Bags are one of the oldest and most popular forms of packaging. They are an important part in daily uses like for food storage, packaging and transporting goods and for waste disposal among many other uses. Polythene bags are defined as a container made of a thin, flexible plastic film which is open at one end. They are made of a multitude of materials, which is sometimes difficult to choose an appropriate one for practical needs of customers. In this article, we would like to present the plastic poly resins in terms of their characteristics and applications for plastic grocery bags.
HIGH-DENSITY POLYETHYLENE (HDPE)
High density polyethylene (HDPE) is a very popular material to make plastic shopping bags. This plastic material is milky white or semi-translucent, with superior puncture, low permeability and temperature resistance. It is suit for the bags with straight molecule chains from start to finish, with very little branching. The dense molecular structure makes HDPE are moderately opaque and lightweight but extremely sturdy.
Thanks to the high tensile strength, HDPE bags can hold heavy weight without falling apart. HDPE plastic is also highly resistant to chemicals, water and temperature. And it is quite transparent, and food-safe. So, HDPE is a good choice for the production of shopping bags like T-shirt bags, Soft loop bags, and D-cut bags, laundry bags, and garbage bags. Also, this plastic is a great option for food handling/serving/packaging applications where no need for an oxygen or CO2 barrier.
Most shopping and grocery bags in the USA are made of this plastic. HDPE is popular for its high strength and low cost.
MEDIUM-DENSITY POLYETHYLENE (MDPE)
As the name suggests, MDPE is the combination of HDPE and LDPE, and has their mixed characteristics. It is less opaque than HDPE but not as clear as LDPE. Retail bags made of this plastic are usually stronger than LDPE but do not stretch as much.
Due to less dense than HDPE, this polymer isn’t as strong and does not make a good choice for bulk storage or transportation. Instead, it is often the material for garbage bags, for consumer packaging as it has a high degree of chemical resistance.
Due to its low tensile strength and stretch properties, this material may not be an ideal choice for plastic shopping bags or bulk storage or transportation, but it can be the material of garbage bags, shrink film and packaging film for certain consumer products including paper towels, toilet rolls, etc.
LOW-DENSITY POLYETHYLENE (LDPE)
Low density polyethylene or LDPE is another very popular plastic material. Bags made from this material are either white in color or clear. Customized plastic grocery bags made from this material are flexible and easy to stretch, clear and glossy. They also have good tear resistance and moisture barrier properties but only fair gas barrier properties.
Thanks to a low density and spread out in various combining lines or branches, LDPE plastic is very lightweight and has moderate tensile strength.
Despite not as strong or stretchable as HDPE, its low melting point makes LDPE ideal for heat-sealing applications. Moreover, it is easier for content identification because of its film-like transparency. LDPE is often the packaging material of choice for consumer packaging where strength is not a requirement, like for restaurants and other commercial food handling operations, like bags for bread, newspapers, frozen food, fresh produce, dry cleaning garments, etc. or produce and meat suppliers, dry cleaners, etc.
LINEAR LOW-DENSITY POLYETHYLENE (LLDPE)
With similar properties as LDPE, but LLDPE is selected for its higher tensile and impact strength and better heat-seal, whereas LDPE is often selected for its higher clarity, ease of processing and higher gloss. As it is not strong tensile as HDPE, manufacturers need to use a thicker and heavier form.
LLDPE grocery bags have moderate clarity and a slightly lower gauge than LDPE bags, but no difference in strength. So, it makes them a cost-effective alternative to LDPE for bulk food storage/packaging and other applications where quality is critical. They are particularly well-suited for freezer or refrigerator storage in commercial kitchens, but popular with clothing stores too.
In Hanpak, we mostly use LLDPE material for Stretch film/ Pallet Wrap production.
Also, see what we are doing in other E-commerce platforms.