Very useful topics about rubberised coir products.

1. RUBBERISED
COIR PRODUCT
Priyabrata Ghosh
B Sc (Cal), LNCRT, LPRI, Grad. PRI, ANCRT, APRI, MPRI(London); FIRI (India)
Consultant Rubber Technologist
Kolkata, India

2. CONTENTS
INTRODUCTION
RAW MATERIALS FOR RUBBERISED COIR
MANUFACTURING / PROCESS
VIDEO CLIP OF R.C. MATTRESS MANUFACTURING
TESTING
CONCLUSION

3. During World war II, the Germans used to air drop tanks and heavy arms on the cushions
made of animal hair of horses and hogs in order to avoid any damage to the arms /
equipments.
The Austrians found it useful as mattresses and naturally after that they started making such
mattresses using animal hair and rubber.
In early 60’s two renowned manufacturers M /S . Dr. Fehrer and Dr. Otto Angliether (DOA) of
Austria were competing each other to supply modern machines to manufacture rubberised coir
products . The design and material of construction were so excellent that the manufacturers in
India started importing them alongwith technology.
In 1964, Bharat Motors ( Now Fibroflex India Pvt. Ltd.) in Tamil Nadu, a dealer of imported
automobiles, diversified into manufacturing rubberissed coir products for the first time in the
whole SE Asia with the technology imported from Dr. Fehrer.
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4. The rubberised coir has since flourished due to easy availability of both rubber and coir in
some tropical countries.
During 1964 -1966, six units were simultaneously started in India all with Austrian
technology using DOA / FEHRER sheeting machines. Now there are more than 100
manufacturing units of R C Products.
As new technology kept on evolving, more and more plants came up all over India.
As of now , there are about 1,00,000 tonnes of R.C. Products a year, growing at a
compounded annual rate of about 5-7%.
Major production of R.C. is for mattresses followed by furniture blocks and automobile /
railway seats.
R.C. has been successful to an extent in replacing cotton and latex / PU foam mattresses.
The annual production of R.C mattresses could be around 70 millions( including branded and
unbranded segments).
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5. 2. CONSUMPTION OF RUBBERISED COIR PRODUCTS
Mattress About 65,000 Tonnes
Furniture Bloks About 15,000 Tonnes
Automobile / Railway Seats About 10,000 Tonnes
Packaging About 3,000 Tonnes
Topping For Spring mattress About 2,000 Tonnes
Others About 5,000 Tonnes
Total About 1,00,000 Tonnes
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6. 3. Raw Materials for Rubberised Coir Products
3.1 Coconut CoirFibre
Coir is a natural fibre extracted from the husk of coconut. It is light, durable,
naturally resilient and resistant to dampness.
Major components of coir are cellulose (36-43)% and lignin (41-45) %. The fibre
becomes stiff and hard due to presence of lignin.
Coconuts grow extensively in the countries of tropical regions of the world. The
coir industry developed on large regions of the world. The coir industry developed
on a large scale only in India and Sri Lanka. India ranks first among the coir
production countries though it ranks third output of coconuts.
Individual fibres are designated as long (>200 mm) , medium (150-200mm) and
short (50 -150 mm) and proportion by mass of fibres in the curled coir fibre rope
should be as-long fibre (10% min ), medium fibre (50 % max) and short fibre (20%
max ) as per IS – 9308 (Part 4) : 1999. 04
Husks are soaked in pits of water to swell and soften the fibres. The long bristle
fibres are separated from the shorter fibres underneath the skin of nut, The fibres
are then separated from dirt pith etc, dried in the sun and packed into bales. The
coir fibre is elastic enough to twist. Twisting is done by simple making a rope
using a machine or by hand.

7. DRC 33 %
Proteins 1.0 – 1.5%
Resins 1.0 – 2.5%
Ash Up to 1.0%
Sugars , Lipids 1.0%
Water Rest
3.2 Natural RubberLatex
The latex requires to be preserved and the best preservative is NH3 which is also a
very effective bactericide if the level exceeds 0.35 %.
The field latex is concentrated to about 60% DRC by various methods - (a)
Evaporations , (b) Creaming ( c) Centrifuging (mostly used ) & (d) Electro decantation.
Transportation becomes economical and many latex articles require high DRC.
Natural Rubber Latex is obtained from the tree called Hevea Brasiliensis:
The composition of field latex is :
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8. A typical recipe Parts by weight
Creamed NR Latex (0.7% NH3) 194
20 % Lissapol D Paste 6.0
10% KOH Solution 3.0
ZnO
ZDC 40% Composite
Nonax D
15.4
40% China Clay Dispersion 30.0
50% Sulphur Dispersion 7.0
PREPARATION OF LATEX COMPOUND
40 % Composite dispersion contains
ZnO – 3.8
ZDC – 1.25
Nonox B – 1.0 On 100 parts of DRC
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9. PREPARATION OF LATEX COMPOUND Cont..
Liissapol D paste is a sulphated fatty alcohol, soluble in warm water at 500C. It is an anionic
surface active agent and stabilizes latex against heat, fillers and mechanical working.
KOH solution is readily soluble in water and it gives stability to latex and also helps to maintain
the alkaline pH and prevents tendency to coagulation.
Nonox B is an antioxidant, condensation products of diphenylamine and acetone.
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10. 4. Manufacturing
Coconut fibres can be bonded by spraying with a suitable latex compound to make
the R.C products. It gives satisfactory resilience, hardness, permanence of network
structure and light weight; and has a cheap and very useful upholstery material like
mattresses, pillows, cushions, seat backrests, carpet underlay etc.
Latex compound only serves as a binder of the coir fibres. The resilience of the final products
depends essentially upon the nature and quality of the fibre used. Only the “ bristle” fibre
contributes to the resilience of the product and it is recommended that the mixed fibres should
contain at least 70 % of bristle fibres.
5. Process
Process essentially consists of making a bed of untwisted coir fibres and spraying on it by a
suitable latex compound, drying the sprayed bed, compressing the dried mass in a mould to
obtain desired thickness and curing it in a hot air vulcaniser for the permanence of the shape.
5.1 Preparation of Latex compound
Prepared latex compound is stored in a tank where a gentle agitation is provided in order to
avoid any sedimentation at the bottom of the tank. The compound is then transported to
spraying device at the sheet machine through pipe-line and filter box under pneumatic
pressure. 08

11. 5.2 STEAMING OF UNTWISTED FIBRES :
A raw coil of coir has the moisture content of 16-19%. After steaming through radiator for a
few hours in a chamber, the moisture content reduces to around 10% .
Steamed coil is then passed through an untwisting machine. Curled fibres (like springs) come
out which provide resilience to the product.
Curling is generally done by spinning the loose fibre while making the ropes and twisting
these ropes to an optimum degree brings about the curling effect.
5.3 SPREADING OF UNTWISTED FIBRES :
Untwisted fibres are arranged in loose consistency either by carding web formation or by
baffled air – blow system in a continuous sheet machine in such a way that the whole mass of
fibres can be sprayed easily throughout. For uniform and consistent spraying of latex compound,
the bed thickness of the fibres should not exceed 2 inch.
5.4 SPRAYING OF LATEX COMPOUND :
Latex Compound is then sprayed on the loosely arranged curled fibres by means of suitable
high – speed spraying devices having to-and-fro movement in such a way that a sufficient
quantity is sprayed throughout the mass without any excessive waste.
It is advisable to spray the fibre bed from both sides so that the inner fibres of the mass get
coated with the latex compound.
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12. 5.5 DRYING OF SPRAYED BEDS
Sprayed beds are dried continuously in the sheet machine through hot air conveyor system at
a temperature of 800 ± 50C. The time of drying should be sufficient for drying the mass without
any apparent vulcanization.
5.6 CURING IN MATTPRESS
Dried beds are compresses in mould preferably in a hydraulic press called “Matt press” and
heated for 30 – 45 mins, depending on thickness, in a hot air or steamed platens at about 1000C
to obtain the desired shape of the products. Compression modulus, hardness and density of the
final product are controlled by the quantities of sprayed fibres in the mould.
5.7 FINAL CURING IN VULCANISER
Beds are then finally cured in a steam radiated vulcaniser. The beds are put in the vulcaniser
at a temp. at 700 – 800 C and then the temp. is raised to about 1050C with circulating fans on
and cured for 45 mins.
Beds are cooled down in the vulcaniser after stopping the steam for 15 -30 mins and then
taken out. The beds are then matured for 24 hours before further processing.
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13. COIR FIBRE BALES TWISTED COIR FIBRE ROPES
Cured beds are then cut to sizes in high – speed vertical cutting machine followed by walling
with latex coated jute cloth to prevent any exposure of coir fibres from the cut edges.
Beds are covered with attractive textile fabrics etc.
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14. BARE RUBBERISED COIR PRODUCTS
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15. MATTRESS
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16. PILLOWS
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17. Bolster
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18. Cushion
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19. SOFA SETS
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20. FLOWDIAGRAMOF RUBBERISEDCOIR
Rubberised coir
sheet
Latex spray gun
Latex spray gun
Cutting
table
Hot Air drier
Top and bottom pin
board
Distributor Fork Clutch
Feeder
Top Hackler
Coconut Coir
Pin Cylinder
Pressure
board
BottomhacklerSHEET MACHINE ( MODEL : FEHRER / DOA)
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21. PROCESS FLOW CHART OF MANUFACTURING OF R.C. MATTRESS
Latex Compound
Preparation
Coir Fibre
Coil
Deomoisturis-
ing by Steaming
Untwisting of
Coir Rope
Spreading
of Coir
fibre
Spraying of Latex
Compound
Cutting in vertical
cutting m/c to sizes
Final Curing of
rubberized beds in
vulcaniser
Curing in Mattpress
to desired final
thickness
Lamination of
dried beds to
desired
thickness
Drying of
sprayed fibre
beds
Inspection Walling of cut edges
and upholstery
furnishing with
fabrics
Storing and
Despatch
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22. 6. MOISTURE CONTENTS AT DIFFERENT STAGES OF PROCESS
% Moisture
Coir fibre coils (as received ) 16 – 19
Coir fibre coils (after steaming) 10 -12
Rubberised fibre beds (after drying) 16 -17
After pressing in Matt press 10 -11
Final Cure after vulcaniser cure ~ 7
After maturing and storing ~ 5
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23. 7. TOTAL RUBBER CONTENT IN FINISHED R.C. PRODUCTS
% DRC
Spraying at sheet Machine 25
Spraying at Mattpress 8
Walling etc. 2
Total 35%
Normally the total rubber content based on DRC, in a finished rubberized coir product should
be stagewise as follows:
8. GRADATION OF R.C. PRODUCT
Grade Density (gms / dm3)
(for guidance only)
Indentation Hardness Index (kg)
Soft 40 – 59 3.00 – 5.99
Medium 60 – 69 6.00 – 8.99
Firm 70 – 79 9.00 – 11.99
Extra firm 80 – 100 12.00 – 15.00
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24. 9 . SPECIAL APPLICATION OF R.C. PRODUCTS
9.1 HOSPITAL / ORTHOPAEDIC MATTRESS
 Rubberised coir being a natural and hygienic product, is preferred in hospital and healthcare
facilities.
 R .C. Mattress are highly recommended for people with orthopedic ailments.
 Higher density product provide a high level of support for the back and the spine.
 R.C. Mattresses are also highly resistant to termites, insects, fungi etc. These are also
permeable which are ideal for babies to sleep on.
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25. Some useful FR additives are :
Zinc chloride
Boric acid (40 g/ l) Antimony trioxide
(100g/l)
Aluminium potassium
sulphate (100 g/ l)
Borax (8g / l)
Sodium tungstate (150
g/ l)
Molybdenum trioxide
(70g / l)
Silicone solution
etc.
9.2 FIRE RETARDANT R.C. PRODUCTS
A certain degree of fire retardance is desired in R.C. products for its application in selected
areas such as automobile cushioning. The fire retardant chemicals to be used should impart fire
retardancy without adversely affecting the resilient quality or service life of the product.
Fire retardant R.C. products can be obtained by judicious selection of self–extinguishable type
of fire-retardant additives. Aqueous solution of some FR additives in specific concentrations
were found to be useful for this purpose. The solutions are hand–sprayed on both sides of R.C.
products and dried in ambient conditions.
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26. 24

27. 10 . TESTING
All testing parameters and methods of R.C. sheets are stipulated in BIS Specification IS : 8391
– 1977. The tests are carried out not before 48 hour after vulcanization of the samples. The test
samples are conditioned for a minimum period of 24 hour at 27 ± 20 C and 65± 5% relative
humidity.
10.1 THICKNESS
Test piece of 100 mm x 100mm cut out from the sample and is placed between two horizontal
plates. Upper plate should weigh 200 grammes.
Distances between the plates are measured on each side and the average of four readings
taken as the thickness of the test pieces.
10.2 DENSITY
Test piece of 100 mm x 100 mm x 100mm size is weighed in grammes to give density in gms /
dm3.
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28. 10.3 HARDNESS
APPARATUS FOR INDENTATION
TEST
Size of the specimen should be minimum
100mm x 100 mm and is placed on the
platform and below the indentor. The weight
of the sample (x) is noted on the dial scale of
the balance. Then the indentor is lowered by
rotating the handle till it gives a reading of x
+ 200 gms on the scale.
Thickness of the sample is taken by the
reading of the pointer at the vertical scale (y) .
Then the indentor is gradually lowered to
apply a load at the rate of 0.5 kg/mm until
the sample is pressed to a thickness of 60% of
‘y’. The load in kg is taken as the Indentation
Hardness Index of the test specimen.
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29. 10.4 Resistance to flexing
Method involves subjecting a sample to
continued flexing with an indentor for 2,50,000
cycles at 4 cycles / sec. and noting the loss in
indentation hardness.
Size of the test specimen should be 100x100
mm. Thickness of the sample is measured as
described in 9.1. Indentation hardness index is
determined as described in 9.3. The stroke of the
crankshaft for a depression of the indentor to
40% of the thickness of the sample . Then the
indentor is raised to the top most position of the
stroke and the test specimen is placed on metal
plate below the indentor. The specimen is
subjected to flexing @ 4 cycle / sec.
After flexing 2,50,000 cycles, the sample is
allowed to recover for 30 mins. Thereafter the
indentation Hardness index is measured and
the variation in the indentation hardness is
calculated as the % of the initial hardness. The
difference in hardness should be within 20%.
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30. 10.5 COMPRESSION TEST
Initial thickness of the test specimen of size 100mm x100 mm is measured. The specimen is
compressed by 40% of its original thickness between the parallel steel plates by using steel
spacers between the plates. After being compressed, it is kept in an over for 22 hours at 70 ±
20C . The test piece is released and the thickness is measured again after 30 mins recovery time.
Compression set at constant strain
T0 – T r
T0
X 100 %
Where ,T 0 = Original thickness of the T.P.
Tr = Thickness of the T.P. after recovery.
Usually the maximum limits of compression set are :
a) 25% at 70± 20C
b) 15% at room temperature
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31. 10.6 AGEING TEST
• Initial Indentation Hardness Index of the test piece of size 100 mm X 100 mm is
measured. Then the T.P. is kept in oven for 48 hours at 70  20 C and kept for 24
hours at room temperature after removal.
• Indentation Hardness Index is measured and the variation is calculated in % of
original.
• Maximum permitted variation should be within 20 %.
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32. 11. CONCLUSION
Rubberised coir industry can safely achieve infinity better days ahead due to its huge potential
growth both in domestic and international markets ; and this is possible absolutely due to the
bountiful availability of both the basic raw materials from the nature i.e. coir fibre and natural
rubber latex.
The average life expectancy of RC mattresses is about 10 – 12 years. There could be about 70
million currently in use in India which covers hardly 6% of the Indian population use R.C.
mattresses.
Though the industry is facing threats from substances such as PU foam and spring mattresses,
it is marching ahead by creating better awareness of the products, its cost competitiveness, eco-
friendly product etc. against other sleep materials. It is hoped that by 2030 every household in
India will have at least one coir mattress.
Lastly, R &s D activities should be focused on :
a) to make lighter and more resilient / cushioning R.C. products.
b) to make it sound absorbent / insulating.
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33. 11. CONCLUSION cont…
c) fire resistant / retardant to higher degree.
d) diversification to other areas of application (for example, aircraft).
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END

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