Functions of Internal and External Lubrication of PVC Lubricant-1

PVC needs different additives to prevent its degradation upon heating and shearing to get desired articles. Lubricants are crucial to add during the processing of rigid PVC. They can greatly influence the flow behavior and viscosity of PVC compositions in the processing machinery. Their role can be summarized as follows:

PVC Lubricants reduce friction within the polymer matrix before PVC melting.

They lower friction between the plastic machinery and the contact surface of PVC melt.

This way, lubricants help smooth and ease the processing of PVC in the machinery. Below we have discussed the phenomenon and purposes of external and internal lubrication in detail.

External Lubrication of PVC Lubricant

External lubricant for PVC sticks to the surface of the processing machine or mold or to the surface of the molten resin to form a molecular layer. In this way, it deals with the interface lubrication mechanism. The presence of the lubricant molecular layer results in the formation of a lubricating interface which lowers the friction between the processing machine and resin. The processing temperature and melting point of lubricant determine the viscosity and efficiency of the lubricating interface film. Lubricants with long molecular carbon chains generally offer better lubrication as they make the two friction surfaces farther away.

The external lubricant for PVC makes the movement of the stock through the machinery easier. It hinders the local formation of thick layers and their burning by preventing the sticking of stock to the hot metal of machinery. External lubricants delay gelation by raising the fusion time and stability of PVC. They also make the end product look glossy.

Polyethylene wax and paraffin wax are commonly used external lubricants for PVC.