• Login
    View Item 
    •   NWU-IR Home
    • Electronic Theses and Dissertations (ETDs)
    • Natural and Agricultural Sciences
    • View Item
    •   NWU-IR Home
    • Electronic Theses and Dissertations (ETDs)
    • Natural and Agricultural Sciences
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Study the effect of alkyl substitution of monomers on properties of polyesters

    Thumbnail
    View/Open
    Bhengu_K_2015.pdf (12.60Mb)
    Date
    2015
    Author
    Bhengu, Kenneth
    Metadata
    Show full item record
    Abstract
    This study concerned the synthesis of modified terephthalic acid monomers and branched dialcohols for the synthesis of polyesters with different properties. Monomers were prepared by esterification of terephthalic acid (TPA) and the alkylation of the ester dimethyl terephthalate (DMT). If alkylation was unsucessful, TPA was brominated using N-bromosuccinimide (NBS) and other brominating agents. However, the bromination reactions were also unsuccessful. Therefore, oxidation reactions of 2-bromoparaxylene were conducted as an attempt to obtain the desired monomers, however a mixture of products was produced that were difficult to separate. Subsequently, the brominated TPA was bought, and the alkylation reactions were performed using tetramethyltin and other alkylating agents; however the alkylation reaction was once again unsuccessful. Despite the difficulties encountered during monomer synthesis, polymerization of the obtained monomers was investigated. Polymer synthesised by the technique of condensation polymerization of branched diols and the brominated TPA. The unbranched diol monomers and unsubstituted DMT were used to synthesize reference polymers for comparison with the novel polymers produced in this study. The following diols were used: 1,2-propanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol. A batch reactor equipped with a mechanical stirrer connected to the vacuum pump was used as polymerization vessel. The polyesters were synthesised and they were characterised using IR and NMR. Additional polymer analysis was performed using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Gel permeation Chromatography (GPC) and Scanning Electron Microscopy (SEM). The results of the analyses indicated that the polymers became flexible and softer with an increasing number of methylene units in the main chain. Consequently, the melting point of the polymer decreased when there was branching present. SEM analyses showed that polymers were softer and had no hard edges, and the SEM also showed the catalyst inside the polymers. The decomposition temperature changed very slightly with alkyl substitution or the presence of bromide in benzene ring. It was concluded that the benzene ring did not become activated as a number of methods were attempted unsuccessfully to facilitate reaction by either alkylation or bromination. The methyl branches on the diols were not held responsible for any changes in the properties of the polyesters. Bromination of the monomers resulted in polymers that were structurally amorphous and that demonstrated a low tensile strength.
    URI
    http://hdl.handle.net/10394/15161
    Collections
    • Natural and Agricultural Sciences [2757]

    Copyright © North-West University
    Contact Us | Send Feedback
    Theme by 
    Atmire NV
     

     

    Browse

    All of NWU-IR Communities & CollectionsBy Issue DateAuthorsTitlesSubjectsAdvisor/SupervisorThesis TypeThis CollectionBy Issue DateAuthorsTitlesSubjectsAdvisor/SupervisorThesis Type

    My Account

    LoginRegister

    Copyright © North-West University
    Contact Us | Send Feedback
    Theme by 
    Atmire NV