In modern industry, silicone and rubber are used more and more widely. But with so many manufacturers popping up, it’s hard to judge the quality of these silicone tubes. So, how do you tell rubber and silicone apart? Next, Orientflex shares five methods.
1. Measure weight
Take a sample. Use an electronic scale or analytical balance, accurate to 0.01 grams. Rubber is heavier. If a sample has a significantly larger specific gravity, it’s likely rubber.
2. Combustion method
First, take a small piece of the product and burn it. Fluorine rubber burns weakly. CR and CSM burn out once the flame is removed. NR and EPDM burn with larger flames.
You can also observe the burning state, color, and smell. For example, NBR/PVC mixed glue splatters when lit. It self-extinguishes after the flame is removed. The smoke is thick and smells sour.
3. Hot air aging test
Take a sample and put it in an aging box. Watch for aging. At 150℃, CR, NR, and SBR become brittle and break. NBR and EPDM stay flexible. Ordinary NBR breaks at 180℃. HNBR becomes brittle and breaks at 230℃. But fluorine rubber and silicone still keep good elasticity.
4. Resistance to media weight gain
Cut a sample from the finished product. Soak it in a chosen medium (or media) at a set temperature for a set time. Then weigh it. Infer the material type from weight change rate and hardness change rate.
For example, soak samples in 100℃ engine oil for 24 hours. NBR, fluorine rubber, ECO, and CR show little change in weight or hardness. But NR, EPDM, and SBR more than double in weight. Their hardness changes a lot, and their volume expands obviously.
5. Cryogenic method
Take a sample and put it in a suitable low-temperature environment. Let it soak for 2–5 minutes. Then feel its hardness at that temperature. For example, at -40℃, silicone is softer than fluorine rubber—even though both resist high temperatures and oils.