What are the main weaknesses of the existing UHMWPE ski base types? – Part V.

Fifth issue of the existing UHMWPE ski base types is their very low ability to bind gliding ski waxes and other gliding agents chemically.

How it works?

Chemical bonds between UHMWPE and wax-based gliding agents are very weak, chemical bonds between carbon black as main structural and reinforcement additiv in modern ski base types are extremelly weak. In other words: if applied on a ski base, wax-based gliding agents cannot rely on chemical bonds, they urgently need mechanical retention.

Mechanical retention is strongly depending 1. on available free spaces or cavities in both very top surface and in bulk material of the ski base, 2. on size and disponibility of these free spaces and cavities = they are avaibale in amorphous and transition areas only, many of them are occupied by soot and other additives), 3. on size and charakter of the wax molecules which need to get inside free spaces when base material is more flexible thanks to heat and get stuck there when base material cools down again, 4. on the level of intertwining of the molecular chain structures of both ski base material and wax-based gliding agents.

Maybe the last forth condition is the most significant one for how strong the final mechanical retention of waxes in the ski base is. At the same time this forth condition = the level of intertwining of the molecular chain structure of ski base material on the one side and ski wax substances on the other side is the most problematic and tricky one.

Why?

For wax-based gliding agents very strong dependency exist between hardness and strogness of intertwining on the one side and softness and weakness of intertwining on the other side. This very strong dependency is defined by the length and charakter of the molecular chains of wax-based gliding agents.

The longer and more branched the molecular chains of the wax-based gliding agents are, the stroger they can be intertwined with extremely long molecular chains of the ski base material (UHMWPE), thus, the stronger is their mechanical retention inside the ski base material.

The shorter and less branched the molecular chains of the wax-based gliding agents are, the weaker they can be intertwined with extremely long molecular chains of the ski base material (UHMWPE), thus, the weaker is their mechanical retention inside the ski base material.

At the same time the length and charakter of the molecular chains of wax-based gliding agents define their gliding properties.

The longer and more branched the molecular chains of the wax-based gliding agents are, the stroger they can be intertwined with extremely long molecular chains of the ski base material (UHMWPE), thus, the stronger is their mechanical retention inside the ski base material, the worse gliding properties.

The shorter and less branched the molecular chains of the wax-based gliding agents are, the weaker they can be intertwined with extremely long molecular chains of the ski base material (UHMWPE), thus, the weaker is their mechanical retention inside the ski base material, the better gliding properties.

Waxes with best gliding properties does not stick to ski base material, the better waxes stick to ski base material, the worse gliding properties they have. Good advice is better than gold.

What are the main weaknesses of the existing UHMWPE ski base types? – Part IV.

Forth issue of the existing UHMWPE ski base types is their low and uneven capacity to take and hold other substances as gliding ski waxes and agents.

How it works?

Only sintered ski base types have sufficiently long chains to create free space to take wax molecules on the very top surface and inside the bulk material.

On the very top surface we call the free spaces “flokati carpet” which are fibres or hairs several hundred nanometers long which are covering the entire ski base surface. Between these fibres is enough space for wax molecules get in and get stuck here. Most wax molecules are allocated here.

In bulk similar free cavities do exist because the bulk material consists of intertwined molecular chains. It is estimated that wax can penetrate the ski base up to 1 micrometer, thus 1000 nanometers, the deeper you go, the less wax molecules you will - however - find.

Both free spaces in flokati carpet on the very top surface and free cavities inside the bulk material are ca. tens of nanometers large which means there is enough space for wax molecules  but...

If we connect this knowledge about size and distribution of free spaces or cavities in the flokati carpet on the very top surface and in the bulk material of the ski base with the knowledge about how especially competetion skis are prepared (several basic wax layers applied as hot appoach, gliding layers applied as block waxes or powder waxes, top coats applied as liquids or sprays), we need to see / understand that the spatial capacity of free spaces and cavities which was available at the very beginning of the ski service process is consumed very fast and each new layer applied on the ski base creates more and more complex mixture than a new layer.

If we combine these types of knowledge about size and distribution of free spaces or cavities in the ski base and about competition ski service processes with the chemical interaction between PE / carbon black as main material components of the ski base on the one side with waxes and wax-based gliding agents on the other side (chemical bonds between ski base and waxes are extremely weak and waxes need to rely on mechanical retention inside the ski base) it must be absolutely clear to us that existing services processes in combination with existing ski base types cannot create any relyable / repeatable and controlable results.

Combination of the existing ski base types and existing ski service processes cannot result in relyable / repeatable and controlable gliding features on the ski base.

What are the main weaknesses of the existing UHMWPE ski base types? – Part III.

Third issue of existing UHMWPE ski base types are the fast changes of the ski base surface.

How it works?

We know that the main component of UHMWPE ski base types is PE with extremely long linear molecular chains (normaly 7 to 12 mil. g/mol) which is enriched with different additives where the most important is soot or carbon black.

Even if we speak about PE with extremely high molecular weight and about carbon black as singular material types, we need to understand that there are plenty of PEs and carbon blacks which very different and specific features.

Particular features of PE and carbon black as two main components of modern ski base types define how they interact if processed in sintration. Normally carbon black has low or no chemical interactions with PE matrix leading to pure “sitting” inside the PE matrix. This weak “sitting” of carbon black corns inside the PE matrix results in fast and easy “breaking out” of whole soot corns out of matrix, “breaking off” of soot corn parts or soot corns abrasion on the very top surface. All these processes - breaking out / breaking off / abrasion - result in quite fast microscopic changes of the very top surface. These changes are the faster and more significant, the larger and more complex the very top surface of the ski base is, i.e. complex structure patterns which enlarge the surface multiple times and create complex details accelerate these changes.

Due to very weak chemical interactions between PE matrix and carbon black the very top surface of the ski base is a subject of very fast - even if with the naked eye invisible - microscopic changes which do cause that skiers run on a new ski base surface latest in the next competition.