Abstract

During the last 10 decades, plastic products have dominated humans’ lives with various applications in different fields, and particularly in food packaging industry. The fact that plastics do have numerous desirable characteristics does not conceal their detrimental effect on the environment and on human health. In order to overcome these problematic issues and to contribute to sustainable development in the future, other alternatives represented in employing biorenewable biodegradable polymers are implemented for plastics production. Poly (lactic acid) (PLA) is one of the most common employed biopolymer owing to its interesting characteristics. However, PLA exhibits poor mechanical and barrier properties. Natural plasticizers and nano-reinforcement are incorporated into PLA matrix in order to overcome its brittle nature and to improve its barrier properties, particularly for the purpose of food packaging applications. This research focused on two parts: (i) improving the toughness and flexibility of PLA by investigating the effect of addition of three different plasticizers, namely, polyethylene glycol (PEG), tri n-butyl citrate (TBC), and triacetin (TA) of different concentrations using cast solution method, and (ii) PLA/TA 10%, the best investigated combination among all in terms of mechanical properties, was then chosen as the base system to further investigate the effect of incorporating four different nano-reinforcements, namely, carbon nanotubes (CNT), COOH functionalized carbon nanotubes (CNTCOOH), graphene platelets (GNP), and COOH functionalized graphene nanoplatelets (GNPCOOH) of different concentrations for fabrication of PLA nanocomposites. The physical, chemical, and barrier properties of all prepared samples were investigated through the stress-relaxation measurements, DSC, TGA, Mercury Porosimetry, biodegradability, water absorption, oxygen permeability, and water vapour transmission. GNPCOOH nanocomposites exhibited the best mechanical behaviour among all samples, while TGA analysis revealed that it had no effect on the thermal stability. Results obtained by Hg porosimetry have shown that the total porosity has tremendously decreased by incorporation of the investigated nanofillers. The biodegradation of PLA nanocomposites in natural compost was investigated and it was observed that the incorporation of nanofillers had no specific effect on biodegradation of PLA nanocomposites. Water absorption test revealed that the functionalized nanofillers showed relative increase in water absorption as compared to pristine nanofillers. Oxygen permeability test showed that lower concentrations of GNPCOOH had higher oxygen diffusion, while higher concentrations revealed a remarkable decrease in oxygen permeability. Water vapour transmission test showed that the incorporation of nanofillers has considerably decreased the rate of water vapour transmission.

Department

Chemistry Department

Degree Name

MS in Chemistry

Graduation Date

6-1-2015

Submission Date

May 2015

First Advisor

Madkour, Tarek M.

Committee Member 1

Abd El Azeem, Abd El Azeem Ahmed

Committee Member 2

El Gendy, Ahmed S.

Extent

114 p.

Document Type

Master's Thesis

Library of Congress Subject Heading 1

Food packaging machinery industry.

Library of Congress Subject Heading 2

Polylactic acid.

Rights

The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy.

Institutional Review Board (IRB) Approval

Not necessary for this item

Comments

Mo Ibrahim Foundation Charles Bailey Fellowship

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