LB/V0N/26/olj 
PREVENTION OF MICROBIAL GROWTH IN PAINTS USING 
HERBAL BIOCIDES AVALIABLE IN SRI LANKA 
By 
G . P . S . P r e m a r a t h n e 
This Thesis was submitted to the Department of Chemical and Process Engineering of 
the University of Moratuwa in partial fulfillment of the Degree of Master of Science 
in Polymer technology 
D e p a r t m e n t of Chemica l and Process Engineer ing 
Universi ty of M o r a t u w a 
Sri L a n k a 
December 2003 
1 Rivert i t} of Mm ; I I I I H . 1 
796.31 
17631 
7 9 6 3 1 
D E C L A R A T I O N 
" I certify that this thesis does not incorporate without acknowledgement any material 
previously submitted for a degree or diploma in any University in the best of my 
knowledge and belief it does not contain any material previously published, written or 
orally communicated by another person except where due reference is made in the 
text" 
Signature of the candidate 
( C P S . Premarathne) 
To the best of my knowledge, the above particulars are correct. 
Supervisor 
(Dr B.A.J.K. Premachandra) 
1 
A B S T R A C T 
Certain fungal types can grow on dried paint films. They cause to deteriorate the dried 
paint films. Currently synthetic fungicides are used to prevent fungal growth. They 
are hazardous compounds, which caused irritation of eyes and skin, skin rashes, etc of 
humans. Therefore it is important to replace synthetic fungicides by environmentally 
friendly natural fungicides (extracted from plants). 
In this work cinnamon leaf oil, citronella oil and neem seed oil were used as natural 
fungicides. 8 fungal types grown on dried paint films were used to investigate the 
anti-fungal activity of the above oils. Quantitative analysis of cinnamon leaf oil and 
citronella oil were done using gas chromatography and quantitative analysis of neem 
seed oil was not done due to unavailability of standards. Modified method of agar 
over-lay technique was used to determine minimum inhibition concentration of the 
fungal types used, after introducing three oils. The results indicated cinnamon leaf oil 
is the best to use as fungicide for exterior emulsion paint out of three oils, as growth 
of all used fungal types were inhibited below at concentration of 2000 ppm, when 
introducing cinnamon leaf oil into each fungal type individually. It was more than 
12000 ppm in citronella oil and more than 20000 ppm in neem seed oil. 
Modified method of ASTM D2373-74 was used to determine the minimum inhibition 
concentration of cinnamon leaf oil to inhibit fungal growth on exterior emulsion paint 
film. Aging tests were done to determine effect of cinnamon leaf oil on viscosity, pH, 
colour of exterior emulsion paint and adherence of binder to the substrate after aging 
for three years. Tropical chamber test was used as an accelerated test method to 
investigate fungal degradation after applying cinnamon leaf oil as fungicide. 
According to the results, fungal growth in exterior emulsion paint could be inhibited 
below 3500 ppm of cinnamon leaf oil and applied paint film on a surface of an 
exterior substrate will not attack by fungi for 2-3 years. Significant changes in 
viscosity, pH, colour of the exterior emulsion paint and adherence of binder to the 
substrate were not detected due to cinnamon leaf oil. Results suggest that cinnamon 
leaf oil can be used as a fungicide to prevent growth of fungi considered and for the 
exterior emulsion paint used. 
ii 
A C K N O W L E D G M E N T 
It is with deep sense of gratitude I thank my supervisors Dr. B.A.J.K. Premachandra, 
Dr. (Mrs) S.H.P. Gunawardane and Mr. S.A.S. Perera, Department of Chemical and 
process Engineering, University of Moratuwa, for the tremendous encouragement, 
guidance and support extended to me during the course of my work. 
My sincere thanks are due to Dr.(Mrs) Padma Amarasinghe, Head, Department of 
Chemical and Process engineering, university of Moratuwa for participating my 
progress review presentations as well as her guidance and help given to me during my 
research work. 
I express my deep appreciation to the Asian Development Bank for financing the 
research and I should thank Prof. (Mrs) N.Rathnayake, Director, Post-Graduate 
Studies, University of Moratuwa and her staff for great support offered through out 
the research project. 
I am greatful to Dr. Priyantha wimalarathna, Department of Chemistry, University of 
Kelaniya for participating my progress review presentations as my external examiner 
and also for kind advices given on essential oil analysis. 
I wish to grant my heartiest thank to Mr. Ananda Abeyratne, factory manager, asian 
paints Lanka Limited for granting permission to use their laboratory facilities 
regarding preparation of exterior emulsion paint and analysis of properties of paints 
and Mr. chandana Herath, chemist and Mr. Taranga Silva Laboratoiy assistant for 
their unhesitant co-operation and help in numerous ways. 
I am very greatful Dr. (Mrs.) Indrika Abeygunawardane, Department of 
Microbiology, University Kelaniya for her guidance and help given to m e regarding 
identification of fungal types and preparation of fungal spore suspensions and non-
acedamic staff of Department of Microbiology, University of Kelaniya for their 
assistance given m e during my course of work. 
I also wish to thank P r . Mahesh Jayaweera, Department of Civil Engineering, 
University of Moratuwa for providing required glass wares as well as for granting 
permission to use environmental laboratory, for autoclave sterilization and his staff 
for kind co-operation given to m e during my course of work. 
I wish to thank Dr. (Mrs) L. Arabawela and her staff at Industrial Technology Institute 
for the analysis of essential oils and Dr. Kitsiri Dissanayake, Head, Department of 
Earth resources, University of Moratuwa for providing required glasswares. 
I also thank very much Mr: Buddhika de Silva, MSc. Student, Department of 
Chemical and Process Engineering for his fullest co-operation given m e during the 
my course of work. I wish to thank non-academic staff of Department of Chemical 
and Process Engineering for the assistance given during my course of work. I am 
grateful my family members for their advices, encouragement and co-operation given 
me in numerous ways. 
iii 
C O N T E N T S 
Page N o 
C H A P T E R - 1 . INTRODUCTION 02 
1.1. Chemical composition 02 
1.1.1. Pigments 03 
1.1.2. Extenders 03 
1.1.3. Binders 03 
1.1.4. Solvents 04 
1.1.5. Additives 04 
1.2. Classification of paints 06 
1.2.1. Emulsion paints 06 
1.3. Methods of degradation of emulsion paints 07 
1.3.1. Biological degradation of emulsion paints 07 
1.4. Most common types of fungi which grow 11 
on paint films 
1.5. Function of fungicide in preventing fungal 12 
growth 
1.6. Fungicides used in paint industry 14 
1.7. Anti- microbial activity of natural oils 14 
1.8. Objectives of the research 16 
CHAPTER-2 . IDENTIFICATION OF FUNGI W H I C H 
G R O W O N PAINT FILMS 
2.1 . Experimental methods 
2.1.1 . Preparation of Potato Dextrose Agar (PDA) 18 
2.1.2. Growth of fungal types 18 
2.1.3. Identification and purification of fungal types 18 
2.2. Results and Discussion 
2.2.1 Identification and purification of fungal types 19 
iv 
C H A P T E R - 3. INFLUENCE O F HERBAL OILS O N F U N G A L 
G R O W T H AND PROPERTIES OF PAINTS 
3.1. Experimental Methods 
3.1.1. Quantitative analysis of oils 26 
3.1.2. Determination the minimum inhibition 26 
concentration of herbal oils 
3.1.3. Preparation of mixed fungal spore suspension 28 
3.1.4. Determination the minimum inhibition 29 
concentration of cinnamon leaf oil for mixed 
fungal spore suspension 
3.1.5. Preparation of exterior emulsion paint 29 
3.1.6. Determination of minimum inhibition 30 
concentration of cinnamon leaf oil 
for liquid paint 
3.1.7. Effect of cinnamon leaf oil on properties 31 
of paints 
3.1.8. Tropical chamber test 32 
3.2. Results and Discussion 
3.2.1. Quantitative analysis of oils 33 
3.2.2. Determination the minimum inhibition 38 
concentration of herbal oils 
3.2.3. Determination the minimum inhibition 42 
concentration of cinnamon leaf oil for mixed 
fungal spore suspension 
3.2.4. Determination of minimum inhibition 42 
concentration of cinnamon leaf oil for liquid paint 
3.2.5. Effect of cinnamon leaf oil on properties of paints 44 
3.2.6. Tropical chamber test 46 
CHAPTER-4 C O N C L U S I O N AND F U T U R E W O R K 
4 .1 . Conclusion 48 
4.2. Future work 48 
LIST OF FIGURES 
Figure Page 
1. Slide culture preparation 19 
2(a). Aspergillus niger colonies on PDA, 7days, 28°C. 19 
2(b). Aspergillus niger conidial head x 400. 19 
2(c). Aspergillus niger conidia xlOOO. 19 
3(a). Aspergillus species type one colony on PDA, 7days, 28°C. 20 
3(b). Aspergillus species type one conidial head x 400. 20 
3(c). Aspergillus species type one conidia x 1000. 20 
4(a). Aspergillusr species type two colonies on PDA, 7days, 28°C. 20 
4(b). 
4(c). 
5(a). 
5(b). 
5(c). 
6(a). 
6(b). 
6(c). 
7(a). 
7(b). 
7(c). 
8(a). 
8(b). 
8(c). 
9(a). 
9(b). 
9(c). 
Aspergillus species type two conidial head x 400. 20 
Aspergillus species type two conidia x400. 20 
Aspergillus species type three colonies on PDA, 7days, 28°C. 21 
Aspergillus species type three conidial head x 400. 21 
Aspergillus species type three conidia x400. 21 
Penicillium species type colonies on PDA, 7days, 28°C. 21 
Penicillium species type one conidial head x 400. 21 
Penicillium species type one conidia xlOOO. 21 
Penicillium species type two colonies on PDA, 7days, 28°C. 22 
Penicillium species type two conidial head x 400. 22 
Penicillium specjes type two conidia xlOOO. 22 
Penicillium species type three colonies on PDA, 7days, 28°C. 22 
Penicillium species type three conidial head x 400. 22 
Penicillium species type three conidia x 1000. 22 
Penicillium species type four colonies on PDA, 7days, 28°C. 23 
Penicillium species type four conidial head x 400. 23 
Penicillium species type four conidia xlOOO. 23 
VI 
LIST OF TABLES 
Table Page 
1. Fungal genera and characteristic morphological features 12 
2. Endemic species of cinnamon 15 
3. Introduced herbal oil concentrations to determine 27 
minimum inhibition concentration 
4. Chemical formula of exterior emulsion paint 29 
5. Composit ion of cinnamon leaf oil 33 
6. Composit ion of citronella oil 35 
7. Some fatty acids present in neem seed oil 37 
with their relative percentage 
8. Some active components present in ncem seed oil 37 
9. Minimum inhibition concentration ranges of introduced 38 
herbal oils (ppm) 
10. Introduced concentrations of cinnamon leaf oil to 42 
prevent fungal growth 
11. Evaluation of fungal growth in samples of exterior 42 
emulsion paint 
• 12. Effect of cinnamon leaf oil on properties of prepared 44 
paint (before aging) 
13. Effect of cinnamon leaf oil on properties of 44 
prepared paint (after aging) 
vii