NR latex information

1. BASIC NATURAL RUBBER PROCESSING
(PST104)
1. INTRODUCTION TO NR LATEX
1
1.1 LATEX STRUCTURE
1.2 LATEX CONSTITUTION
1.3 BIOSYNTHESIS OF LATEX
PREPARED BY: Muhamad Naiman Sarip

2. LESSON OUTCOMES
At the end of this
chapter, students
will be able
To memorise and
write the
structures of NR
latex
To state the
properties of NR
field latex
To list all NR field
latex constitution
To illustrate the
biosynthesis of
NR field latex

3. 1.1 LATEX STRUCTURE
• Chemical compounds can be divided into
two simple classes –
a) inorganic and
b) organic compound
• Organic compounds – compounds
which are made up of carbon atoms
• Inorganic compounds – compounds
which do not belong to the organic
groups
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4. 1.1 LATEX STRUCTURE
Example :
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Molecule Description
Formic acid (HCOOH) Organic
2 atoms of hydrogen & oxygen, 1 atom of
carbon of forming a molecule
Acetone (CH3COCH3) Organic
3 atoms of carbon, 6 atoms of hydrogen & 1
1 atom of oxygen forming a molecule
Sulphuric acid
(H2SO4)
Inorganic
2 atoms of hydrogen, 1 atom of sulphur & 4
atoms of oxygen forming a molecule
Ammonia
(NH3)
Inorganic
1 atom of nitrogen & 3 atoms of hydrogen
forming a molecule

5. 1.1 LATEX STRUCTURE
• Atoms in an organic molecule are
bonded by sharing their electrons
between the atoms
• Ionic or most inorganic compounds are
formed due to the electrons being
donated or being accepted by the
bonded atoms
• Organic compounds in most cases are
non polar but there are polarrisable
organic compounds
• Ionic compounds in most cases are polar
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6. 6
• The molecules discussed above have
low molecular weight and the number or
atoms combining to form the molecules
are not great
• Polymers in general have high
molecular weight and lot of atoms
combine to form polymers
1.1 LATEX STRUCTURE

7. 1.1 LATEX STRUCTURE
• Polymers are formed from simple organic or
inorganic compounds repeating to form the
polymer
• This repeating unit is known monomer
• The number of monomers in a polymer
chain is known as the degree of
polymerisation
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Example:
Polymer : (-A-A-A-A-A-A-A-A-A-)n i.e. An
Monomer : A
Degree of polymerisation : n
1.1 LATEX STRUCTURE

9. 1.1 LATEX STRUCTURE
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• Polymers normally are made up of long chains
which can be straight chains or branched (long
and short) or can be crosslinked.
• Basic polymer structure :
a)Linear chain – stretched
b)Coiled chain – at rest

10. 1.1 LATEX STRUCTURE
c) Short chain branching
d) Long chain branching
e) Crosslinked network
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POLYMERISATION OF NATURAL RUBBER
Natural rubber (NR) is obtained from the tree
Hevea Brasiliensis
Hevea brasiliensis was
first found in the Amazon
Rainforest in 1830
Increasing demand and
the discovery of the
vulcanization procedure
in 1839 led to the rubber
boom in that region

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By 1898, a rubber
plantation had been
established in Malaya
Examples of latex
dipped products :
- Gloves (Surgical,
examination, and
household gloves)
- Baby teats
- Balloons
- Condoms

13. 13
• Natural rubber is a polymer having long
chain-like molecules
• Structurally, the chain is made of isoprene
units as the monomer, and there about
3,000 – 15,000 units of these monomers
• The process of joining these monomers will
be known as polymerisation
1.1 LATEX STRUCTURE

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MONOMER
POLYMER
polymerisation
nCH2 = C – CH = CH2
CH3
(CH2 – C = CH – CH2)n
CH3
1.1 LATEX STRUCTURE

15. 1.1 LATEX STRUCTURE
• The rubber hydrocarbon consists of
isoprene units which will combine to form
the long natural rubber chain as stated
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CH2 = C
CH3
CH = CH2
ISOPRENE
MONOMER

16. 16
Isoprene and Polyisoprene Structures
CH2 = C
CH3
CH = CH2
1 2
3 4 Isoprene monomer
Cis – 1,4 - addition Trans – 1,4 - addition

17. 17
C = C
C = C
B
A
A
A
A
B
B
B
Cis
Trans
1.1 LATEX STRUCTURE

18. 18
• Since double bonds are found at the
following positions: 1,2 & 3,4 carbons in
an isoprene molecule, therefore,
polymerisation can occur at these
positions to give a chain having 1,4 or
1,2 or 3,4 links
• In NR, only 1,4 links are found in great
abundance
• Hence, such polymerisation can be
considered to be 1,4 or head-tail
polymerisation
1.1 LATEX STRUCTURE

19. 1.1 LATEX STRUCTURE
• Natural rubber is made up of many
non-rubber chemical constituents
• These constituents may or may not
play any part in the properties of
natural rubber
• Typical examples of non-rubbers are
amines, and phospholipids which can
act as antioxidants
• Others may act as accelerator,
stabilizer for latex etc.
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20. 1.1 LATEX STRUCTURE
• Natural rubber and gutta-percha are
naturally occurring cis and trans isomers
of polyisoprene
• These conclusions are based on the
following considerations
• The specific gravity of the rubber (0.92)
is less than gutta (0.96), so too is the
melting points (natural rubber crystals
53°C, gutta crystals 60°C)
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21. 21
Natural rubber
(cis)
Gutta percha
(trans)
1.1 LATEX STRUCTURE

22. 22
• The molecules of natural rubber are
made up of long chains of polyisoprene
and the chains are coiled
• On stretching, crystallisation can be
induced and this is known as stress
crystallisation
• During that deformation, the chains
are able to be close contact with other
chains forming crystalline regions
1.1 LATEX STRUCTURE

23. 23
• The crystalline regions will produce high tensile
strength in rubber
Stress Crystallisation
1.1 LATEX STRUCTURE
Streching
direction

24. 24
• Natural rubber is named as cis-1,4 poly 2-
methyl-but-2-ene under the IUPAC system
• Although, the term cis 1,4 polyisoprene is
more commonly used
1.1 LATEX STRUCTURE

25. 1.1 LATEX STRUCTURE
• The physical behaviour of raw rubber
may be related to two components;
viscosity and elasticity, acting
simultaneously
• Viscosity
- measure of resistance to flow
- the viscosity components are
irreversible and account for the ‘cold
flow’ of raw rubber
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Rubber physics

26. 26
• Elasticity
- measure of energy returned by the
rubber immediately after a given energy
in-put
- The elasticity components is reversible
and accounts for the ‘bounce’ of rubber
• The longer the chains, the greater the
average molecular weight, the greater
the elasticity
Rubber physics
1.1 LATEX STRUCTURE

27. 1.1 LATEX STRUCTURE
The ideal conditions for cultivation of NR
plantation
 Suitable in tropical region (warm and
humid weather) like Malaysia, Thailand,
Indonesia, and India
 Temperature 27°C - 30°C
 Annual rainfall not less than 2000mm
 Soil condition; acidic soil pH 4.5 – 6.0
 Suitable area – needs a well-drained,
sloppy area (no accumulating water)
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28. Latex may be simply defined
as a dispersion of a polymeric
material in an essentially aqueous
medium
The polymer may be termed
the disperse, discontinuous or
internal phase and the serum is the
dispersion medium, continuous, or
external phase
1.2 LATEX CONSTITUTION

29. 1.2 LATEX CONSTITUTION
Latex constitution as follows :-
Rubber phase
- Lipids
- Protein
Bottom Fraction (B-Serum)
Serum (C-Serum)
Frey Wyssling
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RHC
Lipid
Protein

30. 2. LATEX CONSTITUTION
35% - Dry rubber
2% - Non rubber
63% - Serum
Total Solid Content (TSC)
= Dry rubber + Non rubber
= 37%
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31. 1.2 LATEX CONSTITUTION

32. 1.2 LATEX CONSTITUTION
• A. RUBBER PHASE
o In fresh latex, rubber particles
constitute 25 – 45% of the volume
of the latex
o The rubber particles in fresh latex
are protected by a complex film
containing protein and lipids
o The rubber particles are usually
spherical with diameters ranging
from about 0.02 – 3μm
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33. 1.2 LATEX CONSTITUTION
Lipids
A group of fatty glycerides
In hevea, lipids are combined with other ions such as
Ca, Mg, Cu, P
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34. 1.2 LATEX CONSTITUTION
Protein
Condensation polymerisation
products of amino acid
Protein molecules contains pendant
amino and carboxyl groups
The pendant amino and carboxyl
groups account for the amphoteric
nature of the protein, since either
negative or positive polarity can be
attained on the influence
of the surrounding medium
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35. 1.2 LATEX CONSTITUTION
• B. BOTTOM FRACTION (B-serum)
o Consists essentially of relatively gelatinous lumps
bonded by semi-permeable membranes
• C. SERUM (C-SERUM)
o Is essentially aqueous and contains the dissolved
materials (including metal ions absorbed from the
bark by the latex during flow down the tree
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36. 1.2 LATEX CONSTITUTION
• D. FREY WYSSLING
o Are cluster of a very hard tiny particles
of the yellow/red pigment carotene
produced in small quantities as a by
product of polyisoprene biosynthesis
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37. RP = Rubber Particle, FW = Frey Wyssling

38. • Biochemically, the polymerisation of NR
takes place through many steps and many
enzymes are involved in the polymerisation
path ways
• The biosynthesis of rubber occurs via
photosynthesis and many intermediates :-
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