The world of plastic bags offers a wide, sometimes even confusing, range of products. We have decided to put things in order and explain the differences between the various polymers used for bag manufacturing. Let’s start with a small tip – Nylon has nothing to do with bags!
A Word or Two About Polymers and Plastic
The word polymer consists of two Latin words: “Poly” for a lot, and “Mer” for a unit and, indeed – polymers are comprised of recurring units of the same molecule (monomer), considered to be the building block of the polymer. Through polymerization, which is a process that takes place under certain conditions of temperature, heat, pressure, and different catalysts, monomers are chemically combined to produce a very large chain-like, or network-like molecule, called a polymer, much like a long beaded chain. Various additives can be added to the polymer, providing the final plastic sheet with various properties.
Polyethylene – One of the Oldest and Most Common Polymers
This polymer was created in the 1950s through polymerization with a catalyst called Ziegler-Natta, which won its inventors a Nobel Prize in Chemistry. However, its industrial production had already begun in the mid-1930s through slower processes. This very versatile polymer can be obtained in a variety of densities and properties. As a result, it has numerous applications in the plastics industry, such as rigid packaging, bags, piping, fibers and toys.
A Bit About the Material ATIFIT’s Sheets Are Made Of
The bags manufactured by ATIFIT are mainly made of LDPE (Low-Density Polyethylene) and LLDPE (Linear Low-Density Polyethylene.)
LDPE has good resistance to chemicals and temperatures up to 80 degrees Celsius. It is easy to process, modest in cost, has high impact resistance, and transparency. Adding LLDPE to a bag adds to its flexibility and good tear resistance. Both polymers are approved for food contact. When you want to add strength and durability to bags, you can also use MDPE (Medium Density Polyethylene) which has a higher density.
Another significant advantage of using products that are made purely of polyethylene is that they are easily recyclable. All Polyethylene types are among the largest recycling streams also in mechanical recycling, and it is preferable, as far as recycling goes, to polypropylene. This is due to the existence of a long-standing array of collection and transfer of polyethylene waste for recycling (rather than landfilling). The production volumes of polyethylene-based packaging are also higher than polypropylene-based packaging, which also leads to a preference for the recycling of polyethylene packages.
Polypropylene – Suitable for High-Temperature Uses
Polypropylene has a higher density than polyethylene and can be used to manufacture two types of films: CPP (Cast Polypropylene), films without orientation, and BOPP (Bi-Oriented Polypropylene), films that undergo bu-axial stretching that gives them higher strength properties.
The processing window of polypropylene is relatively narrow, which poses a manufacturing challenge. Due to its density, both its processing and sealing temperatures are higher. On the other hand, these properties turn it into the preferred polymer for bags that are designed for hot food packaging, high-temperature sterilization packaging, and more. Using polypropylene films increases the bags’ robustness and tear resistance. BOPP films are suitable for printing and for lamination of other films. Polypropylene bags can also be used for packaging pastries, bread, fruit, and even clothing.
In summary, we would be more than happy to advise and assist in finding the right kind of bag to fit your needs and requirements. We can offer polyethylene and polypropylene bags in a variety of sizes, colors, properties, and features, including bags for foodstuff, for maintaining long shelf life, and for freshness.
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