There are two types of commonly used plastic bags, HDPE and LDPE.
HDPE or High Density Polyethylene is a plolyethylene thermoplastic made from petroleum. Known for its large strength to density ration, HDPE is commonly used in the production of plastic bottle, corrosion-resistant piping, geomembranes, and plastic lumber. HDPE is commonly recycled and has the number ‘2’ as its recycling symbol
LDPE or Low Density Polyethylene is a thermoplastic made from the monomer ethylnen. It was the first grade of polyethylene made in 1933 using a high pressure process via free radical polymerization. Its recycling symbol is ‘4’