Cotton Polyester Blend Separation Mechanics during Mechanical Opening
Mechanical opening separates cotton and polyester blends when differences in fiber density, crimp, and friction cause differential transport and waste drop.
Terminal Velocity Segregation
Aerosol Separation
Particle separation techniques using vertical air columns allow mixed particulate materials to be graded by their aerodynamic behavior. The terminal velocity segregation of fibers is a mechanical separation process that divides coarse and fine fibers based on their falling speeds in a controlled airstream. It is commonly used in industrial dehairing plants to isolate fine cashmere from heavy guard hairs.
Airstream Mechanism
Mechanical separation is achieved by injecting the fiber mixture into a rising current of air within a vertical chamber. Under these conditions, terminal velocity segregation occurs because fine down fibers have a lower terminal velocity and are carried upward by the airflow. The heavy, coarse guard hairs, which have a much higher terminal velocity, overcome the lift of the airstream and fall to the bottom of the chamber.
This continuous separation operates efficiently when the air velocity is maintained within precise parameters.
Separation Factor
Shape and fiber density are the critical variables that dictate how filaments behave in the rising air column. High differences in diameter between the coarse outer hair and the fine down increase the efficiency of terminal velocity segregation. Pre-cleaning the fleece to remove large clumps of dirt and tangled locks makes this pneumatic separation more effective.
Mill Assessment
Quality control tests at the output ducts measure the residual coarse hair content to evaluate the separation performance. If the air velocity is too high, coarse hairs are carried into the down collector, which necessitates a second processing run and increases fiber breakage.