Poly Bags: Polyethylene Vs Polypropylene
Poly bags are often referred to as plastic bags, which are used to package a wide range of loose and small items such food, building supplies, candies, consumer goods, and other products. These bags are made from polymer materials, which are stretched into sheets of film, cut to a desired length and sealed to form a bag. Many businesses opt to package their products in poly bags due to low costs, lightweight and flexible properties of the material.
Poly bags can come in many densities, properties, strengths, and applications depending on which material you select to make your bag. The most common types of poly bags are made from polyethylene and polypropylene materials. Polyethylene bags are popular because they can be manufactured in a variety of densities, while others prefer polypropylene for its clarity and strength.
Different Types Of Poly Bags
Polyethylene Bags
Polyethylene is created from the polymerization of ethylene gas, which creates long and straight chains of hydrocarbons. Branches are formed in many different directions from the main strand. The number of branches formed will determine the density of the polyethylene. The more branches there are, the less dense the polyethylene material will be, as molecules have less space from one another. If there are less branches, then the polyethylene will be more dense. as molecules have more space between them.
The density of polyethylene will determine the materials strength, which will indicate how much weight the material can support. Therefore, it is important to obtain the right thickness of polyethylene bags depending on your packaging application.
Polyethylene bags can be categorized and manufactured by density. Densities include: high, low, linear low, and medium.
High Density Polyethylene Bags
High density polyethylene (HDPE) is the strongest and thickest form of polyethylene material. HDPE is created when there are a minimal amount of branches on the main polymer chain during the polymerization process. Molecules are loosely structured together, which creates a more dense, solid, less flexible, durable, puncture and tear resistant product.
HDPE bags can be used to hold one item or multiple items. They are typically used to package heavy, irregular shaped, sharp edged and loose products. For example, they can hold large bulk and loose products such as mulch, fertilizer, seeds, cement, sand, water softener and other products.
Furthermore, HDPE bags are food friendly which makes it safe to package bulk food such as rice, grains and frozen foods. They can also be used as a sturdy shopping bag or take out bag.
Low Density Polyethylene Bags
Low density polyethylene (LDPE) is made from numerous polyethylene branches that occur during polymerization. As a result, molecules are loosely packed together, giving a less dense material. LDPE bags are lighter, have a higher clarity, require less material and are more cost efficient than HDPE. However, these bags are weaker and are more prone to tear or rip.
LDPE bags are commonly used to package small and lightweight items such as candies, toys, snacks, bread, tortillas, and other products. Like HDPE, LDPE can be used as shopping bags or take out bags, but for small and lightweight products. It is not recommended to package sharp or irregular shaped items with LDPE.
Linear Low Density Polyethylene
Linear low density polyethylene (LLDPE) requires a lot of branches that form on the main strand. These branches are short and parallel which enables them to move together with one another without getting tangled (occurs during LDPE polymerization). As a result, it has a higher strength and durability compared to LDPE, while maintaining its flexibility. However, they do have less clarity than LDPE.
LLDPE bags are known for not transmitting chemicals into food or soil, which makes it ideal for both food and lawn packaging applications. In addition, LLDPE can also be used to package toys and dairy products, or be used as a grocery bag.
Medium Density Polyethylene Bag
Medium density polyethylene (MDPE) is formed with a moderate amount of branch strands attached to the main strand. Essentially, MDPE’s properties such as density, strength, durability, flexibility and resistance are in between HDPE and LDPE.
Many businesses choose MDPE as their preferred poly bag as it minimizes the tradeoffs between HDPE and LDPE. It can be used in a variety of packaging applications such as: consumer goods, electronics, cosmetics, food, beauty and more.
Polypropylene Bags
Polypropylene (PP) is a popular alternative to polyethylene bags, these bags are made from the polymerization of the olefin propylene. PP bags are strong, high clarity, chemical and heat resistant, and are used in a wide range of packaging applications.
Typically, PP bags are used to package applications in the medical, food, electronics and beauty industry. Polypropylene is an ideal packaging solution in keeping contents free of contamination, as the material protects against debris, vapors, moisture, virus and bacteria.
Polypropylene bags are used by many businesses that require a product to have high visibility to its content. In addition, PP bags are commonly used in outdoor applications, as it has a higher tolerance for heat over LDPE bags.
Which Should You Choose: Polyethylene or Polypropylene Bags?
The poly bag you will choose will largely rely on your packaging application and will vary from product to product. Polyethylene bags are quite versatile in properties, as they can be manufactured at different densities, which alters their properties (strength, durability and flexibility).. However, Polypropylene is popular among many businesses as it can offer high clarity, heat resistant and contamination free benefits.
We recommend you pick the packaging solution that fits the needs of your project, budget and product goals. If you are interested in selecting the right poly bag for your product, then contact Brown Packaging today to get started.
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