Rubberised coir by p.ghosh

Very useful topics about rubberised coir products.

1. RUBBERISED
COIR PRODUCT
PriyabrataGhosh
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.
01

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 Coir Fibre
Coirisanaturalfibreextractedfromthehuskofcoconut.Itislight,durable,
naturallyresilientandresistanttodampness.
Majorcomponentsofcoirarecellulose(36-43)%andlignin(41-45)%.Thefibre
becomesstiffandhardduetopresenceoflignin.
Coconutsgrowextensivelyinthecountriesoftropicalregionsoftheworld.The
coirindustrydevelopedonlargeregionsoftheworld.Thecoirindustrydeveloped
onalargescaleonlyinIndiaandSriLanka.Indiaranksfirstamongthecoir
productioncountriesthoughitranksthirdoutputofcoconuts.
Individualfibresaredesignatedaslong(>200mm),medium(150-200mm)and
short(50-150mm)andproportionbymassoffibresinthecurledcoirfibrerope
shouldbeas-longfibre(10%min),mediumfibre(50%max)andshortfibre(20%
max)asperIS–9308(Part4):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 Rubber Latex
The latex requires to be preserved and the best preservative is NH
3 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.
NaturalRubberLatexisobtainedfromthetreecalledHeveaBrasiliensis:
Thecompositionoffieldlatexis:
05

8. A typical recipe Parts by weight
Creamed NR Latex (0.7% NH
3) 194
20 % LissapolD 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
06

9. PREPARATION OF LATEX COMPOUND Cont..
Liissapol D paste is a sulphated fatty alcohol, soluble in warm water at 50
0
C. 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.
07

10. 4. Manufacturing
Coconutfibrescanbebondedbysprayingwithasuitablelatexcompoundtomake
theR.Cproducts.Itgivessatisfactoryresilience,hardness,permanenceofnetwork
structureandlightweight;andhasacheapandveryusefulupholsterymateriallike
mattresses,pillows,cushions,seatbackrests,carpetunderlayetc.
Latexcompoundonlyservesasabinderofthecoirfibres.Theresilienceofthefinalproducts
dependsessentiallyuponthenatureandqualityofthefibreused.Onlythe“bristle”fibre
contributestotheresilienceoftheproductanditisrecommendedthatthemixedfibresshould
containatleast70%ofbristlefibres.
5. Process
Processessentiallyconsistsofmakingabedofuntwistedcoirfibresandsprayingonitbya
suitablelatexcompound,dryingthesprayedbed,compressingthedriedmassinamouldto
obtaindesiredthicknessandcuringitinahotairvulcaniserforthepermanenceoftheshape.
5.1Preparation of Latex compound
Preparedlatexcompoundisstoredinatankwhereagentleagitationisprovidedinorderto
avoidanysedimentationatthebottomofthetank.Thecompoundisthentransportedto
sprayingdeviceatthesheetmachinethroughpipe-lineandfilterboxunderpneumatic
pressure. 08

11. 5.2 STEAMING OF UNTWISTED FIBRES :
Arawcoilofcoirhasthemoisturecontentof16-19%.Aftersteamingthroughradiatorfora
fewhoursinachamber,themoisturecontentreducestoaround10%.
Steamedcoilisthenpassedthroughanuntwistingmachine.Curledfibres(likesprings)come
outwhichprovideresiliencetotheproduct.
Curlingisgenerallydonebyspinningtheloosefibrewhilemakingtheropesandtwisting
theseropestoanoptimumdegreebringsaboutthecurlingeffect.
5.3 SPREADING OF UNTWISTED FIBRES :
Untwistedfibresarearrangedinlooseconsistencyeitherbycardingwebformationorby
baffledair–blowsysteminacontinuoussheetmachineinsuchawaythatthewholemassof
fibrescanbesprayedeasilythroughout.Foruniformandconsistentsprayingoflatexcompound,
thebedthicknessofthefibresshouldnotexceed2inch.
5.4SPRAYING 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.
09

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 80
0
±5
0
C. 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 100
0
C
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.
5.7FINAL CURING IN VULCANISER
Beds are then finally cured in a steam radiated vulcaniser. The beds are put in the vulcaniser
at a temp. at 70
0
–80
0
C and then the temp. is raised to about 105
0
C 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.
11

14. BARE RUBBERISED COIR PRODUCTS
12

15. MATTRESS
13

16. PILLOWS
14

17. Bolster
15

18. Cushion
16

19. SOFA SETS
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20. FLOW DIAGRAM OF RUBBERISED COIR
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
Bottom hackler
SHEET MACHINE ( MODEL : FEHRER / DOA)
18

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/ dm
3
)
(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
AcertaindegreeoffireretardanceisdesiredinR.C.productsforitsapplicationinselected
areassuchasautomobilecushioning.Thefireretardantchemicalstobeusedshouldimpartfire
retardancywithoutadverselyaffectingtheresilientqualityorservicelifeoftheproduct.
FireretardantR.C.productscanbeobtainedbyjudiciousselectionofself–extinguishabletype
offire-retardantadditives.AqueoussolutionofsomeFRadditivesinspecificconcentrations
werefoundtobeusefulforthispurpose.Thesolutionsarehand–sprayedonbothsidesofR.C.
productsanddriedinambientconditions.
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26. 24

27. 10 . TESTING
AlltestingparametersandmethodsofR.C.sheetsarestipulatedinBISSpecificationIS:8391
–1977.Thetestsarecarriedoutnotbefore48houraftervulcanizationofthesamples.Thetest
samplesareconditionedforaminimumperiodof24hourat27±2
0
Cand65±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/
dm
3
.
25

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.
Sizeofthetestspecimenshouldbe100x100
mm.Thicknessofthesampleismeasuredas
describedin9.1.Indentationhardnessindexis
determinedasdescribedin9.3.Thestrokeofthe
crankshaftforadepressionoftheindentorto
40%ofthethicknessofthesample.Thenthe
indentorisraisedtothetopmostpositionofthe
strokeandthetestspecimenisplacedonmetal
platebelowtheindentor.Thespecimenis
subjectedtoflexing@4cycle/sec.
Afterflexing2,50,000cycles,thesampleis
allowedtorecoverfor30mins.Thereafterthe
indentationHardnessindexismeasuredand
thevariationintheindentationhardnessis
calculatedasthe%oftheinitialhardness.The
differenceinhardnessshouldbewithin20%.
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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 ±
2
0
C . The test piece is released and the thickness is measured again after 30 mins recovery time.
Compression set at constant strain
T
0–T
r
T
0
X 100 %
Where ,T
0= Original thickness of the T.P.
T
r= Thickness of the T.P. after recovery.
Usually the maximum limits of compression set are :
a)25% at 70±2
0
C
b)15% at room temperature
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31. 10.6 AGEING TEST
•InitialIndentation 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 2
0
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
Rubberisedcoirindustrycansafelyachieveinfinitybetterdaysaheadduetoitshugepotential
growthbothindomesticandinternationalmarkets;andthisispossibleabsolutelyduetothe
bountifulavailabilityofboththebasicrawmaterialsfromthenaturei.e.coirfibreandnatural
rubberlatex.
TheaveragelifeexpectancyofRCmattressesisabout10–12years.Therecouldbeabout70
millioncurrentlyinuseinIndiawhichcovershardly6%oftheIndianpopulationuseR.C.
mattresses.
ThoughtheindustryisfacingthreatsfromsubstancessuchasPUfoamandspringmattresses,
itismarchingaheadbycreatingbetterawarenessoftheproducts,itscostcompetitiveness,eco-
friendlyproductetc.againstothersleepmaterials.Itishopedthatby2030everyhouseholdin
Indiawillhaveatleastonecoirmattress.
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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