On the surface, the difference is not very big, but in fact there is still a difference in quality. If the quality is good, the service life will be relatively longer. Here we will introduce five methods to identify the material of rubber joints.
Medium weight gain resistance test: We can soak the sample removed from the finished product in one or several selected media. After a certain temperature and time, take it out and weigh it, and judge the type of material based on the rate of change of weight and hardness. For example, if soaked in 100-degree engine oil for 24 hours, the mass and hardness change rate of glue, NBR, CR, and ECO will be very small, while the weight of EPDM, NR, and SBR will more than double, the hardness will change greatly, and the volume will increase significantly.
2. Combustion method: Take a small amount of sample and burn it in the air. CR and CSM self-sustain when they are away from the fire. Even if they burn, the flames are much smaller than those of NR and EPDM. Of course, if we investigate carefully, the combustion conditions, color, and smell will also provide us with a lot of information. For example, when NBR/PVC is used together with glue, sparks will fly when there is a fire source, and the smoke will be thick and have a sour smell. It is worth noting that sometimes flame retardants will self-extinguish when removed from the fire, which requires further analysis using another method.
3. Hot air aging test: Take a sample from the product and place it in the aging box for one day to analyze the aging condition. It can gradually heat up in stages. For example, NR, CR, and SBR will break at 150 degrees, while NBR EPDM is still flexible. Generally, NBR will break when it rises to 180 degrees, and HNBR will also break when it rises to 230 degrees. Fluorine rubber and silicone still have excellent elasticity.
4. Measure specific gravity: Use an electronic scale or analytical balance, accurate to 0.01 grams. Generally speaking, fluorine rubber has the largest specific gravity, above 1.8, and CR ECO is also mostly above 1.3. Those with significantly larger specific gravity can be considered as these rubbers.
5. Low temperature method: Take samples from the product and use dry ice and alcohol to create a simple low temperature environment. Soak the sample in a low temperature environment for 2-5 minutes, and feel the change in hardness at a certain temperature. For example, at -50 degrees, compared with fluorine rubber, silicone gel, which has excellent high temperature and oil resistance, is softer than fluorine rubber.
If you want to know the material of rubber joints, as long as you master the above five methods, you can almost easily identify what material the rubber joints are made of.
