4 августа, 2015 
Malyar Sadhan K. De
Indian Institute of Technology, Kharagpur, India
Natural rubber adhesives can be classified into two principal types: latex adhesives and solution adhesives. Natural rubber latex is obtained by tapping the tree Havea brasiliensis. The latex consists of about 35% solids. Ammonia is added to the latex immediately after the tapping to prevent bacterial attack and coagulation. Before marketing, the latex is concentrated to a total solids content of about 60 to 70%.
Solution adhesive is obtained from solid rubber obtained by coagulation of latex as acquired from the tree. The coagulation is effected by dilute aqueous solution of organic acids. The solid rubber can be graded in terms of dirt content, ash content, nitrogen content, and volatile matter. It can also be categorized by plasticity retention index and Mooney viscosity. To maintain uniformity it is necessary to choose solid natural rubber of known characteristics.
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