TexasScholarWorks
    • Login
    • Submit
    View Item 
    •   Repository Home
    • UT Electronic Theses and Dissertations
    • UT Electronic Theses and Dissertations
    • View Item
    • Repository Home
    • UT Electronic Theses and Dissertations
    • UT Electronic Theses and Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Polyamide-layered silicate nanocomposites by melt processing

    Thumbnail
    View/Open
    fornestd039.pdf (19.92Mb)
    Date
    2003
    Author
    Fornes, Timothy Dean
    Share
     Facebook
     Twitter
     LinkedIn
    Metadata
    Show full item record
    Abstract
    Polyamide-layered silicate nanocomposites based on nylon-6, 11, and 12 and organically modified montmorillonites (organoclay) were prepared by twin screw extrusion. Carefully designed component structure-nanocomposite morphology and property investigations on these materials were executed to understand why nylon-6 readily exfoliates organoclay. The polyamide structure strongly influences the extent of clay platelet delamination and level of property enhancement, as determined by X-ray, transmission electron microscopy and stress-strain analyses. High molecular weight nylon-6 materials lead to better organoclay exfoliation and greater nanocomposite moduli and yield strengths than lower molecular weight materials; this is attributed to higher levels of shear stress imparted on the clay by the higher viscosity polymer. The ratio of amide to methylene units in the repeat structure of nylon-6 appears to affect the polymer- organoclay affinity since a large increase in aliphatic content, i.e., nylon-6 versus nylon-12, results in less organoclay dispersion and lower reinforcing efficiency. The structure of the organoclay is also critical for producing wellexfoliated nylon-6 nanocomposites. Alkyl ammonium surfactants that cover less montmorillonite surface in the organoclay are more effective at exfoliating clay and generating improved nanocomposite stiffness and strength; such surfactants facilitate more desirable polyamide-silicate interactions, yet maintain sufficient organoclay gallery spacings needed both to overcome the cohesive forces between neighboring platelets and to facilitate polymer intercalation. The source of sodium montmorillonite used to form the organoclay is also important. The superior properties observed in nylon-6 nanocomposites may be explained by conventional ideas of reinforcement as predicted by composite theories like those of Halpin-Tsai or Mori-Tanaka. Based on good agreement between experimental nanocomposite moduli and model predictions it is clear that superior reinforcement stems from the high modulus and aspect ratio of montmorillonite; however, montmorillonite particles clearly affect the proprieties of the polymer phase which may have additional effects on the composite. Differential scanning calorimetry and X-ray analyses show that the clay can alter the nucleation, growth, and type of nylon-6 crystals formed under certain crystallization conditions. Furthermore, exposure of organoclay surfaces during processing can cause considerable polymer degradation and color formation depending upon the type of nylon-6 used and the surfactant structure in the organoclay.
    Department
    Chemical Engineering
    Description
    text
    URI
    http://hdl.handle.net/2152/577
    Collections
    • UT Electronic Theses and Dissertations

    University of Texas at Austin Libraries
    • facebook
    • twitter
    • instagram
    • youtube
    • CONTACT US
    • MAPS & DIRECTIONS
    • JOB OPPORTUNITIES
    • UT Austin Home
    • Emergency Information
    • Site Policies
    • Web Accessibility Policy
    • Web Privacy Policy
    • Adobe Reader
    Subscribe to our NewsletterGive to the Libraries

    © The University of Texas at Austin

     

     

    Browse

    Entire RepositoryCommunities & CollectionsDate IssuedAuthorsTitlesSubjectsDepartmentsThis CollectionDate IssuedAuthorsTitlesSubjectsDepartments

    My Account

    Login

    Statistics

    View Usage Statistics

    Information

    About Contact Policies Getting Started Glossary Help FAQs

    University of Texas at Austin Libraries
    • facebook
    • twitter
    • instagram
    • youtube
    • CONTACT US
    • MAPS & DIRECTIONS
    • JOB OPPORTUNITIES
    • UT Austin Home
    • Emergency Information
    • Site Policies
    • Web Accessibility Policy
    • Web Privacy Policy
    • Adobe Reader
    Subscribe to our NewsletterGive to the Libraries

    © The University of Texas at Austin