Slip Agents

are processing agents which are distinguished as „internal“ and „external“ slipping agents. Internal slipping agents reduce the internal friction, improve the flow properties and the homogeneity of the melt, make fillers slip and the molding compound form more easily. They are partially soluble in the polymer (amphipolar) e.g. fatty acids, ester of long-chain fatty acids, PE-waxes and white oils. They behave like soft soap and settle on the interface of agglomerates, pigments or polymer chains. External slipping agents (metal soaps like metal stearates, fatty acid amide ester, silicon oils, waxes, paraffin oils, glycols a.s.o.) reduce the friction of plastics on the wall thickness of the processing machine, reduce the friction of the particles among themselves and the adhesion of the polymer melt on the tool. Because of its insolubility in plastics the slipping agent migrates to the surface during the processing action, accumulates here and acts as a slipping agent or lubricant. This additionally increases the smoothness and the sparkle of the surface of the end product. For films (out of polyethylene with a low density) which are manufactured by film blowing, however, fatty acid amides and fluoropolymers are used.

Slipping Agents

A special group of slip agents (silicon oil, graphite, PTFE etc.) is added to plastics for permanent lubrication effect on the surface of end products. Special extrudates are equipped for conversion and compounding in order to achieve a better handling.

Processing Aids

Polymeric materials have a macromolecular structure with melts of high viscosities. The processing of these melts in injection molding machines and extruders is only possible under pressure. In the machines and tools maximum temperature and mechanical forces are built up due to shearing and friction which exceed the chemical stability of the macromolecules. The processing aids improve the rheology of the melt by reducing the internal (molecule/molecule) and external (polymer/metal) dissipations. Especially for the extrusion of highly viscose polyolefins with a high shear rate processing aids are necessary in order to avoid malfunctions on the extrudate surface and to prevent melt fracture.