Labels, silica and China

By David Shaw, ERJ staff

I've been travelling around China's tyre industry and this evening had dinner with two compound engineers who work at a Chinese tyre company. Both of them used to work for a Korean tyre maker. It would not be fair to name the people involved or their current or former employers. But what I took from the conversation was that Chinese tyre makers currently have a different way of operating compared to most of the Western tyre makers.

Inevitably, the conversation turned to tyre labels and how the tyre maker develops compounds to meet the requirements of the label.

I asked whether they currently use silica compounds in their passenger car tyre treads and the response was yes, they do.

The plant was set up about 5 years ago and the design had anticipated the requirement for labels and for silica mixing.

More recently, they had installed an intermeshing mixer to handle silica compounds.

Most of their silica compounds are up to about 50 or 60 phr silica, and the dispersion, I was told is good. For a special product such as a UHP tyre, they can go up to 80 phr, but to go that high, the product needs to have a good profit margin, as the mixing needs at least three stages to achieve sufficient dispersion.

The engineer said they have very good temperature control, running at about 150C in the mixer.

When I said this seems a little high, the engineer said it is possible to mix at a lower temperature, but did not expand on that point.

Asked if the pressures are to design a good all-round tyre, or if there is a temptation to design to the label, getting good grip and fuel economy at the expense of life and other parameters such as handling, the engineer said that in some products-especially at the lower end of the range-then there is a feeling that the parameters highlighted on the label become a development priority. However, for higher-end tyres, the aim is to develop pa well-balanced tyre, but with a good label performance as well.

The engineers asked how European tyre makers develop tyres to meet the label. I said that many of them have 20 years or more experience at mixing silica compounds and that they can achieve good dispersion at loadings of 95phr or more of silica. This helps them to expand the performance triangle linking wear, wet grip and fuel economy.

However the main way they develop such products is by working closely with suppliers of synthetic rubber and other materials to work out what properties are required and then to model the molecular structures and seek molecules which can deliver the right performance. After that it is design work with lots of computer-based simulation to refine the different aspects of the design to optimise the overall performance balance.

One of the critical elements to emerge in the last few years is to treat the tyre as a complete assembly of components, each interacting with the other elements, rather than attempt to design each element separately.

Even having worked for a relatively advanced tyre maker, the engineer said that they are only at the start of putting in place this kind of procedure.

For example, he suggested that when they buy a material or machine, they tend to rely on the supplier to know what is best for them to build good tyres.

Western tyre makers, by contrast have an active dialogue with their suppliers and often put very tight detailed specifications in place to ensure that hat is delivered is indeed the best possible and best suited to their needs and their production processes.

I came away from the meeting with the feeling that Chinese tyre makers still have some way to go in building up good relations with their suppliers in terms of an active, working dialogue over what is required and what can be delivered.