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" Effect of Organically Modified Layered Double Hydroxide and Thyme Oil Loading on the Performance of Poly(Lactic Acid)/Poly[(Butylene Succinate)-Co-Adipate] Biodegradable Polymer Blends for Cosmetics Packaging Applications "
Mhlabeni, Thobile L.
Pillai, Sreejarani Kesavan
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1059096
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| Doc. No
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TL58213
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| Main Entry
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Mhlabeni, Thobile L.
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| Title & Author
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Effect of Organically Modified Layered Double Hydroxide and Thyme Oil Loading on the Performance of Poly(Lactic Acid)/Poly[(Butylene Succinate)-Co-Adipate] Biodegradable Polymer Blends for Cosmetics Packaging Applications\ Mhlabeni, Thobile L.Pillai, Sreejarani Kesavan
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| College
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University of Johannesburg (South Africa)
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| Date
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2019
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| Degree
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M.Tech.
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| student score
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2019
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| Note
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175 p.
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| Abstract
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Poly(lactic acid) (PLA) is a well known biodegradable polymer that can be applied for short term packaging in food and cosmetics. However, PLA is brittle, which significantly limit its industrial packaging applications. Blending PLA and other polymers serve as one of the alternative techniques to improve the toughness of PLA. Blends preparations can be done by melt-compounding using the extrusion technique, which is popular for industrial applications. Blending PLA with equally bio-friendly polymers is preferred to avoid tampering with the degradation rate of PLA. In this study, poly[(butylene succinate) co-adipate] (PBSA) has been investigated as a secondary polymer to improve the flexibility of PLA. Extrusion grades of PLA and PBSA were melt-blended using a twin screw extruder to prepare the PLA/PBSA blends. The weight content of PBSA in the blends was kept at the range of 10-30 wt.% PBSA. The test specimens were made using the compression moulding technique. Fourier-transform infrared spectroscopy (FTIR) was used to study the chemical interaction between PLA and PBSA in the composition of the blends. The scanning electron microscopy (SEM) was used to study the blends phase morphology. Thermal properties were studied using the differential scanning calorimetry (DSC) and thermogravimetric analyser (TGA). Lastly, mechanical properties were investigated using the tensile tests, impact strength tests, and dynamic mechanical analysis (DMA). The FTIR spectra in the fingerprint region showed overlapping characteristics of PLA and PBSA in the blends with increasing PBSA weight content. SEM confirmed the distinct phases suggested by FTIR. The morphologies, as seen on the SEM micrographs, showed a continuous phase and a dispersed phase. Furthermore, it was observed from SEM micrographs that the average diameter of the dispersed phase increased with PBSA weight content. The thermal stability decreased with increasing PBSA weight content at 50 % degradation temperature (T50) and maximum degradation temperature (Tmax). DSC analysis showed that the cold crystallization temperature (Tcc) of PLA in the blends occurred at a relatively lower temperature; however, the total crystallization (Xm) decreased with increasing PBSA weight content. A significant improvement of the elongation at break (EB) and impact resilience was observed at 20 wt.% PBSA. Both the tensile tests and dynamic mechanical analysis showed the loss of modulus of the blends with increasing PBSA weight content. The addition of nanoclays into polymer matrices has the potential to improve barrier properties due to the platelets structure constituting the inorganic clays. When the clay platelets are mostly exfoliated and adequately aligned within the matrix, an improvement in the barrier is seen in most cases. In this study, PLA/clay, PBSA/clay, and PLA/PBSA/clay nanocomposites were prepared by incorporating stearic acid modified layered double hydroxide, the nanoclay (SaLDH). The nanocomposites were processed using a twin screw extruder, and the test specimens were prepared using compression moulding. The effects of clay concentration on the resulting morphology, thermo-mechanical, and permeability properties of PLA/PBSA/clay nanocomposites (optimised) were temperature (T50) and maximum degradation temperatu owed that the cold crystallization temperature (Tcc) of PLA a relatively lower temperature; however, the total crys with increasing PBSA weight content. A significant impro at break (EB) and impact resilience was observed at 2 ensile tests and dynamic mechanical analysis showe the blends with increasing PBSA weight content evaluated. In the B/XSaLDH nanocomposites, where B is 80PLA/20PBSA blend (the blend with 80 wt.% PLA and 20 wt.% PBSA), and X is the concentration of SaLDH, TEM showed that the clay platelets were mostly dispersed within and at the interphase of PLA and PBSA phases. SEM showed a more homogeneous morphology of the nanocomposite at 0.5 wt.% loading of SaLDH (B/0.5%SaLDH). The B/0.5%SaLDH nanocomposite, showed improved thermal stability, mechanical properties, and permeability performance against oxygen gaseous molecules. The results suggest that in the nanocomposites matrices made from blends incorporated with nanoclays, many factors contribute to obtaining high barrier properties. In the present study, for instance, the viscosity difference of the two polymers greatly influenced the localization of the nanoclays platelets within the polymers matrices and therefore the morphologies of the nanocomposites. Novel active packaging based on B/XSaLDH/YTO bionanocomposites incorporated with thyme oil (TO) (where Y represents the concentration of thyme oil) were developed using the extrusion method. The kinetic release rate of the TO into the headspace, antimicrobial properties, mechanical properties, and oxygen transmission rate of the active bionanocomposites were studied. o-Cymene and thymol were identified as the primary active compounds in the bionanocomposites incorporated with TO. The addition of the TO significantly altered the mechanical properties. The tensile modulus and strength reduced while the elongation at break increased. However, the nanocomposites with thyme oil did not show significant antimicrobial activity against the tested microorganisms (bacteria, Escherichia Coli (E. Coli), Staphylococcus aureus (S. aureus) and fungus Aspergillus niger (A. niger) which are pertinent in cosmetic products.
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| Descriptor
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Antimicrobial agents
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Bacteria
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Cosmetics
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Food packaging
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Food science
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Mechanical properties
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Microorganisms
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Nanocomposites
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Oils fats
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Polymer blends
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| Added Entry
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Pillai, Sreejarani Kesavan
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| Added Entry
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University of Johannesburg (South Africa)
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