Greener Rubber Shoe Soles from Vibram: A Step in the Right Direction


Photo credit: M.J.S. @ Flickr

In the 1840's, Charles Goodyear discovered a way to make rubber incredibly stable and a new material was brought into the world. This process still exists today and is called vulcanization; learn more about rubber chemistry from HowStuffWorks. So why is rubber which has been vulcanized, or chemically strengthened, becoming a controversial issue?
Photo credit: zordor @ Flickr
Vulcanized rubber: One and done (and not very green)
The vulcanization of rubber is a process where the material is heated at a high temperature and sulfur is added to chemically change the rubber. Unlike other thermoset polymers, after vulcanized rubber cures, the forming process is irreversible. Additionally, products such as rubber tires have other additives to prevent early decay and photo degradation, making them fit to last... well, possibly as long as we can imagine.

Conventional shoe soles: Not so green
The benefits of having long-lasting, stable synthetic rubber are clear but does this material have to have such a harsh impact on the environment? Vibram, a leading manufacturer of shoe soles, has decided to take a step in the right direction, so to speak. They provide soles to the shoes worn by public employees such as police officers, firefighters and even the U.S. military. In addition, companies such as Patagonia and Timberland have been using their shoe soles for years. What they have developed is called EcoStep.

EcoStep: A greener rubber
This material is described as an eco-compound, capable of reducing waste and the use of virgin materials by up to 30 percent. What Vibram has been able to do is achieve a level of eco efficiency, where they are beginning to offset the need to use new or virgin rubber in making their soles. They can create a shoe sole with the same properties of using virgin material, but have added around 30 percent regrind material to the mix.

The rubber scraps are generated by their production process (post industrial content) and are reground in the mix to produce the EcoStep compound. In addition, I've seen Vibram using their post-industrial scrap for playground surfacing material which can soften the impact of falls. We hope to see more material-based companies looking into the full life-cycle and impact of the products they sell, to determine what areas are best to improve; for now, there's no denying this is a step in the right direction.

Update: This year Timberland introduced the Earthkeepers 2.0 shoe designed to be disassembled and recycled. It employs "Green Rubber" which is a rubber compound derived using a proprietary and patented process called DeLink™ to devulcanize waste rubber. The devulcanized rubber can then be reused as a new raw material for items such as outsoles. The outsoles of the Earthkeepers 2.0 boot are made with 42% recycled tire rubber.
More on rubber
How Rubber Works
Dandelion Rubber Could Be Inexpensive, High Quality Alternative to Tree Rubber
NASA Loses 90 Rubber Duckies in the Arctic, Offers Reward for Return
Recycled Rubber Ice Cube Trays
Materials Monday is a new weekly column written by Matt Grigsby, CEO & Co-founder of Ecolect, where you can discover more about this and other green materials.

Tags: Footwear | Recycled Consumer Goods