EPOXIDISED LIQUID NATURAL RUBBER-VARIATION IN EPOXIDATION RATIO BASED ON MOLECULAR WEIGHT DISTRIBUTION

1. EPOXIDISED LIQUID NATURAL RUBBER-
VARIATION IN EPOXIDATION RATIO BASED
ON MOLECULAR WEIGHT DISTRIBUTION
Saneesh Kumar N
Assistant Professor
Department of Chemistry And Industrial Chemistry
T.K.Madhava Memorial College
Nangiarkulangara
Haripad, Alappuzha

2. NATURAL RUBBER (NR)
Natural polymer – Elastomer
Occurs nearly 500 different Species of
plant
Outstanding
Source
Hevea Rubber
Hevea Brasiliensis

3. Natural Rubber Latex
 Emulsion of polyhydrocarbon
droplets in aqueous solution
 Colloidal dispersion of negatively charged
particles of rubber (1000 nm)
 Percentage of NR in NR latex- 25-35%

4. Coagulation of Rubber
 Separation as crude rubber
from diluted latex by adding
acetic acid
 Coagulum( Coagulated soft white mass)-
treated for preparing smoked rubber,crepe
rubber,gutta percha etc
 Rubber sheet-separated and squeezed by
two roller mill to expel the absorbed serum

5. Chemical Nature of NR
 Polyisoprene (cis 1,4 configuration )
Number average degree of polymerisation of about 5000
Broad distribution of molecular weights

6. Chemical Modification of NR
Epoxidation
Halogenation
Nitrile Rubber
Preparation
Depolymerisation

7. Functionalisation of NR-Degradation
Chain end degradation
 successive release of
monomer units
 reverse of the propagation
step in chain
polymerisation
Random degradation
 practically no monomer is
liberated
 reverse of polymerisation
process
(low mol.wt fragments)
Degradation of NR- important (Mol. Wt. of NR ranges from 1.5 to 2
lakhs)- produces low mol.wt Liquid natural rubber (LNR)
Types of degradation
Thermal degradation Mechanical degradation
Photodegradation Degradation by ultrasonic
waves
Oxiadative Degradation Ozone oxidation Degradation

8. Property modification-
Epoxidation
 Epoxidised Natural Rubber (ENR) –
Chemically modified form of NR
obtained through epoxidation of NR
under controlled conditions
 Property modification through
epoxidation enables the use of ENR as
an important industrial material
 ENR 25 and ENR 50 attained
commercial importance

9. PRESENT STUDY
Natural Rubber
(NR) Photochemical
Degradation
Epoxidation
Hydroxy Terminated
Liquid Natural Rubber
(HTLNR)
Epoxidised Liquid
Natural Rubber
(ELNR)
Random epoxide distribution
in epoxide sample can be compared
with that of depolymerised NR

10. OBJECTIVES OF THE STUDY
 Photochemical degradation of NR - Preparation of
hyroxy terminated liquid NR (HTLNR)
 Physico-chemical analysis of HTLNR -
Determination of viscosity average molecular mass
Chemical analysis of HTLNR
 Estimation of hydroxyl group in LNR
 Estimation of inherent epoxide group in LNR
 Epoxidation of LNR – Preparation of Epoxidised
liquid natural rubber (ELNR)
 Comparison of random epoxide distribution - FTIR
spectral analysis of HTLNR and ELNR

11. NEED, IMPORTANCE AND SCOPE OF THE
STUDY
 Depolymerisation of NR to LNR has been a topic of interest in
the view of the increasing applications involving liquid rubbers
and the status of LNR as a renewable material
 Epoxidation of LNR further increases the functionality in the
already functionalised system
 The degree of epoxidation improved properties of LNR such as
tensile strength, polarity ,air permeability etc.
 Applications such as water proofing compounds, cable jionts,
adhesives, binders, cast rubber products etc. making LNR
important
 This work opens up scope for elaborate studies on various
applications as this work has been done on various fundamental
aspects of LNR such as flow behaviour, viscosity modification
and improvement in technological properties

12. Photochemical degradation of NR - Preparation
of hyroxy terminated liquid NR (HTLNR)
 NR sheet (10g) in finely devided state with
Toluene(100mL) in an R.B flask was kept overnight and
the swelled rubber obtained was dispersed using
sufficient amount of toluene
 The homogenised mixture obtained by vigorous shaking
with H2O2 (40mL) followed by MeOH (20mL) in small
portions was exposed to sunlight for 40 hours with
occasional stirring
 The depolymerised NR present in the organic layer was
precipitated by MeOH and the dry HTLNR obtained after
evaporation below 600C and vacuum evaporation was
used for analysis

13. Determination of viscosity average molecular
mass of LNR
 Intrinsic viscosity of solutions of LNR in
toluene (0.1-2%) was calculated by
measuring time of flow of each solution using
ostwald viscometer
 Viscosity average molecular mass was
calculated using Mark-Honwink-Sakurada
equation
[ŋ] = K Mv1/a

14. Estimation of hydroxyl group in LNR
 Solution of LNR(0.5g) in toluene (100mL)
was acylated by refluxing with acetylating
mixture(10mL) for 2 hours
 Acetic acid liberted by hydrolysis of excess
acetylating mixture(after acetylation) and that
for blank was estimated volumetrically using
alc.KOH
 From the two titre values hydroxyl group in
LNR (mg of KOH/g) was calculated

15. Estimation of inherent epoxide group
in LNR
 Epoxy content in LNR was determined by
pyridinium hydrochloride titration method
 Pyridinium hydrochloride(20mL)(250mL
pyridine with 20mL HCl) is heated and
refluxed with LNR(1g) and the excess
hydrochloride was back titrated with KOH
using phenolphthalein indicator
 epoxy value was calculated from the volume
of KOH required for sample and blank.

16. Epoxidation of LNR – Preparation of
Epoxidised liquid natural rubber (ELNR)
 To the stirred solution LNR(2g) in
toluene(100mL) (below 100C ), CH3COOH(2mL)
followed by Ac2O (0.1mL) and two drops of
H2SO4 (catalyst) and anhydrous CH3COONa
were added
 H2O2(5mL) was added in drops with in a period
of half an hour and was kept stirred for 5 hours
 The ELNR was precipitated by MeOH- H2O (3:2)
mixture and was subjected to vacuum
evaporation after washing with1%NaOH(5mL X

17. HTLNR
 Scheme of photochemical degradation
 Degradation process doesn’t affect the stereo
regularity of rubber

18.  LNR is a modified form of NR with a shorter
polymer chain which allow many chemical
modifications possible
 Degradation implies a decrease in molecular
weight whcih affects the physical and chemical
properties of polymer due to introduction of –OH
group
 Values of intrinsic viscosity and viscosity average
molecular mass gives a clear idea about
degradation of NR to HTLNR
 Number average molecular mass of LNR,
calculated from functionality and functional group
equivalent also leads to this idea

19. Specification of HTLNR
PARAMETER VALUE
Intrinsic viscosity 8200
Mn 14700
Mv 15600
-OH group 19.3 mg KOH/g
Epoxide (inherent) 13.1 mg/g

20. FTIR spectrum of HTLNR

21. IR spectral data of HTLNR
ABSORPTION BAND (cm-1) ASSIGNMENT
3435 Broad, O-H str
2962 C-H asym str, -CH2-
2856 s, C-H asym str, -CH3
1715 m, C=C , cis - vinylene
1450 s, C-H asym def, -CH3
1376 s, C-H sym def, -CH3
1312 m, O-H def, in plane, prim and sec alcohol
1217 ring- breathing frequency of epoxy group
1079 m, C-O str, alph prim alcohol
892 m, -CH3 def
838 Characteristic band of epoxy group
757 s, C-H, out of plane def in CHR=CHR1

22. ELNR
 Random epoxidation observed in NR
was also noticed in HTLNR
 Scheme of epoxidation
(in situ method- peracids formed and
consumed)

23. FTIR spectrum of ELNR

24. IR spectral data of ELNR
ABSORPTION BAND (cm-1) ASSIGNMENT
3435 Broad, O-H str
2962 C-H asym str, -CH2-
2855 s, C-H asym str, -CH3
1717 m, C=C , cis - vinylene
1449 s, C-H asym def, -CH3
1376 s, C-H sym def, -CH3
1312 m, O-H def, in plane, prim and sec
alcohol
1217 ring- breathing frequency of epoxy group
1082 m, C-O str, alph prim alcohol
837 Characteristic band of epoxy group
757 s, C-H, out of plane def in CHR=CHR1

25. Variation in epoxidation ratio based on molecular
weight distribution
HTLNR ELNR

26. CONCLUSION
 Photochemical degradation of NR led to the
formation of low molecular weight HTLNR
 Introduction of functional group is significant
in low molecular weight species
 The reduction in molecular weight due to
degradation of NR to HTLNR was
understood from the molecular weight
determination of HTLNR

27.  Epoxidation of degraded NR (LNR) further
increased the functionality in the already
functionalised system and gave a modified
functional polymer called ELNR
 The degree of epoxidation decided by rate
addition of oxygen atoms in isoprene double
bond, determined the improvement in
properties of LNR such as tensile strength,
polarity, air permeability etc.
 Random epoxidation as in NR was also
noticed in HTLNR and variation in epoxidation
ratio based on molecular weight distribution
was observed because epoxide present in
HTLNR and that in ELNR showed an increase

28. THANK YOU
FOR YOUR
ATTENTION