To understand what material the express packaging bag is, we first need to know what are the classifications of the express packaging bag?The classification of express packaging bags mainly includes express plastic bags, express document seals, express bubble bags, express bone bags, express woven bags, etc.The following is a brief introduction to what materials the various express packaging bags are made of. 1.Express plastic bag material: polyethylene(PE), polyethylene is divided into low density polyethylene(LDPE)and high density polyethylene(HDPE). There are two types of polyethylene courier bags:1.Brand new courier bag,2.Recycled courier bags. 2.Material of express document envelope: Commonly used are gray-bottomed whiteboard, white cardboard, and kraft cardboard. 3.Express bubble bag material: a transparent packaging bag filled with air in the middle layer of the air cushion film. 4.Express bone bag material: polyethylene (LDPE) and high pressure linear polyethylene (LLDPE)It is a resealable plastic bag made by blown film forming and heat-cut machine-made bag. It is generally used for small food and tea packaging. 5.Express woven bag material: polyethylene, polypropylene and other raw materials are used for packaging of goods and are widely used in industry.The above is the answer to what material the express packaging bag is made of.