The PU for air filter is two component: Group A and group B, the A group is maily polyol blend(OH-, hydroxyl), and the B group is isocyanate(-NCO), the color is added into the PU A group.
The ratio A to B is 2~4: 3~1.

The group A should be kept in a dry and more than 0 Centigrade Place, the group B should be kept in a dry and more than 10Centigrade. If the B group kept in the place lower than 10 CentigradeThere would be some solid in it, it should be warmed to 70~80Centigrade For at least 10min. Then the solid would gone.