NATURAL LATEX: Harvested from the sap of rubber trees grown in specific regions of the world. Natural latex is not a perfect product by the vary nature of its being natural. The sap harvested is affected by soil conditions, amount of rain, and other factors that make one batch better than another. The degree of difference is not great but enough that makes it necessary for purchasers of the raw material to test for quality. It is much like buying coffee beans to arrive at different blends. Natural and synthetic rubbers have differing properties. Natural rubber is very soft and elastic, synthetic rubber gives the foam good hardness and processes better (is easier to work with) in production. The difference in quality is derived from the process used to produce the latex mattress cores.
Fundamental fact: Compounders tend to use blends of natural latex and synthetic latex to get the best overall properties, and to stabilize prices. |
When natural rubber is tapped from a tree it is very dilute, the rubber content being only about 30%. It has to be concentrated before use to above 61.5% solids. Of these solids 60.0% is rubber, the remaining 1.5% are compounds that are unique to natural latex (proteins, phospholipids, carbohydrates, aminoacids). These unique ingredients are very important in explaining the behavior of natural latex. |
SYNTHETIC LATEX: Man made from chemicals and petroleum with same cell structure as natural minus the emseimes found in the natural. Now in this day and age the mere mention of chemicals sends some people running, but lets put it into prospective. All foam is made from chemicals and petroleum products, and foam is what what is used in all mattresses. The reason latex is heads and shoulders above foam in quality is the degree to which natural and synthetic are blended together by 2 different manufacturing process.
Before the Second World War, virtually all latex used in production was natural. During WW2 supplies of latex from the Far East were very restricted, hence the search for a synthetic alternative. Scientists tried to copy natural latex (derived from cis-polyisoprene) and largely failed: the latex produced was inferior to the real thing. Instead, they developed a latex based on a synthetic polymer that behaved in a similar way. The word ‘polymer' simply means a compound made up of long chains of molecules, each link in the chain being derived from simple chemicals known as ‘monomers'. A number of synthetic latices were developed, the most useful one being made by polymerizing Styrene (a liquid) with Butadiene (a gas) to give Styrene-Butadiene rubber, abbreviated to SBR. |
