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A Real-time Study on Mechano-optical Properties of Chitosan during Film Formation and Processing

Mu, Shenglong
http://orcid.org/0000-0002-8127-5860
http://rave.ohiolink.edu/etdc/view?acc_num=akron1462885413

Abstract Details

2016, Master of Science in Polymer Engineering, University of Akron, Polymer Engineering.
Chitosan has been intensively studied since 1979 for its vast applications in food packaging due to the promising antimicrobial properties. A fundamental understanding on the processing characteristics is essential in order to achieve desired properties with regarding to the final products. However, the conventional off line techniques where the samples were characterized sporadically are difficult if not impossible to capture the transient evolution of the structures and properties development that take place in the film formation and processing of chitosan. In order to address this issue, a real time measurement system which is able to track the development of weight, thickness, surface temperature, both in-plane birefringence and out-of-plane birefringence during the drying of solution casting was developed and utilized in this study to systematically investigate the optical anisotropy development of chitosan film formation. Meanwhile, another real time measurement system where the birefringence, true stress and true strain can be continuously tracked for a film undergoing all kinds of processing procedures, such as heating, cooling, uniaxial stretching, holding, retracting and cycling was also adopted to study and reveal the mechano-optical properties development in the actual film processing. It has been seen that in the film formation of chitosan/acetic acid solution casting, both in plane and out of plane birefringence remain constant at zero initially indicating that the molecular chains stay random and isotropic in the solution. As the drying process proceeds, beyond a critical time point, the out-of-plane birefringence starts to increase and then levels off while the in-plane birefringence stays zero which illustrates that the molecular chains still remain isotropic in-plane whereas the chain axes rotate to lie parallel in the film plane preferentially. Increasing the concentration of chitosan leads to the decrease in ultimate out-of-plane birefringence due to the lower chain orientation level in the plane. Similarly, higher temperature results lower out-of-plane birefringence value due to higher relaxation. Moreover, the resulting chitosan films from chitosan/acetic acid solution casting dried at ambient environment always contain ~10wt. % solvent (calculated from the weight data above as well as thermogravimetric analysis) which plasticizes chitosan and validates its stretchability at relatively low temperature. Hence, the effects of both solvent content and temperature were studied in the stretching process. Generally, a three-regime of non-linear stress and strain-optical behavior can be seen: stress increase dramatically before yielding point, stress increase with a relatively mild rate after yielding point and a steep rise shows up in the strain hardening point. The increase of solvent content tends to change the deformation behavior from plastic-like to rubber-like behavior, and promotes the relaxation of polymer segments to reduce the final birefringence. Increasing stretching temperature and decreasing stretching rate also enhance the relaxation of polymer chains, causing a lower birefringence value at given true strain value.
Miko Cakmak (Advisor)
Soucek Mark D. (Committee Chair)
Min Younjin (Committee Member)
100 p.
Polymers
Chitosan, Birefringence, Unixial stretching, Drying behavior

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Citations

  • Mu, S. (2016). A Real-time Study on Mechano-optical Properties of Chitosan during Film Formation and Processing [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462885413

    APA Style (7th edition)

  • Mu, Shenglong. A Real-time Study on Mechano-optical Properties of Chitosan during Film Formation and Processing. 2016. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1462885413.

    MLA Style (8th edition)

  • Mu, Shenglong. "A Real-time Study on Mechano-optical Properties of Chitosan during Film Formation and Processing." Master's thesis, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462885413

    Chicago Manual of Style (17th edition)

akron1462885413
766
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This open access ETD is published by University of Akron and OhioLINK.