Effect Of Carbon Nano Tube In Tensile Strength
The effects of multi-walled carbon nanotube (MWCNT) on mechanical properties of polymethyl metha acrylaet composites were studied. In this paper, MWCNT was used as the nano-sized reinforced material. The Poly (methyl methacrylate) composites with different MWCNT contents were prepared by solution casting method. The influence of MWCNT contents on mechanical properties of the composite was analyzed by experimental methods. The results showed that the Tensile strength, Tear Resistance and hardness of PMMA composite with MWCNT were improved greatly. Moreover, the Infrared absorbance studies reveal covalent bonding between polymer strands and the nanotubes is helpful to get better mechanical properties.
Key Words : Polymethyl metha acrylate, solving casting, MWCNT, Tensile Strength, Tear Resistance, Hardness.
Introduction
Nowadays polymers play a very important role in numerous fields of everyday life due to their advantages over conventional materials (e. g. metals) such as lightness, resistance tocorrosion, low-cost production, and ease of processing. Further improvement of their performances still being intensely investigated. Altering and enhancement of the polymers’ properties occur, for example, through doping with various fillers such as metals, semiconductors,organic and inorganic particles and fibers, as well as carbon structures and ceramics; thereby enabling polymers to be used as a structural unit.
Fillers are used in polymers for a variety of reasons: improved processing, density control, optical effects, thermal conductivity, and control of thermal expansion, electrical properties, magnetic properties, flame resistance, and improved mechanical properties, such as hardness, elasticity, and tear resistance. Polymer composites can be used in many different forms in various areas ranging from structural units in the construction industry to the composites of the aerospace applications Poly (Methyl Methacrylate) (PMMA) a transparent thermoplastic polymer, possesses moderate physical properties associated with low cost. High transparency makes PMMA an ideal replacement for glass where impact or weight is a serious concern. PMMA is compatible with human tissue making it an important material for transplants and prosthetics, especially in the field of ophthalmology because of its transparent properties. PMMA is formed through block, emulsion or suspension polymerization of methacrylic acid. Poly(methyl methacrylate) (PMMA) is one of the most important acrylic polymers used widely because of its excellent optical clarity and good weathering behavior. PMMA is one of the well-known brittle materials and which restricts its applications. In order to enhance the physical and mechanical properties of PMMA, numerous studies have been carried out in the past three decades. The most common method for promoting the toughness of PMMA is blending and copolymerization.
Carbon nanotubes (CNT) are structures from the fullerene family which are created when a carbon honeycomb sheet rolls in itself to form a cylinder. CNTs have good physical and mechanical properties and are widely used as the reinforcing materials in polymer matrices to obtain ultra-light structural materials with enhanced electrical, thermal and optical characteristics. There are two main types of nanotubes: Single-walled carbon nanotubes (SWCNTs), individual cylinders of 1-2 nm in diameter, which are actually a single molecule, and multi-walled carbon nanotubes (MWCNTs), which are a collection of several concentric graphene cylinders.
To improvement of physical-mechanical properties of polymer nanocomposites by introduction of polymer nanocomposites by introduction of CNT depends on the dispersion of CNT in the matrix and interfacial interactions between them. In order to be compatible with the non-polar polymers, CNT modification with surfactants or compatibilizers is essential[7]MWCNT are considered as one of the most important nanoreinforcing materials and functional materials in polymer materials due to their excellent mechanical properties and specific such as large aspect ratio, excellent current-carrying capability, and high thermal conductivity. They are suitable for a wide range of applications including electrochemical, field-emission, and electronic devices.
However, perhaps the most promising potential applications are those associated with their mechanical properties. For example, nanotubes’ Young’s moduli can reach 1 TPa, while their strength has been measured at up to 63 GPa, which is an order of magnitude stronger than high-strength carbon fibers. In the case of the PMMA-CNT composite, the mechanical properties, elongation at break and impact strength, decreased as the amount of CNTs in the composite increased. With only a small amount of CNTs, 0. 5 wt%, the mechanical properties were improved, which was attributed to increased matrix crystallinity. Coleman et al. fabricated composites based on poly(vinyl alcohol) demonstrating an increase of ×3. 7 in Young’s modulus and ×3. 9 in strength by adding less than 1 wt% of CNTs that depended in the nucleation of polymer crystallinity by the nanotubes. The resulting crystalline interfacial region plays a dual role. Because of its inherent strength and stiffness, it acts as a reinforcing agent in its own right. More importantly, it is thought that crystalline interfacial regions result in better stress transfer to nanotubes compared to amorphous regions. Arash et al. they proposed a new method for evaluating the elastic properties of the interfacial region of CNT/polymer composites. Their simulation results on the elastic properties of a PMMA polymer matrix with a size of 3. 7×3. 7×8 nm3 reinforced by a (5%) CNT reveal that the Young’s modulus of the composite increases from 3. 9 to 6. 85 GPa with an increase in the length-to-diameter aspect ratio of the CNT from 7. 23 to 22. 0The aim of work used CNT was 0%, 0. 1%, 0. 2%, 0. 3% and 0. 5% respectively.
In this paper, mechanical properties of the composite were characterized by FTIR experiments made on the composite. 1-6 Mechanical Properties To characterize mechanical strength of poly methyl methacrylate generally tensile testing is used, with certain geometry and stretching speed, relationship between the stress and tensile strain are determined which is called Hooke law based on elasticity of the materials like a spring. Stress is defined as the measurement of the average forces (F) per unit area of a surface (A) shown by relation below:[11]σ=F/A
(1) Strain ε is the ratio of total deformation to the initial dimension of the material body in which the forces are being applied seen clearly by the relation:ε=∆L (L-L°) / L° (2)
where :∆L Change in the elongation = L-Lo and L, Lo the instantaneous and original length of the material. Modulus of elasticity (E) is a measure of the stiffness of an elastic isotropic material and is a quantity used to characterize materials. It is defined as the ratio of the stress along an axis over the strain along that axis in the range of stress in which Hooke's law holds σ = E ε
(3)Experimental Work Materials :The following chemicals have used for synthesis of PMMA and carbon nano tube and PMMA/carbon nano tube which have purity were listed in table (1) and Fig (1) show the grain size of MWNT nano tube.
Preparation of PMMA and PMMA/MWNT films: Pure PMMA prepare with weighted grade (2wt%) dissolved in chloroform to obtain 20 wt% solution of PMMA grade by slowly in 60 ◦C for 2 hours. Carbon nanotube dispersions were mixed together with the polymers in suitable solvents. To form a composite, the solvents were then evaporated from the mixture. The formation of a homogeneous mixture was supported by ultrasonic agitation and mixing. An appropriate amount of poly (methyl methacrylate) was added to well dispersed MWNT-in chloroform in order to achieve a desired weight concentration of MWNT with respect to PMMA. The final mixture was then thoroughly mixed and sonicated (200 W) until a stable, black-colored chloroform solution of MWNT/PMMA composite was formed. The MWNT/PMMA samples were prepared with 0. 1, 0. 3, and 0. 5 wt% of MWNT. Then cast on the glass plates and then kept at 60 ◦C in the vacuum oven for 24 hour to ensure complete solvent removal. The thickness of samples is 115 µm. Characterization /Thickness measurement An electronic digital micrometer (IDM) with ± 0. 001 sensitivity was used to measure the thickness of PMMA, PMMA/CNT.
