Toy belt pulley with what material to do the O type circle is better?

Before we receive an inquiry, the customer needs a small belt, with the general rubber O ring on it, but what material suitable for it
The strength and elasticity of the rubber is very good and the flexible polyurethane is very good, and it is not easy to deform! Weight is also light factory production line with a good point of polyurethane!
Perhaps on the assumption is mine coal or similar mines with good rubber belt flex rubber. Good water resistance and water resistance..PU reciprocating work difference. Low temperature difference power. Good wear. At room temperature under static conditions. Conversely PU rubber.
Leather on the polyurethane material is generally attributed to polyester polyurethane products, this material from the principle of the water will be the case of decomposition, decomposition of course, it will not be used.
But now the polyurethane material will be more or less put some anti hydrolysis agent. So don't worry.
If encounter defective O type ring, anti hydrolysis agent without a point. Do not have to say that the water, in the humid air will accelerate its aging.