The cashew (Anacardium occidentale) tree is native to northeastern Brazil, where it is called by its Portuguese name Caju (the fruit) or Cajureiro (the tree). It is now widely grown in tropical climates for its cashew nuts and cashew apple. Originally spread from Brazil by the Portuguese, the tree can now be found in all regions with a sufficiently warm and humid climate.
The true fruit of cashew is the nut, a kidney-shaped structure of approximately 2-3 cm in length, which is attached to the end of a fleshy bulb, generally called the cashew apple. The shell comprises some 50% of the weight of the raw nut, the kernel represents 25% and the remaining 25% consists of the natural cashew nut shell liquid (CNSL), a viscous, reddish brown liquid. CNSL has a variety of industrial uses, which were first developed in the 1930s. CNSL is fractioned in a process similar to the distillation of petroleum and has two primary end products: solids that are pulverized and used as friction particles for brake linings, and an amber-colored liquid that is aminated to create phenalkamine curing agents and resin modifiers.