Dissertation summary: Study on preparation and properties of rubber nanocomposites material based on some kinds of rubber and its blend with carbon nanotubes

VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY

……..….***…………

CHU ANH VAN

STUDY ON PREPARATION AND PROPERTIES
OF RUBBER NANOCOMPOSITE MATERIALS
BASED ON SOME KINDS OF RUBBER AND ITS
BLENDS WITH CARBON NANOTUBES

Major: Organic chemistry
Code: 62.44.01.14

SUMMARY OF CHEMICAL DOCTORAL THESIS

Ha Noi – 2016


A: Overview of the thesis
1. Problem statement
Since having been discovered, carbon nanotube (CNT) is always
a hot topic attracting many researches and practical applications by its
outstanding mechanical-physical-chemical properties. CNT is known
for its high flexibility, low density and high specific surface.
Therefore, many real experiments have shown that this material has
high modular… and durability, and the results of thermal
conductivity, electrical conductivity of polymer nanocomposite
manufactured on the basis of CNT are also very noticable. However,
CNT requires an appropriate dispersion method to avoid being rolled

and sticked together. To increase the ability to link between the CNT
and the polymer substrate, researchers have offered some measures
such as changing the fabrication method or using a combination of
auxiliary materials…, but the additional functional groups attached to
the surface of CNT is more popular. This means that generating the
functional groups which react or physically interact with the polymer
substrate; thus, it can improve interfacial interaction between the CNT
and the substrate, as well as enhance thermodynamic capacity of the
nanotube with the polymer substrate.
Currently, that nanotechnology has become a develpoment
strategy on which researches of different science fields focus like
materials, electronics and biomedical attracts large investments. In our
country, the studies on the applications of CNT to nanocomposite
technology as well as to rubber and plastics industries have already
implemented at the level of exploration. So far, no research on this
field is applied to real production, but only one research result has
been published in journals and conferences. Vietnam has an abundant
human resourses and rational treatment policies so that many large
electronic firms like Samsung and Canon have built pretty many
manufacturing and assembly companies in many industrial areas. The
development of electronic industry leads to the demand for anti-static
mats spread on the assembly-tables in order to avoid conflicts of
unwanted currents with IC, boards in particular and electronic
products in general. Besides, textile industry and atomic explosive
industry also have a high demand for anti-static. Therefore, the study
of fabrication and application of rubber material CNT/nanocomposite
that has not only mechanical durability, abrasion resistance but also
1

anti-static ability is necessary because it brings about high scientific
and practical values. Derived from these reasons, the thesis aims to the
issue: “Study on preparation and properties of rubber
nanocomposites material based on some kinds of rubber and its
blend with carbon nanotubes” as the subject of research.
2. Objectives of research and its content
The objective of the research is to assess the reinforcement
possibility of CNT in the rubber substrate and blend rubber in order to
create rubber nanocomposite materials with a high mechanical
properties, sustainability in the solvent, and suitable electrical
conductivity.
The content of the research:
- Study on the denatured surfaced CNT by various methods.
- Study on the reinforcement possibility of CNT and dispersion
auxiliaries, compatible origin of vegetable oils with natural rubber
(NR).
- Study on manufacturing rubber nanocomposite and its properties
based on the blend of NR/NBR with CNT.
- Study on manufacturing rubber nanocomposite and its properties
based on the blend of NR/CR with CNT.
- Study on the possibility of manufacturing anti-static mats made from
rubber/CNT nanocomposite.
3. Contributions of research
- The carbon nanotubes were denatured by using some organic factors
such as: 24,85 phr bis-(3-triethoxysilylpropyl) tetrasulfide; 3,29phr
polyethylene glycol, 23 phr polyvinyl chloride, which was a basis of
creating rubber nanocomposite.
- Sucessfully manufactured NR/ NBR materials reinforced 4% CNT
or 3% modified CNT, in which CNT-PVC was well compatible with
the NBR substrate.

- Sucessfully manufactured NR/ NBR materials reinforced 4% CNT
or 3,5% modified CNT, in which CNT-TESPT dispersed best in the
NR/CR substrate.
- By the semi-dry method, CNT (CNT-Nanocyl và CNT-Vast) was
dispersed in the substrate of rubber blend based on NR/CR regularly
and isotropously. Besides, applying experimental planning and
building a regression equation to identify the optimal levels of
reinforcement of CNT in the NR/CR substrate quite fitted the results
obtained.
2


- The rubber nanocomposite materials on the basis of NR/CR
reinforced CNT had electrical conductivity that was suitable to
creating anti-static mats.
4. The thesis structure
The research includes 140 pages with 23 tables, 53 figures, 120
references.
The thesis structure:
 Introduction (2 pages)
 Chapter 1: Overview (38 pages)
 Chapter 2: Materials and research methodology (11 pages)
 Chapter 3: Results and discussion (72 pages)
 Chapter 4: Conclusion (2 pages)
 The publications relating to the thesis (1 page)
 References (14 pages)

B: Content of the thesis
Introduction
The introduction mentions the scientific and practical meaning,

then set targets and research content of the thesis.
Chapter 1: Overview
The overview sythesizes materials inside and outside the country
relating to the topic of the thesis such as:
 Nanocomposite materials, nanocomposite rubber with its
classification, its specific advantages and disadvantages.
 Carbon nanotubes and four methods of surface denaturation,
which also indicate that the denaturation method for packaging
the molecular is not applied in nanocomposite rubber
manufacturing technology.
 The situation of CNT applications in nanocomposite rubber
technology.
Some points left open are also the thesis objectives.
Chapter 2: Materials and research methods
2.1. Raw materials and chemicals
 Carbon nanotubes multi wall: NC7000 Nanocyl S.A. ( Kingdom
of Belgium), 95% purity, size 10- 15 nm.
 Bis- (3- trietoxysilylpropyl) tetrasunfide (Si 69. TESPT), China:
the transparent yellow liquid, fat-soluble and aromatic as
alcohol, ether, keton. Boiling point: 250°C, density: 1.08.
3


 Polyetylenglicol: PEG 6000 (BDH Chemicals Ltd company
Poole-UK), the melting temperature of 61°C.
 Polyvinylclorua: 710 SG Vietnam, a white powder, size: 20-150
micrometers, specific mass: 0,46- 0,48g / cm3.
 D01: refined tung-tree oil, yellow liquid, the proportion (at
20°C): 1.500 to 1.520, acid index: 1.4; iodine index: 149.5 to
170.58; soap index: 193.38 to 196.73.

 Cetyl trimetylamoni bromua (CTAB): Merck (Germany), M =
364.46g / mol, purity & gt; 97%.
 Pure AlCl3: Merck (Germany).
 Natural Rubber (NR): SVR- 3L, Viet Trung rubber company,
Quang Binh.
 Natural Rubber Latex: type pH & gt; 7; Dry content 60%, Phuoc
Hoa Rubber Company, Vietnam.
 Nitrile rubber (NBR): Kosyn- KNB35, Korea, containing
acrylonitril 34%.
 Clopren Rubber (CR): Baypren® 110 MV 49 ± 5, Lanxess.
 Vulcanizing additives include:
+ Sulfur, Sae Kwang Chemical Ind firm. Co. Ltd. (South Korea)
+ Indian Zinc Oxide Zincollied
+ Stearic acid, PT. Orindo Fine Chemical (Indonesia)
+ Accelerators DM (Dibenzothiazolil disunfit), China
+ Accelerators D (N, N-diphenyl guanidine), China
+ Aging antioxidants D (Phenyl β-naphtylamin), China
 Other chemicals
Hydrochloric acid, toluene, KOH, iso-octane, ethanol 96%, acid
acetic, DMF, petroleum ether, SOCl2, H2O2, NH3, tetrahydrofuran
(THF), chloroform (CHCl3), CaCl2, acetone, petroleum ether of China.
2.2. Process of denaturing CNT surface and manufacturing
rubber nanocomposite material reinforced-CNT
2.2.1. Denaturing CNT surface by Fischer esterification reaction
The residual metal is removed from CNT by being soaked with
special HCl and stirred for 2 hours at 50° C under a normal condition,
washed several times with distilled water until pH = 7, dried for 12
hours, signed p-CNT. Disperse 0,3g p-CNT in 25ml mixture of
NH4OH and H2O2 (1: 1). Stir the mixture for 5 hours at 80°C under
normal pressure. Mixed product is filtered by a PTFE membrane

(capillary size: 0.2 micron), washed with distilled water in neutral
4


environment and cleaned by acetone several times. The denatured
product (CNT-COOH) is dried for 48 hours at 80°C.
- Chlorinated CNT
Put 0,5gam CNT-COOH into a flask 100ml with 20ml SOCl2
and 10ml DMF available inside, and stir under a normal pressure for
24 hours at 70°C. By the end of the reaction will be a dark brown
mixture CNT-COCl, filter and wash with THF and dry at normal
temperature.
- Synthesis of CNT-PEG
Melt 1g PEG at 90°C, then put into a flask containing 0,1g CNTCOCl, stir for 10 minutes, then add the 40ml mixture of benzene/THF
(3:1). Conduct the reaction at 80°C in 40 hours. When the reaction
ends, put the mixed product in ultrasonic vibration for 30 minutes at
60°C, speed 3000 rpm, then filter it through the PTFE membrane, the
mixed black solid is washed with acetone and petroleum ether 3 times,
dry at 90°C for 12 hours.
- Synthesis of CNT-TESPT
5ml TESPT hydrolyzed in 20ml C2H5OH 96°, 10ml distilled water
and 5ml NaOH 10% at 50°C for 2 hours, conduct to remove the
solvent, then the yellow solid TESPT-OH is dried at 50°C for 4 hours
[106]. Put 0.1g CNT-COCl and 1g TESPT-OH into a flask 100ml
with 30ml anhydrous C2H5OH available inside, start to stir for 5 hours
at 60°C, the mixed product is put in ultrasonic vibration for 60
minutes at 60°C, speed 6000 rpm, then filtered by the PTFE
membrane, washed many times with hot water to remove residual
silane components, dried and washed with acetone. The last product is
vacuum-dried at 60°C in 5 hours.

2.2.2. Alkylize CNT surface
Put 0.2g CNT and 0.5g PVC into a 3-neck flask with 30ml
anhydrous CHCl3 available inside, the flask is connected to a canister
of anhydrous CaCl2 and another pipe embedded in NaOH liquid 10%
to remove HCl released during the reaction. Add 0.5 g AlCl3, and mix
in nitrogen environment at 60°C for 30 hours. After cooling the
mixture down to the normal temperature, the CNT-PVC product is
stirred in ultrasonic vibration in the tetrahydrofuran solvent (THF) for
10 minutes, filtered and washed several times with petroleum ether
and acetone, dried at 60°C in 10 hours.
2.2.3. Denatured by surfactants
5


Fuse 0.1g CTAB, then absorb 1g CNT, place in a warm cabinet
at 60°C for 72 hours. Put 0.1g CTAB into 50ml distilled water and stir
for 1 hour at normal temperature, add more 1g CNT and continue to
stir for 1 hour. Add 50ml distilled water, and put the mixture in
ultrasonic vibration at 60°C for 2 hours. Dry the last mixture at 60°C
in 12 hours.
2.2.4. Method of creating a rubber nanocomposite sample
2.2.4.1. Sample NR/CNT
CNT and NR components are presented in the following table:
Table 2.1. CNT and NR components of researched samples

Ingredients

Content (%)

NR

100
Zinc oxide
4,5
Aging antioxidants A
0,6
Aging antioxidants D
0,6
Stearic acid
1
Accelerators D
0,2
Accelerators DM
0,4
Sulfur
2,0
D01
1-4%
CNT
1-5%
2.2.4.2. Rubber blend sample based on NR
Based on the mixing from NR, the thesis surveyed the effects of
CNT content (denatured or not denatured) on the properties of blend
system NR/NBR 80/20 and NR/CR 70/30 with the following process:
(the sign CNT in this process for both CNT that is denatured and not
denatured)

6


natural rubber

NR or CR
mixer 10 minutes
CNT or CNT/ethanol

mixed

mixer
0
produc 1 8 minutes, 75 C, 50 rpm

ZnO, acid, Antioxidant
produc 2
3 minutes, 500C, 50 rpm

S, accelerator

semi-produc

sheet
20-25 minutes, 1450C

vulcanization

nanocomposite

Figure 2.2. The chart of creating nanocomposite / CNT rubber
To study the possibility of dispersing CNT in a polymer
substrate, the thesis uses 3 different methods such as mixing the
solution, using surfactants or compatible auxiliaries (the additive

content, closed mixing conditions as well as vulcanization are
constant) follow the process:
NR, CR
Toluen, 96 hours

CNT/toluen
ultrasonic, 2 hours

mixer 3 hours, 500C
masterbatch
mixer

D01

(a)

CNT
600C, 72 hours
mixer 3 hours, 500C
CNT/D01

NR

CR

mixer

(b)
7

CNT

CTAB/H2O
mixer, 1 hour
ultrasonic, 2 hours
CNT/CTAB

latex natual rubber
mixer, 3hours, 500C

masterbatch

CR
mixer

(c)
Figure 2.3. Optimizing the CNT dispersion conditions in NR / CR
substrate: the solution method(a), using dispersion auxiliaries (b),
using cationic surfactant (c)
2.2.5. Research methods of structure and properties of denatured CNT
The structure and properties of denatured CNT are determined
by means of Infrared Radiation (IR) on the FTS-6000 P (Biorad,
USA), Raman radiation method with a HR LabRAM 800 (France),
UV -vis on SP3000 nano (Japan) and Thermal Gravimetric Analysis
method on Setaram (France), heating rate is 10°C/ minute in the
atmosphere, the temperature range from 25°C to 800°C.
The image of a denatured CNT is researched on its
morphological structure by means of Transmitting Electron
Microscope (TEM) on JEOL 1010 (Japan).

2.2.6. The method of determining the structure and properties of
materials
Determination of tensile strength, elongation of the blend rubber
material sample follows the standard TCVN 4509 – 2006.
Determination of hardness (Shore A hardness) of the blend rubber
materials follows TCVN 1595-1 : 2007. Determination of abrasion
(Acron) of materials follows TCVN 1594 – 87. Determination of
aging factor follows TCVN 2229-2007. Determination of the swell of
the blend rubber materials in toluene solvent: iso-octane follows
TCVN 2752 - 2008. Studying morphological structure of materials by
means of Field Emisson Scanning Electron Microscope (FESEM) and
thermal stability of materials by Thermal Gravimetric Analysis
(TGA).
8


Chapter 3 - RESULTS AND DISCUSSION
3.1. Denature carbon nanotubes surface
3.1.1. The study on the process of the carbon nanotubes oxidation
Raman radiation results:

Figure 3.3. CNT and CNT Raman oxidation
The increase in intensity ratio ID / IG proved that there was a
change in the CNT structure corresponding with the process of
transforming Csp2 into Csp3 by oxidation to successfully attach
COOH group to the CNT edge. Attaching this functional group
increases CNT’s size significantly.
a

Figure 3.5. TEM of CNT (a) and CNT- oxidation (b)

TGA result showed that about 27.85% COOH and NH2 are
attached successfully during oxidation process.
3.1.2. Fischer esterification reaction with TESPT and PEG
On the Raman spectrum, it can be seen that the ratio ID/IG
increased from 1.7 to 2.05 (CNT-PEG) and to 2.0 (CNT-TESPT),
which means that increased the degree of chaos of the graphite during
denaturation.
The TEM image showed that the sizes of CNT-TESPT and
CNT- PEG increased to about 25 and 30nm, respectively. The content
of the Ester functional group is determined by means of TGA, the
results are shown in Table 3.1 below:

9


Table 3.1. TGA analysis results of the CNT-PEG and CNT- TESPT
The starting The
The
Weight
Material
temperature of maximum
maximum
loss to
samples
decomposition temperature of temperature of 750oC
decomposition decomposition
1
2
0
0

CNT
500 C
577 C
53,67%
0
0
0
CNT-PEG 400 C
443 C
607 C
78,52%
0
0
0
CNT400 C
441 C
687 C
56,96%
TESPT
3.1.3. CNT denatured by polyvinylclorua
CNT’s structure composed of many atoms C sp linked together to
form an equilateral hexagon which are nearly like the benzene circle.
Therefore, the implementation of a reaction between polyvinylclorua
and CNT with anhydrous AlCl3 as a catalyst is determined by the
mechanism of the alkylized Fridel- Craft reaction as follows:
2

(CH2

CH)

n + AlCl3

Cl

(CH2
CHCl3

CH)

n
AlCl4
CH2

+

(CH2

CH) n
AlCl4

CH
CHCl3
Cl

From the result of Thermal Gravimetric Analysis, we could
identify the content of PVC attached to CNT surface is about 23% by
weight (at 400°C). That PVC was attached to CNT edge successfully
increased its size to about 25nm.
3.1.4. CNT denatured by surfactants

As we know, CNT was completely insoluble in water despite
under the ultra-sound condition for a long time, so it can not obtain the
signals in the visible light area . Conversely CNT/CTAB can be fully
dispersed in water, so the signal UV-vis can be obtained in the 200800nm waveband.
Two characteristic absorption peaks in the area of 240- 265 cm-1
*
are corresponding to the shift of the electron π 
 π of conjugate
atom Csp2.
10


TGA results of CNT- CTAB sample is shown in Figure 3.18.

Figure 3.18. TGA schema of CNT-CTAB
Thus, it is possible to estimate that about 17% CTAB are
absorbed at 300°C
3.2. Research on manufacturing and material properties of
NR/CNT by means of melting mixing.
The thesis surveyed CNT content and dispersion auxiliraries,
D01. The results are presented in Table 3.2 and 3.3 below:
Table 3.2. Effects of CNT content on the mechanical properties of the
material on the basis of NR and additives
CNT
content
(%)
0
1
3
5

7
10

Tensile
strength
(MPa)
14,14
15,25
16,03
17,92
16,94
15,96

Elongation
(%)

Abrasion
(cm3/1,61km)

Hardness
(Shore A)

920
900
860
860
820
600

0,93

0,85
0,81
0,75
0,79
0,86

42
44
45
46
47
50

Table 3.3. Effects of D01 content on the mechanical properties of NR /
5% CNT
Content D01 Tensile
(%)
strength
(MPa)
0
17,92
1
18,89

Elongation
(%)

Abrasion
(cm3/1,61km)

Hardness
(Shore A)

860
870

0,75
0,70

46
45,9

11


2
3
4

20,13
19,24
17,03

890
915
940

0,63
0,60
0,58

45,5
44,6
43

- Optimal content of CNT that are reinforced for NR is 5% by weight
(compared to NR). In this denaturation ratio, materials have superior
mechanical properties rather than control samples such as tensile
strength increased by 27%, the starting temperature of decompositon
increased by 7°C, the maximum temperature of decomposition
increased 5,4°C, the aging factor of the material in the environment
also increased significantly.
- With 2% more dispersion auxiliaries, compatibility (D01) made
materials structure tighter and steadier, increased mechanical
properties, thermal durability as well as environmental durability of
the material.
3.3. Research on manufacturing and material properties of NR /
NBR / CNT samples by means of wet mixing
3.3.1. Influences of CNT content on mechanical - thermal properties
of NR / NBR.
Based on the research results of Ngo Ke The and his colleagues
on creating the NR / NBR blend system, the ratio of 80/20 was chosen
to study the reinforement possibility of CNT.
Mechanical properties of NR / NBR reached the maximum value
with 4% CNT content or 3% denatured CNT content. At these levels,
the CNT (not denatured and denatured) has significantly improved
thermal durability of the materials. CNT- PVC interacted well with
the NR / NBR substrate rather than CNT-PEG. Therefore, NR / NBR /
CTN-PVC sample had mechanical properties and thermal stability that
were higher than NR / NBR / CNT- PEG sample.

Figure 3:24. Effects of reinforcing substances content on the
elongation of the materials NR/NBR/CNT
12


That denatured CNT was easily compatible with the polymer
substrate improved mechanical properties of the materials more
clearly than non-denatured CNT. CNT-PEG had hydrogen-bonded
with the rubber substrate as the following model [93]:

Despite not having too much differences, CNT- PVC had higher
mechanical properties than CNT- PEG. This could be explained by the
well compatibility between PVC and NB so that the presence of PVC
on the surface (as well as partially absorbed in the process of
denaturation) made CNT-PVC be compatible with the rubber substrate
better. Therefore, the mechanical properties of the material were
improved better.
Denatured CNT made the structure of the material tighter and
steadier, which increased the environmental durability: the aging
factor in the air and salt water was high, the solvent durability was
improved.

Figure 3:29. Morphological structure of reinforced materials
NR/NBR: CNT (a), CNT-PVC (b), CNT- PEG (c)

13


Table 3.9. Aging factor of NR/NBR/CNT materials at 70°C during 72

hours
Samples

Aging factor in the Aging factor in salt
air
water

NR/NBR

0,82

0,8

NR/NBR/4%CNT

0,89

0,87

NR/NBR/3%CNT-PVC

0,91

0,89

NR/NBR/3%CNT-PEG

0,9

0,88

Độ trương

240
220
200
180
160
140
120
100
80
60
40
20
0
0

8

16

24

32

40

48

56

64

72

Thời gian (giờ)
CSTN/NBR/CNT

CSTN/NBR/CNT-PVC

CSTN/NBR/CNT-PEG

CSTN/NBR

Figure 3:30. The swell levels of NR/NBR reinforced CNT solvent
3.3.2. Influences of carbon nanotubes on vulcanization of the NR/NBR
materials
Mechanical properties of the materials are also presented in the
perspective of vulcanization. Selecting right vulcanization conditions
would increase the durability of technical rubber. The survey result of
the CNT’s influence on the process of vulcanization NR/NBR blend is
shown in Table 3.8.
Table 3.8. Effects of CNT on the process of NR/NBR blend
vulcanization
Mmin
Samples
(kgf.cm
)
NR/NBR/CNT

0,2
NR/NBR/CNT-PVC 0,17
NR/NBR/CNT-PEG 0,16

Mmax
(kgf.cm
)
4,75
5,26
4,83
14

Ts1
(min:sec)

Tc90
(min:sec)

02:19
02:42
02:26

7:57
8:55
7:51


The minimum value of torque presented softness or flexibility of
rubber in soft initial state. The results showed that in which sample
containing CNT, Mmin was highest. This was appropriate because

CNT had no strong polarized groups, so the possibility to mix with the
blend system containing polar rubber NBR decreased. Meanwhile,
samples containing PVC and PEG, the occurrence of polar functional
groups like Cl, NH2, OH will increased the ability to blend.
The maximum value of torque was often related to chemical
bonding or crosslinking density. This value of the samples containing
CNT-PVC was higher, corresponding to the hardness of the samples
containing CNT-PVC was also higher. By that time, S-S bonding of
sulfur reached the highest point.
Vulcanization time Tc90 of the samples containing PEG was
lowest because CNT-PEG contains a NH2 group which was an agent
to boost the process of vulcanization. The pretty high Tc90 value of
the samples containing CNT-PVC was also an obstacle to the process
of manufacturing products.
3.4. Research on manufacturing and material properties of NR /
CR / CNT by means of wet mixing
3.4.1. Effects of CNT on the NR / CR vulcanization
Based on the research results of Do Quang Khang and his
colleagues on creating the NR / CR blend system, the ratio of 70/30
was selected to study the reinforcement possibility of CNT by means
of wet mixing with CNT/ ethanol. They have studied of the possibility
of vulcanization of the material samples containing CNT and
denatured CNT. The maximum and munimum values of torque,
vulcanization time 90% (Tc90) are presented as below:
Table 3.11. Effects of CNT on the possibility of vulcanization of blend
NR / CR
Samples

Mmin
(kgf.cm)

Mmax
(kgf.cm)

Ts1
(min:sec)

Tc90
(min:sec)

CSTN/CR/CNT

2,35

20,58

01: 32

14:54

CSTN/CR/CNT-PVC
CSTN/CR/CNT-PEG

1,6
1,96

18,63
20,03

01: 27

01:28

14:44
14:24

CSTN/CR/CNT-TESPT

1,31

21,71

01:21

12:48

15


Vulcanization time Tc90 of the samples containing TESPT was
lowest (12 minutes 48 seconds). This could be explained that CNTTESPT contained a NH2 as an accelerator and the appearance of S-S
formed by slightly decomposition under high temperature (Figure
3.37), which directly participated in the crosslinking and coupling
system in rubber. This caused a premature vulcanized phenomenon
(ts1 value is lowest) and reduced the vulcanization time. Tc90 short
vulcanization time has an economic value in the process of
manufacturing products so that CNT- TESPT is very noteworthy.
3.4.2. Effects of CNT content on the mechanical properties of
materials NR / CR
From the results above, it can be seen that only 1% CNT (not
denatured and denatured) has significantly increased the mechanical

properties of the blend NR / CR. When the CNT and CNT- TESPT
content increased, the mechanical properties (tensile strength,
elongation) of the materials also increased and reached the maximum
value with 4% CNT by content or 3.5% CNT-TESPT. Mechanical
properties of materials NR/CR/CNT- TESPT were higher than
CSTN/CR/CNT. This was explained that CNT- TESPT had better
interaction than CNT. Also, they created a link with rubber vessel,
because the thermal decomposition process of silane did appear S-S
bond which not only directly involved in vulcanizing a tight network,
but also created a chemical bond with the rubber substrate. Releasing
HCl molecule increased the thermodynamic durability and created a
direct link Si-O-C to consolidate the durability of nanocomposite.
Assuming the links in the nanocomposite network as the following
model 3:37.

Figure 3:33. Effects of reinforced substances content on the
elongation of the materials NR / CR / CNT
16


HO

HO
HO Si (CH2)3 S4 (CH2)3Si(OH)3

Si CH2CH2CH2 S SH

HO

OOC

OOC

t0

NH2

NH2

COO
HO

Si

CH

(CH2)3 S4 (CH2)3Si(OH)3

H3C

HO

C
2
CH

CH2
CH3

HO

S S (CH2)3 Si OH
C
CH2
OOC
CH2

=

CH
C

CH

2

C
=

H2

HO

CH

Si

(CH2)3 S SH

HO

Cl

NH2
COO
HO

Si
HO

HO
CH2
Si OH
S
S
(CH
)
CH3 C
23
CH2
OOC
CH2

COO

2

CH2
(CH2)3 S S

C Cl
CH2
CH2

HO
CH2
CH3 C S S (CH2)3 Si OH
CH2
OOC
CH2

NH2
COO
CH2 t0
(CH
)
S
S
C
HO Si
23
-HCl
Cl CH2
O- H
CH2

NH2
COO
CH2
HO Si (CH2)3 S S C

CH2
O
CH2

Figure 3:37. Description of surfaced link between the CNT-TESPT
and CSTN / CR
The structure of materials NR / CR / CNT- TESPT was tight and
had a steady distribution, so it influenced the thermal durability, the
aging factor as well as the swell in the solvent.

Figure 3:38. Morphological structure of materials NR / CR
reinforced- CNT (a) and CNT- TESPT (b)
17


Table 3.13. TGA analysis results of of some material samples on the
basis of NR / CR

Samples

NR/CR
NR /CR/4CNT
NR/CR/3,5CNTTESPT
NR /CR/3,5CNT-PVC
NR /CR/3,5CNT-PEG

The starting
temperature of
decomposition
(oC)

The maximum
temperature of
decomposition
1
(oC)

Weight loss to
600oC
(%)

349,7
350,2

The
maximum
temperature of
decomposition
2
(oC)
434,5
433,2

268,7
272,4
274,5

353,6

428,4

90,66

273
274

344
347,7

438,8
432,9

91,14
92

91,02
86,67

3.5. Research on optimizing the possibility of CNT dispersion in
the rubber blend substrate NR / CR
From the research results presented above, it can be seen that
NR / CR system has higher properties than NR / NBR when using
CNT and denatured CNT. To further enhance the properties of this
blend system, the thesis also mentions the optimal conditions to
disperse CNT by using 3 methods of dispersion as follow:
- Method of solution: NR / CR / CNT / toluene.
- Method of using a combination of NR latex with surfactants: LNR /
CR / CNT-CTAB.
- Method of using compatible dispersion auxiliraries: NR / CR / CNT /
D01.

The most noticeable result is the ability of the CNT dispersion
under the influence of CTAB within NR latex as the following
mechanism:

18


Figure 3.46: The CNT detached-connected mechanism of CTAB and
the dispersed mechanism of CNT-CTAB in NR latex
The natural rubber latex particles had high flexibility. In spite
of a very small amount, only 1% CNT also significantly increased the
tensile strength from 13,32 to 16,12 MPa for LNR / CR and from
14.32 to 17.02 MPa for NR/ CR. The levels of 3% CNT and 3% CNTCTAB were optimal contents for rubber molecules and CNT to form a
polymeric network – a closed filler. The polymeric network- filler as
described in Figure 3:43 is stabilized by Van der Walls link, hydrogen
link and ion link (generated by negative electrons in the latex
molecule and positive electrons in nitrogen atoms of CTAB). This
increased the tensile strength of the material samples.

Figure 3:43. Interaction between the CNT / CTAB and the polymer
substrate
3.5.1. Manufacturing of rubber nanocomposite material by using
CNT-Vast
Based on the processing of the materials LNR / CR / CNTCTAB, the thesis also did a research on using CNT manufactured at
the Institute of Material Science - Vietnam Academy of Science and
19


Technology Institute (CNT- Vast) to reinforce the properties of the
blend NR / CR. CNT-Vast was ultrasonicly vibrated in ethanol or

dispersed in water with CTAB before being mixed with natural
rubber, rubber clopren as the preparation process in section 2.2. Here
are the results of mechanical properties obtained:
Table 3.17. Effect of CNT- Vast content on the mechanical properties
of materials NR / CR
Samples
NR/CR
NR /CR/1%CNT- Vast/etanol
NR /CR/2%CNT- Vast/etanol
NR /CR/3%CNT- Vast/etanol
LNR/CR/4%CNT- Vast/etanol
NR /CR/1% CNT- Vast/CTAB
NR /CR/2% CNT- Vast/CTAB
NR /CR/3% CNT- Vast/CTAB
NR /CR/4% CNT- Vast/CTAB

Tensile
strength
(MPa)
13,32
15,12
17,28
16,53
15,76
15,52
18,14
17,09
16,76

Elongation Hardness

(%)
(Shore A)
610
603
592
584
578
600
593
567
579

51,2
51,9
52,6
53,0
53,8
51,8
52,3
54,0
54,4

Mechanical properties of the material samples NR / CR / CNTVast / CTAB were pretty better than that of NR / CR / CNT- Vast /
eatnol. To explain this, the thesis used the research results of the
authors [97]. When comparing the size of the CNT- Vast and CNTNanocyl (the kind used primarily in the thesis), it could be seen that
CNT- Nanocyl had small diameter and the equal diametral distribution
rather than CNT- Vast. On the other hand, purity of CNT- Nanocyl
(95%) is also larger than that of CNT- Vast (about 90%). Thus, it was
obviously suitable that the reinforcement ability of CNT- Vast also
declined slightly, and the CNT- Vast content optimally reinforced

(2%) was lower than CNT- Nanocyl (3%).
3.5.2. The regression equation describing the dependence of the
mechanical properties of the material LNR / CR on CNT-CTAB
When calculating by FORTRAN algorithmic language program and
proceeding the data, a regression equation was obtained as follows:
^

-Tensile strength: y1  13,024  4,202 x  0,693x 2 , with θ = 0,958

20





Easily realize that y1 reached the maximum value at:

d

y1
dx

= -2. 0,693


x+ 4,202 =0, solving this equation and refer x = 3,03%, y1 max =
19,394 Mpa.
This result indicated that around the value x = 3,03%, the value of
tensile strength was the highest
^

- Elongation: y 2  614,86  11,14 x with r = -0,973
That r had negative value was completely suitable with the sign of x
^

- Abrasion: y 3  0,836  0,202 x  0,032 x 2

with θ = 0,988

^

-Hardness: y 4  51,67  0,82 x

with r = 0,979
Thus: Proceeding data to find out the regression equations
describing experimental correspondence with high precision, enable to
evaluate the rules of the CNT-CTAB influences on the mechanical
properties of the materials. From that, we can solve optimization
problems, find out the domain of CNT-CTAB for the mechanical
properties of the materials.
3.5.3. Assessment of thermal-mechanical properties of the material
CO- NR / CR sample CNT reinforced by three different dispersal
methods
The curves showed 3 distinct regions: the high module (glass
area), transition area (in which the value E' drops rapidly with
temperature) and the "rubber". Rubber had large accrued modules at
low temperatures, then plummetted at around -60°C (sample
containing CNT/toluene: -66°C, sample containing CNT- CTAB: 64°C, sample containing CNT/D01: -63°C). The strong decrease of E'
at this temperature indicated the transition from glassy state to
"rubber" state. All three material samples were a little bit different

from each other under the effect of load. The value E' of the samples
containing CNT/ toluene was slightly higher due to the even
dispersion of CN. The surface- appearance of CNT became an
absorbing agent.

21


2,50E+009

CNT/D01

2,00E+009

CNT/toluen
Modul E'

1,50E+009

CNT/CTAB

1,00E+009

5,00E+008

0,00E+000

-120

-100

-80

-60

-40

-20

0

20

40

Nhiet do

Figure 3:49. The chart of accrued modules change with temperature

Figure 3:50. The chart of mechanical loss factor change with
temperature
The Figure 3:50 shows that Tg value of NR and CR is in range
of -50°C and -27°C. Vitrification temperature of NR was lower than
that of CR due to the presence of Cl polarized groups. These groups
mutually interacted, which restricted the movement of molecular
circuits. Samples containing CNT / D01 had Tg1 = -51,2°C with high
pic intensity, Tg2 = -27,8°C. Meanwhile, samples containing CNT /
CTAB had Tg1 = -49°C with lower intensity, Tg2 = -27,5°C but with
slightly lower intensity. Tg1 and Tg2 of samples containing CNT /
toluene slightly decreased to -48,8°C and -27°C respectively, but the

decrease of pic intensity of Tg1 was the most significant one. The rise
of the Tg1 algebraic values to samples containing CNTs/D01 was due
to the appearance of a few bundles of CNT as a barrier to the
movement of the polymer chains around the temperature Tg. These
results showed that the blend of NR / CR reinforced CNT / D01 was
less compatible with each other. However, when using surfactants or
dispersing in toluene, the compatibility was increased. This result was
22


consistent with the assessment of the results of TGA analysis,
mechanical properties and morphological structure above.
Besides, the intensity and location of pic tgδ indicated
interaction between rubber substrate and CNT. If pic tgδ is wider, the
aggregation of nano particles into clouds would be greater, the
connection between the CNT and the substrate would became worse.
Conversely, if pic tgδ was narrower, the connection between the CNT
and the substrate would be better, CNT was dispersed evenly and hard
to conglomerate. By comparing 3 pic tgδ, it could be seen that
CNT/toluene and CNT/CTAB samples had narrow pic, the peak of pic
with Tg1 is sharp, which proved the better reinforcement effect.
3.5.4. Influence of the dispersion method on electrical properties of
NR/CR/ CNT materials
Many studies have shown that doing a research on the electrical
properties is also an effective mediate method to study the structure of
the polymer nanocomposite material, which allows to assess
interaction and the dispersion ability of the phases. Below are the
descriptions of the electrical conductivity of the material.

Figure 3:51. Electrical conductivity and the electric absorbent

threshold of the material sample by CNT weight
It could be seen that the CNT dispersion method had a strong
impact the electrical conductivity of the material. Only 2% used CNT
has increased the electrical conductivity of NR / CR / CNT by 106
times and that of LNR / CR / CNT by 104 times. Generally, the
electrical conductivity of polymer synthetic materials was explained
by the mechanism of the conduction theory (form a continuous
23


conductive network) and the mechanism of jump (electromagnetic
radiation) of the electrons overcoming very small distances. Simply
understanding, the arrangement of the CNT particles into the pipelines
created a continuous line. The dielectric loss was very small so that it
could be ignored. Moreover, the specific structure with the presence of
conjugated bonds in CNT supported electronic lines to move
continuously. That the appearance of the positive electron on nitrogen
atom of CTAB atoms became electron transit center of CNT
continuous network made the electronic transportation process more
advantageous; thus, resistivity decreased, which also means electrical
conductivity increased. When the content of CNT reached at 3%, the
electrical conductivity reached 10-5. It means that the network
structure was stable, CNT particles had the shortest average distance,
which led to the formation of a 3-D network of the conductive phase.
By that time, it has reached an electrical absorbent threshold (as
described in Figure 3:51). Therefore, increasing the level of CNT
content also made an increase of connected density among CNTs
without changing the electrical conductivity.
Table 3:21. The influence of the dispersion methods on the
vulcanization ability of the blend NR / CR

Samples
LNR/CR/CNT-CTAB
NR/CR/CNT/Toluen
NR/CR/CNT/D01

Mmin
(kgf.cm)
2,17
2,32
2,18

Mmax
(kgf.cm)
19,5
20,82
19,63

T90
(min:sec)
10:55
10:06
10:18

Vulcanization time Tc90 of the sample containing D01 was
lower due to D01 structure had the link C = C which directly involved
in crosslinking process, accelerated the process of vulcanization.
Although the starting time of the vulcanization and Tc90 of the
mixing solution sample were lowest, the most interesting thing was
that the Tc90 time of the sample using latex was relatively short, even
lower than that of the sample NR / CR / CNT-TESPT (Table 3:11).

This was quite an important orientation to apply CNT in industry.
3.6. Orient to manufacturing experimental anti-static rubber mats
Based on the above findings, they have created a prototype of
anti-static mats. Below is the quality standard of the anti-static mats
manufactured in factories of Technical Rubber Ltd Globe Company
compared to imported samples delivered by The Bao Nguyen Co., Ltd,
24