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.
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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. |
