This document discusses the preparation and properties of castor oil extended modified natural rubber by epoxidation. The objectives were to optimize epoxidized natural rubber synthesis conditions, study the effect of castor oil on properties, and evaluate potential in tire compounds. Natural rubber latex was epoxidized using varying temperatures and times. Castor oil was then added in amounts from 10-40 phr. Characterization showed epoxidation increased with temperature and time. Castor oil improved properties like rolling resistance and reduced filler-filler interactions. The epoxidized natural rubber also acted as a compatibilizer and coupling agent in silica filled NR/NBR blends, improving properties.

1. PREPARATION AND PROPERTIES OF CASTOR OIL EXTENDED MODIFIED NATURAL
RUBBER BY EPOXIDATION
1
MOHAMMAD ANSAR V
16RT60R05 | 2016-2018
Rubber Technology Center ,IIT Kharagpur
Suchismta Sahoo
Assistant Director
IRMRA
Under the guidance of
Dr. N C Das
Associate Professor
RTC, IIT Kharagpur

2. OBJECTIVES
2
• To optimize the reaction conditions for preparing epoxidized natural rubber
(ENR)
• To study the effect of castor oil on various physical, chemical and mechanical
properties of the ENR
• To study the dynamic mechanical characteristic of the synthesized material and
evaluate its potential in tire compounds to reduce rolling resistance
• Complete characterization and structure property correlation of various
synthesized material

3. BACKGROUND
• Epoxidation of natural rubber has been studied extensively. Epoxidation
imparts good oil resistance, damping properties and air impermeability to
natural rubber but simultaneously it also has an adverse effect on the
mechanical properties at higher level of epoxidation due to chain scission and
gel formation.
• In the proposed study, castor oil will be used as a modifier.
• Castor oil contains carboxylic acid groups which can react with the hydroxyl
and carboxyl groups formed due to ring opening reaction during epoxidation
by forming ether and ester linkages. Hypothetically the castor oil may help in
prevent the gel formation creating the soft phase thereby improving the
processibility and restricting the storage hardening. The introduction of the
soft phase might also enhance the damping properties.

4. BACKGROUND
• In the proposed study, castor oil will be
used as a modifier.
• Castor oil contains carboxylic acid groups
which can react with the hydroxyl and
carboxyl groups formed due to ring
opening reaction during epoxidation by
forming ether and ester linkages.
• Hypothetically the castor oil may help in
preventing the gel formation by creating
the soft phase thereby improving the
processibility and restricting the storage
hardening. The introduction of the soft
phase might also enhance the damping
properties.

5. Project Outline
• Preparation of ENR: Reaction in latex phase
• Characterization of ENR by FTIR, DSC
• Compounding of the polymer and measure the properties like rheological
properties, tensile strength, elongation at break, tear resistance, oil resistance,
hardness, DMA, Air permeability
• Morphological studies by SEM
• Study of the effect of ENR as compatibiliser and coupling agent for silica filler
NR/NBR blend.
• Study of the effect of Rice husk ash silica in ENR and NR

6. Preparation of ENR: Reaction in Latex Phase
Chapter 1

7. Preparation of ENR: Reaction in Latex Phase
Latex
stabilization
• 1 hour
Add
H2O2+HCOOH
• Varying
Coagulation
• 18 hourSoaking
Drying • 48 hour at 70℃
The mole% of epoxidation mainly
depend reaction temperature, time
and concentration of ingredients.
The mole% of epoxidation
have minor effects by RPM,
order of addition etc.
Materials used:
• The natural rubber latex (60% DRC)-rubber research
institute (RRII), Kottayam.
• Polyethylene (12) tri decyl ether (sigma Aldrich,
Mumbai),
• Formic acid (98-100 %, concentration),
• hydrogen per oxide (50%) and methanol are supplied by
Merck life Pvt. Ltd, Mumbai.
• Sodium hydrogen carbonate powder

8. Characterization of ENR by FTIR, DSC
FTIR:
Attenuated reflection mode (ATR) mode in the range 4000-400 cm-1 and resolution 6 cm-1
Mole% of epoxidation =
𝐴𝑟𝑒𝑎 𝑜𝑓 𝑝𝑒𝑎𝑘 870
𝐴𝑟𝑒𝑎 𝑜𝑓 𝑝𝑒𝑎𝑘 870 + 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑝𝑒𝑎𝑘 835
DSC:
Samples were quenched below to -80℃ and heated up to 20℃ at the rate of 10℃/min.
Mole% of epoxidation =
𝑇𝑔 𝑜𝑓 𝐸𝑁𝑅−𝑇𝑔 𝑜𝑓 𝑁𝑅
0.93

9. Characterization of ENR by FTIR
Mole % increases with increase in
reaction temperature and time
50 oC and 5 hours was selected to
obtain an epoxidation level of 25%
835
870
835
870

10. Effect of Time on Mole % of Epoxidation
14
19 19
23
25
26.5
0
5
10
15
20
25
30
1 2 3 4 5 6
Mole % of epoxidation at 50℃

11. Characterization of ENR by DSCHeatflow(mW),Endothermic
With increase in Epoxidation % the Tg was observed to increase

12. CONCLUSIONS
• The optimum chemical concentration isoprene: formic acid:
hydrogen per oxide is 1:0.5:0.75
• The optimum reaction time and temperature are 50℃ for 5 hour
respectively
• Mole% of epoxidation increases with temperature and time
• Coagulation content increase as the temperature and time
increases

13. SYNTHESIS AND CHARACTERIZATION OF CASTOR OIL EXTENDED
EPOXIDISED NATURAL RUBBER
Chapter 2

14. CASTOR OIL
The castor oil contain 3 points of functionality in the molecule
1. Carboxyl group-possibility of wide range of esterification
2. Single point unsaturation- which can be altered by hydrogenation,
epoxidation or vulcanization
3. Hydroxyl group give extra stability to the molecule

15. PREPARATION OF CASTOR OIL EXTENDED ENR
• Castor extended ENR was prepared with same reaction conditions i.e. 50oC for
5 hours.
• The castor oil was varied from 10 to 40 phr
ENR
Probable H – bonding between various functional groups

16. PHYSICAL AND CHEMICAL METHODS
Sample Test Standard
After synthesis Acetone extraction ASTM D-297
After mixing RPA ASTM D 5289
After moulding
Hardness ASTM D 2240
Compression set ASTM D 395
Physical properties ASTM D 412 & 624
DSC ASTM D 3418
Rebound resilience BS-903-A8, method A
Oil resistance ASTM D 471
Air permeability IS 3400-XXI

17. COMPOUNDING AND MIXING
Ingredients Phr
Rubber 100
Silica 50
Si69 5
Aromatic oil 5
ZnO 5
Stearic acid 2
TDQ 2
Sulphur 2.5
CBS 1.5
TMTD 0.3
PVI 0.2
MIXING SEQUENCE
Steps Time
Rubber masticated 0
Add TDQ 3
ZnO + stearic acid 5
Silica (50%)+oil 7
Silica (50%)+oil 12
Sulphur + TMTD+MBS+PVI 15

18. FTIR
There is no change in the chemical structure of ENR with the incorporation of castor oil

19. ACETONE EXTRACTION
RUBBER ACETONE EXTRACTION
VALUE (%)
Ratio of oil
Extracted/Oil Loaded
ENR 2.9 ------
C-ENR-10 11.3 1.13
C-ENR-20 16.9 0.84
C-ENR-30 26.9 0.89
C-ENR-40 24.1 0.60
Hydrogen bonding and intermolecular
attraction between the –OH , -COOH,
Epoxide group helps in the retention of
castor oil in the matrix.

20. Cure Characteristics

21. Cure Characteristics
Rubber T90 TS2 T90-TS2 Cure Rate Index (CRI) MH ML
NR 11.75 1.97 9.78 10.22 22.20 3.4
ENR–50-6 2.92 1.22 1.7 58.8 20.48 0.9
C-ENR-10 6.06 2.41 3.65 27.39 21.2 2.93
C-ENR-20 8.48 3.33 5.15 19.42 14.43 1.66
C-ENR-30 15.50 8.05 7.45 13.42 14 1.88
C-ENR-40 22.72 17.35 5.37 18.62 4.02 1.52

22. Payne Effect
2013
1788
451.48
842
428.78
293.81
0
500
1000
1500
2000
2500
NR ENR ENR-10 ENR-20 ENR-30 ENR-40
G*(Complexmodulus)Kpa
Payne effect
Payne effect = G*0.28% - G*100%
Rubber G* @ 0.28% G*@100% Payne effect
NR 2748 735 2013
ENR 2025 237 1788
ENR-10 1093 641.52 451.48
ENR-20 1301 459 842
ENR-30 795.28 366.5 428.78
ENR-40 605.5 331.69 293.81
• Low Payne effect indicates lower filler – filler
interaction and better dispersion.
• Payne effect was lowered with epoxidation by 11%
• With C – ENR – 10 it was reduced by 70% compared
to ENR

23. Physical Properties
PROPERTIES NR ENR ENR-10 ENR-20 ENR-30 ENR-40
Tensile Strength(Kg/cm2) 233 263 268 245 177 145
Tear Strength(Kg/cm) 97 88 92 79 42 34
Hardness, Shore A 68 67 62 53 56 45
Change in Tensile Strength after
aging (%)
-51 -70 -64 -48 -63 -65
Compression Set(%) 27 41 42 47 43 46
Air Permeability(m2/Pa.S) 6.29*10-17 3.15*10-17 4.11*10-17 5.64*10-17 4.68*10-17 5.34*10-17
Rebound Resilience (%) 59 66 62 42 48 43

24. Oil Resistance
Compound Oil Number 1 (Volume Swell)(%) Oil Number 3 (Volume Swell)(%)
NR +71.33 +204.6
ENR +24.61 +136.2
C-ENR-10 +31.57 +194.5
C-ENR-20 +43.4 +217.3
C-ENR-30 +20.1 +215.2
C-ENR-40 +24.45 +237.9
• Oil resistance was improved with epoxidation
• Oil resistance was observed to decrease with the introduction of the castor oil
• At higher loading of castor a decrease in volume swell was observed which can
be due to extraction of the oil

25. Glass Transition Temperature
Glass transition temperature was observed to be marginally affected by the introduction od castor oil.

26. Traction and Rolling resistance
Rolling resistance of the castor oil extended epoxidised was found improved
0.104
0.235
0.114
0.129
0.175
0.202
0.104
0.333
0.1 0.1
0.144 0.146
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
NR ENR C-ENR-10 C-ENR-20 C-ENR-30 C-ENR-40
Tandelta
Traction and rolling resistance
Tan delta @ 30℃ Tan delta @ 60℃

27. Morphology - SEM
Compared to NR the dispersion of silica was observed to be better in ENR and C-ENR

28. CONCLUSIONS
• The optimum chemical concentration isoprene: formic acid:
hydrogen per oxide is 1:0.5:0.75
• The optimum reaction time and temperature are 50℃ for 5 hour
respectively
• Mole% of epoxidation increases with temperature and time
• Coagulation content increase as the temperature and time
increases

29. STUDY OF THE EFFECT OF EPOXIDISED NATURAL RUBBER AS
COMPATIBILIZER AND COUPLING AGENT IN SILICA FILLED NR/NBR
BLEND
Chapter 3

30. COMPOUNDING AND MIXING
INGREDIENTS NR-70/ENR-
0/CA*-10%
NR-70/ENR-
0
NR-65/ENR-
5
NR-60/ENR-10 NR5/ENR-
15
NR50/ENR-
20
NR 70 70 65 60 55 50
NBR 30 30 30 30 30 30
ZnO 5 5 5 5 5 5
Stearic acid 2 2 2 2 2 2
Silica 40 40 40 40 40 40
Si69 4 - - - - -
Sulfur 1.4 1.4 1.4 1.4 1.4 1.4
DOP 4 4 4 4 4 4
DPG 0.5 0.5 0.5 0.5 0.5 0.5
MBTS 1 1 1 1 1 1
PVI 0.2

31. Cure Characteristics
Sample T90 (min) Ts2 (min) T90-Ts2(Min) Cure rate index
NR-70/ENR-0
2.42 0.73 1.69 59
NR 70/ENR-0/CA-10%
2.1 1.1 1 100
NR-65/ENR-5 2.52
1.33 1.19 84
NR-60/ENR-10
2.47 1.12 1.35 74
NR-55/ENR-15
2.45 0.84 1.61 62
NR-50/ENR-20
2.67 1.32 1.35 74

32. Payne Effect
Payne effect = G*0.28% - G*100%
• Low Payne effect indicates lower filler – filler interaction and better dispersion.
• With increasing ENR content the filler-filler interaction is decreasing, implying a better filler-rubber
bonding

33. Physical Properties
PROPERTIES
NR-
70/ENR-
0/CA-10%
NR-70/ENR-
0
NR-65/ENR-
5
NR-
60/ENR-
10
NR-55/ENR-
15
NR-50/ENR-
20
Tensile Strength(Kg/cm2
) 179 169 204 171 151 152
Tear Strength(Kg/cm) 45 50 62 60 62 65
Hardness, Shore A 65 72 69 70 70 73
Change in Tensile Strength after
aging (%)
-49 -28 -50 -53 -50 -42
Compression Set(%) 59 47 52 52 45 48
Air Permeability(m2/Pa.S) 5.12*10-17
5.35*10-17
4.71*10-17
3.85*10-17
3.35*10-17
3.42*10-17
Rebound Resilience (%) 49 52 53 52 53 57

34. Oil Resistance
Sample IRM Oil-901(%) IRM Oil-903 (%)
NR-70/ENR-0 58.09 139.86
NR 70/ENR-0/CA-10% 90.16 199.07
NR-65/ENR-5 62.11 151.08
NR-60/ENR-10 57.7 143.69
NR-55/ENR-15 8.16 137.61
NR-50/ENR-20 47.24 134.13
• Oil-resistance was observed to improve with an increase in ENR content.
• Compatibilization of NR and NBR result in improvement the oil resistance of the blend.

35. Morphology - SEM
Dispersion is better with 5 and 10 parts of ENR probably due to the coupling action of the ENR
to disperse the silica filler homogeneously

36. CONCLUSIONS
• It was identified that ENR acts as both coupling agent for silica and
compatibiliser for NR and NBR
• Vulcanizate with ENR content 5 phr shows optimum properties
than other ENR vulcanizate, which indicates that vulcanizate with
ENR content 5 phr can be used as compatibiliser for rubber-rubber
blend and coupling agent for silica
• Tensile strength shows an increase of 20.71% in vulcanizate with
ENR content 5 phr in comparison to vulcanizate with coupling
agent.

37. SYNTHESIS & CHARACTERISATION OF RICE HUSK SILICA FILLED
EPOXIDIZED NATURAL RUBBER
Chapter 4

38. COMPOUNDING AND MIXING
INGREDIENTS EL-R ED-R ED-V3 NR-R NR-V3
ENR 100 100 100
RMA 100 100
Zinc oxide 5 5 5 5 5
Stearic acid 2 2 2 2 2
Sulfur 2.5 2.5 2.5 2.5 2.5
CBS 1.5 1.5 1.5 1.5 1.5
TMTD 0.3 0.3 0.3 0.3 0.3
TDQ 2 2 2 2 2
Aromatic oil 10 % of filler 3 3
Si69 3 3
RHS (0,10,20,30,40,
50)
30 30
VN3 30 30

39. Cure Characteristics
Sample t90 (min) tS2(min) T90-Ts2(Min) Cure rate index(Min
ENR 0
2.42 1.54 0.88 113
ENR 1
5.99 4.63 1.36 73
ENR 2
6.03 4.37 1.66 60
ENR 3
5.35 3.85 1.5 66
ENR 4
6.09 4.17 1.92 52
ENR 5
6.09 0.57 5.52 18
EV
3.82 1.77 2.05 48
ER
4.86 2.93 1.93 51
NVS
4.46 3.01 1.45 68
NRS
5.24 2.86 2.38 42

40. Payne Effect
Payne effect = G*0.28% - G*100%
• Low Payne effect indicates lower filler – filler interaction and better dispersion.
• Payne effect increases with increase RHS content
• Incorporation of RHS decreases the Payne effect value of NR&ENR. this is due to its lesser particle size
127 198
442
585
1495
3263
1245
2202
694
1066
0
500
1000
1500
2000
2500
3000
3500
E0 E1 E2 E3 E4 E5 ED-R ED-V ND-R ND-V
Payneeffect(kPa)
Payne effect

41. Physical Properties
PROPERTIES
E0 E1 E2 E3 E4 E5 ED-R ED-V NR-R NR-V
Tensile
Strength(Kg/cm2
) 19.1 26.6 26 28.6 26.5 28.3 27.6 29.9 26.4 36.7
Tear Strength(Kg/cm)
3.5 3.8 4.2 4.4 5.1 10.8 5.6 5.6 7.7 8
Hardness, Shore A
46 49 52 57 64 68 64 68 55 59
Compression Set(%) 30 32 49 35 43 48 37 51 46 30
Air
Permeability(m2/Pa.S) 2.93 2.37 2.44 1.92 2.02 2.21 1.9 2.2 2.7 4.47
Rebound Resilience (%)
87 81 72 68 61 51 58 45 77 77

42. Traction and Rolling resistance
• Rolling Resistance- ED-V shows higher tan δ value, which is due to its elastic nature.
• Dry traction - the maximum dry traction value is shown by ED-Compounds with ENR shows higher dry traction, which
may be due to the presence of bulky groups
0.032 0.042 0.047
0.072
0.096
0.124
0.096
0.149
0.077
0.06
0
0.05
0.1
0.15
0.2
E0 E1 E2 E3 E4 E5 ED-R ED-V NR-R NR-V
tanδ
Dry traction ( tan δ at 30℃)
0.015
0.035
0.042 0.047
0.069
0.097
0.068
0.097
0.072
0.049
0
0.02
0.04
0.06
0.08
0.1
0.12
E0 E1 E2 E3 E4 E5 ED-R ED-V NR-R NR-V
tanδ
Rolling resistannce(tan δ at 60℃)

43. CONCLUSIONS
• In Nutshell, from this project we can conclude that, latex stage
mixing of RHS in ENR gives the best properties than dry stage
mixing which may be due to the increased dispersion of filler in
matrix.
• Less energy consumption is one of the advantage of latex stage
mixing. RHS composites shows comparable properties as VN3
composites, so can be used as alternative. It is cost effective &
easy available
• From those values it is clear that RHS added at 30 phr seems to be
the ideal one because its cure properties, tensile properties,
resilience values are higher and compression set, air permeability
values are lower than any of the other batches.

44. REFERENCES
• Sanjoy Roy Ac, B.R. Maitiab & B.R. Gupta; “Latex Stage Epoxidation Of Natural Rubber: Effects Of Agitation ,
Mode Of Addition Of Reagents, Neutralization Technique , And Secondary Acid”; Polymer Reaction
Engineering;(1994);215-240.
• Saowaroj chuayjuljit, thongchai nutchapong; “Preparation And Characterization Of Epoxidized Natural Rubber
And Epoxidized Natural Rubber/Carboxylated Styrene Butadiene Rubber Blends”; Journals Of Metals, Materials
And Mineral; Vol 25 (2015) ;25-36
• Karndasengloyluan , kannikasahakarowilma k. Dierkes ,Jacques W.M.Noordermeer; “silica-reinforced tire tread
compounds compatibilized, by using epoxidized natural rubber”; European Polymer Journal;(2014);69-79
• I.R Gelling: Epoxidised Natural Rubber, Malaysian Rubber Producers Association . Ahmad Kifli Che Aziz*, Siti
Salina Sarkawigreen; “retreaded tyre based on epoxidised natural rubber (ENR) blends in urban buses”; Journal
of Polymer Science And Technology (2017);45-55
• David R. Burfield, Kooi-Ling Lim, And Kia-Sang Law; “Epoxidation Of Natural Rubber Latices: Methods Of
Preparation And Properties Of Modified Rubbers”; Journal of Applied Polymer Science;(1984); Vol. 29;1661-1673
• Suplak Attharngsan, Hanafi Ismail,Mohamad Abu Bakar, and Jamal Ismil;”the effect of rice husk powder on
standard salesian rubber grade(SMR L) and epoxidized natural rubber ENR50composites”;polymer plastics
technology and engineering:2012: 51:3,231-237,DOI:10.1080/03602559.2011.625377.