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

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.

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

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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

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anti-static ability is necessary because it brings about high scientific and practical values Derived from these reasons, the thesis aims to the

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

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- 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)

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

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

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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

acrylonitril 34%

 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

 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

- Synthesis of CNT-PEG

Melt 1g PEG at 90°C, then put into a flask containing 0,1g COCl, 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

CNT Synthesis of CNTCNT 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

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

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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

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)

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:

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mixer mixer, 3hours, 500C

(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 Analysismethod 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

thermal stability of materials by Thermal Gravimetric Analysis(TGA)

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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:

The maximum temperature of decomposition

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The maximum temperature of decomposition

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 200-800nm waveband

Two characteristic absorption peaks in the area of 240- 265 cm-1are corresponding to the shift of the electron π π*

of conjugate atom Csp2

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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

(%)

Tensile strength (MPa)

Elongation (%)

Abrasion (cm3/1,61km)

Hardness (Shore A)

Elongation (%)

Abrasion (cm3/1,61km)

Hardness (Shore A)

- 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

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

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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)