WP, Yellow Phosphorus, P
White Phosphorus (WP) is a solid that is used primarily for screening purposes. It also has been used against personnel and fortifications. It bums vigorously when exposed to air and creates a dense, white cloud.
Plasticized White Phosphorus (PWP) consists of granules of white phosphorus that are coated by GRS rubber, forming a homogenous mass of individual white phosphorus particles separated from each other by a rubber film. This rubbery mass, when dispersed, does not break up and, therefore, pillaring is less marked.
Old Chemical Weapons Reference Guide (1998)
TM 9-1904, Ammunition Inspection Guide (1944)