What is the Difference Between HDPE and LDPE?

HDPE (High-Density Polyethylene) and LDPE (Low-Density Polyethylene) are both popular resins used in injection molding and are cost-effective materials. They have some similarities, but they also have distinct differences that make them suitable for different applications. Here are the main differences between HDPE and LDPE:

Density: HDPE has a higher density than LDPE, which makes it more rigid and opaque. LDPE is a more transparent, branched version of PE.
Structure: HDPE has a linear structure, while LDPE has a branched structure. This difference in structure affects the material's properties, such as strength and flexibility.
Strength and Flexibility: HDPE has higher tensile and shear strength, as well as higher abrasion and tear resistance than LDPE. LDPE, on the other hand, is more flexible and has a higher fatigue life and impact strength.
Processing: Both materials can be processed through injection molding and additive manufacturing techniques, but they are best suited for different techniques. LDPE is best suited for injection molding, while HDPE is best suited for CNC machining.
Applications: Due to its flexibility, LDPE is commonly used in plastic bags. HDPE, with its higher strength and rigidity, is often used in pipes and other applications that require greater durability.
Shrinkage: LDPE has a lower shrinkage value (0.02 - 0.05mm/mm or 2% - 5%) compared to HDPE.

In summary, HDPE and LDPE are both polyethylene materials with differing properties, making them suitable for different applications. HDPE is more rigid, opaque, and stronger, making it ideal for applications like pipes and containers. LDPE is more flexible, transparent, and has a higher fatigue life, making it suitable for applications like plastic bags and cable conduits.