Study on the Damping Mechanism of Chlorinated Butyl
Rubber/C5 Petroleum Resin Composites by Experimental
and Molecular Dynamics Simulation
C Yin, J Zhu, L Lu, M F Wang, Q Zhang and S Z Wu
*
College of Materials Science and Engineering, Beijing University of Chemical
Technology, Beijing 100029, P. R. China
Abstrac t. In this work, the damping mechanis m of C5 petroleum resin/chlorinated butyl
rubber (CIIR) composites were studied by combin ing experimental and mo lecular dynamics
(MD) simu lation. From a macro perspective, the damping parameters (glass transition
temperature T
g
and effective da mp ing temperature region ΔT) and the activation energy (E
a
)
were obtained by dynamic mechanical thermal analysis. In the micro level, four
intermolecular interaction parameters (binding energy E
binding
, fractional free volume, mean
square radius of gyration and mean square displacement) were calculated by molecular
dynamics simulations. These studies are expected to provide the useful information in
understanding the damping mechanism and to offer the theoretical guidance for optimizing
the damping properties of polymer composites.
1. Introduction
In the past decades, how to effectively reduce the noise pollution or mechanical vibration has become
a hot topic[1]. Viscoelastic polymer used as damping materials have attracted a considerable
attention for converting vibration or noise energy to heat energy. As we know, the excellent damping
materials should have suitable glass transition temperature which is better close to application
condition and also should be with the wide effective damping temperature region.
Comparing with other polymer matrices, the chlorinated butyl rubber (CIIR) has preferable
damping properties due to its dense side methyl groups, lower molecular mobility and higher energy
loss. According to reports in the literature[2], CIIR shows a unique relaxation behavior which are the
asymmetrical double-peak structure with a maximum on the high temperature side and the additional
shoulder on the low temperature side. Plazek [3] and Huang[4, 5] examined that different modes of
CIIR molecular motion contribute to the transition region from local segmental motion, sub-Rouse
mode, and Rouse mode. However, the loss peaks of the above three modes of CIIR molecular motion
are located at lower temperature region rather than room temperature. Therefore, in order to broad
the effect damping temperature region of CIIR composites, many ways have been attempted such as
blend modification, copolymerization, gradient polymers, interpenetration network (IPN) polymers
etc[6].
644
Yin, C., Zhu, J., Lu, L., Wang, M., Zhang, Q. and Wu, S.
Study on the Damping Mechanism of Chlorinated Butyl Rubber/C5 Petroleum Resin Composites by Experimental and Molecular Dynamics Simulation.
In Proceedings of the International Workshop on Materials, Chemistry and Engineering (IWMCE 2018), pages 644-650
ISBN: 978-989-758-346-9
Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

Hindered phenols or hindered amines [6] often be used to improve the damping properties of
composites. For example, Yang [7] investigated that hindered phenol AO-80 effectively improved
the damping performance of hindered phenol/polyacrylate hybrids. However, the method of
modifying with small polar molecules also has many shortcomings, such as the easy migration of
small molecule [8], which makes the loss factor tan δ decrease, and consequently the damping
properties of composites fall off. Meanwhile hindered phenols are also relatively expensive. Such as
the price of C5 petroleum resin (Puyang Ruisen Petroleum Resin Factory (China)), which can also
effectively improve the damping properties, is just 3.9 dollar per kilogram in 2017 for reducing the
costs drastically. The C5 petroleum resin is a kinds of amorphous polymers with low molecular
weight (from 300 to 3000) and the glass transition temperature region is located near the room
temperature which shows the capacity to improve the damping performance of rubber composites in
practical application. Wu and co-workers investigated the CIIR/C5 petroleum resin composites with
different contents, the glass transition temperature increased and the effective damping temperature
range was successfully broadened[9,10]. However, the mechanisms for improving the damping
performance is not very clear, some microscopic parameters (such as the interactions and mobility of
the molecular chains) cannot be obtained. With the development of computational technology, the
molecular simulation has provided an effective tool to figure out the microstructural and the
properties of materials at a molecular level. Therefore, in this work the molecular dynamics
simulation is introduced to study the damping mechanism of C5 petroleum resin/CIIR composites.
2. Simulation results and analysis
The construction procedure of the C5 petroleum resin/CIIR composites cells is shown in Figure 1.
The chlorinated isoprene repeat unit, isobutylene repeat unit and isoprene repeat unit were first
randomly copolymerized as a CIIR polymer chain. Subsequently, 500 ps of NVT simulation was
performed at 298 K and 1000 ps of NPT simulation is performed at 0.1MPa pressure to further relax
the polymer chain structure.
Figure 1. Construction procedures of C5 petroleum resin/CIIR systems for MD simulation.
Study on the Damping Mechanism of Chlorinated Butyl Rubber/C5 Petroleum Resin Composites by Experimental and Molecular Dynamics
Simulation
645

The binding energy (E
binding
) is introduced to investigate the influence of intermolecular
interaction on damping properties. Table 1 shows that with increasing content of C5 petroleum resin,
E
binding
increases gradually, which indicates that the intermolecular interactions between CIIR and C5
petroleum resin are constantly increased. Meanwhile, the binding energy is always kept the positive
value which indicates good compatibility in the C5 petroleum resin/CIIR system [11].
Table 1. Binding energy with different C5 petroleum resin contents.
Mass ratio of
C5 petroleum resin/CIIR
E
total
(kcal mol
-1
)
E
C5 petroleum resin
(kcal mol
-1
)
E
CIIR
(kcal mol
-1
)
E
binding
(kcal mol
-1
)
0/100
443.010
0
443.010
0
10/100
-702.808
52.718
-616.450
139.116
20/100
-1290.370
61.386
-1147.060
204.696
30/100
-766.773
90.170
-576.742
280.160
40/100
-1285.420
136.328
-1052.340
369.408
50/100
-1345.920
137.939
-1042.420
441.438
The fractional free volume (FFV) [11] may be used to reflect the efficiency of chain packing in
C5 petroleum resin/CIIR systems which the results are shown in Figure 2. With increasing content of
C5 petroleum resin, the FFV decreases since the stronger intermolecular interaction causes close
packing of molecular chains, shortens the interspace and increases the friction between the molecular
chains, which is resulted the enhanced damping performance.
The mean square displacement (MSD) may be used to describe the activities of the molecular
chain[12]. Figure 3 was the simulation result of MSD. With the increase of C5 petroleum resin
content, the MSD of CIIR chains gradually decreases, which means the movement of CIIR chains
becomes more difficult, and the glass transition temperature (T
g
) of C5 petroleum resin/CIIR systems
should move towards high temperature direction.
The radius of gyration is a parameter commonly used to describe the size of a random polymer
chain. The polymer chain is more flexible with smaller R
g
[13]. Figure 4 shows that the mean square
radius of gyration of CIIR chains with different C5 petroleum resin content. It was noted that as the
content of C5 petroleum resin increases, the mean square radius of gyration of CIIR chains gradually
enhances. This is because with the increase of C5 petroleum resin content, the intermolecular
Figure 2.The fractional free volume
(FFV) of C5 petroleum resin/CIIR
composites with different C5
petroleum resin content.
Figure 3.
The mean square displacement
(MSD) of CIIR chains with different C5
petroleum resin content.
IWMCE 2018 - International Workshop on Materials, Chemistry and Engineering
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interaction between C5 petroleum resin and CIIR gradually increases and there are good
compatibility between these two, which the CIIR chains becomes more stretched resulting in
increasing values of the mean square rotation of CIIR chains and the activity of the CIIR chains falls
off. This result is consistent with the previous MSD effects.
Figure 4.The mean square radius of gyration of CIIR chains with different C5 petroleum resin
content.
3. 3. Experiments and results
3.1.1. Materials and sample preparation. The chlorinated butyl rubber (CIIR, product code: 1066)
with a chlorination concentration of 1.2% is purchased from Japan Synthetic Rubber Co. (Japan).
The C5 petroleum resin is from Puyang Ruisen Petroleum Resin Factory (China). The composites
were prepared according to the following procedures: (1) the CIIR matrix was first plasticized on a
Φ152.4 mm two-roll mill at room temperature for 4 min. Then the C5 petroleum resin was added to
CIIR with mass ratio of 0/100, 10/100, 20/100, 30/100, 40/100, 50/100 respectively, which is as same
as the mass ratio to build the amorphous cell in MD simulations. (2) the blends were mixed on a two-
roll mill at room temperature for 5min with compounding and crosslinking additives (including 5.0
phr of zinc oxide, 1.0 phr of stearic acid, 1.5 phr of tetramethylthiuram disulfidee, 3 phr of 2,2'-
dibenzothiazoledisulfde and 2.0 phr of sulfur). (3) the composites were hot-pressed and vulcanized at
160 °C under the pressure of 15 MPa and then make the samples cool down to room temperature.
3.1.2. DMA analysis of C5 petroleum resin/CIIR composites. The damping properties and the
changes of molecular dynamics of polymer of C5 petroleum resin/CIIR have been studied by DMA
experiments [14]. The damping performance is shown in Figure 5(a). It shows that the T
g
and ΔT
increase gradually with increasing C5 petroleum resin content. Generally, the T
g
values of CIIR can
be extracted from the peak temperatures in the tan δ curves. But it is found that the tan δ curve of
CIIR displays an asymmetrical peak with a shoulder peak at about -38°C and a maximum peak at -
22°C . According to reports in the literature [15], tan δ curve may be divided into three peaks which
can be correspond to the local segmental, sub-Rouse mode and Rouse mode peaks respectively. The
local segmental, which is a cooperative motion of neighboring chains each involve several repeat
units, is the enthalpic and related with the glass transition temperature. Meanwhile the Rouse mode,
which is based on the motions of Gaussian sub-molecules formed by sufficient number of repeat
units in each chain, is entropic in nature. As Figure 5 shows that both the maximum and the shoulder
of the tan δ peak of CIIR move to the higher temperature with the increase of C5 petroleum resin
content, which indicating C5 petroleum resin limits the space for CIIR due to intermolecular
interaction between C5 petroleum resin and CIIR. Meanwhile, it is noted that C5 petroleum resin
Study on the Damping Mechanism of Chlorinated Butyl Rubber/C5 Petroleum Resin Composites by Experimental and Molecular Dynamics
Simulation
647

limits these two relaxation modes (local segmental motion and Rouse modes relaxation) to different
extents.
(a) (b)
Figure 5.(a) Temperature dependence of loss factor (tan  ) for C5 petroleum resin/CIIR composites,
and (b) Peak position of different modes of C5 petroleum resin/CIIR composites with different C5
petroleum resin content.
The activation energy (E
a
) is introduced to quantify the internal friction. According to the storage
modulus (E’)–temperature curves presented in Figure 6 (a). E
a
can be calculated through the
following Arrhenius-type equation [16]:
00
11
exp[( ( )]
a
E
E
E R T T


(1)
Where E’ is the storage modulus at temperature T, E
0
is the storage modulus at reference
temperature T
0
and R is the universal gas constant. Based on Eqn (1), the logarithm of the storage
modulus is almost linear with the inverse temperature, which the result is shown in Figure 6 (b). It
can be seen that the E
a
is almost proportional to the slope of the straight line. For the 50/100 system,
the deviation occurs at a low temperature which may be owed to aggregations of the C5 petroleum
resin. Table 2 listed the results of the E
a
, showing that E
a
of CIIR chains increase gradually with
increasing C5 petroleum resin content. It indicates that more energy is required to overcome internal
friction of CIIR chains, which is consistent with the result of MSD.
(a) (b)
Figure 6.(a) Storage modulus in temperature sweep for C5 petroleum resin/CIIR composites, and (b)
logarithm of storage modulus against inverse temperature for C5 petroleum resin/CIIR composites.
IWMCE 2018 - International Workshop on Materials, Chemistry and Engineering
648

Table 2.Damping properties of CIIR and C5 petroleum resin/CIIR composites
Mass
ratios of
C5 petroleum
resin/CIIR
tan δ
max
tan δ > 0.3
Value
T
g
(°C)
T
1
a
(°C) T
2
a
(°C)
ΔT
a
(°C) E
a
(kJ mol
-1
)
0/100
1.56
-22.00
-57.70 29.45
-54.10 38.25
-50.35 45.60
-45.35 52.10
-44.50 56.45
-39.45 62.40
87.15 1.53
10/100
1.45
-13.30
92.35 2.70
20/100
1.31
-8.40
95.95 3.38
30/100
1.35
-4.60
97.45 4.32
40/100
1.32
1.40
100.95 4.86
50/100
1.31
6.70
101.85 7.27
a.T
1
, T
2
is the starting and ending temperatures with the loss factor tanδ 0.3 range. ΔT is the difference value
from T
1
to T
2
.
4. Conclusions
The damping mechanism of C5 petroleum resin/CIIR composites was studied by combining
experimental and molecular dynamic simulations. With the increase of C5 petroleum resin content,
the damping parameters (T
g
and ΔT) gradually increase, which shows C5 petroleum resin improve
the damping performances of the composites. As the two relaxation processes need different free
volume, the local segmental motion and Rouse mode have different responses to the space limited
from DMA experiments. The simulation parameters (FFV, MSD) are getting smaller, which shows
the C5 petroleum resin plays a key role like anti-plasticizer in decreasing the free volume fraction of
the blends. The presence of C5 petroleum resin slightly confines the molecular mobility of the local
segmental motion of CIIR, but greatly confines the molecular mobility of Rouse mode of CIIR.
Acknowledgements
The authors acknowledge the National Natural Science Foundation of China (Grant No. 51473012).
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