Ethylene polymers in Packaging

                                                                                         

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 packaging.

Below is a description of some of the common ethylene polymers used in various forms, especially for the packaging of perishable consumer items (foodstuff and pharmaceuticals).

Ethylene Vinyl Acetate (EVA)

This is known as foam rubber. Amongst its properties: Flexible, elastic, transparent, good low temp flexibility and it has a high friction co-efficient.
EVA is used primarily as a padding material in packaging cartons e.g. for electronics etc.

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 expensive packaging material. 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 widely blow molded to form soft bottle-containers, e.g. 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. It is not suitable for use at temperatures above 100° C and is recyclable. It is also corrosion-resistant. These properties make it appropriate for the production of general purpose containers for foodstuff (jars etc) and laboratory use and is also used to coat/ laminate cartons and make six-pack-soda-holder rings.

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. C-PET is widely used to produce containers for carbonated beverages and solvents due to its good resistance and barrier properties and is extremely easy to recycle, which makes it very environment friendly.

Crystallized PET is also used to contain frozen dinners, and a thin film of PET (Mylar) can be coated with other materials (like aluminum) to cater to a variety of uses, including as flexible food packaging etc.

About the author:
ABC Packaging Direct works with you to understand your packaging needs and develop specialty packaging solutions including food packaging, thermoformed plastic trays, stand up pouches, low melt bags, autoclave bags, plastic valve bags and VCI bags.

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