Irene Fahim

Abstract

The present study aimed at developing novel polymer nanocomposites (PNC) membranes by investigating the different preparation factors (e.g. cross-linking of the membranes, filler type and wt% of the fillers added to the polymers) on the PNC membranes’ properties such as: pore size, permeability, tensile strength, melt flow index, and thermal stability, recorded at different temperatures (ranging from 23 – 60 ºC). The main goal is to have PNC membranes with enhanced tensile properties as well as improved barrier properties which would make PNCS potential candidates for possible industrial application such as packaging, wrapping materials and filtration membranes. Mainly, two polymers were used in this study: Low density polyethylene LDPE as an example of a synthetic polymer, and chitosan (CS) as another example of a natural polymer. In the current research, emphasis was made on the natural polymer due to its biodegradable nature and for proving better performance in concerning its permeability as membrane matrices. PNCS were prepared by mixing each polymer with two nanofillers (graphene and fullerene) with different concentration (0.1, 0.5 and 1wt.%) for studying their influence on the PNCs membrane properties. LDPE ,CS nanocomposite membranes were fabricated by mixing the polymer with graphene (G) and Fullerene (F) nanofillers. Physical cross-linking of CS by sodium tripolyphosphate (TPP) was carried out in order to enhance the binding between the internal CS chains. F and G with different weight percentages (0.1, 0.5 and 1wt.%) were added on physically cross-linked chitosan (CLCS) as well as the non cross-linked chitosan (NCLCS) membranes by wet mixing technique. In the current research, permeability and the pore morphology of the LDPE, CLCS and NCLCS with and without fillers were assessed at room temperature and as a function of increasing the ambient temperature under constant strain. Scanning electron microscopy (SEM) was employed for the evaluation of the fabricated plain and composite membranes structures and pore size, shape and pore size and nanofiller distribution. The average pore sizes were determined using a porosimeter. Validation of the experimental results was conducted using Abaqus/Standard software provided a simulation modelling of steady-state diffusion of the fabricated membranes. The tensile strength and % elongation were also assessed at 25, 30 and 60oC. Response surface methodology (RSM), a statistical analysis tool, was used to determine the optimized mixture for the various factors (temperature, cross-linking of CS, filler type and wt% of the fillers). The results revealed that cross-linking, filler type and filler wt.% play a crucial role in controlling the pore size and accordingly the rest of the physicochemical and mechanical properties of all fabricated LDPE, CS nanocomposite membranes. The pore size of the fabricated LDPE were found to be microporous(0.1-0.2µm) while, CS nanocomposite membranes were found to be in the mesoporous range (i.e. 2-30nm). Moreover, the addition of G and F nanofillers to LDPE, CLCS and NCLCS solutions aided in controlling the CS nanocomposite membranes’ pore size. It enhanced the barrier effect of the membranes by decreasing the pore size. The theoretical modelling results validated the experimental findings, The simulation showed the mass diffusion along the membrane thickness, which could not be calculated experimentally. Increasing the ambient temperature resulted in the decrease in tensile strength due to coarsening of pores upon heating. The optimum membrane conditions were selected according to the membrane's filtration application The RSM results were found to be in agreement with the experimental results, whereby cross-linking of CS, filler type and filler wt.% were significant factors. The factors had a direct influence on the pore size, diffusion time and tensile strength of the PNC membranes. The current research shows that fabricated CS nanocomposite membranes were effective candidates in membrane filtration systems. They could be used for blocking particles such as atmospheric dust, fumes, paint pigments, viruses and bacteria. NCLCS/1wt. % could be used to filter gases. CLCS/1 wt. %F could be used for combustion smoke filtration. LDPE/1 wt. %G could be used for filtration of bromine and lead smoke particles.

Department

Mechanical Engineering Department

Degree Name

PhD in Applied Science

Graduation Date

6-1-2015

Submission Date

May 2015

First Advisor

Salem, Hanadi, Mamdouh, Wael

Committee Member 1

Elhaggar, Salah

Committee Member 2

Taha, Chakinaz

Extent

144 p.

Document Type

Master's Thesis

Library of Congress Subject Heading 1

Nanocomposites (Materials) -- Industrial applications.

Library of Congress Subject Heading 2

Nanofiltration -- Industrial applications.

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. The author has granted the American University in Cairo or its agents a non-exclusive license to archive this thesis, dissertation, paper, or record of study, and to make it accessible, in whole or in part, in all forms of media, now or hereafter known.

Institutional Review Board (IRB) Approval

Not necessary for this item

Comments

It gives me great pleasure to express my sincere gratitude to my supervisors, Professor Hanadi Salem and Dr Wael Mamdouh, for their supervision through the course of this research work. I have benefited immensely from their considerable help, encouragement and inspiration throughout this time. I was fortunate to receive the help of Dr. Khalil Elkodary in Finite element analysis. I deeply appreciate all that they have done for me. I would like also to thank Dr Hatem Elayat for his help in statistical analysis. I would like to thank the Academy of Scientific Research and Technology (ASRT) for its financial support, which has made this research possible. I am also very grateful to the Yousef Jameel Science and Technology Research Center (YJ-STRC) for providing the equipment and training for performing all the experimental work. I would also like to express my appreciation to all the staff and research students in the Mechanical Engineering department and the chemistry department for their help and support. Last, but not least, I wish to thank my sons, Farid and wahid , for their support during my study.

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