What Methods are used to evaluate combustion performance of flame-retardant fabric ?
2015-12-23 08:25 | writer: admin
There are two aspects for evaluating the flammability of flame-retardant fabric: ignitability and combustibility(fire resistance) of fabric.
There are two main methods for evaluating the combustion performance of flame-retardant fabric:
1. Combustion speed of fabric. Let the fabric contact the flame for a certain amount of time according to prescribed methodologies, then remove the flame and measure the flame combustion time, flameless combustion time and damage length of fabric. The shorter the combustion time ( flame and flameless) and damage length, the better the fire resistance property; otherwise, the fire resistance is not good.
2. Oxygen index value (also called oxygen value). The burning of fabric needs oxygen, oxygen index value (LOI) is a value expression of amount of oxygen that fiber burning requires, therefore the fire resistance property of fabric can be judged by measuring the oxygen index value, the higher the oxygen index value means the fabric burning need higher oxygen concentration, that will prove the fabric is hard to burn. This index can be expressed by minimum volume percentage of oxygen that keep fabric candle burning: LOE= oxygen concentration/ ( oxygen concentration + nitrogen concentration ) * 100%, it belongs to flammable fibers when oxygen index value is lower than 20%; when oxygen index value is between 20~26%, it belongs to combustible fiber; when oxygen index value is between 26~34%, it belongs to flame-retardant fiber; when oxygen index value is higher than 35%, it belongs to mom-flammable fiber.
There many methods for combustion testing, it is hard to compare each test result, and the test result can only show the combustion performance to some extent. Combustion test, it is mainly for testing the combustion breadth ( carbonization area and damage length ), after flame time and hidden-burning time of the sample combustion. According to relative position of sample and flame, it can be divided to vertical method, incline method and horizontal method. Oxygen index value method means put the sample into transparent combustion tube vertically, there is a upward oxygen nitrogen flow in the tube, then set fire to upper end of sample, observe the combustion immediately, compare combustion time and combustion length with specified limit, oxygen index limit method is suitable for manufacturing process testing.