What is the Difference Between HDPE and PET?

In the field of the polymer world, both HDPE (high density polyethylene) and PET (polyethylene terephthalate) are excellent plastic packaging materials because they are lightweight and impact resistant. However, they each have unique characteristics that are important to understand when deciding to use them as shipping materials.

HDPE: an extremely tough "super plastic"

HDPE is like the superheroes of the plastics world, strong, resilient, and ready for action. It's made from something called ethylene gas, which sounds fancy, but it's actually basically petroleum. This plastic is the preferred choice for things like shipping barrels and chemical containers that need to be stable in harsh environments.

However, HDPE is more than just the embodiment of muscle. It also excels at dealing with heat, shock and even malicious punctures. What's more, it's also impervious to corrosion or bacteria, ensuring everything inside the package stays safe and sound.

So, how is HDPE manufactured? Well, it involves converting ethylene gas into something called ethane. Mix that with benzene and some UV radiation and you have your magic potion that turns into HDPE. This potion is then poured into molds and heated at just the right temperature to remove any unwanted ingredients.

The cool thing about HDPE is that it's kind of like a heat-resistant warrior. It stays tough even at elevated temperatures, and we're talking heat that reaches 160°F. However, if you raise the temperature above this point, it becomes soft and pliable. This makes it ideal for manufacturing different containers using high temperature blow molding.

PET: A contender for crystal clear

Now, if you need something that is crystal clear and can withstand the heat, PET is the place to be. PET is the abbreviation of polyethylene terephthalate, which is characterized by transparency and toughness. When it comes to getting FDA approval for food and beverage containers, it's held in high esteem in the world of plastics. Basically, it's a great thing for keeping your snacks and drinks safe.

The process behind PET is like a scientific formula. You take some ethylene glycol, mix it with terephthalic acid, and boom -- you've got a polymer chain that forms the backbone of PET. The strands are cut into small pieces, sort of like plastic confetti, which are then melted and molded into different shapes. And just like that, you have a clear plastic ready to go.

The wonderful thing about PET is that it is also a friend of the environment. It comes from natural sources like natural gas and oil, which means it's a more environmentally friendly choice than other materials like aluminum or glass.

HDPE vs. PET

Well, let's break it down: HDPE and PET both have characteristics that can make a real difference in your packaging process. First, let's talk about temperature. HDPE does not shrink at high temperatures and has a melting point of 160°F, while PET has a melting point of about 145°F. In addition, HDPE is also strong in cold environments and can perform well in temperatures as low as -50°F, while PET can only withstand temperatures as low as -40°F. Therefore, if your product needs to withstand the test of extreme temperature, HDPE is your best choice.

Then, there is a phenomenon called stress cracking. Like when a material wears out from environmental changes. HDPE is a bit sensitive to this, especially in environments with chemicals. But what about PET? It's like an anti-stress superhero with the power of its molecular structure. If you're concerned about your packaging's ability to hold up under pressure, look no further than PET.

Don't forget about moisture - that's the problem with gas barriers. Here, PET is the winner, with a water vapor transmission rate (WVTR) of 2.0, while HDPE has a WVTR of 0.5. Basically, PET is better at keeping items dry, which is great for shipments that need to stay dry.

Choose your packaging partner

As a discriminating packager, ultimately the question comes down to which plastic is better suited to your specific requirements. For example, if you need to transport barrels or containers to carry dangerous goods, then HDPE is the undisputed champion. It's tough, powerful, and ready to take on any challenge.

However, if you work in the food and beverage industry or deal with perishable food, then PET is your right-hand man. It's FDA-approved and crystal clear, ensuring your delicious treats arrive at their destination in perfect condition.

In addition, if you are environmentally conscious, PET can also support you. Its natural origin makes it a green choice in this eco-conscious world.