The method we use to manufacture tyres, hoses and other textile-reinforced rubber products is in many respects outdated and harmful to the environment. RISE is well on the way to identifying the solution to a problem that tyre manufacturers are grappling with all over the world.
Tyres, hoses and airbags are just some of the products that contain textiles – what are known as textile-reinforced rubber products. These products are manufactured in large volumes and currently require the use of resorcinol and formaldehyde, both of which a hazardous to human health and the environment. These chemicals are used to achieve sufficient adhesion between the rubber and textile; however, the method is outdated.
"We conducted a feasibility study that, among other things, revealed that the method of gluing still used today is based on a patent obtained in the 1930s. We therefore felt that we really needed to address this problem in order to identify a more environmentally friendly alternative,” says Elin Johnsson, RISE group manager, a BSc in Textile Engineering and MSc in Polymeric Materials.
A global problem
Many products that combine rubber and textiles are currently manufactured using these chemicals. This presents an urgent problem, both in terms of the major health risks for those manufacturing the products and due to the putative imminent ban on the chemicals used in the process. A statutory limit on the use of these chemicals is currently under discussion, making it even more important to identify less hazardous methods without undue delay.
There are currently no environmentally friendly options available that provide an equally good end product; however, research is ongoing around the world to find alternatives to current manufacturing processes. This also applies to RISE, where the RUBTEX project is aiming to find alternative chemicals and/or processes that can replace the substances used today. Financed by Vinnova, the project also aims to identify new opportunities for Swedish industry to strengthen its competitiveness through more environmentally friendly products and processes.
“Once these chemicals are prohibited, any well-functioning product that is free of them will occupy an extremely strong market position compared to its competitors. This leads to growth for the project’s industrial partners and to more jobs in Sweden,” says Elin Johnsson.
Time for large-scale trials
The project is being conducted in three stages; firstly, alternatives are developed and tested in the lab, secondly a prototype is developed and, finally, large-scale industrial tests are conducted.
In order to achieve adhesion, the current method requires textiles to be dipped in a liquid containing the hazardous chemicals. RISE researchers have examined a number of different methods, including mechanical adhesion instead of chemical, with protruding textile fibres that grip the rubber. This method has been chosen to go forward to large-scale evaluation. Promising chemical processes have also been discovered in which the hazardous chemicals could be either entirely or partly eliminated.
"On conducting small-scale tests resembling actual manufacturing, it became apparent that a couple of our proposals have produced promising results. We will now move on to the final stage, in which this will be tested under actual production conditions and large-scale manufacture,” says Elin Johnsson.
In this case, the final application is a large airbag manufactured by the company Solving, which is used to handle extreme loads of up to a thousand tonnes. Finally, trials and evaluations will be conducted to test whether the method meets all demands and testing requirements the company places on its products.
“It will be exciting to see this final stage completed. I*ve been able to follow the project, from when we stood mixing in small beakers until these enormous machines that will be manufacturing based on our ideas,” says Elin Johnsson.
In addition to the major competitive advantages entailed by the development of a working, nontoxic product, another goal with the new chemicals and processes is to develop a finished product with improved performance.
"It is hoped that, in addition to contributing to existing knowledge, the project will also be able to contribute to better products from a purely technical standpoint. The primary goal is to achieve at least the same level of performance. Rubber composites and textiles are continuously developing, leaving this outdated 1930s technology trailing behind. Even if it works, there must be something that works even better. It is simply a matter of finding it – and we’re well on the way.”