The wet curtain paper is prepared and formed by a paper-making process, and then impregnated with resin, which is adhered to the steel plate after being cured by hot pressing to make a finished product. Because it works in oil, it is called wet paper-based friction material, and it is commonly used in wet-formed clutches, automatic transmissions, and braking devices such as heavy-duty vehicles, engineering machinery, and agricultural machinery. It has the advantages of stable dynamic friction factor, close dynamic / static friction factor ratio, low wear rate, long service life, and protection of dual materials. Compared with resin-based friction materials, metal-based friction materials and semi-metal-based friction materials, wet paper-based friction materials can achieve good wear resistance, thermal stability, sufficient strength and adequate strength through proper fiber ratio. Elastic and has a certain degree of porosity.

The wet curtain paper-based friction material is a porous material, and this structure allows it to store lubricating oil for lubrication and cooling. Therefore, the porosity-will affect the thermal conductivity of the material and affect the thermal wear of the material. On the other hand, it will affect the compression and resilience of the material, as well as the size and stability of the friction factor.

The effect of porosity on the friction and wear properties of wet curtain paper materials shows that the higher the porosity, the higher the initial friction factor and sliding friction factor, especially the initial friction factor. The effect of the porosity of aramid-reinforced paper-based friction materials shows that under the same load, as the porosity increases, the compression rate of the material increases and the rebound rate decreases. The higher the porosity, the greater the friction factor of the material. As the pressure increases, the friction factor of paper-based friction materials with high porosity gradually decreases, and the friction factor of paper-based friction materials with different porosity gradually tends to be the same. As the porosity increases, the friction torque curve tends to be stable: the dynamic friction factor increases, but the wear rate increases. This is because a high porosity means low mechanical properties and the material is prone to wear.