processing and evaluation of low density polyethylene/chitosan antimicrobial films tan yi min ...

223 Pages·2016·4.38 MB·English

by  Tan Yi Min

PROCESSING AND EVALUATION OF
LOW DENSITY POLYETHYLENE/CHITOSAN
ANTIMICROBIAL FILMS

TAN YI MIN

NATIONAL UNIVERSITY OF SINGAPORE

2016
PROCESSING AND EVALUATION OF
LOW DENSITY POLYETHYLENE/CHITOSAN
ANTIMICROBIAL FILMS

TAN YI MIN
B. Eng. (Hons.), National University of Singapore

A THESIS SUBMITTED FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

DEPARTMENT OF MECHANICAL ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE
2016
DECCLARATTION

I hereby ddeclare that tthe thesis iss my originaal work andit has beenn written by
me in its entirety. I hhave duly accknowledgeed all the soources of infformation
wwhich have been used iin the thesiss.

This theesis has alsoo not been ssubmitted foor any degreee in any unniversity
previously.

______________________________
Tan Yi Minn
088 January 20016

i
ABSTRACT
Polyethylene (PE) is a conventional material that is commonly used for
packaging as it is low in cost, has good processability and versatility in
fabrication. However, extensive use and disposal of PE has resulted in serious
environmental pollution as synthetic polymers are non-biodegradable and
resistant to degradation. Rising environmental awareness has led to studies on
the incorporation of natural materials as a degradable component into PE, to
impart biodegradable properties for the reduction of environmental footprint at
the end of life. In this study, low density polyethylene (LDPE)/chitosan films
were fabricated via a compression molding process. Chitosan, a natural
biopolymer has immense potential for applications in food technology, due to
its biocompatibility, non-toxicity, short time biodegradability, excellent film
forming ability and inherent antimicrobial properties. To obtain good
mechanical properties of the blends, interfacial compatibility and miscibility
between the hydrophobic synthetic and hydrophilic natural polymers are
critical. Despite studies conducted with the incorporation of compatibilisers
for better interface adhesion, mixing studies to achieve better miscibility of
LDPE/chitosan films have not been investigated. Experimental results showed
that an increase in the length of compounding enhanced the interfacial
adhesion between the polymers, and a higher degree of miscibility of the
blends was achieved. It could be observed from the experimental results that
the degree of crystallinity increased with increasing compounding length. The
fabricated LDPE/chitosan films also displayed good thermal stability.
Furthermore, an improvement in miscibility of the blends led to improved
mechanical properties of the films. Statistical analysis of data using the
ii
Abstract
variance (ANOVA) procedure was used to verify the results obtained from
mechanical testing. The tensile strength increased by ~ 25 % whereas
elongation at break increased by two-fold. Films that were fabricated from
blends compounded with an L/D ratio of 60:1 had the highest tensile strength
and elongation at break values, and the tensile strength was comparable to that
of LDPE films. In addition, in a preliminary in-vitro bacterial study, the
growth of E. coli was inhibited by LDPE/chitosan films containing 20 wt. %
content of chitosan within 24 h. Hence, LDPE/chitosan films have the
potential to be a useful material in the area of food technology.

iii
ACKNOWLEDGEMENTS
I would like to express my earnest appreciation and gratitude to all the people
who have provided me with their help and support for the completion of this
thesis, and would like to thank the National University of Singapore (NUS) for
awarding me a NUS Research Scholarship.

First of all, I would like to express my sincere gratitude to my supervisors,
Associate Professor Thian Eng San, Dr. Lim Szu Hui Cynthia, Dr. Tay Bee
Yen and Dr. Lee Mun Wai for their guidance, advice and encouragement
throughout the duration of this research study. I would like to thank them for
sharing with me both their invaluable knowledge in scientific research and
also their enriching life experiences.

I would like to express my greatest appreciation to Prof. Ho Bow for his
expert advice and guidance in the antibacterial study, and also to Mr. Ng Han
Chong for his assistance in ensuring that the antibacterial assessments could
be conducted smoothly. Special thanks also go to Dr. Lim Poon Nian for her
patience and guidance in the microbiological experimental techniques during
the study.

I am thankful to Mr. Abdul Khalim Bin Abdul and Mr. Ng Hong Wei of the
Materials Group for their constant kind assistance involving experimental
work, and am grateful for the help of Ms. Ma Cho Cho, Ms. Xie Hong and Mr.
Goh Ming Hao from A*STAR SIMTech for their assistance in the operation
of equipment for the characterisation of experimental samples.
iv
Acknowledgements
I would also like to give my sincere appreciation and thanks to the past and
present members of BIOMAT laboratory, including Dr. Lim Poon Nian, Dr.
Lim Jing, Dr. Li Jinlan, Dr. Chang Lei, Dr. Wang Zuyong, Dr. Zhang Qinyuan,
Mr. Feng Yong Yao Jason, Ms. Lam Ruey Na, Ms. Qiu Xihe Ms. Tong Shi
Yun, Mr. Wu Yang and Mr. Wu Bin, for all their assistance, encouragement
and company throughout the course of my study. The good memories that
were spent with all of you will be remembered fondly. I am very grateful to
Ms. Chia Sing Ling, Mr. Markas Law Lee Lam, Mr. Matthew Law Lee Liong,
Mr. Gong Feng, Ms. Li Liu, Ms. Lu Jia, Dr. Song Bohang, Ms. Jiang Weizhou,
Mr. Sim Xian Hui, Mr. Chan Ng Poh Huat Paul, Ms. Chng Shuyun, Ms. Deng
Xinying, Mr. Eng Hengky, Ms. Munirah Abdul Manan, Ms. Tan Cher Lin
Clara, Ms. Teo Siew Cheng, Mr. Yan Hengchao and Ms. Foong Yuet Ee for
their friendship and support along the way. I will always treasure the great
times that we spent together. I am really appreciative of the encouragement
from many of my friends too.

Most importantly, I would like to give my heartfelt thanks and deepest
gratitude to my family and Mr. Kong Xin Xian for their everlasting love, care
and concern for me. Their unconditional encouragement and unwavering
support have always spurred and motivate me to bring out the best in myself,
to strive for excellence. With love and warmest appreciation, I dedicate this
PhD thesis to them.

v
PUBLICATIONS, CONFERENCES AND AWARDS
International Publications
1. Y.M. Tan, S.H. Lim, M.W. Lee, B.Y. Tay, E.S. Thian. Improve
Miscibility of Low Density Polyethylene/Chitosan Blends through
Variation in Compounding Length. Journal of Applied Polymer Science
(Accepted).

2. Y.M. Tan, S.H. Lim, M.W. Lee, B.Y. Tay, E.S. Thian. Functional
Chitosan-Based Grapefruit Seed Extract Composite Films for Applications
in Food Packaging Technology. Materials Research Bulletin 2015, 69:
142-146.

3. Z. Yang, Z.S. Liu, Z. Ding, J. Hu, Y. M. Tan, S Swaddiwudhipong, K.
Lee. Strength Analyses of the Menisci and the Ligaments of the Knee Joint
under Different Loading Cases. Journal of Life Medicine 2014, 2: 85-9.

4. Z. Yang, Z. Ding, Z.S. Liu, S Swaddiwudhipong, Y. M. Tan, K. Lee.
Comparative Study on Strength of Knee Joint using various Material
Models. International Journal of Computational Materials Science and
Engineering 2012, 1: 1250013.

International Conferences
Oral Presentations
1. Y.M. Tan, X.H. Sim, S.H. Lim, M.W. Lee, B.Y. Tay, E.S. Thian.
Functional Organic Chitosan-Based Grapefruit Seed Extract Hybrid Films:
Enhancing the Hydrophobicity for Extended Food Packaging Applications.
8th International Conference on Materials for Advanced Technologies of
the Materials Research Society of Singapore (ICMAT), Singapore 28th
June 2015 – 3rd July 2015.
vi
Publications, Conferences and Awards
2. Y.M. Tan, S.H. Lim, M.W. Lee, B.Y. Tay, E.S. Thian. An Investigation
on the Effect of Miscibility on the Microstructure and Mechanical
Properties of Polyethylene/Chitosan Composite Films. 31st International
Conference of the Polymer Processing Society (PPS-31), Jeju Island,
Korea 7th June – 11th June 2015.

3. Y.M. Tan, S.H. Lim, M.W. Lee, B.Y. Tay, E.S. Thian. Functional
Chitosan-Based Grapefruit Seed Extract Composite Films for Applications
in Food Packaging Technology. 6th International Symposium on
Functional Materials (ISFM), Singapore 4th August 2014 – 7th August
2014.

Poster Presentations
1. Y.M. Tan, S.H. Lim, M.W. Lee, B.Y. Tay, E.S. Thian. Biopolymer-Based
Composite Thin Films: Application in Food Packaging Technology,
SIMTech Postgraduate Research Poster Exhibition, 16 August 2013.

2. Y.M. Tan, P.N. Lim, E.S. Thian. Synthesis and Characterisation of
Magnesium-Substituted Hydroxyapatite for Tissue Engineering
Applications. International Conference of Young Researchers on
Advanced Materials (ICYRAM), Singapore, 1st July – 6th July 2012.

Conference Proceedings
1. Y.M. Tan, S.H. Lim, M.W. Lee, B.Y. Tay, E.S. Thian. An Investigation
on the Effect of miscibility on the Microstructure and Mechanical
Properties of Polyethylene/Chitosan Composite Films. 31st International
Conference of the Polymer Processing Society (PPS-31), 7th June – 11th
June. 2015, pp. 765.

Awards
1. Best Poster Presenter Award (Second Runner-Up) at the SIMTech
Postgraduate Research Poster Exhibition, 16 August 2013.
vii
Table of Contents
TABLE OF CONTENTS
Declaration………………………………………………………….. ……...i
Abstract……………………………………………………………………..ii
Acknowledgements ...................................................................................... iv
Publications, Conferences and Awards ..................................................... vi
Table of Contents………………………………………………………….ix
List of Figures .............................................................................................. xi
List of Symbols ........................................................................................ xviii
CHAPTER 1 INTRODUCTION
1.1 Background ........................................................................................... 1
1.2 Research Aims ...................................................................................... 8
1.2.1 Objectives ........................................................................................ 8
1.3 Scope ...................................................................................................... 9
CHAPTER 2 LITERATURE REVIEW
2.1 Role of Packaging ................................................................................ 10
2.1.1 Forms of Packaging .................................................................... 11
2.1.2 Functions of Packaging ............................................................... 13
2.1.2.1 Containment ...................................................................................... 13
2.1.2.2 Protection .......................................................................................... 13
2.1.2.3 Convenience ...................................................................................... 15
2.1.2.4 Communication ................................................................................. 17
2.1.3 Improvements in Packaging ........................................................... 19
2.2 Developments in Food Packaging ........................................................ 20
2.3 Technologies in Active Packaging ....................................................... 21
2.3.1 Applications of Active Packaging Technology ............................. 23
2.4 Antimicrobial Packaging ...................................................................... 27
2.4.1 Antimicrobial Agents ..................................................................... 33
2.5 Packaging Incorporated with Natural Antimicrobial and/or
Antioxidative Agents .......................................................................... 33
2.6 Biopolymer Materials ........................................................................... 35
2.6.1 Chitosan .................................................................................... 38
2.6.1.1 Chitosan as a Food Additive Directly Incorporated into Foods ........ 45
2.6.1.2 Chitosan Solutions as an Edible Coating or a Liquid Additive ........ 47
2.6.1.3 Chitosan-Based Films for Controlled Release of Active Compounds ... 53
2.6.1.4 Chitosan Blend Films ........................................................................ 55
ix