Tensile, Flexural and Thermogravimetric Analysis of Carbon Nanotube Reinforced Epoxy Resin Composites

Tensile, Flexural and Thermogravimetric Analysis of Carbon Nanotube Reinforced Epoxy Resin Composites

Subramanian Ravichandran

Department of Physics, Sathyabama Institute of Science and Technology, JEPPIAAR Nagar, sholinganallur, Chennai-600 119. Tamilnadu, India.

Abstract: Nowadays, Carbon nanotubes are one of the foremost materials in nanoscience and nanotechnology. Recently, nanoscale filling materials included nano metal oxides, nano semiconductors, nano ceramics and CNTs. These composites are attracted due to their fascinating behaviours and distinct commercial applications in various industries. The properties of the Nano composite depend on the behaviour of the clays and polymer matrix, and the characteristics of the Nano filler. Hence, the final new Nanocomposite have remarkable enhancement in its structure, thermal and mechanical properties.

In this project, the mechanical properties of Epoxy resin- Multiwall carbon nanotubes- reinforced polymer composites were presented. CNTs are fabricated by the CVD method, and the size and shape of the carbon nanotubes are characterised by SEM, and the length of the carbon nanotube is measured. The other materials, Epoxy resin and hardener, which are used to fabricate the composites, are purchased commercially, and the same materials are used to fabricate the CNTs. The CNTs are then mixed with epoxy resin, and the epoxy resin CNTs composites are fabricated. Further, the materials are taken for mechanical studies and thermal studies. The mechanical studies of the polymers and composites show that CNTs strongly enhance the tensile strength and Youngs modulus. The results indicate that the treatment improves the poor interfacial contact between the CNTs and the polymer matrix.

Keywords: Epoxy resin-CNT Reinforcement-Composites-Mechanical-Thermal properties

I INTRODUCTION

A Carbon Nanotube (CNT) is a tubular form of graphite sheet material having a diameter in the nanometer scale. Carbon Nanotubes have many types of structures, differing in size, length, thickness, and in the type of helicity. They are formed from a graphite sheet. Their electrical properties depend on these variations, acting either as metals or semiconductors. Due to the excellent mechanical, thermal and structural behaviours, CNTs have been reinforced in all types of polymer composite materials. Nowadays, a larger number of researchers have developed a new CNT-polymer matrix to create novel composites for aerospace & automotive parts. Ye Hou (1) studied the mechanical properties of polymer composites with Functionalized Few-Walled Carbon Nanotubes. He also measured the Youngs modulus of composite lms with 0.2 wt % functionalized walled nanotubes, and it shows a remarkable reinforcement value. Liu et al (2) discussed the properties of polymer composite materials with single-walled nanotubes. He has measured the mechanical properties of Polyvinyl alcohol with single-walled carbon nanotube. Venkata Ramana et al (3) had measured the structure and mechanical properties of multi-walled carbon nanotube reinforced with polymer composites. He had developed an epoxy polymer-matrix with MWCNT. Also, the enhanced mechanical properties and surface properties of composites were measured. Fan-Long Jin and Soo-Jin Park (4) have given a detailed review report of CNT-polymer composite materials.

Scientists have measured the surface properties, Youngs modulus, tensile strength, impact properties, and tensile modulus for various types of polymer composites (5-10). Saroj Kumari (11) et al carriedout the investigation towards the improvement of mechanical and thermal properties of semi-coke-based carbon/copper composites reinforced material using carbon nanotubes. Mahmoud Shokrieh (12) investigate the Mechanical properties of multi-walled carbon nanotube/polyester nanocomposites at different weight ratios of polyester. Recently, the mechanical properties, structural and processing studies of carbon nanotube- reinforced composites have been developed, and they proved that the mechanical properties are enhanced with dispersion of CNTs (13-14, 16). Polymer nano composites based on matrices gained signicant interest after the investigation of Nano clays lled with nylon-6 (26). CNT-based polymer composites have been a distinguished area of research in the last couple of decades owing to CNTs high aspect ratios with Nano dimensions, lower mass density and superior electrical (27-32), mechanical (3335) and thermal properties (36-37).

1. MATERIALS AND METHODS

   CNTs are produced from the carbon containing source as it decomposes at an elevated temperature and passes over a transition metal catalyst. A high yield of nanotubes can be achieved by this method, but the nanotubes are more structurally defective than those produced by arc or laser evaporation methods. There are several advantages of the CVD method, which make it preferred to other available synthesis methods. Firstly, the product tends to be purer. Secondly, the growth occurs at a lower temperature. Finally, the metal catalyst can be held on a substrate, which can lead to the growth of aligned nanotubes in a desired direction with

   respect to the substrate. There are two basic mechanisms proposed for the growth of nanotubes by the CVD method related to substrate-bound catalyst, which are now widely recognised.

   The carbon diffusion parameter depends on the dimensions of the particles, the characteristics of the metal used as a catalyst, the temperature and the hydrocarbons and gases involved in the process. When the substrate-catalyst interaction is strong, a CNT grows up with the catalyst particle rooted at its base (base growth model). When the substrate-catalyst interaction is weak, the catalyst particle is lifted up by the growing nanotube and continues to promote CNT growth at its tip. Formation of SWNTs or MWNTs is governed by the size of the catalyst particle.

   .

   A. Fabrication of EPOXY CNTs nano polymer composites

   MWCNTs have been dissolved with acetone for an hour at 2000 RPM at Room temperature. Solution has dispersed with resin and stirred for 1 hr at 80 °C at 2000 RPM. Ethanol has been evaporated in a vacuum oven at 80 °C for 1 hour. The mixture has been stirred for 1 hr at 2000 RPM. After the addition of hardener, the mixture was stirred for 15 minutes at 2000 RPM and cured at 100 °C for 4 hrs. in a vacuum oven. In the first step, an oxidative treatment of the nanotubes was used to develop carboxylic groups. This led to an opening of the CNT cap, which would enable a direct bonding of the tube ends to the matrix via the carboxylic groups. In the second step, the carboxylic groups would react with multifunctional amines and form bonds to these amines via an acid-base reaction. In the third step, with the addition of the epoxy resin, the free amino functions on the surface of CNTs would react with the epoxy molecules, forming equivalent bonds, which lead to an improved nanotube matrix bonding.

   Epoxy resin (LY556) and Harder (HY951) were used to fabricate the composite film. CNTs were uniformly dispersed in the polymer film. Resin was coated on the surface of a glass plate, which is used for the casting method. Suitable CNTs were weighed, and it was mixed with resin in a particular ratio uniformly by magnetic stirring for 1 hour continuously. After uniform mixing with the resin, CNTs were dispersed in solution. The above-mentioned solution was used for making the film. Finally, the fibre reinforced polymer film has been prepared with a thickness of 3-5 mm and cured for 24 hrs. Pressure was applied on the composite film (50 Bar) at 80 °C.

2. RESULTS AND DISCUSSION
3. Morphology and microstructure characterization of CNT by SEM

   A detailed micro-structural characteristic of the CNTs was determined by SEM. In the present article, we investigated the size and structure of CNTs. Figure 1a-c shows the different SEM images for the synthesised carbon nanotube materials, showing the appearance of amorphous-like particles. These nanotubes had a broad length, and a fine image of nano tube was measured. The length of nano tube had been measured as 1.779 µm with a diameter of 1.378 µm. The diameter and length of nano tubes varied. These tubes were visualised in bulk material with a very high volume. The length and diameter of nano tubes consist of different compartments, and these compartments were equal in size. The diameter and length of nano tubes were carefully measured on the different SEM micrographs recorded in various regions of nano tubes.

   Fig.1a. SEM electron images showing a network of MWCNTs

   Fig.1.b. SEM electron images showing a network of MWCNTs.

   Fig.1.c. SEM electron images showing a network of MWCNTs

4. Mechanical properties of Epoxy ResinCNT polymer composites

   The mechanical properties of epoxy resin-CNTs composites were measured and it was compared with pure resin composite in terms of tensile strength, flexural and impact test. The mechanical characteristics of the tested materials are shown in Fig. 2 and Fig. 8.

5. Evaluation of Tensile properties

   Tensile tests were conducted at room temperature on a universal testing machine in a tensile configuration according to ASTM D3039. Dog-bone shape composite samples for mechanical tensile testing had a gauge length of 30 mm, a width and a thickness of 4 mm. The distance between the sample clamping was 40 mm, and the testing speed was chosen to be 1 mm/min. From the resulting stress-strain diagrams, the tensile modulus was determined. The tensile strength was determined from the material’s maximum sustained stress for all types of resin-CNT composites and is shown in Fig.2.

   Tensile strength mostly depends on the properties of the elastomer to partially strain crystallise when it is stretched. Any type of fibre is reinforced with a polymer matrix structure that strain crystallises. As a result, it has high tensile strength. An elastomer with poor tensile strength can be improved by the addition of reinforcing agents, such as a fibre or nano fillers. CNTs are the high strength fibres which possess a tensile strength of nearly 100 GPa. Also, CNTs have good thermal and electrical conducting properties varying from metallic to moderate band-gap semi-conductive behaviours depending on their chirality, size and purity. Therefore, it is possible to improve the physical and mechanical properties and electrical conductivity by adding a certain amount of CNTs to the polymeric structures. In recent years, different types of polymer composites have been synthesized by incorporating CNTs into various polymer matrices such as polyamides, polyimides, epoxy, polyurethane, polypropylene,

   polyethylene, polyethylene oxide, poly(vinyl alcohol), poly(methyl meth acrylate), polycarbonate, poly(butylenesuccinate), polylactide, polyaniline, polypyrrole, poly (N-vinylcarbazole), poly(ethylene 2, 6-naphthalate), poly(butylenes terephthalate) , poly(p-phenylene benzo bisoxazole) (38-40).

   A fibre is the high strength, more rigid, and load-carrying element of the composite material. The composite material is only strong and stiff in the direction of the fibres. Unidirectional composites have predominant mechanical properties in one direction and have mechanical and physical properties that vary with direction relative to natural reference axes inherent in the material. Components made from fibre-reinforced composites can be designed so that the fibre direction produces excellent mechanical properties. Structural properties, such as stiffness, stability and strength of a composite, depend on the stacking sequence of the plies. The stacking sequence describes the distribution of ply orientations through the laminate thickness. As the number of plies with chosen orientations increases, more stacking sequences are possible (41-42). Epoxy resin was used to fabricate the samples, and the hardener material was added to solidify it. This mixture is used to make the matrix. Carbon nanotube powder was used to reinforce the matrix to produce composite materials. Mechanical properties were measured for the pure epoxy resin and different compositions of epoxy resin-CNT composites at room temperature, and they are reported in Table.1.

   TABLE.1. EXPERIMENTAL DATA OF WIDTH, THICKNESS, BREAKING LOAD, TENSILE STRENGTH AND TENSILE MODULUS OF PURE EPOXY AND EPOXYCNTS COMPOSITE

   Type of samples	Width (mm)	Thickness (mm)	Breaking Load (KN)	Tensile strength (N/mm2)	Tensile modulus (N/mm2)
   Pure Epoxy resin	25.02	2.64	1048.5	24.21	1048.5
   Epoxy+(1 gm of CNT)	13.5	3.9	1052.5	24.72	1052.5
   Epoxy +(2 gm of CNT)	14.0	2.9	1047.8	25.31	1047.8
   Epoxy +(3 gm of CNT)	24.07	4.57	1089.0	15.32	1089.0

   TENSILE STRENGTH (N/mm2)

   Epoxy resin Epx+(1 gm of Epx+(2 gm of Epx+(3 gm of

   CNT)

   CNT)

   CNT)

   Epoxy resin with different % of CNT

   Fig.2. Graph shows the variation of tensile strength of epoxy resin and epoxy CNT materials.

   A load of 1, 2 and 3 % of CNTs was uniformly dispersed with epoxy resin, and it was compressed under the pressure of about 10-20 par, for 10-20 minutes. It was noticed that the tensile strength of composite materials has improved, and the tensile modulus of a CNT composite material has slightly decreased due to the reinforcement of 2% carbon nanotube with epoxy resin composites. The variation of tensile strength and tensile modulus of epoxy resin and CNT materials was shown in Fig.3. The enhancement was achieved only in the strength of composites, and it could be constructed because of the reinforcement of CNTs. The general tendency observed from the data is that, due to the inclusion of CNTs, the tensile modulus and the tensile strength are reduced at the same time. This is because of the weak adhesive at the interface between the matrix and all reinforced material (43- 45).

   TENSILE MODULUS

   (N/mm2)

   TENSILE STRENGTH (N/mm2)

   Fig.3. Graph shows the variation of tensile strength and tensile modulus of epoxy resin and CNT materials.

   Experimental data of maximum load, maximum tensile strength, percentage of elongation, length of material extensible at breaking load and modulus of pure epoxy and epoxy-CNT composite in different compositions are given in Table 2. It was observed that the maximum load is decreased at a composition of 0.66% of CNT. But, it is highly improved at 1% of CNT, greater than the pure epoxy composites. Maximum tensile strength, percentage of elongation and modulus are also measured for different compositions of CNT-Epoxy material. Tensile strength is maximum at 0.66% of CNT-Epoxy composite material, while elongation and modulus of material are suddenly decreased at the same concentration. These variations in the mechanical properties were observed due to the reinforcement of CNT with epoxy resin. The variation of tensile modulus and epxy resin with different amounts of CNT materials is shown in Fig.4.

   The increase in tensile modulus may be due to efficient load transfer from the matrix to the CNT in the axial direction. Internal stiffening formed due to the reinforcement of carbon nanotubes results in improved load transfer at the fibre-matrix interface. It had been reported that the increase in elastic modulus between the random and aligned nano composite is a development of carbon nanotube. The increase in the applied loads create to increase in the strain in the composite material, and that cause increase in the effective range for tension force. This tension force will accelerate the formation of primary cracks in the polymer material because of the high increase in inner energy. so that the collapse occurred, then the samples separate into parts, and hence the fracture will occur. A decrease in the tensile strength of the composite material is due to the weakening of network formation in the Epoxy-CNTs composites, which will reduce the tensile strength of the composites. The structure and properties of the fiber- matrix interface play a major role in the mechanical and physical properties of composite materials. Thus, the excellent mechanical properties of fibre composites can only be attained if stress can be effectively transferred from fibres to the polymer matrix. The variations of breaking load and different concentrations of CNT Composite materials were shown in Fig.5.

   TABLE. 2 EXPERIMENTAL DATA OF MAXIMUM LOAD, EXTENSION OF MATERIALS, MAXIMUM STRENGTH, ELONGATION AND MODULUS OF PURE EPOXY AND EPOXYCNTS COMPOSITE.

   Type of material	Maximu m Load(N)	Extension at Maximum Load (mm)	Maximum Tensile Strength (MPa)	% Elongation	Load at Break (N)	Extension at Break (Standard) (mm)	Modulus (MPa)
   Pure Epoxy resin film	1598.76	1.933	24.21	2.762	1598.75	1.933	1048.51
   Epoxy resin with 1 gm of CNT	1301.8	1.804	24.72	1.33	1301.8	1.804	1052.5
   Epoxy resin with 2 gm of CNT	1031.1	1.258	25.31	1.24	1031.1	1.258	1047.8
   Epoxy resin with 3 gm of CNT	1685.83	1.233	15.326	1.761	1115.87	1.254	1089.03

    

   TENSILE MODULUS(N/mm2)

   Epoxy resin Epx+(1 gm of Epx+(2 gm of Epx+(3 gm of

   CNT)

   CNT)

   CNT)

   Epoxy resin with different amount of CNT

   Fig.4 Graph shows the variation of tensile modulus and epoxy resin with different amount of CNT materials.

   BREAKING LOAD (KN)

   Epoxy resin Epx+(1 gm of Epx+(2 gm of Epx+(3 gm of

   CNT)

   CNT)

   CNT)

   Epoxy resin with different amount of CNT

   Fig.5. Graph between the variations of breaking load and different concentration of CNT Composite materials.

6. Evaluation of Flexural properties

   Resin-based composites’ mechanical properties mainly depend upon their microstructures and composition. The characteristics of polymer composites depend on the distribution of nano fillers, the size and morphology of these filler particles and the presence of voids. These characteristics are directly connected with the composition of the mixtures. The fibre-reinforced polymer composites, the materials acquire their high stiffness and strength from the glass fibres. In addition, the bidirectional fibre-reinforced material results to give more resistant to damage and defects than the homogeneous material. Voids and Cracks in the matrix are either shortened by a fibre, causing little effect on the tensile or flexural strength. The flexural strength and breaking load are measured for the Epoxy resin-CNT composites in different compositions (Fig.6), and it was given in Table.3.

   TABLE.3. EXPERIMENTAL DATA OF WIDTH, SPAN LENGTH, THICKNESS, BREAKING LOAD AND FLEXURAL STRENGTH OF A PURE EPOXY AND EPOXY RESIN-CNT COMPOSITES.

   Types of Specimen	Width (mm)	Span Length (mm)	Thickness (mm)	Breaking Load (N)	Flexural Strength ( )x107
   Epoxy resin	11.19	50	3.17	204.7	136.53
   Epoxy+ 1 gm of CNT	12.81	50	4.02	202.4	73.32
   Epoxy+ 2 gm of CNT	12.50	50	3.01	89.71	59.41
   Epoxy+ 3 gm of CNT	11.32	50	3.43	51.45	28.95

   All the specimens are tested on the UTM, and the value of the breaking load is determined. The above study describes the variation in the strength of composite materials with different ratios of CNTs as fillers. The breaking load has decreased with reinforcement of CNTs, and it shows the corresponding decreased flexural strength. Also, it has lower breaking loads due to its lower strength. Flexural strength and breaking load are the most widely used properties in characterising the mechanical behaviour of polymer composite materials. Standard test methods are adopted for the property evaluation of composite materials as specified by ASTM at room temperature. Most of the testing conducted and the tests reported in this work are according to the standard procedures. In the present study, the flexural behaviour of the CNT reinforced in the polymer matrix composite is measured in detail to investigate the influence of CNTs. The results are obtained based on the structure of the materials characteristics and the type of reinforcement material.

   Specimens of rectangular cross section with an approximate width of 11.19mm, 11.32 mm, 12.51 & 12.89mm, thickness of 3.17mm, 4.02, 3.01 mm and 3.43mm and span length of 50 mm respectively, were used to determine the flexural properties of the composite material. This procedure is followed as specified by the ASTM standard. The variations of Extension of Maximum Load, percentage of elongation and maximum tensile strength of pure epoxy, and epoxy-CNT polymer composite materials were shown in Fig.7.

   The flexural strength in each case was defined as the maximum stress in the corresponding load-displacement curve. A comparison of the flexural strengths of the three different types of resin with different concentrations of CNTs is shown in Table 2. The flexural strength of the epoxy resin laminate with CNTs was decreased. The pure epoxy resin has a higher flexural strength than the other composite with Nano filler materials. Due to the presence of CNTs, an immediate crack is formed in the materials due to the scattering and weak bonding of materials (45-48).

   Flexural strength

   Epoxy resin Epx+(1 gm of CNT) Epx+(2 gm of CNT) Epx+(3 gm of CNT)

   Epoxy resin composites with different concentration of CNTs

   Fig.6 Graph between the variations of flexural strength and the different type of materials.

   load,elongation,max.strength

   Pure Epxy Epxy+1%CNT Epxy+2%CNT EPXY+3%CNT

   different CNT composites

   Fig.7 Graph beween the variations of Extension of Maximum Load, percentage of elongation and maximum tensile strength of pure epoxy, and epoxy-CNT polymer composite materials

7. Impact Characteristics of EpoxyCNT polymer composites

   The properties of a polymer nano composite are greatly influenced by the shape, size of its component phases and the degree of mixing between the two phases of a system (Fig.8). Significant differences in composite properties can be obtained depending on the nature of the components used in the polymer matrix. Material and structural parameters of nanoparticles, such as shape, size, inclusion ratio, concentration, etc., play important role for properties of nanocomposites. The quality of the interfaces between particles and matrix is no less important. The presence of rigid nano filler usually deteriorates the strength and toughness, impact strength of polymeric materials. Quality dispersion of nanoparticles in the matrix plays a key role for an improvement of impact properties of nanocomposites. Dispersed particles are generally in a thermodynamically non-equilibrium state. Improvements in mechanical properties are dependent upon the nature of the interactions between the matrix and the filler. Impact strength was measured for the Epoxy resin and Epoxy resin with 1gm, 2gm and 3gm of MWCNTs and the data were given in Fig.8 (Table.4). The impact values of resin-CNTs composites are increased compared with epoxy resin film.

   TABLE .4 DATA SHOWS THE IMPACT TESTS OF EPOXY-CNTS COMPOSITES IN DIFFERENT CONCENTRATIONS.

   Specimen	Width of the sample (mm)	Thickness (mm)	Impact strength of the specimen (KJ/m2)
   Pure Epoxy resin	11.19	3.17	22.33
   Epoxy+ 1 gm of CNT	12.81	4.02	27.45
   Epoxy+ 2 gm of CNT	12.50	3.01	35.66
   Epoxy+ 3 gm of CNT	11.32	3.43	24.12

   impact strength(KJ/m2)

   Pure Epxy Epxy+1%CNT Epxy+2%CNT EPXY+3%CNT

   Epoxy with CNT composites

   Fig.8. Shows the Impact strength of Epoxy resin-CNTs composites in different composition

   Epoxy resin-1gm of CNT shows the values of 27.45, Epoxy resin-2gm of CNT shows the values of 35.66 and with 3gm of CNT shows the values of 24.12KJ/m2. These results are obtained by the reinforcement of MWCNTs with resin. The impact strength decreased with a higher composition of CNTs. It may be due to the agglomeration of CNTs with the resin matrix. Therefore, it concluded that the impact strength is enhanced only at a particular percentage of CNTs, and the dispersion of CNTs in resin also improves the impact strength of composites (49-50).

8. Thermogravimetric Analysis of Epoxy and Epoxy based CNT polymer composites.

   Thermogravimetric analysis (TGA) is one of the thermal analysis techniques used to characterize a wide variety of materials. TGA provides important and supplementary characterization information to the most commonly used thermal technique, DSC. TGA measures the amount and rate of change in the mass of a sample as a function of temperature. Temperature is a fundamental state that directly affect the chemical reactions, physical properties and structural transformations. Table.5 summarizes the several measurements of TGA analysis of a samples on residue temperature, weight loss and weight percentage and step transition temperatures and initial and decomposition temperatures of composites (Fig.9-10)).

   TABLE.5. INITIAL, DECOMPOSITION TEMPERATURES AND PERCENTAGE OF TOTAL WEIGHT LOSS FOR EPOXY- CNTS NANO COMPOSITES BY TGA ANALYSIS.

   Type of material	Residue			Step Transition
   	Temperature C	Weight Loss (mg)	Weight Loss (%)	Onset C	End C	Weight (mg)
   Epoxy resin	684.33	0.01380	0.6358	334.89	415.38	1.917
   Epoxy- MWCNTs (1%)	744.66	0.004923	0.1481	340.26	419.91	2.925

   These measurements are used to determine the thermal and oxidative stabilities of materials as well as their composite properties. The technique can analyse materials that exhibit either mass loss or gain due to decomposition or oxidation. It is especially useful for the study of polymeric materials, including thermoplastics, thermosets, elastomers, composites, films, fibres, coatings and paints. One major application of TGA is the assessment of the filler content in polymers and composites. The level of fillers can have a significant impact on the end-use properties, such as thermal expansion, stiffness, and damping, of the new composite materials. This is particularly important for mechanical applications where the level of filler affects the coefficient of thermal expansion.

   .

   Sample: Ravichandran 2 June 27 2014

   Size: 2.1700 mg Method: test Comment: test

   DSC-TGA

   File: C:…\Ravichandran 2 June 27 2014.001 Operator: TA

   Run Date: 2014-06-27 11:02

   Instrument: SDT Q600 V8.0 Build 95

   Weight (%)

   Deriv. Weight (%/°C)

   Residue: 0.6358% (0.01380mg)

   Temperature (°C)

   Universal V4.1D TA Instruments

   Fig.9. Thermogravimetric analysis curves for pure epoxy resin.

   In this work, TGA was performed by a thermal analyser with a scanning range from 100C-1000C and the weight of the samples was taken between 1-100 weight percentage ratios. The TGA curve for pure epoxy resin is given in Fig.9. The results obtained for the resin- CNT nano composites thermo degradation of CNT/resin at different weight percentages of CNT are plotted in Fig.10. The TGA curve is almost the same as the curve of pure epoxy resin. Very small changes were observed at the degradation place. Decomposition range starts from 334 °C for pure resin and 340 °C for epoxy resin-CNT composites. Also, it can be observed that the complete decomposition of pure epoxy resin and resin-CNT composites appeared at a similar temperature around 550

   °C. And a final residue was obtained at 950 °C. The decomposition temperatures of a material are also the same as 376 °C. Initially, decomposition percentage is very less up to a temperature 250C. The second region starts from 200-500 °C, which is due to the decomposition of nano composites. Also, it can be clearly observed that the two samples exhibit minimum weight loss until the temperature reaches 200 °C. The above results have good agreement with the earlier reports (55-60). This result reveals that when the heating rate is increased, the decomposition temperature also varies.

   Sample: Ravichandran 1 a July 7 2014

   Size: 3.3230 mg Method: test Comment: test

   DSC-TGA

   File: C:…\Ravichandran 1 a July 7 2014.001 Operator: TA

   Run Date: 2014-07-07 11:05

   Instrument: SDT Q600 V8.0 Build 95

   Deriv. Weight (%/°C)

   Weight (%)

   Residue: 0.1481% (0.004923mg)

   <>Temperature (°C)

   Universal V4.1D TA Instruments

   Fig.10. Thermogravimetric analysis curves for epoxy resin-MWCNTs composite of 1%.

9. CONCLUSION

Multiwall carbon nanotubes were synthesised by the CVD method, and characterisation was studied by SEM. The images of nano tube were measured by SEM, and the length of nano tube has measured as 1.779 µm with a diameter of 1.378 µm. Mechanical properties (i.e) Tensile strength, Tensile modulus, breaking load, percentage of elongation) are carried out for CNT-Resin polymer composite materials in different compositions. It was noticed that the tensile strength of composite materials has improved, and the tensile modulus of a CNT composite material has slightly decreased due to the reinforcement of 2% carbon nanotube with epoxy resin composites. Tensile modulus has improved for CNT-Polymer matrix at a concentration of 3 g (1%). Also, it was observed that the maximum load is decreased at a composition of 0.66% of CNT. But, it is highly improved at 1% of CNT, greater than the pure epoxy materials. Maximum tensile strength, percentage of elongation and modulus are also measured for different compositions of CNT-Epoxy material.

Tensile strength is maximum at 0.66% of CNT-Epoxy composite material, while elongation and modulus of material are suddenly decreased at the same concentration. The percentage of elongation of polymer-CNT composites is lower than the elongation of pure epoxy resin material. Impact strength of Epoxy resin-2gm of CNT composites shows the values of 35.66 KJ/m2. This result is obtained by the reinforcement of MWCNTs with resin. The impact strength decreased with a higher composition of CNTs. It may be due to the agglomeration of CNTs with the resin matrix. Thermal properties of CNT-Polymer resin composites are measured by TGA, and it is found that the decomposition range starts from 334 °C for pure resin and 340 °C for resin-CNT composites. Also, it can be seen that complete decomposition of pure epoxy resin and resin-CNT composites appears at a similar temperature around 550 °C. And a final residue was obtained at 950 °C. Also, it can be clearly seen that the two samples, pure resin and CNT-resin polymer matrix, exhibit minimum weight loss until the temperature reaches 200 °C.

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