Rubber latex is a naturally occurring substance. It is the sap of the Hevea Brasiliensis tree. This is more commonly know as the rubber tree. The sap dries to form a soft, flexible, self-adhesive and highly extensible film. In this form the film is too weak to use in the manufacture of rubber articles. However, it is used in the manufacture of self seal, cold seal and other types of adhesives.
To impart physical strength to the dried rubber it is necessary to crosslink, cure or vulcanise it. This is achieved using sulphur in combination with other chemicals which accelerate the crosslinking reaction. This process takes place at elevated temperatures, typically around 15O0C. Crosslinked rubber exhibits high tensile strength, tear resistance and abrasion resistance making it suitable for the manufacture of items such as tyres, conveyor belting, rubber matting, drive belts and so on.
Natural rubber can also be crosslinked in the wet state i.e. as a latex. This process uses sulphur and accelerators but occurs at around 30oC and typically takes around 3 weeks. This process is known as prevulcanisation. Prevulcanised natural rubber latex is used to make balloons, household gloves, rubber moulds and so on.
Prevulcanised natural rubber latex does not need heat to produce a crosslinked film. It will dry at room temperature to form soft, strong, flexible and highly extensible rubber products. Although it will dry at room temperature the drying process can be accelerated by heating the film to a maximum of 70oC.
Formulated Polymers supply a range of low ammonia, low and medium modulus prevulcanised natural rubber latices. These are available at low viscosity for dipping applications and at high viscosities, so they can be painted onto moulds. We can also supply thickeners.
At Formulated Polymers we have over 40 years’ experience in the manufacture and use of prevulcanised natural rubber latex. We can supply a wide range of prevulcanised latex based grades and can tailor products to meet end users’ specific needs. We also supply air drying, prevulcanised latex based compounds for carpet, rug and protective coating applications.