Polyolefins are a class of polymers formed from the polymerization of olefins such as ethylene and propylene. These polymers include polyethylene, polypropylene, and other polymers made from alkenes. Polyolefins exhibit many useful properties that have enabled their widespread use in a variety of industries and applications.
Chemical Structure and Properties
Polyolefins are hydrocarbon polymers, meaning they are composed purely of hydrogen and carbon atoms in long molecular chains. The main difference between polyolefin types is the structure of these repeating molecular units — polyethylene contains an ethane repeating unit (–CH2–CH2–) while polypropylene contains a propene repeating unit (–CH2–CH(CH3)–).
The carbon backbone structure gives Polyolefin Resins their main mechanical properties. The strong covalent carbon-carbon bonds make polyolefins rigid yet flexible and resistant to chemicals and corrosion. The lack of polar chemical groups also means polyolefins are generally non-polar and hydrophobic — this property enables uses where water or moisture resistance is important. Polyolefins also have low densities, ranging from 0.89–0.97 g/cm3 for LDPE and 0.90–0.92 g/cm3 for polypropylene.
Polyethylene
Polyethylene (PE) is produced in various forms depending on process variables used during Polyolefin Resins. Low-density polyethylene (LDPE) resin is lightly branched with densities around 0.915–0.940 g/cm3. LDPE products have good clarity and flexibility ideal for food packaging films, shrink wrap, and trash bags.
Linear low-density polyethylene (LLDPE) has a linear polymer chain structure with short branches, lowering densities to 0.910–0.940 g/cm3. LLDPE resins can be processed at higher rates than LDPE and offer good impact resistance suitable for industrial films and lamination applications.
High-density polyethylene (HDPE) has fewer and shorter branches, making it essentially linear. HDPE has densities in the range of 0.941–0.970 g/cm3, imparting high strength and stiffness properties useful for pipes, bottles, containers, and durable household goods.
Get more insights on Polyolefin Resins
