Natural rubber is derived from the “rubber tree”, or Hevea brasiliensis and unlike synthetic rubber, which is made from petroleum-based chemicals.
When the tree reaches maturity, at the age of about six or seven years, an incision is made in the trunk of the tree. It’s a very similar process to a maple tree being tapped for its sap, only a slightly different type of incision is made to account for the differences in the growing patterns between the two kinds of trees. However, just like tapping a maple tree, the tapping process of a rubber tree doesn’t harm the tree, and it will repair the wound within a few years.
But what’s the catch?
It’s not all good news though. Deforestation is the main concern when it comes to natural rubber. The ideal climate necessary to grow rubber trees is found in parts of Asia, between India and Vietnam, and southern China and Indonesia. Places that include some of the most endangered forests in the world. So, what’s the solution? Major brands are becoming aware of the ethical and environmental impact of choosing to sell products made with unethical natural rubber (Michelin Tires, in particular, has been incredibly open about this topic). Just make sure to do your research into the brands you’re buying, and make sure the natural rubber is ethically sourced.
Now for a breakdown of the process:
The sap from a rubber tree contains an incredible amount of natural latex, which is later processed into natural rubber.
- Rubber trees are tapped and “field latex” is collected in cups
- The collected latex is quickly moved to coagulation tanks (keeping it in the collection cup for too long results in the latex coagulating and being rendered unusable). At this point, the latex may be mixed with ammonia to preserve it in its uncoagulated state for longer
- Latex is chemically coagulated using formic acid before being processed into specialized types of rubber
- The material then goes through a cleaning process to remove any impurities or particulates, after which it’s dried and palletized for shipment
- Depending on what it’s used for, it is often vulcanized as well (rubber is heated and mixed with either sulfur, peroxide, or bisphenol), which improves the elasticity and durability of the rubber
Synthetic rubber is made from petroleum-based chemicals, and produces an incredible amount of waste. And while it’s important to note that some of it can be recycled, not all of it can.
All synthetic rubber starts off as rubber polymers, which are palletized for shipment, or cut into strips for further processing. There are three main processing methods for synthetic rubber:
- Synthetic rubber polymers are mixed with other ingredients (ingredients vary, but are used to improve elasticity, durability, etc.) and heated
- The heated rubber is then fed through a small opening, which forms “strings” or “strands” as it cools
- As the rubber cools, it is either vulcanized or cured
- Strips of unprocessed rubber are heated and mixed with other ingredients
- Rubber is placed, under high pressure, into a premade mold, then steam vulcanized
- After the molded rubber has cured, it is released from the mold and further shaped (often by hand)
- Similar process to injection molding, but the strips of rubber are not steam vulcanized