Polypropylene Bags
Polypropylene bags are made of completely transparent, strong, rigid material that doesn't stretch but provides a good vapor and moisture barrier. Polypropylene comes from a combustible gas found in petroleum and is the less frequently used plastic resin for bag production next to polyethylene. Mostly used for food packaging and retail display, polypropylene bags are totally clear for product presentation. They extend the shelf life of perishable foods by delaying evaporation and dehydration, and are less expensive than their main competitor, cellophane, which is also less flexible. Polypropylene bags are durable, offer a consistent thickness and high clarity, but may be tinted different colors while still remaining transparent. They are often said to have an inflexible, "crinkly" feel to them.
Since polypropylene bags are used so often within the food packaging industries, they are non toxic, waterproof and meet strict FDA and USDA regulations for safety purposes. These bags come in many different varieties and forms. They may be gusseted to expand to fit a product, flat, resealable, reclosable, stand-up or tube-shaped. The bags may have a zipper, a crimped or fold-over bottom, a center seam, fin seal or hang holes. Polypropylene can also be woven to form very sturdy, durable bags used to hold pet food and building materials. This woven material is often laminated with bi-oriented polypropylene in order to enhance the printing done on the bag's exterior.