While the material itself has been around for nearly a century, latex is still a relatively new concept for many mattress consumers. It’s important for retailers to be well versed in the unique benefits of all the different types of latex that are available so that they can most effectively communicate its value.
Offering superior durability and a uniquely contouring comfort feel, latex can enhance the overall sleep environment. It is more resilient than memory or polyurethane foams, instantly adapting to the body to relieve pressure points and reduce pain while properly aligning the spine. While the material is widely known for its conforming qualities, not all latex is the same. In fact, it is available in many different types and forms, as categorized by their source materials and methods of production.
Natural vs. Synthetic
Natural rubber latex is a polymer derived from the milky sap of the tropical rubber tree, typically grown on plantations in areas such as Malaysia and Sri Lanka. When the weather permits and it is planted and harvested correctly, these trees provide a renewable material that can create a vulcanized rubber foam. After collecting the sap from the trees, it is whipped with air to form a foam that is inherently anti-microbial, hypoallergenic and dust-mite resistant.
Synthetic rubber latex is a polymer produced from styrene and butadiene and specifically designed to mimic natural rubber. This polymer is produced in water on both batch and continuous production lines. After being polymerized this synthetic latex is stripped of residual reactants and then concentrated for commercial use.
Both natural and synthetic latex options offer distinct benefits. In addition to its renewable properties, natural latex is often touted for its superior comfort. On the other hand, synthetic latex brings with it a more consistent feel and greater reliability when it comes to sourcing the materials. As such, many manufacturers have opted for a combination of the two, blending both natural and synthetic latex to deliver a more consistently contouring feel.
Dunlop vs. Talalay vs. Continuous
In addition to the source of the latex compound, the process through which the foam is formed can have an effect on the overall feel of the final product. There is considerable debate between latex rubber suppliers over which formation process is the better choice, but each method has its own distinct advantages.
First introduced in 1929, the Dunlop process is known for creating a denser latex product. In this method, the rubber sap is put in a centrifuge and whipped into a froth, poured into a mold, covered and steam baked. During this process, the specified latex compound is injected with air and a gelling agent then frothed to form foam. The gelling agent destabilizes the foam and when the foam is poured, it completely fills the mold. With the mold closed, the foam settles as the rubber destabilizes and the rubber particles coalesce forming a continuous open-cell, solid block of foam rubber. The foam is heated to vulcanize it, then cooled, removed from the mold and washed and dried.
With the advancement of technology during World War II came the newer Talalay process, which adds two additional steps to the Dunlop method. After being poured into a mold, the sap is vacuum-sealed to remove air and chemically flash-frozen before it is baked. For this method, the specified latex compound is injected with air and frothed up to form a foam. From there, an aluminum mold is filled part way with the now pourable foam. The mold is sealed and the pressure inside reduced. This decrease in pressure causes air bubbles to expand and the foam redistributes itself evenly to fill the mold, causing a uniform density. Next, the foam is then frozen inside the mold before carbon dioxide is added to stabilize the rubber in the latex and the foam is heated to vulcanize the rubber. After it cools, the mold is opened and the newly created foam block is washed and dried.
The latex industry’s most common method of production is the Continuous Process, which is a more simplified version of the Dunlop process. In this method, the latex is poured, cured, washed and dried on a long belt without a mold—eliminating the air extraction and freezing stages. The result is a denser, more consistently firm latex.
In general, latex manufactured with the Talalay method tends to be softer, with a more springy feel than Dunlop. While the Talalay process provides a more consistently buoyant feel, the Dunlop process is simpler—which allows for shorter production times. Other suppliers favor the density, gauge and consistent feel of the Continuous process, which makes it better suited for mattress base cores.
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