EXPERIMENTAL PROCEDURES

2.0 EXPERIMENTAL PROCEDURES:

2.1 MATERIAL DETAILS:

Matrix – HDPE

Supplier - Haldia Petrochemicals

Trade name - Halene – H, B 6401

Melt Flow Index (2.16 kg, 190°C) - 0.30 g / 10min

Density - 0.964 g / cm³

Melting temperature - 132 ° C

Calcium carbonate

Particle size - 2.25µm

LLDPE

Melt Flow Index (2.16 kg, 190°C) - 50

2.2 PREPARATION OF POLYEYHYLENE COMPOUNDS:

According to the formulation obtained from the design table of CCD, the calcium carbonate and LLDPE are mixed in five different levels of calcium carbonate namely 56, 60, 70, 80, and 84. The calcium carbonate is incorporated into the LLDPE matrix using a twin-screw extruder and the extrudate was pelletized. Then the masterbatch was mixed with HDPE matrix in five different let down ratios namely 1, 5, 15, 25, 29. From these mixtures (mixed by simple hand mixing) test samples were prepared using injection molding technique.

2.3 SPECIMEN PREPARATION TECHNIQUE:

The injection molding process is best suited for producing articles made up of thermoplastic materials. In injection molding, a definite quality of molten thermoplastic material is injected under pressure into a relatively cold mold where it solidifies into the shape of the mold.

The process consists of feeding the compounded plastic material as granules or powder through the hopper at definite time intervals into the hot horizontal cylinder where it gets softened. Pressure is applied through a hydraulically driven cylinder into a mold fitted at the end of the cylinder. While moving through the hot zone of the cylinder, the plastic material is uniformly spread around the inside wall of the cylinder thereby ensuring uniform heat distribution. The molten plastic material is then injected into the mold cavity. By using a mechanical locking device, the mold is properly held in position as the molten plastic material is injected under high pressure. Proper flow of the molten material to interior portions of the mold is achieved by preheating the mold to an appropriate temperature. After the mold has been filled with the molten material, it is cooled and then opened to eject the molded article[6].

2.4 TENSILE TESTING (ASTM D638):

2.4.1 INTRODUCTION:

A tensile test is also known as a tension test is probably one of the most fundamental mechanical tests that can be performed on a material. Tensile tests are simple, relatively inexpensive and determine how the material will react to the forces being applied in tension. Tensile test in board sense is the measurement of the ability of the material to withstand forces that tend to pull it apart and to what extent the material stretches before breaking. As the material is, being pulled you will find its strength along with how much it will elongate. Materials, which exhibit the largest strengths during tensile testing, have the lowest impact values. Tensile modulus is an indication of the relative stiffness of the material, and can be determined from the stress strain diagram. Many plastic are very sensitive to the rate of straining and environmental conditions. Therefore the data obtained from this method cannot be considered valid for applications involving load time scales or environmental widely different from this method. The tensile property data helps in preferential selection of a particular type of plastic from a large group of plastic material and such data are of limited use in actual design of the part. This is because the test does not take in to account the time dependent behavior of plastic material. As the pull of the material is continued until it breaks, a complete tensile profile is obtained. A curve will result showing how it reacts to the forces being applied. The point of failure is of much interest and is typically called its ultimate strength or “UTS” on the chart. Uniaxial tension test provides important information about the mechanical properties of the material[2,12].

2.4.2 SCOPE OF THE EXPERIMENT:

This test method covers determination of tensile properties of un reinforced and reinforced plastics in the form of standard dumbbell shaped specimen when tested under defined condition of pretreatment, temperature, humidity, and testing machine speed. This method can be used for testing materials of any thickness above 1.0mm to14mm. This test method includes the option of determining the Poisson’s ratio at room temperature. Test data obtained by this method are relevant and appropriate for use in engineering design.

2.4.3 SIGNIFICANCE AND USE:

This test method is designed to produce tensile property data for the control and specification of plastic materials. These data are also useful for qualitative characterization, research and development. It is advisable to refer to the material specification before using this test method. Tensile properties may vary with the specimen preparation in exactly the same way. Many plastics are very sensitive to the rate of straining and environmental conditions. Therefore the data obtained from this method cannot be considered valid for application involving load time scales or environmental widely different from this method. When uniaxial tensile force is applied to a solid, the solid stretches in the direction of the applied force but it also contracts in both directions lateral to the applied direction of force. If the solid is homogeneous and isotropic, the material remains elastic under the action of the applied force; the lateral strain bears a constant relationship to the axial strain. This constant is called poisons ratio, is defined as the negative ratio of the reverse to axial strain under uniaxial stress.