The nature of the characteristics of the Marcus polyethylenes are harnessed in dispersion, emulsion and micronized forms to great effect for a variety of applications in this field, the prime reasons for use being:
- Mar, scratch and abrasion resistance
- Slip modification
- Rheological modification
- Flatting
The presence of fine particles of a hard polyethylene, both at and protruding from the surface of a film, reduces the coefficient of friction. This means that other surfaces do not directly abrade the surface, and thus mar, scratch and abrasion resistances are improved. The additional slip created also provides an external lubricating action, useful in finished metal which subsequently has to undergo forming.
The addition of a dispersion to a varnish or lacquer reduces the gloss, having a flatting action. The extent of flatting depends upon many parameters and is not as great as with a colloidal silica. However, a polyethylene dispersion has very food transparency and smoothness, giving a soft silky feel. Most commonly the two are used in combination.
The polyethylene dispersions possess thixotropic characteristics. Consequently they impart good anti-settling and anti-sagging feature to pigmented finishes. In this respect, the oxidized grades are of particular value and these rheology properties make them a goal choice for aluminum flake control in automotive base coat lacquers.