Process aids are added in small quantities to minimize defects in finished products and to improve processing characteristics. Some lubricants and impact modifiers also have beneficial effects on processing. The functions of process aids include:
• Avoidance of defects such as melt fracture and sharkskin
• Improve surface finish
• Reduced formation of crosslinked gel and other kinds of build-up in the extruder die, or as it exits.
• Reduce pressure in the die, reduce motor torque
• Increase strength of end product
• Easier mould release in injection moulding
• Improve cavity filling in injection moulding
It is sometimes possible to achieve satisfactory processing conditions and production rates without using process aids, simply by altering other variables such as process temperature or polymer composition.