In 1933 low density polyethylene (LDPE) was the first type of polyethylene to be synthesised. LDPE has more branches than HDPE, and the branches are long. Because of this chain configuration the molecules cannot order as well as with the linear HDPE chains, and the crystallinity is lower. This is the reason why the density of LDPE is lower than of HDPE.
Due to the lower crystallinity the Young's Modulus is also lower, because the glass transition temperature is (as with all PE’s) far below room temperature. However, this makes LDPE very ductile, even at low temperatures.
LDPE is being converted in enormous quantities to blown foils. It is also often used in multi layer foils and as coating layer on cardboard for packaging. Other important applications are in containers and bottles, and as cable sheath.
Density: 0.91 - 0.94 g/cm3.
Mechanical properties: Young's Modulus around 200 - 300 MPa.
LDPE is very ductile (high impact resistance), even at very low temperatures.
Thermal properties: Tm around 120 °C. Tg < -100 °C.
Chemical resistance: Very good resistance against acids and bases, good resistance against most organic liquids. Dissolves at elevated temperatures in aromatic and halogenated solvents.
White translucent, thin foils almost transparent. Can be easily coloured.
Processable using film blowing, blow moulding, rotational moulding, injection moulding and extrusion. Printing, painting and gluing is difficult due to the low surface energy, but corona treatment is a common solution for this. (Ultrasonic) welding is an often used joining technique for LDPE.
Packaging: foils, shrinkage wrap, plastic bags, (squeeze) bottles, garbage bags, coatings for cardboard beverage packaging (milk, juices) Industry: large storage tanks, produced by rotational moulding or blow moulding, hot-melt adhesive, lining for (steel) storage barrels for chemicals.
Laboratories: wash bottles and chemicals storage bottles
Electronics: cable insulation
Consumer articles: food storage containers, toys
Agriculture: agricultural foils, pipes for heating and irrigation systems.
|Minimum service temperature||-30||°C|
|Maximum service temperature||70||°C|
|Dielectric loss factor||0.0006|