Chemistry manufacture and applications of natural rubber

Chemistry, Manufacture and Applications of
Natural Rubber


Related titles:
Smart polymers and their applications
(ISBN 978-0-85709-695-1)
High temperature polymer blends
(ISBN 978-1-84569-785-3)
Natural fibre composites
(ISBN 978-0-85709-524-4)


Chemistry,
Manufacture and
Applications of
Natural Rubber
Edited by
Shinzo Kohjiya and Yuko Ikeda

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Contents

Contributor contact details

xiii



Introduction

xvii



S. Kohjiya, Kyoto University, Japan and Y. Ikeda, Kyoto Institute
of Technology, Japan

Part I Properties and processing of natural rubber

1

1

Biosynthesis of natural rubber (NR) in different
rubber-producing species



K. Cornish, The Ohio State University, USA

1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10

Introduction
Rubber biosynthesis
Rubber particles and rubber biosynthesis
Kinetic analyses of rubber transferase
Regulation of biosynthetic rate
Regulation of molecular weight
Identification and purification of rubber transferase
Conclusions
Acknowledgments
References

3
6
10
12
13
19
23
24

25
25

2

Natural rubber (NR) biosynthesis: perspectives from
polymer chemistry

30



J. E. Puskas and K. Chiang, University of Akron, USA and
B. Barkakaty, Oak Ridge National Laboratory, USA, formerly of
University of Akron, USA

2.1
2.2
2.3
2.4
2.5

Introduction
Background on natural rubber (NR)
Synthetic polyisoprenes (PIPs)
Biosynthesis of NR
In vitro biosynthesis of NR

3

30
31
36
41
47


vi

Contents

2.6
2.7
2.8
2.9

NR in health care
Future trends
Acknowledgments
References and further reading

51
54
57
57

3

Chemical modification of natural rubber (NR) for
improved performance

68



P. Phinyocheep, Mahidol University, Thailand

3.1

Introduction: The role of chemical modification in
creating high-performance natural rubber (NR)
The main types of chemical modification of NR
Chemical modification by changing the structure or
weight of rubber molecules
Chemical modification of the carbon–carbon double bond
Chemical modification by grafting molecules of a
different polymer type
Conclusions: Key issues in improving the properties of
NR
Future trends
Sources of further information and advice
References

104
106
108
110

4

Understanding network control by vulcanization for
sulfur cross-linked natural rubber (NR)

119



Y. Ikeda, Kyoto Institute of Technology, Japan

4.1

Introduction: The importance of sulfur cross-linking of
rubber
Using small-angle neutron scattering to analyze the
network structure of sulfur cross-linked cis-1,4polyisoprene
Network control in sulfur cross-linked cis-1,4polyisoprene
Effect of network structure on strain-induced
crystallization of sulfur cross-linked cis-1,4-polyisoprene
Future trends: Key issues in improving the properties of
natural rubber (NR)
Acknowledgments
References

3.2
3.3
3.4
3.5
3.6
3.7
3.8

3.9

4.2
4.3
4.4
4.5
4.6
4.7
5

The effect of strain-induced crystallization (SIC) on
the physical properties of natural rubber (NR)



S. Toki, National Metal and Materials Technology Center, Thailand

5.1

Introduction

68
70
71
80
95

119
122
126

127
131
131
132
135
135


Contents

vii

Temperature-induced crystallization (TIC) and straininduced crystallization (SIC)
Stress relaxation and SIC
Stress–strain relation and SIC
Tear resistance and SIC
Green strength and SIC
Conclusions
Acknowledgment
References

136
137
144
154
158
162
163
163

6

Generating particulate silica fillers in situ to
improve the mechanical properties of natural
rubber (NR)

168



A. Tohsan and Y. Ikeda, Kyoto Institute of Technology, Japan

6.1
6.2
6.3
6.4
6.5

Introduction: Silica as a filler for rubber
Particulate silica generated in situ
Recent processes for adding filler to rubber
Applications of in situ silica
Conclusions: Key issues in improving the properties of
natural rubber (NR)
Future trends
Acknowledgments
References

5.2
5.3

5.4
5.5
5.6
5.7
5.8
5.9

6.6
6.7
6.8
7

Hydrophobic and hydrophilic silica-filled cross-linked
natural rubber (NR): structure and properties



A. Kato, NISSAN ARC Ltd, Japan and Y. Kokubo, R. Tsushi and
Y. Ikeda, Kyoto Institute of Technology, Japan

7.1

Introduction: Silica reinforcement of natural rubber
(NR)
Testing hydrophobic and hydrophilic silica fillers: sample
preparation
Methods for analyzing silica filler behavior in crosslinked NR matrix
Understanding the behavior of hydrophobic and
hydrophilic silica fillers in cross-linked NR matrix
Comparing hydrophobic and hydrophilic silica-filled

cross-linked NR
Conclusions
Future trends
Acknowledgments
References

7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9

168
170
171
188
188
188
189
189
193

193
196
196
199
208

211
212
212
212


viii

Contents

8

Computer simulation of network formation in natural
rubber (NR)



T. Nakao, The University of Tokyo, Japan, formerly of Sumitomo
Bakelite Co. Ltd, Japan and S. Kohjiya, Kyoto University, Japan

8.1
8.2

Introduction
Simulation methods for cold mastication of natural rubber
(NR)
Simulation methods for vulcanization of NR
Summary
Future trends
Sources of further information and advice

Acknowledgement
References
Appendix: Basic concept of cascade theory

8.3
8.4
8.5
8.6
8.7
8.8
8.9

Part II Applications of natural rubber
9

Eco-friendly bio-composites using natural rubber
(NR) matrices and natural fiber reinforcements



A. B. Nair and R. Joseph, Cochin University of Science and
Technology, India

9.1
9.2

Introduction
The importance of eco-friendly bio-composites from
natural rubber (NR)
Natural fiber reinforcement materials for NR biocomposites

Factors influencing the effectiveness of fiber
reinforcement
Methods to improve the properties of NR bio-composites
Physical properties of NR bio-composites
Processing of NR bio-composites
Applications of NR-based bio-composites with NR
reinforcements
Future trends
Sources of further information and advice
References

9.3
9.4
9.5
9.6
9.7
9.8
9.9
9.10
9.11
10

Natural rubber (NR) composites using cellulosic
fiber reinforcements



R. C. R. Nunes, Universidade Federal do Rio de Janeiro, Brazil

10.1

Introduction: The importance of natural rubber
(NR)/cellulose composites

216

216
217
222
229
229
231
232
232
236
247
249

249
254
257
264
265
268
272
276
278
280
282
284

284


Contents

ix

10.2
10.3
10.4
10.5
10.6
10.7

NR/cellulose composites
NR/natural cellulose nanocomposites
NR/regenerated cellulose nanocomposites
Applications
Future trends
References

285
288
290
297
298
298

11

Soft bio-composites from natural rubber (NR) and
marine products

303



S. Poompradub, Chulalongkorn University, Thailand

11.1
11.2

Introduction
Processes and materials for developing natural rubber
(NR) composites
Effects of marine product fillers on rubber composites
Conclusion
Future trends
Sources of further information and advice
References

303

325

11.3
11.4
11.5
11.6

11.7
12

Natural rubber (NR) for the tyre industry



Y. Hirata, H. Kondo and Y. Ozawa, Bridgestone Corporation, Japan

12.1
12.2
12.3

Introduction
Tyre types, manufacture and requirements
Natural rubber (NR) properties required in tyre
manufacture
NR properties required in tyre products
Examples of NR use in demanding tyre applications
Quality standards for NR as a raw material
Future trends
References

12.4
12.5
12.6
12.7
12.8
13

Application of epoxidized natural rubber (NR) in
pressure sensitive adhesives (PSAs)



A. S. Hashim and S. K. Ong, Universiti Kuala Lumpur, Malaysia

13.1
13.2
13.3
13.4
13.5
13.6
13.7
13.8
13.9

Introduction to pressure sensitive adhesives (PSAs)
Processing of natural rubber (NR) and NR-based PSAs
Assessing the performance of a PSA
The use of epoxidized NR as an adhesive
Effect of coating thickness
Effect of tackifier and filler
Effect of molecular weight
Effect of testing rate
Other factors affecting performance

306
309
319

320
321
322

325
326
335
337
343
349
350
352
353
353
354
354
357
358
361
364
367
368


x

Contents

13.10 Future trends
13.11 Sources of further information and advice

13.12 References
14

Use of natural rubber (NR) for vibration isolation and
earthquake protection of structures



Y. Fukahori, Queen Mary University of London, UK

14.1
14.2

Introduction
The concept of vibration isolation and earthquake
protection
Vibration isolation and earthquake protection systems
Characteristics of natural rubber (NR) for vibration
isolation and earthquake protection
Conclusion
References

14.3
14.4
14.5
14.6

Part IIIEnvironmental and safety issues

369

369
369
371
371
372
374
375
380
381
383

15

Improving the sustainable development of natural
rubber (NR)



S. Kohjiya, Kyoto University, Japan

15.1
15.2

Introduction
Supply and demand of natural rubber (NR) in the twentyfirst century
Biodiversity
Applications of state-of-the-art biotechnology
Biosafety
Conclusion and future trends
References

385

395

15.3
15.4
15.5
15.6
15.7
16

Recycling of natural and synthetic isoprene rubbers



A. I. Isayev, University of Akron, USA

16.1
16.2

Introduction
Approaches to the reuse and recycling of natural rubber
(NR)
Reuse of NR
Recycling of NR
Recycling of synthetic isoprene rubber
Future trends
Conclusions
Acknowledgements

References

16.3
16.4
16.5
16.6
16.7
16.8
16.9

385

387
389
391
392
392
393

395
398
400
405
421
427
428
429
429

Contents

xi

17

Recycling of sulfur cross-linked natural rubber (NR)
using supercritical carbon dioxide

436



Y. Ikeda, Kyoto Institute of Technology, Japan

17.1

Introduction: Key problems in recycling sulfur crosslinked natural rubber (NR)
17.2 Advantages of supercritical CO2 (scCO2) for the
devulcanization of sulfur cross-linked rubber
17.3 Devulcanization of sulfur cross-linked NR in scCO2
17.4 Devulcanization of carbon black-filled sulfur cross-linked
NR
17.5 Devulcanization of an NR-based truck tire vulcanizate
17.6 The role of scCO2 in the devulcanization of sulfur crosslinked rubber
17.7 Conclusion: Key issues in ensuring effective recycling of
sulfur cross-linked NR
17.8 Future trends
17.9 Acknowledgements
17.10 References

18

Recent research on natural rubber latex (NRL)
allergy



T. Palosuo, National Institute for Health and Welfare, Finland

Introduction: The problem of natural rubber latex (NRL)
allergy
18.2 Medical background to NRL allergy
18.3 Mechanisms of development and clinical presentation of
NRL allergy
18.4 Recent trends in the prevalence of NRL allergy
18.5 Key issues in reducing NRL allergy
18.6 Future trends
18.7 Conclusion
18.8 Sources of further information and advice
18.9 References
18.10 Appendix: Abbreviations

436
438
439
440
442
443
448
449

449
450
452

18.1



Index

452
453
457
464
466
471
472
473
474
481
483


Contributor contact details

(* = main contact)

Editors

Chapter 2

Professor Emeritus S. Kohjiya
Kyoto University
7-506, Ohnawaba 6
Umezu, Ukyo-ku
Kyoto, 615-0925, Japan

J. E. Puskas*
Departments of Chemical and
Biomolecular Engineering, and
Polymer Science, Integrated
Bioscience and Chemistry
University of Akron
Akron Engineering Research
Center (AERC)
264 Wolf Ledges, Rm# 209
Akron, OH 44325-3906, USA

E-mail:

Y. Ikeda
Kyoto Institute of Technology
Matsugasaki, Sakyo
Kyoto, 606-8585, Japan
E-mail:

Chapter 1
K. Cornish
Department of Horticulture and
Crop Science

Department of Food, Agricultural
and Biological Engineering
The Ohio State University
Ohio Agricultural Research and
Development Center
1680 Madison Avenue
Wooster, OH 44691-4096, USA
E-mail:

E-mail:

K. Chiang
Department of Polymer Science
University of Akron
Akron, OH 44325, USA
B. Barkakaty
Center for Nanophase Materials
Sciences
Oak Ridge National Laboratory
P.O. Box 2008
Oak Ridge, TN 37831-6496, USA


xiv

Contributor contact details

Chapter 3

Chapter 7

P. Phinyocheep
Department of Chemistry
Faculty of Science
Mahidol University
Rama VI Road, Payathai
Bangkok, 10400, Thailand

A. Kato
Material Analysis Department
NISSAN ARC Ltd
1 Natsushima-cho
Yokosuka 237-0061, Japan

E-mail:

Chapters 4 and 17
Y. Ikeda
Kyoto Institute of Technology
Matsugasaki, Sakyo
Kyoto, 606-8585, Japan
E-mail:

Chapter 5
S. Toki
National Metals and Materials
Technology Center
Faculty of Science
Mahidol University Salaya Campus
Nakon Pathon

73170, Thailand
E-mail:

Y. Kokubo, R. Tsushi and Y.
Ikeda*
Kyoto Institute of Technology
Matsugasaki, Sakyo
Kyoto, 606-8585, Japan
E-mail:

Chapter 8
T. Nakao
Institute for Solid State Physics,
Neutron Science Laboratory
The University of Tokyo
5-1-5 Kashiwanoha
Kashiwa, Chiba, 277-8581, Japan
Professor Emeritus S. Kohjiya*
Kyoto University
7-506, Ohnawaba 6
Umezu, Ukyo-ku
Kyoto, 615-0925, Japan
E-mail:

Chapter 6
A. Tohsan and Y. Ikeda*
Kyoto Institute of Technology
Matsugasaki, Sakyo
Kyoto, 606-8585, Japan
E-mail:

Contributor contact details

Chapter 9

Chapter 12

A. B. Nair and R. Joseph*
Department of Polymer Science
and Rubber Technology
(PS&RT)
Cochin University of Science and
Technology (CUSAT)
Kochi 682 022
Kerala, India

Y. Hirata*, H. Kondo and Y.
Ozawa
Central Research and Tire
Materials Development
Division 1
Bridgestone Corporation
3-1-1 Ogawahigashi-cho
Kodaira-shi, Tokyo 187-8531,
Japan

E-mail:

xv

E-mail:

Chapter 10
R. C. R. Nunes
Instituto de Macromoléculas
Professora Eloisa Mano
Universidade Federal do Rio de
Janeiro
P.O. Box 68525
Rio de Janeiro 21945-970, Brazil
E-mail:

Chapter 11
S. Poompradub
Department of Chemical
Technology, Faculty of Science
Chulalongkorn University
Phaya Thai Rd, Wang Mai,
Patumwan
Bangkok 10330, Thailand
E-mail:

Chapter 13
A. S. Hashim* and S. K. Ong
Universiti Kuala Lumpur
Malaysian Institute of Chemical
and Bioengineering Technology
Lot 1988, Kawasan Perindustrian
Bandar Vendor

Taboh Naning
78000 Alor Gajah, Melaka,
Malaysia
E-mail:

Chapter 14
Y. Fukahori
School of Engineering and
Materials Science
Queen Mary University of London
Mile End Road
London E1 4NS, UK
E-mail:
ne.jp


xvi

Contributor contact details

Chapter 15

Chapter 18

Professor Emeritus S. Kohjiya
Kyoto University
7-506, Ohnawaba 6
Umezu, Ukyo-ku
Kyoto, 615-0925, Japan

T. Palosuo
National Institute for Health and
Welfare
Mannerheimintie 166
Helsinki, FIN-00271, Finland

E-mail:

E-mail:

Chapter 16
A. Isayev
Department of Polymer
Engineering
University of Akron
Akron, OH 44325-0301, USA
E-mail:


Introduction
S. K ohjiya, Kyoto University, Japan and Y. I keda,
Kyoto Institute of Technology, Japan

Introduction to the unique qualities of natural rubber
Natural rubber is in widespread daily use. It is unique among types of rubber,
biopolymers and other materials in general use [1–10]. Its unique qualities
may be summarised as follows:
1. Among rubbers, it is the only biomass [3, 7]. All other rubbers are
chemically synthesised [5]. Natural rubber is extracted from a tropical
plant in which the cis-1,4-polyisoprene molecule is bio-synthesised.

2. It is the only polymeric hydrocarbon among biopolymers, i.e, cis-1,4polyisoprene is composed of carbon and hydrogen atoms alone. All
other biopolymers contain other covalently bonded elements (not as
impurities) such as nitrogen, oxygen, sulphur, in addition to carbon and
hydrogen.
3. A biopolymer may be obtained from a variety of natural sources, i.e.,
plants, animals or fungi. However, natural rubber is obtained almost
entirely from a tropical plant, Hevea brasiliensis [8–10]. Its natural
habitat is the Amazon River valley, but at present, 99% of natural rubber
is obtained from domesticated Hevea trees in Asia. Figure 0.1 shows a
Hevea tree under cultivation. By means of tapping (making a cut in the
trunk), latex (a milky liquid containing rubber molecules) is exuded and
drops into a cup. The latex is collected and used in its original form or
coagulated to give a solid natural rubber.
4. Chemical synthesis of natural rubber has not yet been established,
although many industrially valuable biopolymers have been successfully
synthesised by chemists [10].
5. As it is an agricultural product, natural rubber is renewable.
6. It is carbon neutral, as are many plant products. The initiating material
for the bio-synthesis of natural rubber is carbon dioxide, thus making it
carbon neutral. It therefore does not contribute to global warming [10].
At the end of its life, it decomposes to carbon dioxide, so there is no
net increase of the gas.
7. Natural rubber will remain available despite the depletion of petroleum


xviii

Introduction

0.1 Cultivated Hevea tree in a plantation under tapping operation.

(Photo taken by S. Kohjiya in 1975.)

and is expected to contribute to sustainable development throughout the
twenty-first century (see Chapter 15). This is of particular importance
in organic industrial materials.
8. Natural rubber is scientifically unique because of its elasticity. From the
thermodynamics viewpoint, this is due to an entropy change resembling
that of ideal gas. It differs from energetic elasticity and standard organic,
inorganic or metallic solid materials [4, 10, 11].
9. Due to its unique elasticity, natural rubber has become an essential
material for automobile tyres, and has historically contributed to a society
characterised by high-density transportation networks [10].
Hevea brasiliensis is the botanical name of a commercially grown plant
producing natural rubber [8–10]. Hevea is the generic name and brasiliensis
is one of the 11 species of the genus Hevea, in accordance with Linnaean
nomenclature. Other plants growing in the wild have been used for the
extraction of natural rubber. These include Castilla elastica (commonly
known as Castilloa), which is grown in Central and South America, and
Manihot glaziovii (Ceara), grown in Brazil. Ficus elastica is widespread
in tropical Asia. The genera Landlphia (vine rubbers) and Funtumia are


Introduction

xix

common in mid-western African jungles. These are known as typical rubber
producing trees [8–10]. More types of rubber yielding trees are described
in Chapter 15.
American scientists continue to work on Parthenium argentatum (Guayule)

[10, 12–16] (see Chapter 1), a shrub found in Mexican deserts. This was
cultivated in the United States during the Second World War, when synthetic
rubbers underwent rapid development due to the scarcity of natural rubber
[16–18].
Russian scientists cultivated Taraxacum kok-saghyz (Russian dandelion
rubber) during the 1930s and 1940s. Thomas Alva Edison (1847–1931),
with the support of Henry Ford, investigated many types of Goldenrods
as possible sources of rubber in addition to Cryptostegia grandiflora [16].
(Goldenrods are a group of weeds widely found in the United States which are
now abundant in other countries, including Japan, as non-native plants.)
In addition to Hevea, more than 2,000 plants are now known to yield
rubber, though the quality and quantity are inferior. The superiority of Hevea
was recognised as early as the middle of the nineteenth century, although
the well-known Collins report [19] failed to state this clearly. Natural rubber
from Hevea brasiliensis has historically been preferred (see Chapter 15).
Neither the reasons for, nor the significance of, so many plants being
rubber-yielding has yet been fully elucidated. When one of the present authors
visited RRIC (Rubber Research Institute of Ceylon, now RRISL) in 1977,
he asked bio-related officers (including a physiologist), why plants produce
rubber. The reply was that there is as yet no evidence for the physiological
function of rubber in plants. Although rubber appears to be of no use to the
plants themselves, they enable the bio-synthesis of highly stereo-regular
cis-1,4-polyisoprene, the perfect stereo-regularity of which has not yet been
achieved by chemical synthesis [10, 20]. This unsolved puzzle as to why
cis-1,4-polyisoprene (a polymeric isoprenoid) is produced in plants or in
vegetables may be a unique quality associated with natural rubber.

The history of natural rubber
Rubber was first used during the Olmec civilisation (circa 1300–300 BC),
and its use continued among the Mayans (mainly on the Yucatan peninsula

in Mexico, from circa 300 BC to AD 1500), the Incas (the Andes highlands
around Peru, from circa AD 1100 to 1500), and the Aztecs (from the twelfth
century in central Mexico) until the Spanish destruction of the Central and
South American civilisations. The Olmec had been known to tap plants,
most probably Castilla elastica, and to have made rubber goods.‘Olmec’
may mean ‘rubber people’.
One of the most notable usages of rubber was the manufacture of balls.
These were thought to have been used in a game [2, 10, 21] which was


xx

Introduction

considered an important religious and political event, in which victory or
defeat was used to determine the outcome of wars. Figure 0.2 shows an
athletic field at Chichen Itza, a well-known site of the Mayan civilisation. A
stone ring attached to the wall at a height of about seven metres is assumed
to be a goal. This game is thought to symbolise the harmonious nature of
civilisations in South and Central America. In the twentieth century, rubber
became an important military material, but remained a symbol of peace for
the people associated with its origin.
The discovery by Columbus of the ‘New World’, which may have marked
the end of the Middle Ages in Europe, was the beginning of a European
invasion of that new continent by a military force, despite there being few
counter-attacks due to the peaceful nature of the local Indians. The rubber
ball which Columbus observed during his second voyage may be assumed
to have been manufactured by Olmec craftsmen using rubber obtained from
Castilla elastica trees [10, 22]. A Spanish priest, P. Martyre d’Anghiera,
attached to the invading army, first wrote about rubber in his book ‘De Orbo

Novo’, which was published in 1530. Further literature was published, but
the useful application of rubber remained unknown among Europeans for
nearly 200 years.
A breakthrough on rubber came from two French scientists [23]. F. Fresneau
(1703–1770) was an agricultural scientist working at the colonial office in
French Guiana. While travelling in Guiana and the Amazon in search of
economically useful plants, he became interested in rubber-producing trees
on which he prepared a report. The other scientist, C. M. de la Condamine

0.2 Athletic field in the Mayan ancient site of Chichen Itza. A ringshaped goal can be seen on the wall to the left. (Photo from K.
Aoyama with permission.)


Introduction

xxi

(1701–1774), was a geographer, and a member of the expedition to Quito
(1735–1745) whose task was to measure longitude just below the equator.
While in Cayenne in French Guiana, he obtained the report authored by
Fresneau, and later gave a lecture on rubber at the meeting of the French
Academy of Science in Paris. This was the first scientific report on rubber
[10]. (Historically, this achievement may be attributed to Fresneau [10, 23,
24].)
In 1765, an encyclopedia entitled ‘Encyclopedie, ou dictionaire raisonne
des sciences, des arts et des métiers’ was published in France. It included
the term ‘caoutchouc’ – the French word for rubber. It is probable that one
of the editors, Denis Diderot (1713–1784) drew on Condamine’s scientific
paper. In England, the chemist Joseph Priestley, who discovered oxygen,
noticed in 1770 that pencil marks could be erased (rubbed out) by rubber

[25]. This means of erasure led Priestly to coin the English word ‘rubber’.
In the nineteenth century two Englishmen, Charles Macintosh (1766–1843),
an entrepreneur and Thomas Hancock (1786–1865), an engineer, began the
industrialisation of rubber products [25, 26]. Macintosh applied rubber solution
to a cloth and found that it became highly water-resistant. In cooperation
with Hancock, he began to manufacture raincoats using the rubberised cloth
[10, 26]. London coachmen were the first to welcome this material which
then grew in popularity due to its excellent water-proof performance.
As the use of rubber products became more widespread, a significant defect
was recognised: at low temperatures they became hard and lost elasticity,
while at high temperatures they became too soft to retain their original shape.
This change of properties was found difficult to control, even though much
work was devoted to the problem. In 1839, Charles Goodyear developed
the process of ‘vulcanisation’. [1, 10, 25]. This consisted of a cross-linking
reaction of rubber molecules with sulphur to give a three-dimensional and
stable network structure. As a result of this process, natural rubber became
an industrially important resource and a strategically indispensable material
during times of war. However, the mechanical details of the reaction have
only recently been investigated and a full explanation of the process has not
yet appeared [27].
It was necessary for natural rubber to show its potential for mass production
if the demands of modern industry were to be met. Hevea brasiliensis was
introduced into Britain from the Amazon in the nineteenth century [8–10,
28–32]. From Kew Gardens in London, Hevea was transplanted to Ceylon
where it was successfully cultivated, and later spread to the Malay Peninsula
[10, 30, 31]. Figure 0.3 shows a Hevea tree transplanted from Britain to
Ceylon in 1876. This is one of the ‘Wickham trees’, the seeds of which were
brought by H. Wickham (1846–1928) from the Tapajos River Valley to the
Royal Botanic Gardens at Kew [8–10, 28–33]. These trees were successfully
cultivated at the Henaratgoda Botanic Gardens in Ceylon [10, 34, 35] and

xxii

Introduction

0.3 Wickham tree transplanted in 1876 to the Henaratgoda Botanic
Gardens in Ceylon. Its seed was collected in the Amazon by H.
Wickham, and transported via the Royal Botanic Gardens at Kew to
be cultivated in Ceylon. It was 101 years old and a huge tree. In the
plantations, the trees were replaced every 30 years, and did not grow
as tall as the tree in this figure. (Photo taken by S. Kohjiya in 1977.)

the seeds widely distributed in South and South-east Asia by H. Ridley
(1855–1956), Director of the Singapore Botanic Gardens [10, 28–33].
The production of natural rubber from Asian estates was timely in the
light of growing demands from the automobile industries, especially in the
United States. The Ford Motor company attempted to establish a Hevea
plantation in the Amazon (which it named Fordlandia) to supply natural
rubber for their automobile tyres [10, 36–38]. Figure 0.4 shows Fordlandia
seen from the Tapajos River. Its symbol was the water tank which is still in
use. However, the venture failed and although Ref. 38 describes it in detail,
there is insufficient information to draw conclusions from an agricultural
point of view [10].
During the Second World War, synthetic rubbers were developed in the
United States [6, 17, 18, 39], Germany and Soviet Russia to supply tyres to
the military [6]. After the war, industrially manufactured synthetic rubbers
became widespread in the international rubber market [39], and since that
time, natural and synthetic rubbers have continued to co-exist [10, 40–42].
However, natural rubber is still preferred for many applications, probably

Introduction

xxiii

0.4 Fordlandia on the right bank of the Tapajos River. (Photo taken by
Y. Ikeda in 2005.)

because of its strain-induced crystallisation ability [10, 11, 43–47]. This
trend is likely to continue for the foreseeable future due to the superior
characteristics of natural rubber, as described in this book.

Types of rubber tree
A note on a familiar ‘rubber tree’ may be necessary for some readers. It
differs from Hevea or the ‘Para’ rubber tree and should not be confused with
the rubber tree described in this book. This is the popular house plant Ficus
elastica, which is a native of South and South-east Asia. Among the genus
Ficus, Ficus benjamina is also well known as the ‘Banyan’ or ‘umbrella’
tree, and is found in many urban areas of tropical Asia where it is planted
to provide shade.
The Hevea trees described in this book are native to the Amazon and are
botanically different from so-called ‘rubber trees’, although both produce
natural rubber. However, Ficus has not been widely used for the extraction
of natural rubber as both the quality and quantity are inferior to that of
Hevea trees [10]. Almost all natural rubber for tyres and other rubber articles
comes from Hevea brasiliensis. Hevea rubber collected from wild trees in
the Amazon Valley contributes less than 1% of current total natural rubber
consumption. The concluding remarks of Professor R. E. Schultes on the
history of taxonomic studies in Hevea should be noted [48]:

xxiv

Introduction

Few economic plants have more deeply affected civilisation than the Para
rubber tree, Hevea brasiliensis, the product of which has made possible
present-day transportation and much of modern industry and technology.
Furthermore, this tropical tree represents one of man’s most recently
domesticated plants.
Here, ‘Para rubber’ refers to wild natural rubber exported from the northeastern Brazilian port of Para (now Belem) in Para state.

Future trends
The introduction explains the characteristic features of natural rubber which
make it indispensable to contemporary society. It seems probable that natural
rubber will contribute to sustainable development for the foreseeable future,
as described in Chapter 15.
Currently, the main natural rubber-producing countries are Thailand,
Indonesia, Malaysia, India, China, Sri Lanka and Vietnam. As the demand
for natural rubber grows, Cambodia, Laos, Bangladesh and some African
countries may also become major producers.
The application of techniques such as genome analysis is likely to become
significant in the scientific study of natural rubber, particularly among
biochemists and agriculturalists [10, 49, 50]. A deeper understanding of
the unique qualities of natural rubber is also an important area for scientific
and academic study. Discussions on the performance of natural rubber are
expected to give rise to new applications.

References

1. Goodyear, C.: ‘Gum-Elastic and Its Varieties, with a Detailed Account of Its
Application and Uses and of the Discovery of Vulcanization’, published for the
author, New Haven (1855). (Reprinted in 1939 by the Rubber Division, American
Chemical Society.)
2. Davis, C.C., Blake, J.T., eds.: The Chemistry and Technology of Rubber, Reinhold
Publishing Co., New York (1937).
3. Bateman, L., ed.: The Chemistry and Physics of Rubber-Like Substances, Maclaren
& Sons, London (1963).
4. Treloar, L.R.G.: The Physics of Rubber Elasticity, 3rd edn, Clarendon Press, Oxford
(1975).
5. Eirich, F.R., ed.: Science and Technology of Rubber, Academic Press, New York
(1978).
6. Morawetz, H.: Polymers: The Origins and Growth of a Science, John Wiley & Sons,
New York (1985).
7. Roberts, A.D., ed.: Natural Rubber Science and Technology, Oxford University
Press, Oxford (1988).
8. Webster, C.C. & Baulkwill, W.J., eds.: Rubber, Longman Science & Technical,
Harlow (1989).