What are the differences between EPDM rubber expansion joints and ordinary rubber expansion joints?

Now many EPDM rubber expansion joints on the market are the inner rubber layer is EPDM, the middle of the curtain cloth and the outer rubber layer are ordinary natural rubber, so that not only the rubber expansion joint temperature resistance received a great impact, even life will have a great impact.
Observe the color. That is, carefully observe the color of the rubber sphere, many counterfeit goods due to the use of low-end, sub-quality rubber, so the production of the sphere color is often particularly gray, in order to prevent experienced people uncovered at a glance. Most of them will take the black shoe polish before leaving the factory to expand the oil polishing disposal, so that it looks black and bright with light. But the real EPDM rubber production out of the rubber expansion joint, the color is pure, emitting sunken color. Not particularly bright or dark.
Odor. In fact, the taste is the best way to judge, because the composition of rubber contains alkene, so rubber will have a normal people feel the pungent smell. But EPDM rubber is ethylene, propylene polymer, and is a highly filled with the material, so after the vulcanization and filling of EPDM rubber instead of the ordinary rubber pungent smell, but instead of an aromatic taste. So as long as the user pays attention, it is not difficult to determine the really good goods.
Tactile. As for the sense of touch, that is, you carefully rub the inner layer of the rubber sphere, there will be a fine slippery feeling, because the authentic EPDM rubber texture is excellent and expensive. So the production of rubber joints in the sense of touch is particularly smooth, while ordinary rubber touch up the feel is far worse, will have the feeling of touching rough skin.
Burning. Burning is said to use a lighter to ignite a small part of the sample of EPDM, the lighter ignited the white powder of the ash, white ash means that it is EPDM material of rubber.
Freezing. Take a small part of the EPDM rubber sample, put it in the freezer and freeze it inside for 24 hours, take it out and no change before it means that this rubber is possible.