HDPE and PET are both types of plastic that are commonly used for manufacturing bottles. Both are similar only superficially. Many differences in the type of material, production and usage set these two types of plastic apart.
Contents
- 1 What is HDPE plastic?
- 2 What is PET plastic?
- 3 What is the difference between HDPE and PET?
- 4 The Difference Between HDPE and PET: Recyclability
- 5 The Difference Between HDPE and PET: Gas Barrier
- 6 The Difference Between HDPE and PET: Stress crack resistance
- 7 The Difference Between HDPE and PET: Temperature range
- 8 What is the difference between HDPE and PET? Conclusion
What is HDPE plastic?
HDPE stands for high-density polyethylene. It is one of the most coon types of plastic used in manufacturing. HDPE plastics are well-known for their strength and durability. HDPE bottles can withstand high temperatures from -110 degrees to 165 degrees Fahrenheit. 
HDPE is not a clear type of plastic. They can be semi-opaque and see-through. These plastics can be color-matched and is most popular in white.
What is PET plastic?
PET stands for polyethylene terephthalate and is mostly used for packaging. PET plastic is popular because of its clear nature. It is widely used for clear plastic bottles and other uses. PET is not as temperature resistant as HDPE and can only handle the heat from -40 degrees to 130 degrees Fahrenheit. The specialty of PET is that it withstands diluted acids, oils and alcohols that typically attack other types of plastic. 
What is the difference between HDPE and PET?
- HDPE stands for high-density polyethylene, and PET stands for polyethylene terephthalate.
- HDPE is an opaque and petroleum-based thermoplastic, and PET is a clear plastic that can only stand temperatures up to 145 degrees.
- HDPE is highly durable and resistant to punctures and impacts. It also has better gas barrier protection than PET. But PET is not very durable.
- PET plastic has better stress crack resistance than HDPE. In HDPE plastic, stress cracks occur due to chemicals in the environment that attack the semi-crystalline plastic material.
- PET offers easier recyclability than HDPE. Both types of plastic can be recycled but require different types of processes and must be separated.
- HDPE plastic is ideally used for plastic drums and shipping containers. PET plastic, on the other hand, is best for one-time-use plastic bottles for beverages and clear packaging.
The Difference Between HDPE and PET: Recyclability
Both PET plastic and HDPE can be recycled. But they both require different processes to break down the materials and hence must be separated before recycling.
Look for the number within the triangular shape at the bottom of plastic bottles. This number indicates the recycling rating of the plastic. PET has a recycling rating of 1, and HDPE has a recycling rating of 2. 
Plastic with a 1 rating is only intended for single use. These plastics can be recycled easily by shredding them into pellets.
Plastics rated 2 are suitable for both reuse and recycling. HDPE types of plastic can be recycled up to 10 times before they are disposed of. Recycled HDPE can be remolded into pipes, lumber, toys and even floor tiles.
The Difference Between HDPE and PET: Gas Barrier
A plastic’s gas barrier is also known as Water Vapor Transmission Rate (WVTR) and is measured in g-mil/100in. PET plastic has a WVTR of 2.0, and HDPE has lower than 0.5. A lower WVTR shows that the packaging type protects its contents from moisture for longer.
It’s important to choose a type of plastic packaging that complies with the necessary WVTR for barrier performance. This is crucial, especially when shipping hazardous goods.
The Difference Between HDPE and PET: Stress crack resistance
This refers to the ability of the type of plastic to withstand environmental pressure. A stress crack can be an internal or external crack caused by tensile stresses. HDPE plastics, stress cracks occur frequently.
Resistance to environmental stress cracking when the molecular weight of the plastic polymer increases and the crystallinity decreases. Pet plastic has a higher resistance to stress cracking than HDPE plastic.
The Difference Between HDPE and PET: Temperature range
Both plastics are quite heat resistant. HDPE has a higher melting point than 160 degrees. It also has a lower cold brittleness than PET plastic and can resist cold up to -50 degrees Fahrenheit. PET plastic can only handle temperatures as low as -40 degrees Fahrenheit.
What is the difference between HDPE and PET? Conclusion
HDPE and PET plastic have many differences in terms of temperature range, recyclability, gas barrier and stress crack resistance. PET plastic is mostly a one-time-use plastic, and HDPE plastic can be reused. Both plastics can be recycled, but PET is easier to recycle.
Read this article for more interesting information on the plastic revolution.
Also read: How to recycle plastic? the plastic recycling process in 2023
*All pics are courtesy of Unsplash.com
