Polyethylene (Plastic Sheeting Liners or plastic "poly" sheet) is classified into several different categories based in part on its density and mechanical properties. The most prevalent grades of polyethylene sold is HDPE, LLDPE and LDPE: High Density Polyethylene (HDPE) has minimal branching of its’ polymer chains. Because it is denser it is more rigid and less permeable … [Read more...] about Understanding Thickness of Plastic Sheeting