Scientists invented synthetic latex during World War II when the supply of natural latex was sparse. They hoped to mimic the chemical structure of the key ingredient in natural rubber, polyisoprene. After initially unsatisfying results scientists finally succeeded by combining butadiene and styrene into a compound called styrene-butadiene rubber or Neolite
Synthetic latex is derived from petroleum products. Various chemicals are used as catalysts in the production of synthetic latex that are washed out at the end of the manufacturing process.
Differences Between Natural and Synthetic Latex
Some confusion in recent years has been created by the labeling of blended latex as “synthetic latex,” and then branding all blended latex mattresses as “synthetic.” However, there are some important differences between natural, synthetic, and blended latex.
Typically harvested in tropical regions of the world, 100% natural latex comes from rubber trees. Natural latex is not a perfect product by the very nature of its being natural. The sap collected is affected by soil conditions, the amount of rain, and other factors that make one batch better than another. The degree of difference is not significant, but it is enough to make it necessary for purchasers of the raw latex to test for quality.
Natural rubber tapped from a rubber tree is dilute, with the rubber content being only about 30%, so it must be concentrated before use to above 61.5% solids. Of these solids 60.0% is rubber, 38.5% is water, and the remaining 1.5% are compounds that are unique to natural latex such as proteins, phospholipids, carbohydrates, amino acids. These unique ingredients are necessary to attain the unique properties of natural latex.
The History of Synthetic Latex
Before the Second World War, virtually all latex used in production was natural. During WW2 supplies of latex were very restricted, hence the search for a synthetic alternative. Scientists attempted to copy natural latex, deriving a mimic from cis-polyisoprene plastic. They mostly failed: the latex produced was inferior to natural latex.
Instead, they developed a latex based on a synthetic polymer that behaved in a similar way. The word “polymer” means a compound made up of long chains of compounds. Each link in the chain derived from simpler molecules (usually carbon-based) known as “monomers.” There are several synthetic lattices, the most valuable made by polymerizing Styrene (a liquid) with Butadiene (a gas) to give Styrene-Butadiene rubber, abbreviated to SBR.
The two types of latex have similar properties, but synthetic latex has superior strength compared to the natural. Natural latex also has more elasticity (softer) but will tear more easily. Both types of latex have properties that are useful for different reasons. Typically Talalay latex is made with some type of blend of synthetic and natural latex, while Dunlop latex is made of just natural latex. This is because Talalay latex made with only natural latex is less durable than its blended counterpart.
The difference in quality with latex mattresses comes from the process used to produce the latex mattress cores. Compounders tend to use blends of natural and synthetic to get the best overall properties and to keep prices low. Creating the best latex foam is much like buying coffee beans to arrive at different blends. Because natural rubber is very soft and elastic and synthetic rubber gives the foam hardness it is easy to see how combinations of the two can be used to create a useful material.