Polyethylene Packaging
While polyethylene is available in many varieties (liner low density, high density, high molecular weight, etc...), it is low-density polyethylene that is used extensively in the rigid packaging industry because of several favorable physical properties. Low-density polyethylene (LDPE) has a low vicat softening point, which makes its use very favorable in the form-fill and seal packaging industry. The low vicat softening point aids in low temperature forming and heat sealing, attributes that enable the form-fill and seal package industry to optimize equipment cycle-times. LDPE also has better clarity than other polyethylenes, good organoleptic properties, and reasonably low moisture vapor transmission properties. In fact, LDPE is often used in conjunction with polystyrene because of its much improved moisture barrier transmission properties.
Advantages of Polyethylene
- Low cost material.
- Broad range of properties.
- Very good moisture barrier properties.
- Very good chemical resistance.
- Food grades available.
Disadvantages of Polyethylene
- High thermal expansion.
- Low stiffness with standard grades.
- Most grades not considered to be microwave safe.
- Poor UV properties i.e. sunlight can degrade.
EVA
Ethylene vinyl acetate (EVA) is another member of the branched polyethylene family that has a significant presence in the rigid packaging industry. EVA, produced by copolymerizing ethylene and vinyl acetate, is used as a tie layer in many coextruded structures in both rigid and flexible packaging.
