DENSITY AND SPECIFIC GRAVITY
Density is the mass per unit volume of a material. Specific gravity is a measure of the ratio of mass of a given volume of material at 23°C to the same volume of deionized water. Specific gravity and density are especially relevant because plastic is sold on a cost per pound basis and a lower density or specific gravity means more material per pound or varied part weight.
There are two basic test procedures- Method A and Method B. The more common being Method A, can be used with sheet, rod, tube and molded articles. For Method A, the specimen is weighed in air then weighed when immersed in distilled water at 23°C using a sinker and wire to hold the specimen completely submerged as required. Density and Specific Gravity are calculated.
Specific gravity = a/[(a + w)-b]
a = mass of specimen in air.
b = mass of specimen and sinker (if used) in water.
W = mass of totally immersed sinker if used and partially immersed wire.
Density, kg/m 3 = (specific gravity) x (997.6)
Instruments used: We use Digital density testing instrument.
BARCOL HARDNESS
Barcol Hardness is used to determine the hardness of both reinforced and non-reinforced rigid plastics.The specimen is placed under the indentor of the Barcol hardness tester and a uniform pressure is applied to the specimen until the dial indication reaches a maximum. The depth of the penetration is converted into absolute Barcol numbers.
Specimens are required to be a minimum thickness of 1/16th of an inch.
Instrument used: We use Barcol Hardness tester
SHORE A HARDNESS
Durometer Hardness is used to determine the relative hardness of soft materials,usually plastic or rubber. The test measures the penetration of a specified indentor into the material under specified conditions of force and time. The hardness value is often used to identify or specify a particular hardness of elastomers or as a quality control measure on lots of material.The specimen is first placed on a hard flat surface. The indentor for the instrument is then pressed into the specimen making sure that it is parallel to the surface. The hardness is read within one second (or as specified by the customer) of firm contact with the specimen.
The test specimens are generally 6.4mm (¼ in) thick. It is possible to pile several specimens to achieve the 6.4mm thickness, but one specimen is preferred.
The hardness numbers are derived from a scale. Shore A and Shore D hardness scales are common, with the A scale being used for softer and the D scale being used for harder materials.
SHORE A HARDNESS
Shore (Durometer) hardness test. Shore hardness is a measure of the resistance of a material to penetration of a spring loaded needle-like indenter. Hardness of Polymers (rubbers, plastics) is usually measured by Shore scales. Shore A scale is used for testing soft Elastomers (rubbers) and other soft polymers.
ULTIMATE LOAD BEARING STRENGTH
In essence, bearing strength is the maximum stress load that the unit can “bear” or hold before the structure fails. This parameter necessary for composite materials in construction industry.
Instruments used: We use UTM for testing Ultimate Load Bearing Strength.
COMPRESSION STRENGTH
Compressive properties describe the behavior of a material when it is subjected to a compressive load. Loading is at a relatively low and uniform rate. Compressive strength and modulus are two common values generated by the test.
The specimen is placed between compressive plates parallel to the surface. The specimen is then compressed at a uniform rate. The maximum load is recorded along with stress-strain data. An extensometer attached to the front of the fixture is used to determine modulus.
ZETA POTENTIAL
Zeta potential is a scientific term for electrokinetic potential in colloidal dispersions. In the colloidal chemistry literature, it is usually denoted using the Greek letter zeta (ζ), hence ζ- potential. The usual units are volts (V) or millivolts (mV). From a theoretical viewpoint, the zeta potential is the electric potential in the interfacial double layer (DL) at the location of the slipping plane relative to a point in the bulk fluid away from the interface. In other words, zeta potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle.
The zeta potential is caused by the net electrical charge contained within the region bounded by the slipping plane, and also depends on the location of that plane. Thus, it is widely used for quantification of the magnitude of the charge. However, zeta potential is not equal to the Stern potential or electric surface potential in the double layer, because these are defined at different locations. Such assumptions of equality should be applied with caution. Nevertheless, zeta potential is often the only available path for characterization of double-layer properties.
The zeta potential is a key indicator of the stability of colloidal dispersions. The magnitude of the zeta potential indicates the degree of electrostatic repulsion between adjacent, similarly charged particles in a dispersion. For molecules and particles that are small enough, a high zeta potential will confer stability, i.e., the solution or dispersion will resist aggregation. When the potential is small, attractive forces may exceed this repulsion and the dispersion may break and flocculate. So, colloids with high zeta potential (negative or positive) are electrically stabilized while colloids with low zeta potentials tend to coagulate or flocculate as outlined in the table.
PARTICLE SIZE ANALYSIS BY DYNAMIC LIGHT SCATTERING
Particle size analysis, particle size measurement, or simply particle sizing is the collective name of the technical procedures, or laboratory techniques which determines the size range, and/or the average, or mean size of the particles in a powder or liquid sample .Particle size analysis is part of particle science, and its determination is carried out generally in particle technology laboratories.
The particle size measurement is typically achieved by means of devices called Particle Size Analyzers (PSA) which are based on different technologies, such as high definition image processing, analysis of Brownian motion, gravitational settling of the particle and light scattering (Rayleigh and Mie scattering) of the particles.The particle size can have considerable importance in a number of industries including the chemical,food, mining, forestry, agriculture, nutrition, pharmaceutical, energy, and aggregate industries.
MOONEY VISCOSITY & SCORCH TIME
Our established Mooney line Viscometer is the perfect choice for all professionals, suited for the modern laboratories at all stages of the rubber production process, efficiently producing accurate data on a variety of elastomeric compounds.
The rotor and die assembly of our Mooney Viscometer are fundamental for producing a controlled test environment of heat and pressure at a constant rotor speed. A sample of test material is placed above and below the rotor and the platens then closed under pressure. By the means of microprocessor based PID control system, the temperature of the dies and sample contained are accurately maintained.
The rotor rotates at a constant speed to two revolutions per minute (2 RPM) and by means of a precise transducer system located below the die assembly, the torque exerted on the rotor head is measured and recorded within the system data files.
The Mooney line Viscometer has the ability to be programmed for measuring the Stress Relaxation index of material samples. This feature enables the user to measure the decay of viscosity by firmly locking the rotor after the programmed test time has elapsed. In addition to this the equipment conforms to international standards and meets the requirements of ASTM D1646 performing industry standard tests on a wide range of compounds prior to manufacturing processes, such as:
MELT FLOW INDEX
Melt Flow Rate measures the rate of extrusion of thermoplastics through an orifice at a prescribed temperature and load. It provides a means of measuring flow of a melted material which can be used to differentiate grades as with polyethylene, or determine the extent of degradation of the plastic as a result of molding. Degraded materials would generally flow more as a result of reduced molecular weight, and could exhibit reduced physical properties. Typically, flow rates for a part and the resin it is molded from are determined, and then a percentage difference is calculated. Alternatively, comparisons
between “good” parts and “bad” parts may be of value.
Approximately 7 grams of the material is loaded into the barrel of the melt flow apparatus, which has been heated to a temperature specified for the material. A weight specified for the material is applied to a plunger and the molten material is forced through the die. A timed extrudate is collected and weighed. Melt flow rate values are calculated in g/10 min.
Test Method: ASTM D1238.
Instruments Used: Melt Flow Tester and Weighing Balance.
GLOW WIRE FLAMMABILITY
Historically a number of methods have been developed to evaluate material flammability and fire resistance. These include both direct flame and indirect flame testing methods. An example of the direct flame method is defined in the UL 94 specification. This long accepted test method involves applying a flame directly to a vertically or horizontally mounted specimen under controlled conditions. On the other hand, the indirect flame method features a non-flaming heat source applied to a sample. Glow wire testing is an example of the indirect flame method. Test results from applying these methods provide a way to compare the materials’ tendency to resist ignition, self-extinguish flames (should ignition occur), and to not propagate fire via dripping.
Glow wire testing is performed by heating an element to a pre-determined temperature. The heated element is referred to as the glow wire. The sample to be tested is fixture in place and tissue paper is positioned directly below the sample. After reaching the pre-determined temperature, the element is then pressed into a sample material under a set force of 1N for 30 seconds. If ignition occurs, recordings are made to note the duration and flame height.
The results of this test will be either PASS or FAIL at a given temperature. Passing the test requires that the sample does not ignite or self-extinguishes within 30 seconds after removal of the heated element. Also, the sample may not ignite the tissue paper if drips occur.
Test Method: ASTM D6194
VICAT SOFTENING TEMPERATURE
The Vicat softening temperature is the temperature at which a flat-ended needle penetrates the specimen to the depth of 1 mm under a specific load. The temperature reflects the point of softening to be expected when a material is used in an elevated temperature application.
A test specimen is placed in the testing apparatus so that the penetrating needle rests on its surface at least 1 mm from the edge. A load of 10N or 50N is applied to the specimen. The specimen is then lowered into an oil bath at 23 degrees C. The bath is raised at a rate of 50° or 120° C per hour until the needle penetrates 1 mm.
Test Method: ASTM D1525
Instrument Used: VSP/HDT Tester.
HEAT DEFLECTION TEMPERATURE OF PLASTICS
Heat deflection temperature is defined as the temperature at which a standard test bar deflects a specified distance under a load. It is used to determine short-term heat resistance. It distinguishes between materials that are able to sustain light loads at high temperatures and those that lose rigidity over a narrow temperature range.
The bars are placed under the deflection measuring device. A load of 0.45 MPa or 1.80 MPa is placed on each specimen. The specimens are then lowered into a silicone oil bath where the temperature is raised at 2° C per minute until they deflect 0.25 mm
Test Method: ASTM D648
Instrument Used: VSP/HDT Tester.
