Natural vs. Synthetic Rubber
When we first started looking into making shoes, we wanted to create a product that was more environmentally-friendly from the sourcing, production, to its eventual disposal. However, we were a little surprised that almost all shoe (soles especially) are not made from natural rubber, but synthetic rubber.
A video from the Fair Rubber Association about how rubber is made.
Synthetic rubber was heavily developed in the 1940s. As the bulk of rubber plantations were in Asia, and therefore, not-so-friendly territory, the US needed to secure a source of reliable rubber for all of those tires for the war effort. What's a good chemist to do? Turns out, petroleum by-products make for great synthetic rubber. The downside is that synthetic rubber is not at all biodegradable because it is made from inorganic materials. Because natural rubber is plant-based, the key advantage is that it is biodegrade, and a renewable resource.
Baby rubber trees. Aww...
Rubber is fascinating. The the topic of rubber came up a lot in our house because the majority of our family worked for Goodyear from the 1920's, so growing up we heard a lot about tires and factories. But it wasn't until we started working on this project that we really began to learn more a lot about the tree itself.
Rubber comes from the tree (hevea brasiliensis), which produces a natural latex sap. When the tree is seven, it is considered to be mature and ready to be tapped.
Maple tree Rubber tree
A diagonal incision is made on the bark of the tree, and sap is collected daily (except when it rains). If you're wondering, the health of the tree is not affected. Rubber has been harvested this way for more than 3,500 years. (If you would like to know more about the history of rubber, read our blog post). In fact, it is not unlike the way maple syrup is collected from maple trees. Rubber trees are grown for seven years, and then tapped three times in seven-year cycles, and after 28 years, a new forest is planted. The old rubber trees are processed into furniture, mulch, or other products.
Once the rubber is collected, it is squeezed, dried, graded and bailed.
Rubber after it's been squeezed
Rubber drying room
Rolls of rubber
Different grades of rubber