Hand or Rotary Brush - That Is the Question? Service People Version - Wax Layers - Part. No. 1/1

 1. What Actually Remains on the Ski Base After Hot-Wax Application

To describe correctly how manual and rotary brushes remove wax from a ski base, we must first explain where the wax is actually located after hot-wax application.

The wax does not remain on the surface as a single homogeneous layer. After ironing, cooling, and scraping, it is present in several geometrically and physically distinct regions. The individual parts of this wax “reservoir” differ in their accessibility to the scraper and brush filaments, and they also play different roles in the resulting properties of the ski base.

For the following discussion, it is useful to distinguish three basic wax reservoirs:

1. a macroscopic wax layer above the ski-base surface,
2. a thin wax film retained within the surface microstructure,
3. wax that has penetrated into the uppermost polymer zone of the UHMWPE.

This division cannot, however, be understood solely as a variation in the direction perpendicular to the surface, that is, along the Z-axis. The actual ski-base surface also changes continuously across the plane, along the X- and Y-axes. Consequently, the thickness of the surface wax, its adhesion, and the possibility of its penetration into the polymer may differ from one location to another.

1.1 The Ski Base Is Not a Homogeneous Solid Surface

A ski base made from sintered UHMWPE is not a perfectly homogeneous material. UHMWPE is a semicrystalline polymer in which the following regions alternate on the nanometre scale:

• crystalline regions,
• amorphous regions,
• transitional or intermediate regions between them.

The existence of these three distinct populations of polymer chains—crystalline, intermediate, and amorphous—is supported, among other methods, by NMR measurements of molecular mobility in UHMWPE.

Crystalline regions consist of relatively regularly arranged sections of polymer chains. The chains are tightly packed and their mobility is significantly restricted.

Amorphous regions have a less ordered structure. They contain more free volume between the chains, greater molecular mobility, and a higher degree of polymer-chain entanglement.

Transitional regions are located at the interface between a crystalline lamella and the fully amorphous matrix. The chains in these regions are partially oriented and constrained by the crystalline phase, but they are not ordered sufficiently to form a perfect crystal lattice.

These regions do not form simple, clearly separated blocks. On the nanometre scale, crystalline lamellae are interspersed with amorphous and transitional regions. In studied UHMWPE films, for example, nanodomain layers with thicknesses on the order of several tens of nanometres have been described, showing that the individual structural regions may alternate over extremely small length scales.

1.2 Variations in the Ski Base Along the X-, Y-, and Z-Axes

The ski-base surface must be understood as a three-dimensionally variable environment.

Z-axis: changes with depth

In the direction perpendicular to the surface, the following regions are encountered progressively:

• free or continuous wax above the original surface,
• wax retained within the ground structure and surface microroughness,
• a UHMWPE surface zone affected by grinding, thermal processing, and use,
• deeper polymer material that is mechanically less disturbed.

The amount of wax that may have penetrated during normal hot-wax application generally decreases rapidly with depth.

X- and Y-axes: changes across the surface plane

Changes parallel to the surface are equally important.

As one moves across the ski-base surface, the following properties continuously change:

• the relative proportion of crystalline, amorphous, and transitional regions,
• the orientation of the polymer lamellae,
• the density and size of microdefects,
• the amount of loose fibrils,
• the presence of carbon black and other additives,
• the local surface topography produced by grinding,
• the degree of thermal and mechanical damage.

Even at a constant depth, there is therefore no perfectly continuous and chemically homogeneous layer.

At one location, the exposed surface may be dominated by a relatively inaccessible crystalline phase, while only several tens or hundreds of nanometres away there may be an accessible amorphous region, a transitional interface, a microcrack, or a space surrounding an additive particle.

The result is a spatially highly non-uniform capacity to absorb wax.

The ski base should therefore not be described as a container with uniformly distributed pores. It is more accurate to imagine it as a three-dimensional mosaic of regions having different densities, molecular mobilities, and levels of accessibility to wax molecules.