Linear Low density polyethylene is a copolymer ethylene and an olefin such as 1-butene/1-hexene/4-methyl-1-pentene and 1-octene. The addition of the olefin in the polymerisation process adds strength and impact resistance to the end LLDPE product. This process is called free radical polymerisation. LLDPE resins occur in the form of odourless white granules. These can then be processed by extrusion, injection moulding and/or blow and cast film.
In recent times due to easy processing and its favourable properties, much of the LDPE market has moved to LLDPE. However, LLDPE being inert to degradation, is considered an environmental hazard, even though it is often recycled into things such as lumber, floor tiles, trash bin and liners, landscaping ties, shipping envelopes, etc.
Both LDPE and LLDPE have more or less the same density, however LLDPE displays better impact and crack resistance than LDPE. Because of the linear linkages, LLDPE also exhibits a better appearance with enhanced gloss. However in its natural form, it has a poorer clarity or transparency. This allows for the production of thinner sheets without affecting the strength and resistant properties of the product.
LLDPE is very flexible, has higher tensile strength and under stress, it can elongate. In addition, LLDPE is highly resistant to chemicals, can withstand punctures and has good electrical properties. However, with a lower capacity for heat sealing, it is not as easy to process as LDPE.
Sometimes to make the most of appearance and strength, blends of LDPE and LLDPE granules are processed to make the finished product.