Co-reporter:
Journal of Applied Polymer Science 2017 Volume 134(Issue 9) pp:
Publication Date(Web):2017/03/05
DOI:10.1002/app.44527
ABSTRACTIn this work, the silane coupling agent bis-(triethoxysilylpropyl) -tetrasulfide (TESPT) is used to modify the carbon nanotubes. After modification, carbon nanotubes can be well dispersed in the natural rubber (NR) matrix and form a strong and flexible network. Based on the original real-time crack tip morphology monitoring, crack propagation and scanning electronic microscopy tests, it is revealed that modified carbon nanotubes filled NR samples (NR/F-CNTs) have better crack resistance. It is found that modified carbon nanotubes can resist the cavitation process during cyclic loading. Crack tip morphology monitoring tests indicate that the crack tip of NR/F-CNTs is rougher and the ligaments are thinner and densely distributed. A crack branching phenomenon is also observed. It proves that F-CNTs increase the energy consumption of NR during cyclic loading. It is concluded that the F-CNTs used in this work improve the crack resistance of NR in two ways: the one is cavitation resistance and the other is the increase of energy consumption for crack propagation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44527.
Co-reporter:Gengsheng Weng, Aijun Chang, Kun Fu, Jian Kang, Yaxuan Ding and Zhongren Chen
RSC Advances 2016 vol. 6(Issue 10) pp:8406-8415
Publication Date(Web):20 Jan 2016
DOI:10.1039/C5RA26238K
The crack growth mechanism of rubber composites has not been explored clearly. Here, we focus on the microstructure evolution of styrene-butadiene rubber/silica (SBR/silica) composites during crack propagation. Two groups of SBR/silica composites are constructed. The silica nanoparticles used in the two groups have different sizes but the same surface properties. By crack propagation and small angle X-ray scattering measurements, the crack growth rate, nanocavitation and silica distribution morphology of the rubber composites are investigated. The role of damage structure nucleation and growth during crack propagation of the SBR/silica composites is discussed. It is demonstrated that the damage structure nucleation is the key factor for the crack growth at large tear energies, while the growth feature of damage structure dominates the crack growth at smaller tear energies. This work provides us with better understanding on the crack growth mechanism of rubber composites.
Co-reporter:Aijun Chang;Kun Fu;Yaxuan Ding;Dirong Gong
Journal of Applied Polymer Science 2016 Volume 133( Issue 6) pp:
Publication Date(Web):
DOI:10.1002/app.42972
ABSTRACT
In the present work, functionalized liquid isoprene rubber (FLIR) was used to improve the filler dispersion and filler–rubber interaction in the silica filled natural rubber system. By the infrared spectra and scanning electron microscopy, it was proved that the FLIR was successfully grafted on the silica and the functionalized silica was dispersed in the NR matrix homogeneously. Based on the real-time crack tip morphology monitoring method, the influence of FLIR on the crack growth behavior of NR filled with silica was analyzed. By the adding of FLIR, the crack resistance of the natural rubber embedded with functionalized silica is remarkably increased. When the weight ratio of FLIR to silica is 3:10, the NR composite has the best crack resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42972.
Co-reporter:Jian Kang, Zhengfang Chen, Jinyao Chen, Feng Yang, Gengsheng Weng, Ya Cao, Ming Xiang
Thermochimica Acta 2015 Volume 599() pp:42-51
Publication Date(Web):10 January 2015
DOI:10.1016/j.tca.2014.11.011
•We prepared a series of β-nucleated iPP with varying molar masses.•We tuned their melt structures by controlling heating temperature and studied their crystallization behavior.•We explored the influences of iPP molar mass on crystallization of β-iPP with different melt structures.•We studied the thermal stability of the ordered structures with β-nucleation efficiency and the role of molar mass.To elucidate influence of molecular weight on crystallization behavior of β-nucleated isotactic polypropylene (β-nucleated iPP) with different melt structures, a series of β-nucleated iPP with varying molecular weights were prepared. Results revealed that higher iPP molecular weight was more favorable for formation of high β-phase proportion (βc). By tuning heating temperature (Tf), the melt structure (content of ordered structures within melt) of β-nucleated iPP was controlled. It was found that for all samples, βc evidently elevated with decrease of Tf, indicating occurrence of synergetic effect between ordered structures and β-NA (ordered structure effect, OSE); with decrease of iPP molecular weight, βc triggered by OSE increased gradually and Tf temperature range for occurrence of OSE gradually decreased. Moreover, as holding time at Tf increased from 1 to 120 min, subsequent melting curves of samples stayed unchanged, reflecting very high thermal stability of the ordered structures, being independent to iPP molecular weight.
Co-reporter:Hong Yao;Yanpeng Liu;Kun Fu;Aijun Chang ;Zhong-Ren Chen
Journal of Applied Polymer Science 2015 Volume 132( Issue 20) pp:
Publication Date(Web):
DOI:10.1002/app.41980
ABSTRACT
Based on the real-time crack tip morphology monitoring, the influence of silane coupling agent (SCA) on the crack-growth behavior of silica-filled natural rubber (NR) was analyzed. By using SCA, silica particles can be well dispersed and a filler–matrix network can be formed, which leads to lower crack-growth rate. Results indicate that a dosage of 5 wt % (with respect to silica loading) is the optimal content. The real-time observation and scanning electron microscopy (SEM) analysis proved that thin ligaments and dimples with homogeneous distribution appear on the crack tip. These crack tip morphologies reflect the low crack-growth rate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41980.
Co-reporter:Gengsheng Weng, Hong Yao, Aijun Chang, Kun Fu, Yanpeng Liu and Zhongren Chen
RSC Advances 2014 vol. 4(Issue 83) pp:43942-43950
Publication Date(Web):03 Sep 2014
DOI:10.1039/C4RA06518B
The present paper deals with the crack growth behavior of vulcanized natural rubber under fatigue loading. Our research focuses on the crack tip morphology evolution and its relationship with the crack growth rate. For this purpose, an original real-time monitoring method is applied to capture the crack tip morphology during standard fatigue testing. This method involves the use of a high speed microscopic camera and a dynamic mechanical analyzer with a crack growth testing unit. The tear energy (T) dependence of the crack tip morphology is discussed. It is revealed that there are two characteristic cracking morphologies: at T < 600 J m−2, the power law slope of dc/dn versus T is 6. Surface buckling and peeling at the crack-front surface occur, which result in the appearance of secondary cracks; at T > 600 J m−2, the power law slope of dc/dn versus T is 2. A ligament break-up mechanism dominates. This work gives us new opportunities to study the crack growth mechanism of rubbers from the viewpoint of real-time crack tip morphology investigation.
Co-reporter:Geng-Sheng Weng;Jin-Biao Bao;Yu-Ci Xu;Zhong-Ren Chen
Journal of Polymer Research 2013 Volume 20( Issue 3) pp:
Publication Date(Web):2013 March
DOI:10.1007/s10965-013-0104-x
Real time synchrotron wide angle and small angle X-ray scattering (WAXS and SAXS, respectively) were used to characterize the stretch induced structural evolution of α trans-1,4-polyisoprene (trans-PI). 2D WAXS results indicated two ensembles of crystalline modifications with distinctive orientation modes coexisted during stretching. Stretching transformed part of the monoclinic α phase into highly oriented orthorhombic β phase at strain ε = ~0.4. The β phase had rather high orientational degree with polymer chains parallel to the stretching direction, while the orientational degree of α phase was much lower. Complemented by qualitative 2D SAXS analysis, it was found that amorphous layer deformation and intralamellar chain slip dominated at different stretching stage. The melt and recrystallization process of α phase which led to the formation of β phase was also investigated. Formation of two interpenetrating networks of crystalline skeleton (constructed by residual α and β crystals) and amorphous entanglement accounted for the stress-hardening in the late stage.
