A Rubber Crumb Cake for the Environment

Every year hundreds of thousands of old care tires are thrown out in Germany. Most are chopped up to make granules or rubber crumbs. The pulverized tires are then used as fuel by industry or as insulating material for road and rail construction.

But most of the material in car tires is still natural rubber – a high-quality and expensive raw material. That means shredding tires is a wasteful way of reprocessing the natural resource.

Scientists in Chemnitz, Germany, however, have developed an alternative method for recycling the rubber crumbs using, of all things, a baker’s mixing machine. Dr. Hannes Michael of the Technical University in Chemnitz says his team has set themselves the goal of finding a new method that "makes a contribution towards recycling materials from old and thrown away tires."

Baking rubber

The rather unconventional method is firmly rooted in hard-core science. First, the Chemnitz laboratory obtains finely powdered crumb rubber from companies in Germany, Europe and the world. Then they take the granulated rubber and mix it with a plastic so that it turns into a new material.

At around 90 degrees Celsius (194 ° F) the plastic and the rubber powder begin to blend. With a little help from a dough mixing machine – exactly the type a baker would have – the two substances bond to form "Elaplasta". The scientists from Chemnitz chose the name because the new substance maintains the elastic or stretchy characteristics of rubber (think of a rubber band) while the plastic component helps to stabilize it.

Elaplasta is flexible and durable at both high and low temperatures. That means it’s especially suitable for making parts in auto manufacturing. Moreover, the new rubber blend is about two-thirds cheaper than natural rubber products.

From mixer’s bowel to industry

It’s a big jump from a backer’s mixing machine to large-scale recycling. But expanding the mixing process for industrial applications shouldn’t require much. The rubber is already pulverized before it comes to this stage, and the blended substance can easily be cut into small pieces and formed into specific shapes and parts using standard injection molding machines. A factory near Dresden has already planned to integrate the blending process in large scale rubber product production.

The Elaplasta inventors are also hoping for additional applications. That’s why they plan to offer the substance in a variety of hardness grades. Right now they’re carrying out several tests on the materials, such as one to determine tensile strength.

Ultimately, the goal is to make bumpers, dashboards and engine parts entirely out of Elaplasta. The best thing about the product, say the inventors, is its continuous recyclablity. It can be recycled again and again before it finally ends up in a furnace.