The document discusses the production of SMR GP (general purpose natural rubber), which is a major material for tire production. SMR GP is made from a 60:40 mixture of latex-grade sheet rubber and field coagulum. It is prepared from a blend of latex rubber, unsmoked sheet rubber, field coagulum rubber, and plasticizer. SMR GP production is important for tire manufacturing because its dark color and blending of materials ensure high quality suitable for tires. The document outlines the general properties and composition of SMR GP, as well as the process flow for its production through co-coagulation of latex and wet crumbs.

1. GENERAL PURPOSES
NATURAL RUBBER (SMR GP)
PRODUCTION
PST 161
UNIVERSITI TEKNOLOGI MARA
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2. DEFINITION
• SMR GP, general purposes natural rubber
is the major material for tire production.
• Made from 60:40 mixture of latex-grade
sheet rubber and field coagulum.
• Prepared from:
blend of latex rubber,
unsmoked sheet rubber,
field coagulum rubber and
plasticizer.
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3. IMPORTANCE OF SMR GP
PRODUCTION
• Dark colored rubber
Make it suitable for tire production.
• Blending of latex and sheet rubber
ensure high quality of SMR GP.
• Uses of plasticizer in SMR GP gives
beneficial to tire manufacturers.
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4. GENERAL PROPERTIES
• Contains blending of latex
rubber, unsmoked sheet rubber, field
coagulum rubber and plasticizer.
• The properties of this materials are
by following proportions:
– 30% weight of latex rubber
– 30% weight of sheet rubber
– 30% weight of coagulum rubber
– 10% weight of rubber plasticizer
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5. • There are two types of SMR GP which
have different composition from one
another:
– SMR GP 1
– SMR GP 2
Weight (%)
Raw materials
SMR GP 1 SMR GP 2
Field latex 60 30
Rubber coagulum 40 40
Unsmoked sheet
rubber - 30
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6. PROCESS FLOW OF SMR GP
• Production of SMR GP involves the
method of blending which is involving co-
coagulation of latex-oil mixture and wet
crumbs.
• Wet crumbs use prepared from a blend of
unsmoked sheet and field coagulum.
• Subsequent processing gives:
– Very uniform blend
– Minimum mechanical working
• The process flow are presented
below:
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8. • The process above involving the following
steps:
1. Field coagulum is pre- cleaned and then
formed into a blanket.
– depends on the quality of raw material
and should give a blanket with less than
0.12% wt. dirt.
2. The unsmoked sheets are milled into a
blanket.
3. The unsmoked sheet and field coagulum
blankets are blended
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9. 4. The crumbs are transferred and spread
evenly into a latex coagulation tank, then
manually sprayed with 10% formic acid
solution.
5. required amount of emulsified aromatic
oil and then mixed into a pre- determined
quantity of latex.
– Hydroxylamine Neutral Sulphate is
added to the latex as viscosity stabilizer.
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10. 6. The latex- oil mixture is adjusted to pH 7.0
to 7.5 and poured into the coagulation
tank.
7. Latex-crumb coagulum then processed
and dried.
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