properties are synthesized by co-condensation of poly(amic acid) terminated with (3-aminopropy)triethoxysilane (APTES) and tetraethoxysliane (TEOS) via a sol–gel method. The silica networks formed in the hybrid films act not only as permanent crosslink points, but as atomic oxygen (AO) resistant moieties. The results show that the PI/silica composite films possess high thermal decomposition temperature (Td > 550 °C), high glass transition temperature (Tg > 265 °C) as well as good shape fixation ratio (Rf > 98%) and shape recovery ratio (Rr > 90%). The mechanical properties, surface topography and shape memory performance of PI/silica composite films were evaluated before and after AO irradiation in simulated space environment. Compared to pristine PI, the mechanical properties, surface topography, and shape memory performances of PI–SiO2-15 were less affected by AO exposure, which results from the silica protective layer formed on the composite film surface, indicating good AO-resistant ability of PI/silica composite films. This work may provide a strategy toward the design of promising shape memory materials for applications in the field of severe conditions.
Co-reporter:Mei Lv, Chao Wang, Qihua Wang, Tingmei Wang and Yongmin Liang
RSC Advances 2015 vol. 5(Issue 66) pp:53543-53549
Publication Date(Web):02 Jun 2015
DOI:10.1039/C5RA23240F
Space exploitation and development need high-performance materials for spacecraft so as to maintain the long service life and reliability of mechanical equipment. The purpose of the present study was to exploit a new material with durable life, stable friction coefficient and low wear rate in harsh space environments. Two kinds of solid–liquid synergetic lubricating composites have been prepared using perfluoropolyethers (PFPE) or chlorinated phenyl and methyl terminated silicone oil (CPSO) filled in porous polyimide (PPI). The tribological performance and hydrophobicity of the oil-filled PPI were evaluated by contact angle analyses and a ball-on-disk tribometer before and after proton irradiation in a simulated space environment. After proton irradiation, two composites can maintain stable hydrophobic performance. More importantly, the friction coefficients of CPSO/PPI and PFPE/PPI increased slightly from 0.07 and 0.05 to 0.1 and 0.14, respectively. The wear rates of CPSO/PPI and PFPE/PPI also increased slightly from 5.13 × 10−5 mm3 N−1 m−1 and 4.23 × 10−5 mm3 N−1 m−1 to 5.75 × 10−5 mm3 N−1 m−1 and 6.19 × 10−5 mm3 N−1 m−1, respectively. The CPSO/PPI composite showed the smallest change in hydrophobicity, friction coefficient and wear rate before and after proton irradiation. The mechanism of highly stable hydrophobicity and tribological performance was mainly based on a continuous self-healing surface; the stored oil in the pores of PPI can creep to the surface of the material to repair the damage induced by proton irradiation, which ensured that the material had stable and durable hydrophobicity and tribological properties in a proton irradiation environment.
Co-reporter:Fei Zheng;Mei Lv;Tingmei Wang
Polymers for Advanced Technologies 2015 Volume 26( Issue 8) pp:988-993
Publication Date(Web):
DOI:10.1002/pat.3516
The tribological properties of polyimide (PI) under four oils (including two perfluoropolyether oils and two silicon oils) lubricated conditions were comparatively investigated at room temperature in vacuum and Fomblin M30 and chlorine-containing silicon oil were selected to study the friction and wear behaviors of PI-based solid–liquid lubricants against steel at different temperatures in vacuum. Significant improvement in tribological performance of PI was found under oil-lubricated conditions. The friction coefficient increased as the test temperature decreased for the mobility of liquid lubricant was limited at lower temperatures, while the wear rate exhibited distinct rule. Besides, no tribochemical reaction was detected at the contact surface of PI and chlorine-containing silicon oil. However, the –CF3 and fluorinated CO groups were detected on the worn tracks of PI/Fomblin M30 by X-ray photoelectron spectroscopy, which indicated that tribochemical reaction happened to PI and Fomblin M30 under high temperature as well as the simulation of friction heat. Copyright © 2015 John Wiley & Sons, Ltd.
Co-reporter:Mei Lv, Fei Zheng, Qihua Wang, Tingmei Wang, Yongmin Liang
Tribology International 2015 Volume 92() pp:246-254
Publication Date(Web):December 2015
DOI:10.1016/j.triboint.2015.06.004
•The introduction of fibers decreased the friction coefficient and wear rate of polyimide.•AO/UV irradiations could damage the molecular chain of polyimide.•The start–stop friction process aggravated the wear of materials.•Carbon fibers/polyimide composites displayed excellent tribological property in irradiation environment.The friction and wear behaviors of carbon and aramid fibers reinforced polyimide composites have been investigated in simulated space irradiation environment and start–stop friction process. The experiment results showed that the introduction of fibers decreased the friction coefficient and improved the wear-resistance of polyimide matrix after atomic oxygen and ultraviolet irradiations especially for the carbon fibers. A start–stop friction process aggravated the wear of various composite materials against the counterpart ball. Carbon fibers reinforced polyimide displayed excellent tribological property in irradiation environment and start–stop friction condition, which was expected to become a kind of potential tribological material for the application of spacecraft.
Co-reporter:Mei Lv, Qihua Wang, Tingmei Wang, Yongmin Liang
Composites Part B: Engineering 2015 Volume 77() pp:215-222
Publication Date(Web):August 2015
DOI:10.1016/j.compositesb.2015.03.029
The effects of atomic oxygen exposure on pure polyimide and nano-ZrO2 reinforced polyimide composites were investigated in a ground-based simulation facility. The experimental results indicated that the surface structure of both pure polyimide and ZrO2/polyimide composites were destroyed by atomic oxygen attack, but the addition of nano-ZrO2 particles in polyimide could obviously decrease the mass loss, which showed that ZrO2 could enhance the atomic oxygen resistance. The results of ZrO2/polyimide composites before and after atomic oxygen exposure showed that atomic oxygen irradiation aggravated the friction and wear of the ZrO2/polyimide composites. The wear mechanism was mainly abrasive particles wear arising from the ZrO2-rich layer on the surface of composites. The ZrO2/polyimide composites with 1 wt% nano-ZrO2 owns the lowest varying rate of the friction coefficient and wear rate before and after atomic oxygen exposure, which showed stable friction and wear properties and was expected to become a kind of potential tribological materials for practical spacecraft designation.
Co-reporter:Yongkang Bai, Yu Chen, Qihua Wang and Tingmei Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 24) pp:9169-9177
Publication Date(Web):19 Mar 2014
DOI:10.1039/C4TA00856A
In this work, polymer networks are prepared by a simple cross-linked reaction of poly(vinyl butyral) (PVB) and hexamethylene diisocyanate. The cross-linked reaction was evaluated by Fourier transition infrared spectroscopy, degree of swelling and gel content. The polymer networks show high mechanical strength with tensile modulus and tensile strength over 1 GPa and 40 MPa, respectively, at rt. With PVB as switching domain, the polymer networks exhibit excellent thermal- and solvent-induced shape memory properties. Also, the influence of cross-linked density and solvents' properties on solvent-induced recovery speed were carefully investigated. Moreover, with the assistance of a shape memory effect, the polymer networks also show scratch self-healing behavior which was monitored using optical and scanning electron microscopy.
Co-reporter:Yongkang Bai, Xinrui Zhang, Qihua Wang and Tingmei Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 13) pp:4771-4778
Publication Date(Web):06 Jan 2014
DOI:10.1039/C3TA15117D
In this study, a tough shape memory polymer network based on polydopamine, poly(ε-caprolactone) and diisocyanate was synthesized in three steps. Fourier transform infrared spectroscopy was used to confirm the synthesis process. The tensile tests demonstrated the good mechanical properties of the materials with a tensile modulus and tensile strength reaching 362 and 43 MPa, respectively, at room temperature. The thermal properties of the polymer networks were investigated using differential scanning calorimetry and dynamic mechanical analysis. With two broad transition temperatures, the dual-shape memory properties were greatly affected by the deformation temperature, which was investigated in detail. Moreover, the polymers also showed good triple-shape memory and two-way shape memory effects.
Co-reporter:Yu Chen, Yongkang Bai, Shoubing Chen, Junping Ju, Yuqi Li, Tingmei Wang, and Qihua Wang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 16) pp:13334
Publication Date(Web):August 13, 2014
DOI:10.1021/am504124a
The polymer-grafted magnetic composite particles have been synthesized and developed to harvest oil by use of their speical wettability. Different from gravity-driven oil–water separation, the prepared polymer brushes-grafted magnetic composite particles can act as solid-stabilizers that diffuse to the oil–water interfical region and effectively minimize the direct oil–water interfical area by volume exclusion, whereas the magnetic Fe3O4 core allows easy separation of Pickering emulsions from oil–water mixture under an external magnetic field. When the emulsions were heated from room temperature to 50 °C, the coil-to-globule transition of poly(N-isopropylacrylamide) (PNIPAM) acts as the driving force for the destabilization of the emulsion, thereby achieving the release of oil. The novel materials can be used in aspects of oil–water separation, inducing oil droplet transport and release of lipophilic substrates.Keywords: drop transport; oil harvesting; Pickering emusion; poly(N-isopropylacrylamide); polymer brushes; stimuli-responsive
Co-reporter:Li-Ming Tao, Fang Niu, Di Zhang, Ting-Mei Wang and Qi-Hua Wang
New Journal of Chemistry 2014 vol. 38(Issue 7) pp:2774-2777
Publication Date(Web):13 May 2014
DOI:10.1039/C4NJ00476K
Amorphous covalent triazine frameworks are used as high performance room temperature ammonia gas sensor materials. These chemiresistive sensors exhibit high response values, low concentration detection ability, excellent stability, as well as reliable reversibility without the aid of UV-light or thermal treatment.
Co-reporter:Fei Zheng;Xinrui Zhang;Gai Zhao;Tingmei Wang
Journal of Applied Polymer Science 2014 Volume 131( Issue 18) pp:
Publication Date(Web):
DOI:10.1002/app.40774
ABSTRACT
The polyimide (PI) composites reinforced with carbon fibers, glass fibers, and aramid fibers were fabricated by means of a hot-press molding technique and irradiated by electron or proton for a certain time. The friction and wear behavior after irradiation, sliding against GCr15 steel balls, were evaluated in a ground-based simulation facility using ball-on-disk tribosystem. The change of the chemical composition of the radiated surface was examined by X-ray photoelectron spectroscopy. The worn morphologies and radiated surfaces of the materials were observed by scanning electron microscope to reveal the wear mechanism. Experimental analysis indicated that the chemical composition of the materials changed and an irradiated layer was formed at the surface. This irradiation layer had an important effect on the friction and wear behavior of the PI composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40774.
Co-reporter:Fei Zheng;Yongkang Bai;Tingmei Wang
Journal of Materials Science 2014 Volume 49( Issue 24) pp:8394-8401
Publication Date(Web):2014 December
DOI:10.1007/s10853-014-8549-9
In this study, the thermal-responsive polymer networks based on poly(vinyl butyral) (PVB) are prepared, and their friction properties in response to external stimuli are investigated. Under dry sliding condition, the materials show low friction (COF ~0.14) at room temperature, but show ultra-high friction (COF ~1.09) at 100 °C above the glass transition temperature of PVB. This marked variation is due to the effect of recovery stress caused by the shape memory effect of polymer networks. Additionally, the recovery stress would increase with the increase of cross-linked density and test temperature above Tg, leading to a higher COF. The polymer networks also show excellent mechanical strength with tensile modulus and elongation at break over 60 MPa and 100 %, respectively. To the best of our knowledge, this is the first paradigm about tunable friction properties realized by shape memory polymer. These interesting properties would enable the polymer networks with potential application in the design of intelligent device in future.
Co-reporter:Mei Lv, Fei Zheng, Qihua Wang, Tingmei Wang, Yongmin Liang
Wear 2014 Volume 316(1–2) pp:30-36
Publication Date(Web):15 August 2014
DOI:10.1016/j.wear.2014.04.011
•PI surface was carbonized after proton irradiation.•TRIM simulation indicated that proton irradiation at 25 keV damage PI within 514 nm from the surface.•Proton irradiation increased the initial friction coefficient and decreased the steady friction coefficient of PI.•A transition from initial short adhesive wear to three-body abrasive wear was observed for proton irradiated PI.Effect of 25 keV proton irradiation with fluence of 2.25×1017 ion/cm2 on the structural and tribological properties of polyimide blocks were investigated in a ground-based simulation facility. The changes in surface structure were characterized by FTIR-ATR, laser micro-Raman, contact angle measurement and nanoindentation. The experimental results indicated that the proton irradiation induced bond breaking to form the carbon-enriched structure on polyimide surface, and then increased the surface hardness and the surface energy. The irradiation depth was restricted within 514 nm from the surface by TRIM simulation.The carbonized layer induced by irradiation was worn out in friction test, which was proved through Raman spectra analysis of the wear track. Proton irradiation increased the initial friction coefficient and decreased the steady friction coefficient of polyimide. In the initial stage, the friction coefficient was closely related to surface hardness of material, and the main wear mechanism was adhesive wear. In the steady stage, the main wear mechanism was three-body abrasion wear, three-body abrasion and the low surface energy could reduce the wear rate and the friction coefficient.Graphica abstract
Co-reporter:Yongkang Bai, Cheng Jiang, Qihua Wang, Tingmei Wang
Carbohydrate Polymers 2013 Volume 96(Issue 2) pp:522-527
Publication Date(Web):25 July 2013
DOI:10.1016/j.carbpol.2013.04.026
•A novel biocompatible polymer is prepared with ethyl cellulose and polycaprolactone.•The polymer exhibits excellent mechanical strength and shape memory property.•The shape memory switching temperature of the polymer is tunable.•The polymer shows potential application in biomedical suture.A novel biological friendly shape memory polymer (SMP) based on ethyl cellulose (EC) and polycaprolactone (PCL) was prepared. The network structure of the polymer was formed by linear EC backbones which were linked by grafted PCL chains, and the results showed outstanding mechanical strength and shape memory property of this polymer. The tensile modulus varied from 104.9 to 373.4 MPa while the tensile strength ranged from 155.4 to 323.6 MPa. And the elongations at break were all above 621%. The shape memory switching temperature could be modulated to 37.2 °C by decreasing the chain length of graft PCL. As EC and PCL are both biodegradable and biocompatible materials, this new polymer has potential application in biomedical field, like biomedical suture, which would be further studied in the future.
Co-reporter:Yu Chen, Qihua Wang and Tingmei Wang
Dalton Transactions 2013 vol. 42(Issue 38) pp:13940-13947
Publication Date(Web):16 Jul 2013
DOI:10.1039/C3DT51546J
A general method has been developed for the fabrication of highly dispersed and thermally stable bimetallic Au–Ag nanoparticles (NPs) stabilized on the inner wall of a mesoporous silica shell. In our approach, gold particles were formed in the first step on carbon spheres decorated with Sn2+ cations. Upon Ag+ adsorption and reduction by L-ascorbic acid in the second step, specific nanoparticles with a gold–silver alloy core and a silver nanoshell have been formed. Important evidence of the core–shell configurations of the bimetallic Au–Ag nanoparticles were clearly characterized by UV-vis, TEM and HAADF-STEM observations combined with elemental mapping and line scans. The mesoporous silica outer shell was obtained through the hydrolysis and condensation of the precursors tetraethoxysilane (TEOS) in a basic condition and cetyltrimethylammonium bromide (CTAB) as a structure-directing agent. On this basis, the nanoreactors were fabricated after calcination, which further serves as a nanoreactor for the reduction of p-nitrophenol. Furthermore, such particles have been found to be thermally stable and their sizes remain substantially unchanged even upon calcination in air at 500 °C and a reduction treatment in H2. Potentially, the method can be developed into a general approach to synthesize other highly dispersed and thermally stable bimetallic nanoparticles stabilized on the inner wall of a mesoporous silica shell.
Co-reporter:Cheng Jiang, Qihua Wang and Tingmei Wang
New Journal of Chemistry 2013 vol. 37(Issue 3) pp:810-814
Publication Date(Web):18 Jan 2013
DOI:10.1039/C2NJ40970D
Poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes were grafted onto the surface of multiwalled carbon nanotubes (MWCNTs) by surface-initiated atom transfer radical polymerization (ATRP). The coating of the PMETAC modified MWCNTs (MWCNT-PMETAC) was prepared on the copper substrate by a spraying method. The wettability transition of the MWCNT-PMETAC surface between superhydrophobicity and hydrophilicity can be easily achieved via counterion exchange. In addition, the MWCNT-PMETAC surface showed an oil contact angle about 138.6 ± 1.4° with a 5 μL hexadecane droplet and exhibited superoleophilicity after proper anions exchange, and this switch was also reversible. The counterion exchange of the MWCNT-PMETAC surface was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurement.
Co-reporter:Cheng Jiang;Yaoming Zhang;Tingmei Wang
Journal of Applied Polymer Science 2013 Volume 129( Issue 5) pp:2959-2965
Publication Date(Web):
DOI:10.1002/app.39024
Abstract
A superhydrophobic surface was prepared by spin-coating trimethylsiloxane functionalized SiO2 (TMS-SiO2) solutions onto a precoated polyurethane (PU) layer. The superhydrophobic coatings showed high stability with time, and the prepared coatings remained superhydrophobicity even after 6 months. Furthermore, the as-prepared surface showed high transparency with a transmittance above 70% in visible light region (400–800 nm). The transition of the composite surface from superhydrophobicity to hydrophilicity can be achieved by increasing the drying temperature. More interestingly, the surface showed excellent fluorescent property by the incorporation of fluorescent Europium (Eu) complex into the surface and without deteriorating the superhydrophobic and transparent properties. It was believed that the superhydrophobic surface with multifunction would broaden the applications of superhydrophobic materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Yongkang Bai;Cheng Jiang;Tingmei Wang
Macromolecular Chemistry and Physics 2013 Volume 214( Issue 21) pp:2465-2472
Publication Date(Web):
DOI:10.1002/macp.201300389
Co-reporter:Liming Tao, Junping Ju, Fang Niu, Tingmei Wang, Qihua Wang
Polymer 2013 Volume 54(Issue 20) pp:5358-5362
Publication Date(Web):6 September 2013
DOI:10.1016/j.polymer.2013.07.075
Microporous, hypercrosslinked poly-p-phenylenes with surface area of up to 1735 m2 g−1 have been prepared by combination of super acid catalyzed polymerization and the double aromatic nucleophilic substitution reaction. The surface area and pore size can be controlled by varying the amount of the crosslinking reagents, which tuned the crosslinking degree effectively. The capacity of adsorption of CO2 of the MPNs largely depends on their specific surface areas.
Co-reporter:Shoubing Chen;Tingmei Wang
Journal of Polymer Research 2012 Volume 19( Issue 11) pp:
Publication Date(Web):2012 November
DOI:10.1007/s10965-012-9994-2
A series of polyurethanes (PUs) based on poly (tetramethylene glycol) (PTMG), poly (ethylene adipate) (PEA) diol, polycaprolactone (PCL) diol and castor oil (CO) were synthesized. The tensile, damping and thermal properties were studied systematically in terms of the composition and isocyanate index (R). Results showed that when R is 2, the PUs exhibit a relatively high tensile strength more than 30 MPa. The PTMG-PU, PCL-PU and PEA-PU show high elongation at break compared to the cross-linked CO-PU. When R is 1.5, tensile strengths decrease compared to R is 2. But, the elongations of PTMG-PU, PCL-PU and CO-PU increase. DMA analysis showed that the glass transition temperature (Tg) is increasing as the sequence of PTMG-PU, PCL-PU, PEA-PU and CO-PU. The Tg of CO-PU is as high as 60.6 °C when R is 1.5 and 93.4 °C when R is 2. The Tg ranges of the other linear PUs are between −50 and −12 °C. The damping temperature ranges of these PUs are relatively broad. Further, TG results showed the start degradation temperatures of them are approx 260 °C. These results show a good guidance to select a kind of PU when prepare the PU-polymer composites for given properties.
Co-reporter:Yu Chen, Qihua Wang and Tingmei Wang
Dalton Transactions 2013 - vol. 42(Issue 38) pp:NaN13947-13947
Publication Date(Web):2013/07/16
DOI:10.1039/C3DT51546J
A general method has been developed for the fabrication of highly dispersed and thermally stable bimetallic Au–Ag nanoparticles (NPs) stabilized on the inner wall of a mesoporous silica shell. In our approach, gold particles were formed in the first step on carbon spheres decorated with Sn2+ cations. Upon Ag+ adsorption and reduction by L-ascorbic acid in the second step, specific nanoparticles with a gold–silver alloy core and a silver nanoshell have been formed. Important evidence of the core–shell configurations of the bimetallic Au–Ag nanoparticles were clearly characterized by UV-vis, TEM and HAADF-STEM observations combined with elemental mapping and line scans. The mesoporous silica outer shell was obtained through the hydrolysis and condensation of the precursors tetraethoxysilane (TEOS) in a basic condition and cetyltrimethylammonium bromide (CTAB) as a structure-directing agent. On this basis, the nanoreactors were fabricated after calcination, which further serves as a nanoreactor for the reduction of p-nitrophenol. Furthermore, such particles have been found to be thermally stable and their sizes remain substantially unchanged even upon calcination in air at 500 °C and a reduction treatment in H2. Potentially, the method can be developed into a general approach to synthesize other highly dispersed and thermally stable bimetallic nanoparticles stabilized on the inner wall of a mesoporous silica shell.
Co-reporter:Yu Chen, Qihua Wang and Tingmei Wang
Dalton Transactions 2015 - vol. 44(Issue 19) pp:NaN8875-8875
Publication Date(Web):2015/03/27
DOI:10.1039/C5DT00925A
We demonstrate the fabrication of yolk–shell catalysts consisting of a single M (M = Ag, Au) nanoparticle encapsulated within a hollow mesoporous organosilica shell via an organosilane-assisted strategy. The advantages of our method lie in its good controllability of the void space as well as the thickness of the mesoporous shell. The M@CTAB/SiO2 synthesized through a modified Stöber method can transform to yolk–shell structures after adding (3-aminopropyl)trimethoxysilane (APTMS)/TEOS or (3-aminopropyl)triethoxysilane (APTES)/TEOS into the synthetic medium. We give unambiguous evidence that the middle CTAB/SiO2 layer transforms into a less dense APTMS-rich organic–inorganic layer which was selectively removed in alkaline aqueous solution, while the amino-functionalized hybrid shells remain intact. Moreover, we discuss the role of alkylamino groups in the shell in the transformation from Ag@SiO2 nanorattles to hollow structures when impregnating the as-synthesized Ag@SiO2 nanorattles in HAuCl4 aqueous solution. The nanorattles also exhibit high catalytic activity for the catalytic reduction of p-nitrophenol.
Co-reporter:Zenghui Yang, Qihua Wang and Tingmei Wang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 26) pp:NaN13833-13833
Publication Date(Web):2017/05/31
DOI:10.1039/C7TA02842C
The combination of shape memory with other new-fashioned functions will facilitate great potential in the development of shape memory materials. Demonstrated here is a multifunctional polymer based on hyperbranched polyimides (HBPIs) that integrates shape memory into a gas capture membrane. The new kind of shape memory gas capture HBPIs were prepared by branching conventional thermoplastic polyimides via a two-step method with 2,4,6-triaminopyrimidine (TAP) as the branched center. The optimized HBPIs exhibit good shape-memory properties with shape fixity above 98% and recovery values above 82%. Moreover, they show large Brunauer–Emmett–Teller (BET) surface areas (218–387 m2 g−1), mesoporous characteristics (3–5 nm) and narrow pore size distribution, which endow them with preferable CO2 capture (up to 36.93 cm3 g−1) and selectivity (up to 66.3). The comprehensive properties, especially the shape recovery ratio and CO2 uptake, of the HBPIs can be effectively controlled by adjusting the degree of branching (DB) or the content of the rigid heterocyclic diamine, 5-amino-2-(4-aminobenzene) benzoxazole (BOA). Our multifunctional shape memory polymer (SMP) may expand the application field of shape memory and accelerate the development of SMPs.
Co-reporter:Yongkang Bai, Yu Chen, Qihua Wang and Tingmei Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 24) pp:NaN9177-9177
Publication Date(Web):2014/03/19
DOI:10.1039/C4TA00856A
In this work, polymer networks are prepared by a simple cross-linked reaction of poly(vinyl butyral) (PVB) and hexamethylene diisocyanate. The cross-linked reaction was evaluated by Fourier transition infrared spectroscopy, degree of swelling and gel content. The polymer networks show high mechanical strength with tensile modulus and tensile strength over 1 GPa and 40 MPa, respectively, at rt. With PVB as switching domain, the polymer networks exhibit excellent thermal- and solvent-induced shape memory properties. Also, the influence of cross-linked density and solvents' properties on solvent-induced recovery speed were carefully investigated. Moreover, with the assistance of a shape memory effect, the polymer networks also show scratch self-healing behavior which was monitored using optical and scanning electron microscopy.
Co-reporter:Yongkang Bai, Xinrui Zhang, Qihua Wang and Tingmei Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 13) pp:NaN4778-4778
Publication Date(Web):2014/01/06
DOI:10.1039/C3TA15117D
In this study, a tough shape memory polymer network based on polydopamine, poly(ε-caprolactone) and diisocyanate was synthesized in three steps. Fourier transform infrared spectroscopy was used to confirm the synthesis process. The tensile tests demonstrated the good mechanical properties of the materials with a tensile modulus and tensile strength reaching 362 and 43 MPa, respectively, at room temperature. The thermal properties of the polymer networks were investigated using differential scanning calorimetry and dynamic mechanical analysis. With two broad transition temperatures, the dual-shape memory properties were greatly affected by the deformation temperature, which was investigated in detail. Moreover, the polymers also showed good triple-shape memory and two-way shape memory effects.
![Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl
)phenyleneoxyphenylene]](http://img.cochemist.com/ccimg/104500/104491-51-2.png)
![Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl
)phenyleneoxyphenylene]](http://img.cochemist.com/ccimg/104500/104491-51-2_b.png)
![Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/26700/26615-45-2.png)
![Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/26700/26615-45-2_b.png)
![Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)oxy(1,3-dihydro-1,3-dioxo-2H-isoindole-5,2-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/25800/25735-00-6.png)
![Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)oxy(1,3-dihydro-1,3-dioxo-2H-isoindole-5,2-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/25800/25735-00-6_b.png)