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Yu Sun PhD Dissertation.pdf (3.51 MB)

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VULCANIZATION AND DEVULCANIZATION OF RUBBER

Sun, Yu
http://rave.ohiolink.edu/etdc/view?acc_num=akron1594830138675509

Abstract Details

2020, Doctor of Philosophy, University of Akron, Polymer Science.
The research in this dissertation includes two parts: vulcanization of isobutylene-isoprene rubber (IIR) containing geminal vinylidene-acrylate groups and surface devulcanization of ground rubber particles (GRPs) for rubber recycling. In Chapter 2, EIIR was synthesized by grafting ethyl propiolate to IIR via EtAlCl2-catalyzed Alder-ene reaction. Methods for crosslinking EIIR using dicumyl peroxide (DCP) with m-Phenylene-N,N’-bismaleimide (BMI) as a coagent were investigated. The strength, extensibility, and overall toughness of the peroxide-cured EIIR significantly exceed those of previously reported peroxide-cured IIR derivatives. A wide range of stiffness can be realized without sacrificing the strength. The crosslinking density achieved using such curatives is indexed as a function of DCP/BMI ratio, and the curing efficiency of peroxide as a function of DCP/BMI ratio and DCP loading. The role of the geminal vinylidene-acrylate moiety in curing was studied by model reactions, which suggest that the geminal vinylidene-acrylate moiety undergoes both radical addition and hydrogen abstraction. Coagent trimethylolpropane trimethacrylate (TMPTMA) was studied to replace BMI due to high toxicity of BMI. Low degrees of crosslinking (~50%) were found in all vulcanizates cured by DCP and TMPTMA, likely because of a mismatch between the reactivities of DCP and TMPMTA. Benzoyl peroxide (BPO) was then used in conjunction with TMPTMA. EIIR was successfully cured with BPO and TMPTMA to give high stress and strain at break, and toughness exceeding those achieved with DCP and BMI as the curing agents. Atomic force microscopy and transmission electron microscopy indicate that phase-separated nanodomains presumably of polymers or oligomers of TMPTMA are present in the continuous rubber phase. These domains are likely also responsible for achieving the observed superior mechanical properties. The combination of BPO and BMI are also capable to sufficiently cure EIIR, but the resultant vulcanizates have tensile properties somewhat worse than those cured by DCP and BMI. In Chapter 3, recycling of GRPs was studied. Poor interfacial bonding and interfacial modulus contrast were identified as two inherent causes for the inferior mechanical properties of vulcanizates containing GRPs in comparison to vulcanizates of fresh rubber. The poor interfacial bonding is caused by limited depth of mixing and molecular contact between the polymer chains in the GRPs and fresh rubber. The interfacial modulus contrast is caused by diffusion of curatives from the fresh rubber to the GRPs. Surface devulcanization of GRPs gives rise to strong interfacial bonding equal to the cohesive strength of the rubber but only improves the tensile properties of vulcanizates containing GRPs to a limited extent. When the interfacial modulus contrast is erased, the tensile strength of vulcanizates containing GRPs become equal to that of the fresh rubber vulcanizate. This study also shows that oxidative aging harms the interfacial bonding more than it does the bulk properties. When the surface devulcanization method was applied to GRPs, the vulcanizates containing aged GRPs display similar tensile properties to those of the vulcanizates containing GRPs without aging.
Li Jia (Advisor)
Toshikazu Miyoshi (Committee Chair)
Gary Hamed (Committee Member)
Junpeng Wang (Committee Member)
Kevin Cavicchi (Committee Member)
187 p.
Polymer Chemistry; Polymers

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Citations

  • Sun, Y. (2020). VULCANIZATION AND DEVULCANIZATION OF RUBBER [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1594830138675509

    APA Style (7th edition)

  • Sun, Yu. VULCANIZATION AND DEVULCANIZATION OF RUBBER. 2020. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1594830138675509.

    MLA Style (8th edition)

  • Sun, Yu. "VULCANIZATION AND DEVULCANIZATION OF RUBBER." Doctoral dissertation, University of Akron, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1594830138675509

    Chicago Manual of Style (17th edition)

akron1594830138675509
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This open access ETD is published by University of Akron and OhioLINK.