How to distinguish the type and material of the seal? (3)


How to identify the specific material of rubber product […]

How to identify the specific material of rubber products
There are many kinds of O-rings produced by our company, including Ding Qing O-rings, fluorine rubber O-rings, silicone O-rings, EPDM O-rings, neoprene O-rings, etc. What about these materials?
1.Medium weight resistance experiment
Samples can be taken from the purchased O-rings, immersed in the selected medium or media after determining the temperature, weighed after a certain period of time, and the type of material can be inferred based on the rate of change in weight and rate of change in hardness. For example, when immersed in 100 degree engine oil for 24 hours, the quality and hardness change rate of Ding Qing, fluorine rubber, neoprene is small, while natural rubber and ethylene propylene have more than doubled the weight and the hardness changes greatly, and the volume expansion is obvious.
2.Combustion method
Take a sample and burn it in the air. Observe the phenomenon. Generally speaking, the fluorine rubber, natural rubber will extinguish after leaving the fire, even if the flame is burned, it is much smaller than EPDM. Of course, if you look closely, the burning state, color, and smell will also provide us with a lot of information. For example, NBR / PVC is used in combination with glue. When there is a fire source, the fire splashes and splatters. It seems to be water-like. It extinguishes itself from the fire, and the smoke is thick and acid. It should be noted that sometimes flame retardants but halogen-free glues will self-extinguish from the fire, which must be further inferred by other methods.
3. Hot air aging test
Take a sample and place it in an aging box for one day to observe the phenomenon after aging. In order to classify the aging, the temperature can be gradually increased. For example, at 150 degrees, neoprene, natural rubber, SBR will be brittle, Ding Qing, EPDM and elastic. When it rises to 180 degrees, ordinary Ding Qing will be brittle; while at 230 degrees, hydrogenated Ding Qing will also be brittle.
4.Low temperature method
Take a sample and make a suitable low temperature environment with dry ice and alcohol. Soak the sample in a low-temperature environment for 2-5 minutes, and feel the softness and hardness of the O-ring at the selected temperature. For example, at -40 ° C, compared with silica gel and fluorine rubber, which have the same high temperature and oil resistance, silica gel will be softer.
5.Measure specific gravity
Use a precision electronic scale, plus a glass of water, a piece of hair is fine. Generally speaking, the proportion of fluorine rubber is the largest, more than 1.8, and CR and ECO are more than 1.3, and the proportion is obviously higher.
The above methods can only simply test the rubber composition. If you want a specific test report, you need to send it to a special testing agency for testing.