Polypropylene vs Polyethylene: What's the Difference?
Industrial applications have a wide range of products and components. There are versatile materials that are used for manufacturing components, among which polypropylene and polyethylene are commonly chosen. The two of these materials have similarities and some differences.
The guide below features an extensive comparison of polypropylene vs polyethylene, so let's take a look.
What is Polypropylene?
Polypropylene is a type of thermoplastic polymer. It has propylene units, which are combined through different methods of manufacturing. It is from the family of polyolefin.
Polypropylene is in carpets, caster wheels, food packaging, and much more. It has excellent resistance against moisture and chemicals and has a high rigidity. However, it also has a high melting point.
Due to the high melting point of polypropylene, it can be used in applications where the temperature is high, and it maintains its strength and durability very well.
What is Polyethylene?
Polyethylene is a thermoplastic that belongs to the family polyolefin. It is a combination of different monomers, among which ethylene is the most common. The products of polyethylene are manufactured using many methods, among which injection molding and extrusion are quite popular.
Polyethylene is a vertical polymer and hence can be used in applications like insulation of wire, toys, bottles, etc. It also has different grades, and hence, to meet the specific requirements, it can be altered. Some of the characteristics it has consist of flexibility, high impact strength, and resistance against chemicals and moisture.
The two grades of polyethylene are low-density polyethylene and high-density polyethylene. LDPE is a flexible and soft material and is used for grocery bags and food packaging. HDPE is strong and highly rigid and can be used in buckets, pipes, and bottles.
Comparison of Physical Properties
The comparison of the physical properties of polypropylene and polyethylene at a glance is given in the table below.
| Properties | Polypropylene | Polyethylene |
| Heat Resistance | Offers excellent heat resistance | Offers moderate heat resistance |
| Tensile Strength (GPa) | 0.5-3 | 3.7-19 |
| Density | 0.9 g/cm3 | 0.96 g/cm3 |
| Flexibility | Moderately flexible | Highly flexible |
| Impact Resistance | Good | Good |
| Chemical Resistance (dilute alkalis) | Good | Excellent |
| Chemical Resistance ( dilute acids) | Good | Excellent |
| UV Resistance | Poor | Poor |
| Purity | Needs polymerization with ethylene | 100% purity |
| Melting Point | 163.8oC | LDPE: 110oC
HDPE: 120oC |
| Static Charge | High | Low |
| Translucency | By nature, it is opaque but can be made translucent | Some variants offer translucency |
| Water Absorption | Resistant to water absorption | Resistant to water absorption |
| Surface Hardness | High | Low |
Polypropylene vs Polyethylene: Applications and Uses
Polypropylene and polyethylene are highly versatile and are used for various products. Some of their applications are the following:
- Ropes
- Buckets
- Carpets
- Grocery bags
- Packaging for food
Some products use polypropylene, and some use polyethylene. For instance, some materials that are not translucent use polypropylene, as polyethylene is used for translucent materials.
Cost Comparison of Polypropylene vs Polyethylene
The cost of polypropylene is around $0.55-$0.80 per kg, and the cost of polyethylene has a cost of $0.80 to $1.6 per kg. However, the price may vary based on the grade you choose.
Processing Methods of Polypropylene vs Polyethylene
Polypropylene is a rigid material and is processed using various methods which support its rigidity. The injection molding process is used for polypropylene, which helps manufacture complex components with good dimensional stability. Similarly, extrusion is also used to produce pipes, films, and sheets of polypropylene.
Polyethylene processing is also carried out using injection molding to create components like closures and caps, as it offers quick moldability. Also, pipe extrusion is done to manufacture plumbing and gas pipes.
Alternative Materials to Polypropylene and Polyethylene
The materials that can alternatively be used instead of polypropylene and polyethylene are as follows:
Polycarbonate
Polycarbonate is a thermoplastic polymer from the family of polyolefins, and it is used for applications that need transparency and impact resistance.
Polyvinyl Chloride (PVC)
PVC belongs to the family polyolefin, and it is flexible and rigid. It is used to manufacture frames for windows, pipes, and cables.
Polystyrene
Polystyrene is a thermoplastic known for its rigidity, and it can be made using various monomers. The process of injection molding is used to make products through polystyrene and is used in packaging, construction, and insulation.
Conclusion
The selection of the right materials plays a vital role in the performance of the component, and the same is the case with thermoplastics. Polypropylene and polyethylene are used commonly in many industries, but choosing the right form matters.
We at DEK provide you with the manufacturing of custom components using these two thermoplastics. So, don't hesitate to get in touch with us.
