LLDPE

LLDPE: is defined by a density range of 0.915–0.925 g/cm3. LLDPE is a substantially linear polymer with significant numbers of short branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins (for example, 1-butene, 1-hexene and 1-octene). The most common process used for LLDPE is extrusion (tubes, blow and cast films, cables, ...). LLDPE can also be processed by injection molding or rotomolding.

LLDPE has higher tensile strength than LDPE, it exhibits higher impact and puncture resistance than LDPE. Lower thickness (gauge) films can be blown, compared with LDPE, with better environmental stress cracking resistance but is not as easy to process.

LLDPE is used in packaging, particularly film for bags and sheets. Lower thickness may be used compared to LDPE. Cable covering, toys, lids, buckets, containers and pipe. While other applications are available, LLDPE is used predominantly in film applications due to its toughness, flexibility and relative transparency. Product examples range from agricultural films, saran wrap, and bubble wrap, to multilayer and composite films.

Key Points: The co-monomer distribution may cause clarity difference in the same gra de of LLDPE pol ymer because of the hindrance in the growth of crystal is restricted by short chain branching distribution.

Extrusion moulding: 

Melt temperature : 205-260°C

A three zone screw with a L/D ratio of around 25 is recommended.

Injection moulding:

Melt temperature : 160-260°C

APPLICATIONS OF LLDPE 

Agriculture 

Lateral for drip irrigation, pond and canal liners, sprinkler parts, nursery bags

Automotive 

Dash board liners, washers, handles, air filter parts, seals.

Medical 

Saline water bottles and holders, contact lens caps, tubes for fluid transfer.

Electrical 

Wire coating, cable sheathing, marine cable sheathing, optical fibre Coating.

Packaging 

Bubble film for safety packaging, stretch films, shopping bags, shrink warp for different products.

Household 

Air tight boxes & containers, garbage bags, toys

Strengths:

1. Higher tensile strength than LDPE

2. Higher impact and puncture resistance than LDPE

3. Lower thickness films can be blown compared to LDPE

4. Improved sealability

5. Excellent chemical resistance

6. Very good processablity

7. High impact strength at low temperature

8. Excellent electrical insulating properties

9. Very low water absorption

10. High environmental stress crack resistance

Limitations:

1. Lower gloss than LDPE

2. Narrower temperature range for heat sealing than LDPE

3. Lower processability than LDPE

4. Susceptible to stress cracking

5. Lower stiffness than polypropylene

6. High mold shrinkage

7. Poor UV resistance

8. Low heat resistance

9. High-frequency welding and joining impossible.

Properties 

1. Resistance to solvents, acids and alkalies 

2. Water repellent

3. Higher puncture resistance than LDPE

4. Higher tear resistance than LDPE

5. Elongation at break is high

6. Improved impact strength

7. High toughness even at high temperature

8. Improved sealability 

9. High environmental stress crack resistance

10. Better low temperature flexibility