1. Base Polymer (Primary Raw Material)
Medium-Density Polyethylene (MDPE) resin
Typically derived from ethylene via polymerization (often using Ziegler-Natta or metallocene catalysts).
Density range: 0.926–0.940 g/cm³
Common material classifications:
PE80 (older generation, still widely used)
PE100 (higher strength, sometimes overlaps into HDPE range but can be formulated toward MDPE behavior)
2. Carbon Black (for Black Pipes)
Added at ~2–2.5%
Functions:
UV resistance (prevents polymer degradation outdoors)
Improves long-term durability
Particle size and dispersion are critical for performance
3. Antioxidants
Prevent thermal oxidation during:
Extrusion processing
Long-term service life
Typically includes:
Primary antioxidants (hindered phenols)
Secondary antioxidants (phosphites)
4. UV Stabilizers (for Non-Black Pipes)
Used when pipes are colored (e.g., yellow for gas, blue for water)
Alternatives or supplements to carbon black:
HALS (Hindered Amine Light Stabilizers)
5. Pigments / Masterbatches
For identification and coding:
Yellow → gas pipes
Blue stripes → potable water
Must be compatible with PE and not compromise mechanical properties
6. Processing Aids (Optional)
Improve extrusion stability and surface finish
Examples:
Lubricants
Anti-block agents
Key Material Characteristics Achieved
The combination of these raw materials gives MDPE pipes:
Excellent flexibility (better than HDPE)
High impact resistance, especially at low temperatures
Good slow crack growth resistance (SCG)
Reliable chemical resistance
Practical Note (Engineering Perspective)
Compared with HDPE:
MDPE has lower stiffness but higher ductility, making it preferable for:
Gas distribution networks
Installations requiring bending or ground movement tolerance
