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Graphic element Research > Growth > Research projects > Products & processes projects > Tyres tread the same path twice
Graphic element Tyres tread the same path twice

Recycling old tyres by retreading is an established technique. By buying retreads, drivers can help prevent scrap tyres from ending up in landfills and on illegal dumps. In the EU, only 12% of all car and truck tyres are currently retreaded and reused. Thanks to a CRAFT project which aimed to improve the quality control and performance of retreaded tyres made by SMEs, new inspection and testing equipment has been developed, along with environmentally friendly water-based adhesives to replace organic solvent-borne formulations. Such innovations in monitoring quality will lead to economical and environmental benefits in a European market worth 1 billion.

New inspection equipment for improving the reliability of retreaded tyres has just won its first customer. Such equipment was just one development resulting from a CRAFT project that aimed to help SMEs improve their retreading business by providing a better quality control.

The process of retreading involving recycling a tyre by removing a worn tread and replacing it with a new one, allows tyres to be reused. While a car tyre may be retreaded only once, lorry tyres are often retreaded two or three times, and aircraft tyres many times.

Tyres are highly recyclable

There are many millions of tyres made each year in Europe and every year, at the end of their useful life of a few years, over 250 million are thrown away. But tyres can be recycled. The main problem is economic: recycling costs more than dumping, so many tyres end up in landfills or on illegal dumps, adding to those already polluting the landscape. Tyre dumps are potentially dangerous: they can catch fire, and when they do, toxic chemicals are released, leaving an oily residue that can contaminate groundwater.

Currently only about 12% of the EU's scrap tyres are retreaded and reused, so a long-term goal of the project was to help boost this level by increasing consumer confidence in the reliability of retreads.

The project co-ordinator is Dr Alan Roberts, deputy director of the Tun Abdul Razak Research Centre, the British arm of a Malaysian rubber research organisation. John O'Connell used to work for the organisation in Malaysia before starting up his own company, Bandvulc Remoulds, a UK SME retreader based in Devon. Dr Roberts and his colleagues, with their wealth of experience in retreading research, were in contact with many SME retreaders. He knew about CRAFT projects and Mr O'Connell knew about making retreads. They both recognised the need for tyre retreading to become as scientific and technological as possible. Together they began to form the project consortium.

A six-month exploratory award was granted to evaluate the proposal before it was accepted as a two-year CRAFT project, which addressed the three major technical issues in retreading tyres.

Looking for rust

Firstly, modern tyres are usually reinforced with steel cord and over time, water can penetrate into the tyre and rust the cord. The retreader has to examine the tyre to see if any corrosion has already developed. To reach the cord the old tread has to be removed by being ground away. To minimise inspection costs, a non-destructive test was needed to indicate quickly whether a tyre should be accepted or rejected before this process.

Secondly, depending on the retreading process employed, a cement or adhesive may be needed to stick the new tread to the old tyre. Current cements use potentially harmful organic solvents, which must be replaced with water.
Finally, since the tread rubber is in contact with the road, this is normally the only part of the tyre to wear away. The service life of the retread thus depends mainly on the wear or abrasion resistance of the new tread. Retreaders must be able to guarantee the service life (in kilometres) of their products. To do this, they need a new abrasion tester capable of predicting tread wear and tyre life under service conditions.

  Technology transfer

The final consortium comprised 21 partners: 11 SME car and truck retreaders, two SME test equipment or instrument manufacturers, five large raw material suppliers, and three research organisations. It included not just SMEs but also large companies such Bekaert, the world leader for manufacturing steel cord for reinforcing tyres; Cabot, a global supplier of carbon black (which is used to improve the wear resistance of rubber treads); and Gummiwerk Kraiburg, a leading rubber products manufacturer.

The project team also benefited from a technology transfer from the German steel industry to the European rubber field. The RWTH Technical University of Aachen provided expertise in tyre wear to design the new abrasion test method, and detecting surface corrosion of steel pipes to develop a electromagnetic device to check tyre cords for rust.

The team met all their objectives. The first rust detector is now operational - manufactured by one project partner and bought by another. The used tyre is checked for its suitability for retreading in less than 10 seconds. It is spun round once in front of the electromagnetic detector and either gets a green light for 'go' or a red light for 'no go' if rust is detected. Water-based cements are now being used in production and the new abrasion tester is now ready for commercialisation.

Better monitoring of retreads will increase the reliability of the life of retreaded tyres. It will lead to clear economical and environmental benefits. An important project spin-off is the ongoing co-operation between the partners, who are now behaving as a 'network'. Along with new members, they are already working on a new CRAFT project. Each percentage increase in the market share of re-used tyres represents potential annual Europe-wide sales of an estimated € 100 million for the retreaders.

Tyres are highly recyclable
Looking for rust
Technology transfer

Key data

New inspection and testing equipment developed in a CRAFT project will improve the quality control and performance of retreaded typre. The project that falls within the Products, processes and organisation key action will lead to economical and environmental benefits for this € 1 billion market.

Project: Improvements in quality control and performance of retreaded tyres (BRST-CT96-5077)

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