Ultrafiltration membranes are polymeric semi-permeable membranes used in the ultrafiltration process to separate polymeric colloids or suspended particles of a certain size from the solution. Driven by pressure, the membrane pore size is 1 to 100nm and is an asymmetric membrane type. The pore density is about 10/cm and the operating pressure difference is 100-1000 kPa. It is suitable for removing colloidal level particles and macromolecules and can separate solutions with a concentration of less than 10%.