Ethylene polymers are thermoplastic polymers which are used in the production of various packaging materials. These polymers (especially the ones mentioned below) generally have good resistance to alcohols, oils grease and dilute acids and alkalis. One of the most important features of this type of material in the context of packaging is that it has moderate to good barrier properties to oxygen and carbon dioxide which makes is suitable for Food Containers packaging.
Below is a description of some of the common ethylene polymers used in various forms, especially for the packaging of perishable consumer items.
Ethylene Vinyl Alcohol Copolymer (EVOH)
This is a formal copolymer of ethylene and vinyl alcohol. It is used as a high barrier material to gases (O2 and CO2) but is a low moisture vapor barrier material. These properties diminish in a humid environment. . This is a kind of expensive packaging material, and is widely used as the barrier film in a laminate. EVOH is used primarily for food packaging and usually as a thin layer within cardboard or foil to improve the shelf life of food.
High Density Polyethylene (HDPE)
HDPE is a polyethylene thermoplastic made from petroleum. It is semi-rigid, translucent, very tough, and also has low water absorption. HDPE has moderate barrier properties but is not suitable for use at high temperatures. It is generally molded to form soft bottle-containers to store milk, detergents, etc. It is a low cost and easily produced material.
Low Density Polyethylene / Linear Low Density Polyethylene (LDPE -LLDPE)
LDPE is a thermoplastic made from oil. It is extremely tough but flexible, waxy, moisture/ weather-proof, has good low temperature toughness and is easy to process by most methods at low cost and has good overall resistance and moderate barrier properties. It is widely used for its heat sealing properties in a laminated material. However, it is not suitable for use at temperatures above 100° C but is recyclable. It is also corrosion-resistant. These properties make it appropriate for the production of general purpose containers for foodstuff and laboratory use, and so on.
Polyethylene Terephthalate (PET or PETE)
PET is a thermoplastic polymer resin of and is used in synthetic fibers. It is rigid, extremely tough and impact-resistant, has good creep and fatigue resistance, wide range temperature resistance (-40 to 220° C) and does not flow on heating. This material is usually oriented to improve its barrier properties to gasses and water vapor. It has excellent clarity and is often used as a glass replacement. On the other hand, C-PET is widely used to produce containers for carbonated beverages and solvents due to its good resistance and barrier properties.