Metallurgy and materials Engineering, University of Punjab, Lahore

1. Hafiz Majid Ali
14MME-S1-343
The University of the Punjab, Lahore

2.  Rubber is a polymer, which is a word that is derived from
the Greek meaning “many parts”.
 Natural rubber is a naturally occurring polymer obtained
from the latex of rubber trees.
 Natural rubber (NR) is also known as cis-1,4-
poly(isoprene).
 Natural rubber is found in the latex that comes from the
rubber trees.
 It is collected in a cup mounted on each tree, by slashing
the bark to reach the latex vessels.
 The liquid is 30-40% rubber.

3. Monomer

4.  The commercial source of natural rubber latex is the
Para rubber tree (Hevea brasiliensis).
 Other plants containing latex include:
 Gutta-percha (Palaquium gutta)
 Rubber fig (Ficus elastica)
 Panama rubber tree (Castilla elastica)
 Spurges (Euphorbia spp.)
 Common dandelion (Taraxacum officinale)
 Russian dandelion (Taraxacum kok-saghyz)

5.  The physical and chemical
properties of the rubber are
influenced by the presence of the
non-rubber substances.
 NR is a natural polymeric
substance having high molecular
weight, possessing visco-elastic
properties.
 Natural rubber is cis-1,4-
polyisoprene, i.e. a diene,
because of this, it shows all the
reactions of an unsaturated
compound.
 It gives addition compounds with
hydrogen chloride, halogens,
ozone and several other
reactants that combine with
olefins.
Mechanical properties of NR

6.  An interesting reaction of NR
is its combination with
sulphur, called
‘vulcanization’.
 This reaction converts the
raw rubber into an elastic
material.
 Vulcanized rubber
possesses high tensile
strength, hardness and
abrasion resistance.
 Because of the unique
combination of these
properties, NR finds
application in the
manufacture of various types
of products.
Chemical resistance of NR

7.  Production of rubber is followed by processing into final
products consists of :
Compounding
Mixing
Shaping
Vulcanizing.
 Processing techniques for natural and synthetic rubbers
are virtually the same, differences being in the
chemicals used to effect vulcanization.

8. COMPOUNDING
 Rubber is always compounded with additives to satisfy the given application in terms of
properties, cost, and processability
 Compounding adds chemicals for vulcanization.
 Mainly used reinforcing filler used in NR is carbon black.
 Other additives include antioxidants , antiozonants colouring pigments, plasticizers and
softening oils, blowing agents in the production of foamed rubber; and mold-release
compounds
 The additives must be thoroughly mixed with the base rubber to achieve uniform dispersion of the
ingredients.
 A two-stage mixing process is usually employed.
 In the first stage, carbon black and other non vulcanizing additives are combined with the raw
rubber.
 After thorough mixing has been accomplished, and time for cooling has been allowed, the second
stage is carried out in which the vulcanizing agents are added.
 Equipment for mixing includes the Two-roll mill and internal mixers such as the Banbury mixer
MIXING

9. SHAPING
 Shaping processes for rubber products can be divided into four basic categories:
 Extrusion
 Calendering
 Coating
 Molding and Casting
VULCANIZATION
o Vulcanization is a chemical process for converting natural rubber or related polymers into more durable
materials via the addition of sulphur or other equivalent curatives or accelerators.
Applications

10. RESEARCH ARTICLE
REINFORCEMENT OF NATURAL RUBBER WITH SILICA/CARBON BLACK HYBRID
FILLER
 Abstract:
• Carbon Black & Silica Used as
reinforcing fillers that increase the
usefulness of NR.
• Enhance mechanical & dynamic
properties.
• Increases such as
• Tensile strength.
• Tear Strength.
• Rolling Resistance.
• Crack Growth Resistance.
Reference
Polymer testing by N. Rattanasom, T. Saowapark, C.
Deepraserkul (May 2007, vol 26)

11.  http://www.allsealsinc.com/Natural_Rubber-popup.html
 http://www.tutorvista.com/content/chemistry/chemistry-
ii/carbon-compounds/natural-rubber.php
 http://rubberboard.org.in/ManageCultivation.asp?Id=196