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Tribological Characterization Of CNT/HDPE Polymer Nano-Composites
Shashi Kant Thakur, Ajay Sharma & N. K. Batra Maharishi Markandeshwar University, Mullana
E-mail : [email protected], [email protected]
Abstract - Carbon nanotubes (CNT) used with polymers to make composite having remarkable properties, in order to enhance wear and tribological properties of the composite material used in the load bearing application. The objective of the present work is to prepare nanocomposites and do mechanical characterization of these nanocomposites using UTM techniques and wear properties carried out by using wear and friction monitor model (TR-20LE). The material used for the present work was high density polyethylene having melting point 125- 1350c and multi walled carbon nanotubes having diameter of 5-15 nanometer and length of 60 to 100 µm.
Keywords - CNT, HDPE, MWCNT, SWCNT, UTM I. INTRODUCTION
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally nanotechnology deals with developing materials, devices or other structures possessing at least one dimension sized from 1 to 100 nanometers (nm).
Nanoscience is the study, and nanotechnology is the exploitation, of the strange properties smaller than 100 nanometers (nm) to create new useful objects.
Nanotechnology address our ability to understand and manipulate the physical and technological characteristics that govern the behavior of systems that posses at least one physical dimension that is (typically) on the order of 100 nm or less.[1] It is the field of applied science focused on the design, synthesis, characterization and application of materials and devices on the nanoscale. A nanometer is used to measure things that are very small. Atoms and molecules, the smallest pieces of everything around us, are measured in nanometers. [1]
Nanocomposites are presently an area of new growth in the field of composite materials. They are fabricated by dispersing prepared nanoparticles into matrix material. A nanocomposites is defined as a
composite compounded by two or more nanoscale-sized solid phases that are 1–100 nm in at least one dimension Nanomaterials are materials possessing grain size on the order of a billionth of a meter. All materials are composed of grains, which comprises of atoms.
These grains are usually invisible to the naked eye, depending upon their size. A micron (µm) is a micro meter or a millionth (10-6) of a meter. A nanometer (nm) is even smaller a dimension than a µm, and is a billionth (10-9) of a meter. In a nanocomposite system, the addition of a small amount of nanofiller (2–10%) can greatly improve the system performance. The introduction of nanoparticles not only improves the polymer strength, rigidity, and flexibility, but also facilitates the improvement of the polymer light transmission, barrier property, thermal resistance, electrical conductivity.
II. EXPERIMENTAL TECHNIQUES 2.1 Materials
HDPE (High Density Polyethylene)
CNT (carbon nanotubes)
HDPE material had provided by Indian Oil. Propel is the registered trade mark of high density polyethylene. 180M50 is a film grade and it has excellent mechanical strength.
Physical and chemical properties of HDPE (high density poly ethylene) are as follows:
Physical state : Pellets
Flash Ignition Temperature : 3350c
Yield strength : 25 MPa
Auto Ignition Temperature : 3500c
Odour : Slight waxy odour
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Colour : Clear to white
Density : 0.950gm/cm3
Melting point : 125-1350c
Elongation at break : 1000%
Weight impact : 250 gm
Fig 2.1: HDPE (high density polyethylene) virgin pellets taken from IOCL.
Carbon nanotubes
The specifications of multi walled carbon nanotubes are as follows:
Range of diameter : 60-100 nm Length of the tube : 5-15 µm Purity : 95%
Density of MWCNTS : 2.16gm/cm2
Fig 2.2: Powder form of MWCNT (Multi Walled Carbon Nanotubes).
2.2 Chemical Treatment
The effective utilization of the nanotubes in composites depends on the ability to disperse CNTs homogeneously throughout the matrix without or less destroying their integrity. By chemically treatment on CNTs a better interracially bonding between CNTs and polymer was expected to be made the required sample
of CNTs was suspended in the mixture of concentrated nitric acid and sulphuric acid by the volume ratio 1:3 and refluxed at 600c for 30 min.
2.3 Preparation of nanofluid
The chemically treated 2 gm of CNTs were mixed with 500 ml of distilled water for making the 0.01 wt % of CNT/HDPE specimen similarly for making 0.03 wt
% of CNT/HDPE 6 gm of CNTs are mixed with 500 ml of water and for 0.05 wt % of CNT/HDPE 10 gm of CNTs were mixed with 500 ml of distilled water. After that each nanofluid was then sonicated for one hour in a bath sonicator to have a homogenous dispersion of CNTs with water.
Fig 2.3: Carbon Nanofluids of different wt% of CNT 2.4 Preparation of CNT- HDPE pellets
The nanofluid which was prepared with required quantity of CNT was mixed with HDPE pellets. This mixture was heated and stirred continuously to have a uniform coating on the HDPE .once the fluid was evaporated, these pellets were kept in an oven for 15 min at 600c to evaporate moisture present on the CNT coated pellets.
2.5 The tensile specimen preparation by using injection moulding machine
Injection moulding machine is used in the manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials.
Material was fed into a heated barrel, mixed, and forced into a mould cavity where it cools and hardens to the configuration of the mould cavity. For thermoplastics, the injection moulding machine converts granular or pelleted raw plastic into final moulded parts. An injection moulding machine consists of the major components are injection system, hydraulic system, mould system, clamping system, control system. The CNTs coated HDPE pellets were used as raw material in an injection moulding machine. HDPE was melted at the plasticized unit of the injection moulding machine which was kept at 2000c to induce sufficient of polymer
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34 to mix with CNTs and this mixture was injected into tensile specimen mould. The sample was prepared at different concentration of CNT in HDPE. The test specimen has a shape of dog bone which was 100 mm long with a centre section 10mm wide by 2mm thick.
Fig 2.4: Tensile specimen prepared by an injection moulding machine of all concentration CNT/HDPE nanocomposites 2.6 Tensile test of specimen on UTM
The tensile testing of sample was carried on model H25K-S universal testing machine to carry out tensile strength and maximum force. The tests were carried out at the speed of 50 mm/min at room temperature.
2.7 Flexural test of specimen on UTM
In the present work, three point bend test was conducted for the entire three nanocomposites specimen following the universal testing machine (UTM) model H25K-S test standards. The determination of flexural strength is an important characterization of any structural material.
2.8 Wear test of specimen on UTM
The Wear and Friction Monitor (Pin/Ball on Disk) records friction and wear in sliding contact in dry, lubricated, controlled environment and vacuum conditions. The machine used for the wear testing is Wear and Friction Monitor Model (TR -20 LE).
III. RESULT AND DISCUSSION
3.1 Tensile test on universal testing machine (UTM) The dog bone shaped sample has tested on UTM and carried out tensile strength, and max force. The tension test was performed on pure HDPE and the different wt % of CNT/HDPE nanocomposite had been carried out on universal testing machine. In this work,
the tensile strength values obtained for various nanocomposite specimens are shown in table 3.1
Table3.1: Comparison of different wt % CNT added on HDPE polymer for tensile test.
WT % of CNT
Tensile Stress (MPa)
Load (N)
Elongation of
% 0.00 19.19 691 Up to 100 mm 0.01 19.29 695 Up to 100 mm 0.03 19.67 708 Up to 100 mm 0.05 19.77 712 Up to 100 mm Comparison of all concentration of CNT/HDPE tensile specimen
Fig 3.1: Shows the load capacity of nanocomposites increased when the wt % of CNT is mixed with pure polymer. So the load capacity of .05 wt % of CNT/HDPE nanocomposite is higher than .01, .03 wt % of CNT/HDPE and pure polymer.
The tensile strength value obtained for various specimen are shown in fig 3.2
Fig 3.2 : Shows the tensile strength of HDPE and all wt % of CNT nanocomposite. It seems the tensile strength of pure
HDPE is 19.19 MPa and 0.05 wt % of CNT/HDPE nanocomposite is 19.67 MPa. Therefore if CNT added with
pure material shows remarkable properties.
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35 3.2 Flexural strength on universal testing machine
(UTM)
The three point bend test was conducted of all wt % of CNT/HDPE nanocomposites with pure HDPE specimen on UTM to determine the flexural of this specimen. The flexural strength of material measured by resistance to bending shown in table 3.2
Table3.2 Comparison of different wt % CNT added on HDPE polymer for flexural test.
WT % of CNT
Flexural strength
(MPa) Elongation of % 0.00 15.63 up to 20mm 0.01 16.15 up to 20mm 0.03 16.84 up to 20mm 0.05 19.62 up to 20mm Comparison of all concentration of CNT-HDPE flexural specimen
Fig 3.3: Shows that load capacity of nanocomposites increased when the wt % of CNT is mixed with pure polymer. So the load capacity of .05 wt% of
CNT/HDPE nanocomposite is higher than .01, .03 wt%
of CNT/HDPE and pure polymer in flexural test.
The flexural strength value obtained for various specimen are shown in fig 3.4
Fig 3.4: Shows the flexural Strength of pure HDPE with all wt % concentration.
3.3 Wear testing
Wear is related to interactions between surfaces and more specifically the removal and deformation of material on a surface as a result of mechanical action of the opposite surface.
.
Table3.3: Wear reading of HDPE and 0.05 wt % of CNT/HDPE nanocomposite at a load of 10N and 30N specimen Load(N) Sample Speed
(rpm) Time(min) COF Initial wt(grams)
Final wt (grams)
Net wt (grams)
Specific wear rate mm3/Nm ×
Pure HDPE
10
1 200 26.52 0.42 0.8790 0.8782 0.0008 0.000042
2 300 17.68 0.49 0.8784 0.8778 0.0006 0.000031
3 400 13.26 0.52 1.0138 1.0131 0.0007 0.000036
4 500 10.61 0.58 1.0131 1.0124 0.0007 0.000036
30
5 200 26.52 0.53 1.0380 1.0328 0.0021 0.000036
6 300 17.68 0.58 1.0328 1.0322 0.0023 0.000040
7 400 13.26 0.61 0.9875 0.9859 0.0025 0.000043
8 500 10.61 0.73 0.9859 0.9854 0.0022 0.000038
Composite (HDPE+0.05
wt % CNT)
10
9 200 26.52 0.31 1.1245 1.1241 0.0004 0.000021
10 300 17.68 0.33 1.1243 1.1238 0.0005 0.000026
11 400 13.26 0.36 1.1085 1.1079 0.0006 0.000031
12 500 10.61 0.37 1.1079 1.1075 0.0004 0.000021
30
13 200 26.52 0.48 1.0850 1.0833 0.0017 0.000029
14 300 17.68 0.53 1.0844 1.0825 0.0019 0.000033
15 400 13.26 0.58 1.0059 1.0041 0.0018 0.000031
16 500 10.61 0.71 1.0041 1.0026 0.0015 0.000026
.
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36 Comparison of coefficient of friction betwen pure HDPE and 0.05 wt % of CNT/HDPE composite
Fig 3.5: Shows the coefficient of friction of pure HDPE and 0.05 wt % of CNT/HDPE composite under 10N and 30 N
loads.
According to Wang’s the volumetric wear is inversely proportional to toughness. Hence the nanocomposite shows the higher toughness and reduces the friction to enhance the wear resistance properties.
IV. CONCLUSION
1. If volume fraction of carbon nanotubes is increased into the material reduce volumetric wear of the material.
2. The improvement on young’s modulus, stiffness, toughness, wear resistance and rigidity with an addition of CNT. The carbon nanotubes (CNT) have been used with polymer to make composite having remarkable properties.
3. A considerable improvement on mechanical as well as tribological properties of the material when volume fraction of CNT increased the composite reinforcement shows a good load transfer and interface link between CNT and HDPE.
4. If the wt fraction of CNT particles increases the load required to fracture gradually increases.
V. REFERENCES
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[2] Chang L, Mo C, “Nanomaterial and Nanostructure,”
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[3] Ke Y C, Strong P, “Polymer Inorganic Nanocomposite,” Wunan Books, pp. 64–65, 2004.
[4] Wan P, Di K, Di M H, “Synthesis and application of polymer montorillonite nanocomposite,” Mudanjiang Teachers College Journal, pp. 3-17, 2003.
[5] Hsu G C, Chang D, “Nanocomposite” Wunan Books, pp. 324–326, 2004.
[6] Chen K, Yang R C, “Theoretical analysis of percolation of polymer-montmorillonite exfoliative nanocomposites,” Lanzhou University Technology journal 31, pp. 29, 2006.
[7] Runqing O, Rosario A, Gerhardt C M, “Assessment of percolation and Homogeneity in ABS carbon black composites by electrical measurements,” Composites, vol. 34, pp. 607-614, 2003.
[8] Jeon H S, Rameshwaram J K, Kim G,“Characterization of polyisoprene-clay nanocomposites prepared by solution blending,” Polymer, vol. 44, pp. 5749–5758, 2003.
