Waxes have also been used to improve slip and thereby abrasion
Waxes have also been used to improve slip and thereby abrasion. Hard waxes resist abrasion better than soft materials. Hard waxes like PE and PTFE waxes function by the ball bearing mechanism, while the softer microcrystalline waxes work via the layer (bloom) mechanism. Microcrystalline wax is a petroleum-based wax that has very different physical properties than paraffin wax.
- The Blooming Mechanism:Molten wax particles float (or bloom) to the surface. The coating cools down, and re-crystallization of wax particles takes place, forming out a thin but continuous wax-enriched surface layer. Generally, the softer (low-melting) the wax, the more predominant the blooming mechanism. Incompatibility between wax and coatings can enhance the migration phenomenon. Soft waxes like microcrystalline wax and paraffin wax work through this mechanism.
- The Ball Bearing Mechanism:In this case, solid wax particles migrate individually to the surface. Here they act as a physical spacer by protruding above the coating surface, preventing another surface from coming into close contact. Hard and high-melting-point waxes [high-density polyethylene (HDPE), PTFE] work through this mechanism in some conditions. Both the particle density and the extent of protrusion influence the degree of effects.
Once at the surface, the wax particles (or layer) have the ability to modify the coefficient of friction (CoF) of the film, imparting the required effect(s). This explains why waxes are often classified as surface conditioner additives.