What makes High Density Polyethylene "high density"?
Posted by Nana Hinsley on Tue, Dec 27, 2011 @ 03:02 PM
Question: When does polyethylene go from regular old "polyethylene" to "high density polyethylene" or HDPE?
Answer: The density of polyethylene is measured in grams per cubic centimeter or g/cm³. The mass density of high density polyethylene can range from 0.93 to 0.97 g/cm³. Surprisingly, the difference in density between Low Density Polyethylene (LDPE) is 0.02g/cm³. LDPE had a density range of 0.910–0.940 g/cm3. As you can see, there is very little difference in the density. What makes HDPE stronger is the way the structure of the molecules lines up. HDPE has stronger intermolecular forces and tensile strenghth which translates into a higher specific strength. It is harder, more opaque, and can tolerate higher temperatures (120 °C/ 248 °F for short periods, 110 °C /230 °F continuously). than LDPE . LDPE can withstand temperatures of 80 °C continuously and 95 °C for a short time.