Polymer ID Codes
PE - HD - Polyethylene (High Density)

Polyethylene High Density is known for its large strength to density ratio. The difference in strength exceeds the difference in density giving PE-HD a higher specific strength. PE-HD bottles are harder more opaque and can withstand somewhat higher temperatures.
PVC - Polyvinyl Chloride

Polyvinyl Chloride is naturally clear, has extremely good resistance to oils, and has very low oxygen transmission. It provides an excellent barrier to most gases and its drop impact resistance is also very good. This material is chemically resistant, but it is vulnerable to some solvents.
PE - LD - Polyethylene (Low Density)

Polyethylene Low Density is similar to PE-HD in composition. It is less rigid and generally less chemically resistant than PE-HD, but is more translucent. PE-LD is used primarily for squeeze applications.
PP - Polypropylene

Polypropylene is used as a rigid package with excellent moisture barrier. The compatibility of PP with high filling temperatures is responsible for its use with hot fill products. PP has excellent chemical resistance, but provides poor impact resistance in cold temperatures.