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The Effects of Carbon Black Reinforcement Systems on Crosslinked Shape Memory Elastomers

Bethea, Robert A
http://rave.ohiolink.edu/etdc/view?acc_num=akron1418301296

Abstract Details

2014, Master of Science, University of Akron, Polymer Engineering.
Shape memory polymers (SMPs) have been used for several decades with various transition mechanisms and microstructures. Traditional SMPs have used a block copolymer system to generate widely varying glass transition temperatures. When the polymer is heated above one block’s glass transition temperatures, the polymer can be deformed, cooled below the glass transition temperature, and the shape will then be locked into place. Further stimuli, typically heating, will cause the material to return to its original shape. The present thesis attempts to make use of a second method of shape memory polymers. Prior work has shown that rubber can be made into a SMP when it is swollen with stearic acid, where the melt point of stearic acid, rather than a glass transition temperature, acts as the activation temperature. There are many advantages to this simple system including inexpensive materials, ease of handling stearic acid and rubber, and the wide use of rubber in industry. The first set of experiments aimed to determine a compound formulation that would allow the polymer to exhibit excellent shape memory behavior. A low state of cure enabled this and when tested on a DMA resulted in shape fixity of 73% with recovery in excess of 95%. Tensile and elongation testing helped in characterizing the physical and rheological properties of each compound. A solubility curve was completed showing that this sample needed at least 45 minutes to attain maximum swelling of stearic acid and, vicariously, maximum shape fixity. A second set of experiments aimed to identify the effects of carbon black on the polymer’s shape memory behavior. While carbon black increased the modulus tremendously, it did not necessarily result in the expected monotonic increase in fixity. Fixity showed to have a sharp increase up to about 25 PHR carbon black but then plateaued with about 95% fixity. Recovery, however, showed a direct, negative relationship, steadily decreasing from about 100% to 93% as carbon black loading increased. The stress-strain curves identified a percolation point at which the tensile strength produced a minimum value at approximately 10 PHR carbon black. Finally, cross-link density also showed to relate directly with PHR carbon black loading, similar to the modulus, which increased proportionally with relative cross-link density, as calculated by the Flory-Rehner equation.
Kevin Cavicchi, Dr. (Advisor)
Avraam Isayev, Dr. (Committee Member)
David Simmons, Dr. (Committee Member)
134 p.
Engineering; Polymers
rubber; carbon black; shape memory rubber; shape memory elastomer;

Recommended Citations

Citations

  • Bethea, R. A. (2014). The Effects of Carbon Black Reinforcement Systems on Crosslinked Shape Memory Elastomers [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1418301296

    APA Style (7th edition)

  • Bethea, Robert. The Effects of Carbon Black Reinforcement Systems on Crosslinked Shape Memory Elastomers. 2014. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1418301296.

    MLA Style (8th edition)

  • Bethea, Robert. "The Effects of Carbon Black Reinforcement Systems on Crosslinked Shape Memory Elastomers." Master's thesis, University of Akron, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1418301296

    Chicago Manual of Style (17th edition)

akron1418301296
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This open access ETD is published by University of Akron and OhioLINK.