Things you have to know about flame retardantCommon flame retardant tests include combustion tests, limit oxygen index, glow wire tests, and smoke test. The purpose of the flame retardant test is to evaluate the burning characteristics of the material, that is, to test the sample using conditions that simulate actual combustion, and evaluate the burning characteristics of the sample from different dimensions such as ignitability, ignitability, fumes, and flammability.
I. Burning test
The combustion test refers to igniting the sample by means of an open flame, and comprehensively evaluating the flammability of the sample according to indicators such as burning speed, flame duration, and presence or absence of molten droplets. Because of its scientific evaluation method and universality, UL94 is widely used in flame retardant evaluation of various materials. Most of the combustion test standards are based on and improved based on the UL94 combustion evaluation method.
Second, the limit oxygen index test
The limiting oxygen index evaluates the flammability of the sample. Under the specified test conditions, the minimum oxygen concentration that can just maintain the material's combustion is determined. The test method is to fix the sample vertically in the combustion cylinder and fill it with a certain concentration of oxygen and nitrogen, ignite the top of the sample with an igniter, observe the sample combustion, and adjust the oxygen concentration accordingly, until the measurement sample just maintains the lowest level of equilibrium combustion. Oxygen concentration, expressed as a percentage of oxygen content.
Third, the glow wire test
The glow wire test simulates whether the high-heat metal wire core generated when the circuit inside the polymer shell of the electronic appliance is short-circuited will cause the shell to burn and ignite. The glow wire itself is a fixed-gauge resistance wire ring. During the test, it is electrically heated to the specified temperature, so that the tip of the glow wire contacts the sample for the standard required time, and observe the ignition situation. There are two types of indicators for the glow wire test, the flammability index GWFI and the light-off temperature GWIT. The evaluation indicators are different.
Fourth, the smoke test
The polymer carbon chain is long, and a large amount of oxygen is required for combustion. The oxygen concentration in daily life is difficult to support the complete combustion of the sample. Incomplete combustion will generate a large amount of suffocating poisons such as carbon monoxide and benzene which are harmful to the human body and the environment. substance. During the smoke test, the sample is fixed in the box, and the sample is burned in the box with electric heating to generate smoke, and the transmittance change of the equal light beam passing through the smoke is measured, and then the specific optical density is calculated, that is, the unit area test The smoke generated by the sample spreads out the smoke density per unit path of the unit light path.
In addition to the above conventional flame retardant tests, there are also a large number of finished product standards for finished materials such as building materials, rail transit, wires and cables. These tests will perform corresponding flame retardance simulations according to specific applications, such as cigarette ignition tests, smoldering tests, Smoke toxicity test, heat radiation flux test, etc.