Latex, in this case, natural rubber latex (from the Hevea Brasiliensis tree that originated from Brazil) is made up of an ultra-fine emulsion of
rubber particles suspended in aqueous (watery) phase. It is very much like milk or blood, if you need a comparison. The aqueous phase, called serum,
contains several non-rubber matters such as carbohydrates, proteins, lipids, minerals, micro-organisms and of course, water. The rubber phase is made
up of billions of rubber globules or particles. Each of these particles contains pure rubber surrounded by a layer of soapy-like substances that keep
the particles apart. The manner this is done is through the negative electric charge on the surface of the particles, so that the particles repel each
other and remain separate. These soapy-like substances are made up of proteins and phospholipids.
Making Natural Latex Useable
The natural latex direct from the trees besides being too watery for use also contains a significant amount of non-rubber and is not a commercially
acceptable raw material. The process of centrifugation concentrates the rubber particles and at the same time removes about two-thirds of the
non-rubber from the serum and the particle surface. Some artificial soap is added to compensate for the loss of the natural soap to prevent premature
coagulation of the latex. Centrifuged latex is the basic material for the manufacture of latex gloves. However, without the necessary vulcanizing
chemicals, the latex will not have the elasticity and strength of making the gloves stretch and not tear.
Understanding Vulcanization
To begin to understand vulcanization, remember that rubber molecule is a very long thread polymer made up of millions of monomer units called
isoprene. The chemical name of natural rubber is therefore polyisoprene, or more accurately, cis 1,4 polyisoprene. Some of these polymer are longer
than others but they are all thread-like and together, still does not have any 'network' strength. Imagine these molecules as cut pieces of cotton
threads and when they are pulled they just fall apart. This is the situation with dry film of unvulcanized latex. |
