Properties and Test methods
ASTM VS ISO
For manufacturing and understanding resin properties, we often use a resin property table withmerican Society for Testing Material (ASTM) standards. In recent years International Organization for Standardization (ISO) standards have also been increasingly used. Below is explained some of the tests used to provide standards.
Melt Index Test (ASTM D-1238)
This test shows relative flowability of resin in the melt form. It is one of the most basic and critical tests used by plastic processors--as an incoming quality control check, and as a post-processing check of molded plastic parts. A significant change in the flow rate of a resin after processing is quite often indicative of improper processing.
Tensile Properties (ASTM D-638)
Tensile properties are tested to indicate the strength in a material. The force necessary to pull an item apart is determined, as well as how much the material stretches before breaking. Tensile and a variety of basic mechanical properties can be obtained on a single Universal Testing Machine (UTM).
Flexural Properties (ASTM D-790)
This test is used to calculate the flexural strength of a material. Its measurement is obtained by placing a specimen on two supports. A load is applied in the center at a specified rate and the load at failure is used to calculate the strength.
Notched Izod Impact testing (ASTM D-256)
This test shows the energy needed to break notched specimens under standard conditions. It is done by clamping a specimen in the base of a pendulum testing machine so that it is cantilevered upward with the notch facing the direction of impact. The pendulum is released, and the energy consumed in breaking the specimen is calculated from the height the pendulum reaches on followthrough. It is useful in comparing various types of grades of a plastic. The test may indicate a need to avoid sharp corners in parts made of notch-sensitive materials.
Rockwell Hardness test (ASTM D-785)
This test can differentiate relative hardness of different types of a given plastic. Rockwell hardness is not an index of wear qualities or abrasion resistance; it is more a measure of a material's resistance to indentation.
Deflection Temperature test (ASTM D-648)
This test shows the temperature at which an arbitrary among of deflection happens under established loads. It may be useful in comparing the relative behavior of various materials in these test conditions, but it is primarily used for control and development purposes.
Vicat Softening Point (ASTM D-1525)
This test is a good way to compare the heat-softening characteristics of many thermoplastic materials. A temperature-regulated oil bath with a flat needle penetrator is mounted to register degree of penetration on a gauge. A specimen is placed with the needle resting on it. The temperature of the bath is raised, and the temperature at which the needle penetrates 1 mm. is the Vicat softening point.