How Natural Latex Foam is Made
Where Does Natural Latex Come From?
Natural Latex is the natural product of certain latex-bearing trees. It starts as a milky substance that flows from holes made in the tree. It is the main ingredient in the production of rubber and other natural latex products.
When tapping Natural Latex from trees, it typically is dilute, and so it must be purified. The upper limit on the purity of latex is about 60% rubber solids, with small amounts of other compounds (about 1.5%) remaining. These compounds include proteins, phospholipids, carbohydrates, and amino acids the makeup of which is unique to the trees from which the latex is tapped.
Soaps – Potassium Oleate
Latex foam is made using soaps such as Potassium Oleate which are added to stabilize the mix. They prevent the foam from coagulating until it is in the mold. Soaps also allow latex mixture to foam up when it is whipped later in the process.
Sulfur is added to the mix during compounding to vulcanize the latex. Without Sulfur, the foam would resemble chewing gum and would have little resilience. Sulfur atoms attach to chains of latex polymers and bond with each other causing the polymers to “cross-link.” That term means that the polymers attach to each other and become intertwined. This process gives the latex the properties it is known for, elasticity and resilience.
The Manufacturing Process
The Dunlop Process
In the Dunlop Process for making latex foam the latex (natural or synthetic), soaps, and various other trace ingredients are mixed. This mixture is whipped to introduce air and make it foamy after which machines pour the mixture into a mold.
Sulfur and chemical catalysts are added to cause the latex polymers to cross-link and harden, and the foam is heated to approximately 350 degrees Fahrenheit causing it to cure in the mold. Latex foam is a poor conductor of heat, so many ‘pins’ are present to help cool and heat the foam. The pins are responsible for the holes that are characteristic of latex foam.
After curing the foam is removed from the mold and is washed and dried. After it is dry, it is cut to be used, in this case, for mattresses.
The Talalay Process
The Talalay Process is similar to the Dunlop Process but has a few key differences that affect the final product in key ways. After the latex is mixed, whipped, and poured into the mold, it is then vacuum sealed. The vacuum sealing process causes the bubbles introduced by the whipping to expand. The foam is then flash frozen further helping to gel the foam.
After the vacuuming and freezing steps, the process proceeds in a manner that parallels the Dunlop Process. The foam is then cured, washed, and cut. The result of the vacuuming and freezing that takes place in the Talalay Process is that the foam has larger bubbles of air in it, creating a foam that is softer and lighter.
Typically, Talalay latex is made by blending natural latex with synthetic latex. Sleep EZ offers both blended Talalay latex as well as 100% natural. For more information about how synthetic latex is made see our article about synthetic latex.