‘Green’ tire compounds from the magic kitchen
January 28th, 2010Car and truck tires are made up to a large extent from natural rubber – in other words, they are produced from renewable raw materials. Working in their laboratories – their mysterious ‘magic kitchens’ – chemists are constantly searching for new mixtures and compounds to help them to come up with tyres which meet consumers’ high demands. It was this research that enabled the experts at Continental, Europe’s leading car tyre manufacturer, to substantially reduce the use of those chemicals considered potentially harmful to the environment. At the same time, tire performance is constantly increasing.
The composition of compounds is one of the biggest secrets of the tire industry (Image: Continental)
Evaluating this development, Boris Mergell, head of material evaluation and processing car and truck tires from Continental, sees a clear trend towards ‘downsizing’ in the use of chemical products, with no end in sight. In his view the ‘green tire’ has already arrived in the trade. After all, natural rubber accounts for two-thirds of a car tire, with a good proportion of this renewable raw material obtained from rubber trees in Central America. Production is in the hands of smallholders, with international corporations owning just a few plantations, so revenues from the plantations remain largely with the producers themselves.
“Our modern car tires are highly specialised industrial products well able to handle the balancing act between renewable raw materials and essential chemical additives” Mergell comments. “Virtually every day we try out new materials and compounds in our labs in the hope of achieving further progress.” His aim in this context is to do without fossil raw materials as far as possible and use recycling materials instead. Natural and re-processed oils have both been used at Continental now for over ten years. “We are working very closely with our suppliers and with independent research institutes to find a substitute specifically for those tire ingredients that are based on mineral oil” he explains. To this end he is focusing on polymers made from biomass, process oils, different types of carbon black, mineral nano fillers and, in particular, recycling materials.. “We are currently developing a tire prototype which does without over 90% of the fossil raw materials.” For the structural supports in the tire Continental uses recycled steel. Recycling products or products based on renewable raw materials, such as rayon, are used to replace textile cord materials. One positive side effect is that tires using alternative structural supports are ten per cent lighter than conventional products and so reduce a car’s overall weight, resulting in lower fuel consumption.
By now almost all oils containing PAHs (polycyclic aromatic hydrocarbons) have completely disappeared from tyres. “Previously they were indispensable to ensure tires had a long service life; they were also needed to maintain the tyre’s characteristics in the wet at a very safe level” Mergell explains. “By now, though, we’ve been able to reduce these PAKs in all tires, so that we come in well below the strict limits valid from early 2010.” Not an easy task – one single tyre consists of around 15 different rubber compounds and each compound contains such oils. This meant that Mergell and his colleagues had to change each of the compounds, whilst maintaining the tyre’s driving characteristics at the same level. Explaining the aim of his ‘magic kitchen’, he reveals: “The secret is the way the different compounds in the tyre interact.” Each minor modification can lead to substantial variations in the overall picture. The wrong composition in the compound can already result in considerably poorer braking performance. “It is, after all, the tyre – and not the brakes – that stops the car” he states clearly. “If the composition of the tire results in a blow-out at the crucial moment, then the best brakes are no good.”
Continental’s ‘magic kitchen’ continues to look for solutions that will make tires safer and more environment-friendly. “Our objective here is to gain greater sustainability, both in terms of raw materials and also in production” Mergell explains. To do this, he wants to keep the use of fossil base materials as low as possible, dispense with potentially harmful compounds where possible, and make that industrial product – the tire – safer, more durable and more economical. For him, though, one thing is certain – in terms of tire colours, things still look black.
