Polyethylene are used in many different ways. This article will describe more about these polymers and the differences between LLDPE, LDPE, and HDPE.
What are polyethylene?
Polyethylene are thermoplastic polymers that have numerous applications. In the 1950s, German and Italian scientists, Karl Ziegler and Giulio Natta, discovered the polymerization process that produces polyethylene.
Made from the chemical compound ethylene, polyethylene has fairly straight branches that can branch out. The variations in the branching structure are what separates different polyethylene from each other.
Different types of polyethylene
The strength and structure of its molecular bonds determine the polyethylene’s level of density and elasticity, which is what distinguishes one type of polyethylene from another. We will cover three different types of polyethylene right now.
Low-density polyethylene (LDPE)
Out of all the polyethylene, LDPE has the most branches. With a thickness of 0.5 mils to 40 mils, this widely used plastic is reasonably flexible, making it suitable for a variety of surfaces.
Its high number of branches decreases its density to a range of 0.91-0.925g/cm3. It’s important to note that this lack of density increases the risk of puncture damage.
The most common applications for LDPE include:
- Construction;
- Agriculture;
- Surface Protection;
- Tarps;
- Coverings;
- Films;
- Bottles;
- Pipes;
- Telecommunication Cables,
- Power Cables.
Linear low density polyethylene (LLDPE)
LLDPE products are the most agile of the plastics. This polymer is often combined with other films in order to increase the elasticity and durability of the materials being used.
The molecules of an LLDPE compound remain firmly united even when the material is pulled or strained. It has many short branches that glide against each other.
This keeps the film from tearing even when subjected to high impacts. And because the branches are shorter in length, they don’t get into a tangled mess
An LLDPE material also has the following traits:
- Thickness – 0.5 mils to 40 mils;
- LLDPE Density – 0.91-0.94g/cm3;
- Crystallinity – Around 5%, which makes it a low crystalline polyethylene. This is the reason for its flexibility,
- Stress Cracking – Is not sensitive to stress that would cause cracking, making it a smart choice when needing a material that can tolerate low
- temperatures.
Here are a few of the ways linear low density polyethylene materials are used:
- Stretch Films;
- Garment Packaging;
- Agriculture Film;
- Carpet Films;
- Food Packaging;
- Non-Food Packaging;
- Industrial Liners;
- Power Cables,
- Telecommunication Cables.
High density polyethylene (HDPE)
This type of polyethylene is the most durable and chemical resistant, but it’s also less flexible than LDPE and LLDPE.
Tightly combined cells form HDPE compounds. These cells band together so strongly that invading molecules have an extremely hard time getting through.
HDPE compounds have very little branching that is almost nonexistent, giving this polymer its rigid and impermeable properties. HDPE is the polymer of choice when needing materials that can endure chemical exposure.
Here are some other qualities that make HDPE products different from other polyethylene:
- Thickness – 12 mils to 100 mils;
- Density – 0.941-0.965g/cm3;
- Crystallinity – 50%, making it a semi-crystalline polymer that is able to resist chemicals;
- Stress Cracking – Its crystallinity increases the risk of HDPE cracking under stress,
- UV Resistant – There is no need to include UV additives in HDPE materials because these polymers are readily equipped to handle sun exposure.
Some common HDPE applications include:
- Plastic Bottles;
- Toys;
- Chemical Containers;
- Pipe Systems;
- Grocery Bags;
- Flower Pots;
- Recycling Bins;
- Telecommunication Cables,
- Power Cables.
How to choose the right polyethylene
Now that you know more about the different polyethylene, how do you know which of the three is right for your project? That depends on what you are working on.
It’s important to realize that one polyethylene is not better than another. They are simply different, meaning they can fulfill different purposes.
When determining which polymer is right for your needs, you should ask yourself the following questions:
- How durable does the material need to be? HDPE has the most strength, but keep in mind that it’s more likely to undergo stress-cracking and isn’t flexible.
- What level of flexibility is required for the desired design? Linear low density polyethylene is fairly flexible and isn’t as likely to experience stress-cracking.
- Will there be chemicals involved? In that case, you would need the chemical resistant polymer, HDPE.
- Will there be constant stress on the material? If so, the linear low density polyethylene would be a better option than HDPE.
To sum it up, if your project requires durable or chemical resistant products, HDPE is probably the best option for you. But if you are looking for something that’s easy to install and doesn’t require the same level of strength as HDPE polymers, LLDPE might be a better choice.
If you are feeling overwhelmed and don’t know what to choose, contact us. We can help you choose the right products for your project. With our help, your next project will be a success!
