High and Low Density Polyethylene
Low Density Polyethylene (LDPE) is a semi-rigid and translucent polymer. It is produced by high pressure polymerization process. LDPE is cost effective and can be processed easily. Low Density Polyethylene exhibits good resistance to alcohols, dilute alkalis and acids. It has a limited resistance to aliphatic and aromatic hydrocarbons, mineral oils, oxidizing agents and halogenated hydrocarbons. Low Density Polyethylene can resist temperatures up to 80 °C continuously and 95°C for shorter times. This limits its usage in applications requiring extreme temperatures. LDPE shows good weatherability. The impact resistance of low density polyethylene are worth mentioning too. Also its electrical properties have made it ideal for several applications. In the present day scenario Linear low density polyethylene (LLDPE) has been quite successful in replacing Low Density Polyethylene. LDPE applications mainly include manufacturing of plastic bags, containers, bottles etc.
High Density Polyethylenelow-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength than LDPE. The difference in strength exceeds the difference in density, giving HDPE a higher specific strength. It is also harder and more opaque and can withstand somewhat higher temperatures (120 °C/ 248 °F for short periods, 110 °C /230 °F continuously). High-density polyethylene, unlike polypropylene, cannot withstand normally required autoclaving conditions.