Lubricants

Classification of Lubricants
Depending on their way of action, one distinguishes between internal and external lubricants, with continuous transition. Internal lubricants often exhibit a certain external lubrication and vice versa. Lubricants having both effects are called “combined”.

Internal lubricants reduce friction occuring between the molecular chains of PVC, thus lowering the melt viscosity. They are polar, highly compatible with PVC, give excellent transparency even in high dosages and do not tend to exudate which could impair the weldability, printability and bonding properties.

External lubricants mainly reduce wall adhesion between PVC and metal surfaces. Most of them are non-polar substances, such as paraffins or polyethylene. The external lubrication is influenced by the length of the hydrocarbon chain, the branching or the functional groups. In high dosages “over-lubrication” can lead to haziness and exudation. External lubricants increase the fusion time.