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.

How to use REX NF 41 liquid glider - comments...

Rex recommends to use the NF41 liquid glider as special glider for men-made snow. As we know, men-made snow is very abrasive in wet and extremely abrasive in cold conditions.

In other words: the main parameters which decide about the quality of the product and gliding features on men-made snow are hardness and wear resistance combined with hydrophobic and dirt-repelling features.

I was quite surprising for me that REX NF 41 works a liquid glider and is applied cold.

Below some comments and ideas related to the product and application method.

NF41 seems to be a very interesting product... it obviously does not rely on mechanical retention inside the micro-structure of the ski base only. Why? First it is applied cold only which means, the nano-structure inside the ski base cannot be reached for mechanical retention, mechanical retention inside the micro-structure cannot be sufficent for men-made snow which is extremely abrasive. Second the preparation steps before application do not include brushing with fine steel brushes to open the ski base, remove old wax residues and refresh the micro-structure... Conclusion: NF41 needs to be fixed chemically directly to UHMWPE. To achieve reliable chemical bonds the product needs to develop stronger bonds than the normal van der Walschen bonds which are too weak or modify the UHMWPE surface slightly to get inside the polymer without ironing! Both apporaches are very interessting, especially if combined 

What seems to be a bit strange is the use of nylon brush for preparation. It could be explained by the fear of the developers of NF41 that the use of a fine steel brush could contaminate the surface with old wax residues which could impact the chemical reactions on the surface negatively. The presence of hard and very hard nano-components in the product is showing the deep understanding of NF41 developers for what really matters when gliding on hard abrasive snow like men made snow below zero. To fix the hard layer on the surface instead inside the surface of the ski base could be also very befefitial... I personally do not like any movements against the gliding direction during the application process and need to check the function and composition of GOLD LIQUID product, but after long time a very interesting product with a very reasonable application method. If it works, it would be a great development step!

How does the wax stick to the ski base? - part I.

It is common knowledge that ski bases are waxed. Many wax manufacturers offer liquid waxes where the wax is dissolved in a rapidly evaporating agent. With a sponge you just apply liquid solution of wax and solvent on the ski base and after the solvent evaporation your ski is ready to be used with improved gliding features!

Is it really true?

To answer this question, we need to understand how the wax sticks to the ski base. Does it stick by chemical bonds or by mechanical retention?

The way how waxes stick to the ski base depends especially on the type and features of the ski base. Cheaper extruded ski base types do not have NANO fibril structure to retain waxes mechanically, thus they need to stick to the ski base by chemical bonds only.

 

Chemical bonds are – however – very weak, thus the abrasion resistance of such a wax layer is very low. In other words: a wax layer – especially liquid wax layer – applied on the cheaper extruded ski base will wear off in several hundred meters or max. kilometers depending on snow conditions.

 

More expensive sintered ski base types have NANO fibril structure on the very top surface to retain waxes mechanically, thus waxes are mixed with the base material to a new layer consisting of both wax and ski base material.

 

Mechanically retained wax molecules are protected against abrasion forces, thus their life time is relatively good. Mechanical retention is – however – supported by heat, thus hot wax application is recommended here. Cold liquid wax application will hardy penetrate deep enough.

Conclusions

Waxes stick to cheap extruded ski base types by weak chemical bonds only with very low life time of wax coating. Waxes stick to more expensive sintered ski base types by mechanical retention with good life time. Liquid wax application seems to be waste of money in both cases.