What is the Difference between High, Medium and Low Density Polyethylene?
Three characteristics of polyethylene resins are usually used to classify the properties of the final product: density, molecular weight, and molecular weight distribution. Of these properties, only density is usually considered by the user of PE pipe. PE pipe was originally manufactured using only one process that resulted in a material that would currently be classed as low density. As time passed and polyethylenes with varying properties were produced through a variety of processes, there arose a need for an industry standard that would classify the resin according to density. The American Society for Testing of Materials (ASTM) established the following classification system, still in use today. It is a part of ASTM D1248, Standard Specification for Polyethylene Plastics Molding and Extrusion Materials [2,5].