Polypropylene (PP)
PP is a translucent plastic resin used in bottles for shampoo, conditioner, jars for creams and products containing a high concentration of vegetable or mineral oil such as bath and sun tanning oils. It has lower porosity than PE, thus reducing the potential for migration of product components through the packaging.
PP is used to produce the majority of lids for containers, which can be flip top, top disc or a blind cover. The discs that are placed under the cover of a cream so that the product has no direct contact with the lid are also generally composed of PP.
Source: Cosmetic Formulation Principles and Practice - Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters