Polypropylene Bags

Polypropylene Bags

As polypropylene bags are completely clear they are sometimes used as a more economical substitute to archival baggies in museum and gallery settings to store collectibles and valuables. Because they resist moisture and other environmental contaminants they extend the shelf life of perishable foods by delaying evaporation and dehydration. In reverse, they help preserve sensitive materials such as photographic paper by impeding the entry of water or acid vapors. The FDA and USDA carefully monitor the quality or polypropylene bags used in food related industries to ensure quality and security for consumers. Codes require that the polymeric film used to create polypropylene bags be non-toxic and waterproof when used for food or drug containment. In addition to these qualities, these receptacles are lightweight and durable. Thickness is determined prior to production and should be carefully considered with regards for the intended use. Further considerations include size, strength, tear resistance, style and design.

Polypropylene comes from a colorless, combustible gas found in petroleum. Like all polymers, this thermoplastic consists of long chains of molecules that consist of several smaller monomers held together by covalent bonds. In the production of bags, these resins are melted to form a viscous fluid that is extruded through a die. Cool air is blown through the center of the die in order to stretch the film into a bubble. The air enters at a uniform rate to ensure an even thickness for the walls, often only less than two millimeters thick. Cooling is important as well as it sets the plastic in a more solid state. When the desired size and thickness is reached, the bubble is popped to allow for further processing such as rolling or curing. Die cutting is often used to size the material while heat treatments are popular in creating seams and seals. Other less popular processes for creating the bags include winding, casting and sheet extrusion. As an alternative to film bags, polypropylene plastic fibers may also be woven together to produce much more durable bags. Such bags are increasingly common for consumers who place emphasis on environmentally friendly practices as they are readily reusable. Both woven and film polypropylene bags are commonly printed on to provide information about their contents.