What is High-density Polyethylene (HDPE)?
High-density polyethylene (HDPE) is often regarded as a “cheap and cheerful” thermoplastic polymer for plastic injection moulding. It is a resin found typically in pellet form and designed to provide excellent processability for moulders. It can withstand high impact, possess high-stress crack resistance, and have extreme durability.
Injection moulded HDPE material properties
| Test | Typical Value/Unit |
|---|
| Flexural Modulus (0.05 – 0.25 %) | ISO 178 | 900 MPa |
| Tensile Strength at Yield | ISO 527-2/1A/50 | 23 MPa |
| Elongation at Break | ISO 527-2/1A/50 | > 100 % |
| Elongation at Yield | ISO 527-2/1A/50 | 10 % |
| IZOD Impact | ISO 180-1A | 4 KJ/m2 |
| Temperature of Deflection Under Load1 | ISO 75-Be | 71 °C |
| Environmental Stress Crack Resistance2 | ASTM D 1693 | 3 hrs |
Advantages of HDPE injection moulding
- Excellent Impact Resistance: HDPE has exceptional toughness and impact resistances flowing it to withstand heavy loads and impacts without deformation or breakage.
- Chemical Resistance: HDPE is highly resistant to a wide range of chemical, including acids, bases and solvents. This makes it suitable for applications in the chemical, agricultural and industrial sectors.
- Moisture Resistance: HDPE has low water absorption properties, meaning it is highly resistant to moisture and does not swell or degrade in wet environments.
- Lightweight: High-density polyethylene is particularly beneficial for applications where weight reduction is desired without compromising strength and durability.
- Good UV Resistance: HDPE can withstand prolonged exposure to sunlight without significant degradation, making it ideal for outdoor applications.
Disadvantages of HDPE injection moulding
While high-density polyethylene has many advantages, its not without its disadvantages. It’s important to evaluate these limitations against the specific requirement of the application of your part before selecting HDPE as a material choice.
- Limited Temperature Resistance: HDPE has lower heat resistance compared to some other engineering plastics, which limits its suitability for applications exposed to high temperatures.
- Lower Strength and Stiffness: HDPE has lower strength and stiffness compared to engineering plastics like ABS or nylon.
- Susceptibility to Environmental Stress Cracking: Exposure to substances like detergents, oils and certain solvents can lead to micro cracks or premature failure in moulded HDPE parts.
- Poor Bonding Qualities: Similar to polypropylene (PP), HDPE has low surface energy. This makes it difficult to bond, glue and paint compared to other plastics.
- Limited Design Flexibility: HDPE’s flow characteristics and shrinkage behaviour may restrict the design possibilities for complex or intricate parts. It may be challenging to achieve intricate details or thin walls without encountering moulding defects like sink marks or warpage.
What is HDPE material used for?
High-density polyethylene is a versatile material with a wide range of applications across the automotive, electronics and many other industries. Some typical applications of HDPE include:
- Agricultural products
- Medical devices
- Recycling bins
- Cleaning containers
Get injection moulding parts in HDPE material
At HLH Rapid, we offer an extensive selection of resins to cater to your specific custom injection moulding needs, including High-Density Polypethylene. To obtain a quote, simply upload your CAD file HERE and provide us with the details of your project including quantity, material and any surface finish requirements. Our dedicated team will then get back to you with a quote within a day.
