Good article for education and general information.

2. PRIYABRATA GHOSH, IRI, KOLKATA
EPR & EPDM
• EPR IS SATURATED AND EPDM IS AN UNSATURATED POLYMER.
• THE SATURATED CO-POLYMER OF ETHYLENE AND PROPYLENE
HAS THE FOLLOWING BASIC STRUCTURE.
~~~~~~~~ CH2 – CH2 ~~~~~~~~~~~~~~CH – CH2 ~~~~~~~~
x CH3 y
• THE MONOMERS ARE COPOLYMERISED WITH ZIEGLER-NATTA
TYPE CATALYST, THE CHOICE OF WHICH DETERMINES THE
RATIO OF ETHYLENE TO PROPYLENE AND THE MW
DISTRIBUTION.
P-1 …………….CONTD………….

3. PRIYABRATA GHOSH, IRI, KOLKATA
EPR & EPDM……………………….
• USUALLY 60 – 70 MOLE% OF ETHYLENE AND 40 – 30 MOLE% OF
PROPYLENE ARE ADDED. MATERIAL SHOULD PRESENT A RANDOM
SEQUENCE.
• MOONY VISCOSITY IS IN THE RANGE OF 30 – 50.
• OIL EXTENDED TYPES CONTAIN 100 – 150 P.H.R. ABOVE 100 P.H.R.
PARAFFINIC OIL SHOULD BE USED.
• SPECIFIC GRAVITY IS QUITE LOW (0.86); THEREFORE VOLUME COST
IS LOW.
• EPDM IS DEVELOPED FOR SULPHUR VULCANISATION. 2 – 3%
DIENE, THE THIRD MONOMER, IS INTRODUCED TO PRODUCE AN
UNSATURATED POLYMER IN THE RANDOM SEQUENCE OF
ETHYLENE AND PROPYLENE (E.G., ETHYLENE – 69%; PROPYLENE –
29% AND DIENE – 2%).
P-2 ……………CONTD………….

4. PRIYABRATA GHOSH, IRI, KOLKATA
EPR & EPDM………………………
• THE DIENES ARE COSTLY. ADDITION OF DIENE SHOULD NOT ….
a) INFLUENCE THE RATE OF POLYMERISATION.
b) INFLUENCE RANDOM SEQUENCE.
c) TAKE PART IN CRYSTALLISATION.
• BECAUSE OF THESE REQUIREMENTS, CHEAP DIENES (E.G.,
BUTADIENE) CANNOT BE USED. THE MATERIAL USED IS NON-
CONJUGATED DIENE (I.E., ONE DOUBLE BOND IS USED FOR
POLYMERISATION AND THE OTHER IS USED FOR SULPHUR
VULCANISATION.)
P-3 ………….CONTD………….

5. PRIYABRATA GHOSH, IRI, KOLKATA
EPR & EPDM ………………………..
TYPICAL DIENES USED :
R1
CH2 = CH – CH2 – C = C POLYMERISATION
R2
R3 1 2
~~~~~~~ CH2 – CH ~~~~~~~
R1
CH2 – C = C
R2
R3
(1, 2 ADDITION)
P-4 ………………CONTD…………..

6. PRIYABRATA GHOSH, IRI, KOLKATA
EPR & EPDM………………
• DOUBLE BOND LEFT AFTER POLYMERISATION IS IN BRANCHED
CHAIN. SO OXIDATION DOES NOT DETERIORATE PROPERTIES
MARKEDLY AS IT DOES WITH BUTYL RUBBER.
• EXAMPLES OF DIENES ARE :
ETHYLIDENE NORBORNENE – EXPENSIVE, BUT GIVES FAST CURE,
MOST WIDELY USED.
DICYCLOPENTADIENE NORBOMADIENE – RELATIVELY CHEAPER,
BUT SLOWER CURE.
1,4 HEXADIENE – RELATIVELY EXPENSIVE, GIVES FASTER CURE.
CYCLO-OCTADIENE
P-5

7. PRIYABRATA GHOSH, IRI, KOLKATA
OUTSTANDING PROPERTIES
• THEY ARE EASY PROCESSING.
• MODERATELY GOOD PHYSICAL PROPERTIES WITH REINFORCING
FILLERS. (BETTER THAN IIR). T/S – 3000 P.S.I. (IIR – 2500 P.S.I.)
• IT HAS VERY GOOD RESISTANCE TO OXIDATION AND OZONE DUE
TO ITS VERY LOW UNSATURATION AND THAT TOO IN PENDANT
SIDE GROUP.
• REINFORCED STOCK SHOWS GOOD ABRASION RESISTANCE.
• IT HAS BETTER RESILIENCDE THAN IIR AT ORDINARY
TEMPERATURE.
• IT HAS GOOD RESISTANCE TO KETONE AND ESTER TYPE SOLVENTS.
(NR AND SBR ARE ALSO RESISTANCE TO THESE SOLVENTS).

8. PRIYABRATA GHOSH, IRI, KOLKATA
OUTSTANDING PROPERTIES…………………….
• IT HAS VERY GOOD LOW TEMP. FLEXIBILITY (EVEN IT HAS 200C
LOWER TEMPERATURE THAN THE BRITTLE POINT OF NR.)
• IT HAS SLOW RATE OF CURE DUE TO LOW UNSATURATION.
• PERMEABILITY TO GASSES IS HIGHER THAN IIR AND EQUAL TO
THAT OF NR (ADVANTAGE OVER IIR IS BETTER PROCESSING AND
FABRICATION).
• THE POLYMER DOES NOT CRYSTALLISE ON STRETCHING,
THEREFORE LOW GUM STRENGTH.
P-7

9. PRIYABRATA GHOSH, IRI, KOLKATA
COMPOUNDING
• CURING :-
• EPR IS CURED WITH PEROXIDE.
LARGE AMOUNT OF PROPYLENE IN EPR LEADS TO SCISSION,
GIVING LOW CROSS-LINK DENSITY [X], LOW SET PROPERTIES, LOW
MODULUS AND HIGH HEAT BUILD-UP.
• IDEAL CURED NETWORK IS TO HAVE LONG RUBBER CHAINS WITH
MODERATE NUMBER OF X-LINKS.
• POOR CURED NETWORK LEADS TO SHORT CHAINS WITH LARGE
NUMBER OF CROSS-LINKS. SO LOWER AMOUNT OF PEROXIDE IS
USED FOR LOWER CHAIN SCISSION AND LONG CHAIN MOLECULES
WITH MODERATE X-LINKS.
• THUS BETTER PHYSICAL PROPERTIES ARE OBTAINED.
E.G., 2 P.H.R. PEROXIDE GIVES 5 X 104 MOLE/CM3 [X]
3 P.H.R. PEROXIDE GIVES 7 X 105 MOLE/CM3 [X]
4 P.H.R. PEROXIDE GIVES 10 X 105 MOLE/CM3 [X]
P-8 ……………CONTD…………

10. PRIYABRATA GHOSH, IRI, KOLKATA
COMPOUNDING…………………
• THE USE OF CO-AGENTS IMPROVE THE PROPERTIES, E.G., DIVINYL
ADEPATE, DIVINYL BENZENE, TRIALLYL CYANURATE.
2 P.H.R. DICUMYL PEROXIDE IMPROVES THE MODULUS AND
2 P.H.R. DIVINYLADEPATE COMPRESSION SET PROPERTIES,
BUT DOES NOT AFFECT THE
STRENGTH.
• A THIRD INGREDIENT (SULPHUR) IS ADDED NOT AS A
VULCANISING AGENT, BUT TO RAISE T/S (~ 20% T/S IS INCREASED)
WHILE MODULUS IS UNAFFECTED. MAXIMUM 1 P.H.R. SULPHUR
ACTS WELL, BUT ABOVE THIS, MODULUS MAY DROP. USUAL DOSE
IS 0.5 – 1.0 P.H.R.
• CHANGES IN OVERALL PROPERTIES OCCUR BY ~ 25% INCREASE
WITH CO-AGENT AND SULPHUR OVER PEROXIDE ALONE.
• PEROXIDE CURE GIVES BETTER INSULATION PROPERTIES AND
HENCE WIDELY USED IN CABLE INDUSTRIES.
P-10 …………..CONTD……………

11. PRIYABRATA GHOSH, IRI, KOLKATA
COMPOUNDING……………………..
• EPDM RESPONSES TO SULPHUR VULCANISATION (ALSO RESPONSES
TO PEROXIDE CURE). PEROXIDE GIVES BETTER INSULATION
PROPERTIES THAN S – CURE, BUT GIVES POOR FLOW PROPERTIES.
• EXAMPLES FOR EPDM CURE:
SULPHUR…………..1.5
ZnO……………………5
ST. ACID……………..0.5 (NO NEED TO USE, RETARD
CURE, USED AS LUBRICANT)
TMT…………………..1.5
MBTS…………………1.0
ZDC……………………0.25
(OR DPG………………1.0)
• IF AMOUNT OF ONE ACCELARATOR IS MORE THAN 1.5 P.H.R., BLOOM
MAY OCCUR IN EPDM COMPOUND. MBT OR CBS MAY BE USED AS
SECONDARY ACCELERATOR. (S – 1.5, ZnO – 5, ST.ACID – 0.5, TMT – 1.5,
MBT – 0.5 – 0.8)
P-11

12. SOME USEFUL CURING SYSTEMS FOR EPDM P. GHOSH. IRI. KOLKATA
A. SULPHUR 1.5
TMT 1.5
MBT 0.5
 LOW COST; EARLIEST CURE SYSTEM
MEDIUM CURE RATE AND SATISFACTORY VULCANISATE PROPERTIES
 MAJOR DISADVANTAGE IS ITS SEVERE BLOOMING TENDENCY
B. SULPHUR 0.5
ZDBC 3.0 (ZINC DIBUTYL DITHIOCARBAMATE)
ZDC 3.0 (ZINC DIMETHYL DITHIOCARBAMATE)
SULFASON R 2.0 (DITHIO DIMORPHOLINE)
 EXCELLENT COMPRESSION SET AND GOOD AGEING PROPERTIES
 VERY HIGH COST AND TENDENCY TO BLOOM
P-12

13. SOME USEFUL CURING SYSTEMS FOR EPDM CONTD…. P.GHOSH , IRI . KOLKATA
C. SULPHUR 2.0
MBTS 1.5
ZDBC 2.5
TMT 0.8
 GENERAL PURPOSE ; NON – BLOOMING SYSTEM AND OFFERS GOOD
PERFORMANCE.
 WIDELY USED EPDM CURING SYSTEM
D. SULPHUR 1.0
ZDBC 2.0
TMT 1.0
TBBS 2.0 (N – TERT – BUTYL BENZOTHIAZOL SULFENAMIDE)
 BALANCED PROPERTIES OF FAST CURE, GOOD PHYSICALS , GOOD
RESISTANCE TO COMPRESSION SET AND HEAT AGEING
P-13

14. PRIYABRATA GHOSH, IRI, KOLKATA
FILLER P-14

15. PRIYABRATA GHOSH, IRI, KOLKATA
FILLER………………………
EXTRAORDINARILY VERY HIGH AMOUNTS OF FILLERS AND
OILS MAY BE ADDED IN EPR/EPDM COMPOUNDS. AS MUCH
AS 600 P.H.R. FILLER AND 200 P.H.R. OIL CAN BE ADDED, BUT
PROCESSING BECOMES POOR.
EPR/EPDM DOES NOT CRYSTALLISE ON STRETCHING, SO
REINFORCING FILLERS ARE ADDED TO ACHIEVE DESIRED
STRENGTH PROPERTIES.
ACIDIC FILLERS (E.G., CHANNEL BLACKS, SILICA, SOFT
CLAYS) SHOULD BE AVOIDED WHILE CURING WITH
PEROXIDES.
HIGH TEMPERATURE MIXING WITH REINFORCING FILLERS
AND PROMOTERS IMPROVE THE PHYSICAL PROPERTIES AS IT
DOES WITH BUTYL RUBBER. HEAT TREATMENT WITH CLAYS
ALSO IMPROVES PROPERTIES OF EPR/EPDM.
P-15

16. PRIYABRATA GHOSH, IRI, KOLKATA
SOFTNER
 PETROLEUM AND PARAFFINIC OILS IMPROVE
PROCESSABILITY AND CAN BE USED IN LARGE QUANTITIES
WITH LITTLE DETERIORATION IN PHYSICAL PROPERTIES.
 AROMATIC OILS TEND TO SLOW DOWN THE RATE OF CURE.
 UNSATURATED OILS DO NOT UPSET VULCANISATION AS IT
DOES WITH IIR.
 TACKINESS OF EPR/EPDM IS LOW. NON-VULCANISABLE PF
RESINS AND CI RESINS ARE RECOMMENDED TO IMPROVE
THE TACKINESS.
ANTIOXIDANTS :
 NOT REQUIRED, AS IT IS HIGHLY RESISTANT TO OXYGEN AND
OZONE ATTACKS.
P-16

17. PRIYABRATA GHOSH, IRI, KOLKATA
PROCESSING
 TWO-ROLL MILLS :
-- PREMASTICATION IS NOT REQUIRED AS THERE IS NO
CHANGE IN PLASTICITY DURING MILLING. BUT PLENTY OF
TEMPORARY CHANGE OCCURS DUE TO TEMPERATURE AS THE
POLYMER IS HIGHLY THERMOPLASTIC.
-- COLD ROLLS ARE GENERALLY RECOMMENDED FOR
MIXING. MIXED STOCK TENDS TO SAG EASILY WHERE BLACK
AND OIL PROPORTIONS ARE VERY HIGH.
-- MIXING TIME IS QUITE SHORT WITH EPR/EPDM.
 EXTRUSION :
VERY LOW DIE-SWELL DURING EXTRUSION. BEST
COMBINATION OF TEMPERATURE IS :
HEAD/DIE – 950 – 1000C
BARREL – 650C
SCREW – COLD
P-17 ……….CONTD………

18. PRIYABRATA GHOSH, IRI, KOLKATA
PROCESSING………………..
 CALENDERING :
-- SMOOTH CALENDERING IS POSSIBLE WITH WIDE RANGE
OF TEMPERATURE.
-- THERE ARE VERY FEW PROBLEMS OF BLISTERING ETC.
AS COMPARED TO IIR.
-- AS HIGH LOADINGS OF FILLER AND OIL ARE USED IN
EPR/EPDM, DIE-SWELL AND CALENDER GRAIN ARE LOWER.
-- WITH NR AND SBR, AN WIDE RANGE OF TEMPERATURE
DURING PROCESS IS NECESSARY TO MINIMISE EXCESSIVE
DIE-SWELL, BLISTERS AND CROW’S FEET. WITH EPR/EPDM,
IT IS EXPERIENCED THAT IF RUBBER IS NOT FLOWING WELL,
SLIGHT INCREASE IN TEMPERATURE WILL RESULT IN EASY
FLOWABILITY.
 MOULDING :
EPR/EPDM HAVE GOOD TEAR RESISTANCE; MOREOVER, NOT
MUCH MOULD SHRINKAGE OCCURS SINCE HIGH LOADING OF
FILLERS ARE GENERALLY INCORPORATED.
END