Materials Sciences and Applications, 2011, 2, 196-199
doi:10.4236/msa.2011.23024 Published Online March 2011 (http://www.SciRP.org/journal/msa)
Preparation and Properties of PVC/ELNR-30
Blends
Owen Egharevba1, Felix Ebhodaghe Okieimen2, Uzoma Ndubuisi Okwu1, Dosu Malomo3
1Rubber Research Institute of Nigeria (RRIN), Benin City, Nigeria; 2Industrial Agricultural Products Research Lab., Department of
Chemistry, University of Benin, Benin City, Nigeria; 3Department of Basic and Industrial Chemistry, Western Delta University,
Oghara, Nigeria.
Received October 12th, 2010; revised January 6th, 2011; accepted February 17th, 2011.
ABSTRACT
The mechanical and thermal properties of solution-cast blends of Polyvinyl chloride (PVC) and Epoxidized Liquid
Natural Rubber having 30 mole% epoxidation (ELNR-30) have been examined using Zwick materials testing machine
and heating in air circulating oven (200˚C) at different time intervals respectively. The ELNR was prepared by oxida-
tive degradation of natural rubber latex using Phenylhydrazine/Oxygen system and subsequent epoxidation with formic
acid and 30% H2O2. Tensile strength of unblended PVC was 26.5 ± 0.5 MPa. The blends had lower tensile strength
which decreased with increase in blend ratio of ELNR-30. Experimental data revealed that there was greater homoge-
neity in the PVC/ELNR-30 (80/20) compared with PVC/ELNR-30 (90/10). The PVC/ELNR-30 (80/20) also showed su-
perior elongation at maximum (%) than the unblended PVC and PVC/ELNR-30 (90/10) in that order. Thermal stab ility
decreased in the order PVC, PVC/ELNR-30 (90/10), PVC/ELNR-30 (80/20).
Keywords: Polyvinyl Chloride (PVC), Epoxidation, Liquid Natural Rubber (LNR), Blends, Mechanical an d T he rmal
Properties
1. Introduction
Thermoplastic elastomers such as PVC/ELNR-30 blends
are of wide interest in materials research and develop-
ment. This class of polymers describes a wide variety of
materials that have elastomeric properties at ambient
temperatures and obviate the need for the vulcanization
step to develop typical rubberlike elasticity. Thermoplas-
tic elastomers are beginning to replace specialty rubbers
in a wide variety of uses such as in adhesives, wire and
cable insulation.
Poly (vinyl chloride), PVC, being a proton donating
polymer interacts with oils and hydrocarbons resulting in
plasticization of the resin. Epoxidized liquid natural rub-
ber (ELNR) could be prepared from natural rubber (NR),
in its latex form, by the oxidative degradation of NR into
liquid natural rubber (LNR) using phenylhydrazine/oxy-
gen system and subsequent epoxidation with performic
acid generated in situ from the reaction of formic acid
and hydrogen peroxide [1,2]. Natural rubber is a high
molecular weight polymer while liquid natural rubber
usually has molecular weight less than Mv 100,000.
Blending is an attractive technique of polymer modi-
fications. There is scientific evidence to show that a par-
ticular polymer mixture can be made more miscible by
reducing the molecular weight of one or both compo-
nents [3]. Th is theory is based on the Flory-Huggins the-
ory. According to the theory the enthalpy gained on
mixing polymers is inversely related to their number av-
erage molecular weights. Most polymer blends are im-
miscible, as the formation of two or more distinct phases
are usually evident. Disso lution, incorporation or abso rp-
tion phenomena do take place in any blend system. It
should be noted that the adhesion between the phases is
particularly important in the blending process because it
influences the mechanical properties of blends. The ma-
jor component forms the matrix or continuous phase
while the minor component forms the discrete phase.
Blends of PVC and ELNR have been of great interest to
researchers [3-5].
The present work involves the prep aration and ch arac-
terization of blends of PVC and ELNR-30. This has the
potential of plasticizing the vinyl chloride polymer. A
solution of PVC in 2-butanone is blended with ELNR-30.

Preparation and Properties of PVC/ELNR-30 Blends 197
PVC constitutes the continuous phase while ELNR-30 is
the discrete phase.
2. Experimental
2.1. Materials
PVC (k-value 65 and density 1.37) was produced by LG-
DAGU, China. LNR (MV 75,000) was prepared by the
depolymerization of natural rubber latex obtained from
the NIG 804 clonal series; the characteristics [6] of
which are given in Table 1. ELNR having 30 mol% ep-
oxidation (ELNR-30) was prepared by the epoxidation of
LNR. Phenylhydrazine (analytical grade) was made by
Fluka. 30% hydrogen peroxide was obtained from Merck.
98% formic acid; toluene and 2-butanon e were BDH Ltd
products. All chemicals were used as commercially sup-
plied.
2.2. Preparation of LNR
Three hundred milliliters of Natural Rubber Latex (20%
DRC), stabilized with Vulcastab LW (3% by weight of
DRC of natural rubber latex) was poured into a 1 L glass
reactor, equipped with mechanical stirrer, condenser,
dropping funnel and air inlet tube . After heating the latex
to 60˚C in a water bath, a desired amount of phenylhy-
drazine was slowly added and air was introduced into the
latex slowly to avoid frothing. The reaction mixture was
stirred for 3 h. During this period, depolymerization or
degradation of natural rubber latex to liquid natural rub-
ber (LNR) took place. About 10 mL of the reaction mix-
ture was taken at the end of the reaction for chemical
molecular weight determination. This was carried out
using a Ubbelohde-type viscometer.
2.3. Preparation of ELNR
Two hundred milliliters the LNR was cooled to room
temperature and diluted with 100 mL distilled water.
Thereafter 15 mL of 98% formic acid was added drop
wise. 61 mL of 30% H2O2 was slowly added after the
Table 1. Typical characteristics of latex from NIG 804.
Parameter
Total Solid Content (TSC) (%) 45.0
Dry Rubber Content (DRC) (%) 38.5
Mechanical Stability Time (MST) (sec) 550
Coagulum Content (%) 0.05
Sludge Content (%) 0.10
Volatile Fatty Acids (VFA) (%) 0.17
Source: Okieimen and Akinlabi, 2002, [6].
reaction mixture had been stirred for 15 min. The epoxi-
dation reaction was allowed to proceed for 3 h. At the end
of the reaction, the ELNR was soaked in 0.1 M Na2CO3
overnight in order to neutralize the epoxidizing acid. The
ELNR was recovered by precipitation in methanol and
the coagulum obtained was dried under vacuum at 50˚C.
2.4. Preparation of Blends
5% (w/v) solution of PVC in 2-butanone was blended
with 3% solution of ELNR-30 in 1:1 w/v (toluene/uta-
ne). PVC solution was added to the solutions of ELNR- 0
at different blend compositions. The blends were mixed
using mechanical stirrer (1 500 rpm) for 5 h at 50˚C and
cast on glass plates. The samples were dried under vac-
uum at 70˚C for 2 days to remove traces of residual sol-
vents.
2.5. Designation of Blends
The blends were designated as follows: PVC/ELNR-30
(90/10); meaning a blend of 90 parts of PVC and 10 parts
of epoxidized liquid natural rubber with 30 mol% epoxi-
dation. PVC/ELNR-30 (80/20); meaning a blend of 80
parts of PVC and 20 parts of epoxidized liquid natural
rubber with 30 mol% epoxidation.
2.6. Mechanical Tests
The tensile tests were carried out using Zwick material
testing machine (BTI-FBOO5TN.D14) on a dumbbell-
shaped samples at room temperature (30˚C). The load
cell for the machine was 1kN with a Crosshead speed of
100 mm/min.
2.7. Thermal Studies
Thermal properties of the blends were studied by heating
in an air circulating oven (200˚C) at different time inter-
vals. % weight-loss was recorded as a function of time
(minutes).
3. Analysis and Discussion
3.1. Tensile Properties
Analytical results of the tensile properties of PVC and its
blends are presented in Table 2. The tensile strength of
the PVC sample was 26.5 MPa while those of PVC/
ELNR-30 (90/10) and PVC/ELNR-30 (80/20) were 16.2
MPa and 11.8 MPa respectively. The same trend was
observed for Force at 50% Elongation. The implication
of these observations is that the strength of the materials
decreased with increasing ratio of ELNR-30. It worth
noting that the PVC/ELNR-30 (90/10) was unable to
attain 100% elongation. This could be attributed to insuf-
ficient amount of ELNR-30 in the composite leading to
low level of phase homogeneity. The same arguments

Preparation and Properties of PVC/ELNR-30 Blends 198
also accounts for its having the lowest Elongation at
break (48.7%) and Elongation at Maximum (5.2%). The
PVC/ELNR-30 (80/20) material exhibits the highest
Elongation at Maximum (289.1%) as against 134.4% for
PVC suggesting that replacement of 20 parts per hundred
(pphr) of PVC with ELNR-30 was sufficient to effect
plasticization of PVC.
3.2. Thermal Studies
Results of thermal stability in terms of percentage weight
loss on heating for PVC, PVC/ELNR-30 (90/10) and
PVC/ELNR-30 (80/20) are given in Table 3. It was ob-
served that thermal stability decreased with increase in
blend ratio of ELNR-30. Whereas both the upper service
temperature of natural rubber in intermittent and con-
tinuous usage are 100˚C and 80˚C respectively, PVC
degrades completely at about 250˚C; commencing with
elimination of HCL gas at much lower temperature [7].
Overlay plot of % weight loss against time of heating
(min) using JMP statistical software (version 3.25), pre-
sented in Figure 1, showed two distinct regions in the
graph for PVC/ELNR-30 (80/20) and PVC/ELNR-30
(90/10). This could be associated with the 2 phase nature
of the blend. The graph for PVC showed that degradation
increased steadily from 5.5 %wt loss at the 30 minute
mark up to 9.1 wt% loss at the 90th minute until the 150 th
minute. We are of the opinion that the 1st region of PVC
was associated with the elimination of HCL gas from the
molecule without scission of the main chain. The 2nd
region which remained virtually constant represented a
Table 2. Tensile data of PVC and its blends.
PVC PVC/ELNR-30 (90/10) PVC/ELNR-30 (80/20)
Tensile Strenght (MPa) 26.5 ± 0.5 16.2 ± 0.5 11.8 ± 0.4
Elongation at Break (%) 341.3 ± 0.5 48.7 ± 0.6 295.7 ± 0.5
Force at 50% Elongation (MPa) 16.3 ± 0.2 10.3 ± 0.2 7.2 ± 0.2
Maximum Force (N) 53.2 ± 0.4 19.3 ± 0.3 30.4 ± 0.3
Force at 100% Elongation (MPa) 17.2 ± 0.1 - 8.4 ± 0.1
Elongation at Maximum (%) 134.4 ± 0.2 5.2 ± 0.2 289.1 ± 0.2
Table 3. Thermal data of PVC and its blends.
Material Heating time (min) Initial wt. (g) Final wt. (g) wt. loss (g) wt% loss
30 0.1371 0.1282 0.0089 5.5
60 0.1216 0.1130 0.0089 7.1
90 0.1283 0.1179 0.0103 9.1
120 0.1213 0.1113 0.0100 9.2
PVC
150 0.0846 0.0764 0.0082 9.7
30 0.0671 0.0622 0.0049 7.3
60 0.0571 0.0528 0.0043 9.2
90 0.0600 0.0537 0.0063 10.5
120 0.0571 0.0506 0.0065 11.3
PVC/ELNR-30(90/10)
150 0.0966 0.0771 0.0195 20.2
30 0.1446 0.1300 0.0146 10.1
60 0.1621 0.1431 0.0190 11.7
90 0.1410 0.1220 0.0193 13.7
120 0.1484 0.1220 0.0264 17.8
PVC/sELNR-30(80/20)
150 0.1334 0.1046 0.0288 21.6

Preparation and Properties of PVC/ELNR-30 Blends 199
Figure 1. Overlay plots of % weight loss against heating
time (min) for PVC, PVC/ELNR-30 (90/10); PVC/ELNR-30
(80/20).
situation where almost all the HCL gas in the sample was
eliminated and further loss of weight could not occur
since a temperature of 250˚C had not been attained.
4. Conclusions
The study has shown that in corporation of ELNR-30 in to
PVC at a blend ratio of 20 pphr had a plasticizing effect
on the polymer blend [PVC/ELNR-30 (80/20)]. Thermal
stability of the blend was inferior to that of the unblended
PVC. A further study on the properties of the blends is
ongoing.
5. Acknowledgements
The authors are grateful to the Executive Director and
Management of the Rubber Research Institute of Nigeria
(RRIN), for access to equipment and other laboratory
facilities throughout the period of this study.
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