Lubricants also save on stabilizer use because they reduce frictional heat buildup between particles during fluxing and between molecules during calendering. Lubricants are classified as either external or internal, depending on where they are most effective. Stearic acid, organic and inorganic stearates, and soaps of many kinds are mostly classified as internal lubricants. Paraffin and polyethylene waxes are almost entirely external, but montan waxes combine both internal and external properties. As little as 0. 1 to 0.5 percent lubricant is normal.
Thicker sheet requires less lubrication because it generates less frictional heat on the calender.
Plasticizers make PVC more flexible but therebv lower melt viscosity, moduli, and transition temperatures. When plasticizers are used in amounts less than 5 percent. In either case, the effect on calenderability is nearly the same as lubricants. Two common plasticizer groups are phthalates such as diocryl phthalate and epoxides such as epoxidized soybean oil. Blending Blending the raw materials is one of the most underrated aspects of calendering technology.