Mullins Effect and Crack Growth in Natural Rubber Vulcanizates during Heat Aging and Cyclic Loading
Main Article Content
Abstract
The effect of thermal aging and cyclic loading on mechanical properties and development of cracks in natural rubber vulcanizates was studied. After aging at 70oC and 110oC vulcanizates were subjected to cyclic loading. At a certain number of loading cycles, the samples were conducted in a tension test. At the aging condition of 70oC, the static tensile properties of material stay almost unchanged even after 88 aged hours and 8000 loading cycles. On the contrary, the dynamic fatigue resistance of vulcanizates decreases with increasing aging time. These results are attributed to the post-curing and the development of microcracks that might be caused by Mullins effect: in the case of static loading, the strain-induced crystallization may prevent cracks growth, but in the case of cyclic loading the strain-induced crystallization does not occur, so cracks develop without hindrance. However, at 110oC both static properties and dynamic fatigue resistance of material reduced dramatically because at high temperature the heat degradation exceeds both post-curing and strain-induced crystallization. Crack formation and propagation were examined by a digital optical microscope in the progress of cyclic loading. Results showed that natural rubber vulcanizate filled with carbon black has the best crack growth resistance (CGR) while the addition of modified and unmodified silica reduces CGR of materials. Moreover, the vulcanizate with unmodified silica has the lowest CGR.
Keywords
Natural rubber, silica modified and unmodified, crack growth, cyclic loading, Mullins effect
Article Details
References
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[10] Byungwoo Moon, Jongmin Lee, Soo Park, Chang-Sung Seok, Study on the aging behavior of Natural Rubber/Butadiene Rubber (NR/BR) blends using a Parallel Spring Model, Polymer. 10 (2018) 658. https://doi.org/10.3390/polym10060658
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[2] E. Mark, Burak Erman, Frederick R. Eirick, The Science and Technology of Rubber, Elsevier Academic Press, 3rd Ed., San Diego, CA. 2005, pp.744.
[3] Julie Diani, Bruno Fayolle, Pierre Gilormini, A review on the Mullins effect, European Polymer Journal. Vol. 5 (2009) 601-612. https://doi.org/10.1016/j.eurpolymj.2008.11.017
[4] G. Chagnon, E.Verron, G.Marckmann, L.Gornet, Development of new constitutive equation for the Mullins effect in rubber using network alteration theory, Int. J. of Solid and structure. Vol. 43 (2006) 6817-6834. https://doi.org/10.1016/j.ijsolstr.2006.02.011
[5] Bui Chuong, Dang Viet Hung, Nguyen Thuong Giang, Using TESPT modified silica as a reinforcement filler for a blend of natural rubber-butadiene rubber, Part I: Preparation and characterization of TESPT modified silica, Vietnam J. Chem. Vol. 45 (2007) 67-71.
[6] Nguyen Trong Quang, Dang Viet Hung, Bui Chuong, Hoang Nam, Nguyen Thi Yen, Study on the effect of modified and unmodified silica on the properties of Natural Rubber vulcanizates, Vietnam Journal of Chemistry. Vol. 57 (3) (2019) 357-362. https://doi.org/10.1002/vjch.201900040
[7] Samy Merabia, Pane Sotta, Didier R. Long, Unique plastic and recovery behavior of nanofilled elastomers and thermoplastic elastomers (Payne and Mullins effects), J. of Polymer Science, Part. B: Polymer Physics. 48 (2010) 1495-1508. https://doi.org/10.1002/polb.22046
[8] Lei Yan, David A. Dillard, Robert L. West, Loren D. Lower, Glenn V. Gordon, Mullins effect recovery of nanoparticle filled polymers, J. of Polymer Science, Part B: Polymer Physics. 48 (2010) 2207-2214. https://doi.org/10.1002/polb.22102
[9] Hsien-Tang Chiu, Pier-An Tsai, Aging and Mechanical properties of NR/BR blends, Journal of Materials Engineering and Performance. 15 (2006) 88-94. https://doi.org/10.1361/105994906X83448
[10] Byungwoo Moon, Jongmin Lee, Soo Park, Chang-Sung Seok, Study on the aging behavior of Natural Rubber/Butadiene Rubber (NR/BR) blends using a Parallel Spring Model, Polymer. 10 (2018) 658. https://doi.org/10.3390/polym10060658
[11] Present Ghosh, Rabindra Mukhopadhyay, Radek Stock, Durability prediction of NR/BR and NR/SBR blend tread compounds using tear fatigue analyzer, Testing and Measuring, (2016) 53-55.