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The processing/structure/property relationships of polyvinyl alcohol hydrogels

Trieu, Hai Hong
http://rave.ohiolink.edu/etdc/view?acc_num=case1058540388

Abstract Details

1995, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.
Polyvinyl alcohol (PVA) hydrogels were prepared using aqueous PVA solutions containing various dimethyl sulfoxide (DMSO) concentrations. Remarkably different PVA hydrogels were obtained by varying processing parameters, i.e. DMSO concentration, initial PVA concentration and quench temperature. A large variation in the surface and bulk structures of PVA hydrogels was observed by scanning electron microscopy for samples prepared by freeze-etching and critical point drying techniques. The processing conditions have a dramatic effect on the physical and mechanical properties of PVA hydrogels. PVA hydrogels prepared at low quench temperature using moderate to high DMSO concentrations have a low water content and a significantly improved hardness, tensile strength, elongation and tear resistance. Maximum properties are typically obtained near 75 wt% DMSO and at -60°C quench temperature. Under such conditions, gelation occurs rapidly before significant phase separation due to spinodal decomposition takes place, which results in a homogeneous gel structure. On the other hand, freezing that normally causes phase separation is dramatically retarded by the formation of DMSO-water complexes. This allows post-gelation crystallization to proceed that leads to a stable gel structure before freezing occurs. As a result, a homogeneous gel structure with maximum optical and mechanical properties is obtained. By varying the processing parameters, the gelation mechanism is altered which leads to three different types of hydrogel structures: (1) homogeneous gel, (2) heterogeneous gel without orientation, and (3) heterogeneous gel with oriented domains. Structural models representing the three types of hydrogels are proposed. The swelling behavior of PVA hydrogels in aqueous solutions of organic salts was investigated. The reswelling behavior of hydrogels was also studied using dehydrated specimens. Attempts were made to characterize the crystallinity of PVA hydrogels using a differential scanning calorimeter. The viscoelastic behavior of hydrogels was studied using a dynamic mechanical analyzer
Syed Qutubuddin (Advisor)
222 p.
Chemistry, Polymer
Polyvinyl alcohol hydrogels

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Citations

  • Trieu, H. H. (1995). The processing/structure/property relationships of polyvinyl alcohol hydrogels [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1058540388

    APA Style (7th edition)

  • Trieu, Hai. The processing/structure/property relationships of polyvinyl alcohol hydrogels. 1995. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1058540388.

    MLA Style (8th edition)

  • Trieu, Hai. "The processing/structure/property relationships of polyvinyl alcohol hydrogels." Doctoral dissertation, Case Western Reserve University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058540388

    Chicago Manual of Style (17th edition)

case1058540388
1,330
© 1995, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.