GB/T 29285-2012 "Pulps - Laboratory wet disintegration - Disintegration of mechanical pulps" specifies the method for the laboratory wet disintegration of mechanical pulps, applicable to all types of mechanical pulps. The method involves mixing an oven-dry pulp sample with water to form a suspension, which is then placed in a disintegrator and subjected to disintegration at a specified rotational speed and duration. The standard defines requirements for pulp concentration, disintegration time, and equipment parameters. After disintegration, the pulp is filtered through a standard sieve to assess the degree of disintegration, ensuring that fibers are adequately dispersed without excessive cutting. This process provides a uniform pulp sample for subsequent fiber analysis or papermaking.