Characterisation and antimocrobial activity of poly(lacitc acid)/kenaf bio-composites containing a natural agent

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Tawakkal, ISMA (2016) Characterisation and antimocrobial activity of poly(lacitc acid)/kenaf bio-composites containing a natural agent. PhD thesis, Victoria University.


The use of materials based on poly(lactic acid) (PLA) as alternatives to petroleum-based polymers for a range of applications has increased in recent years. In the case of food packaging in particular, PLA has experienced growth in combination with the use of a wide range of other materials and/or additives derived from natural and renewable resources. However, the initial costs associated with new technologies to produce PLA and/or other bio-based polymers are typically high, so new techniques are required to reduce costs without compromising material properties and biodegradability. Naturally sourced lignocellulose fibres such as kenaf (Hibiscus cannabinus L.) are often used as cost-reducing fillers and/or reinforcing agent for biopolymers such as PLA. This study explores the characteristics and antimicrobial (AM) activity of PLA and PLA/kenaf composites incorporated with thymol, a natural bio-active AM substance/agent. The production of PLA/kenaf composites containing thymol is intended for potential use in AM packaging applications such as rigid and/or flexible packaging and coatings. Composites of PLA incorporated with 5 to 40% w/w kenaf fibre loadings and thymol concentrations ranging from 5 to 30% w/w were prepared and compared with control systems containing either no kenaf or no thymol. Kenaf fibres can be treated by alkalisation to improve compatibility with polymer matrices. It was found that the PLA/kenaf composites containing treated kenaf possessed significantly higher tensile strength and stiffness than composites prepared with untreated kenaf. Micrograph images of the fracture surface revealed better adhesion between the treated kenaf fibres and the matrix, thereby resulting in improved reinforcement of the composite. Moreover, PLA/kenaf composites containing thymol exhibited lower tensile strength than those without thymol, suggesting a possible plasticizing effect in the presence of the additive.

Additional Information

This thesis includes 2 published articles for which access is restricted due to copyright (Chapters 2 & 6). Details of access to these papers has been inserted in the thesis, replacing the articles themselves.

Item type Thesis (PhD thesis)
Subjects Historical > FOR Classification > 0303 Macromolecular and Materials Chemistry
Historical > FOR Classification > 0912 Materials Engineering
Current > Division/Research > College of Science and Engineering
Keywords packaging materials; polymers; fibre chemical treatment; storage stability; composite films; Kenaf fibre loadings; algorithms; TG analysis; thymol; thesis by publication
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