High Density Polyethylene Rod Engineering Plastic Rod
Scientific Characteristics and Advantages Analysis
Molecular Structure and Basic Properties
HDPE's molecular chain is formed by the polymerization reaction of ethylene monomer (CH₂=CH₂). Its structural characteristics determine the core properties of HDPE rod:
• High Crystallinity and Linear Structure: The molecular chains are densely packed and regular (crystallinity of 60%-80%, significantly higher than the 40%-60% of low-density polyethylene (LDPE)). The density is 0.94-0.97 g/cm³ (lower than ordinary plastics), giving the material lightness (weighing only 1/7-1/8 of steel of the same volume) and high rigidity.
• Non-polar Molecular Chain: The molecular chain contains no polar groups (such as hydroxyl or carboxyl groups), resulting in low surface energy (approximately 31 mN/m), a coefficient of friction of only 0.2-0.3 (compared to 0.3-0.4 for ordinary plastics such as PA6), and excellent self-lubrication.
Excellent Mechanical Properties
• High Toughness: Charpy notched impact strength ≥ 20 kJ/m² (ISO 179 standard, ≥ 15 kJ/m² maintained at -40°C), 2-3 times that of standard PP (8-15 kJ/m²), capable of withstanding everyday collisions and minor impacts (such as accidental drops of equipment components).
• High Tensile Strength: Tensile strength ≥ 20 MPa (ISO 527 standard), superior to LDPE (8-15 MPa), meeting most structural support or load-bearing requirements (such as auxiliary components for mechanical guide rails).
• Creep Resistance: Creep strain ≤ 5% (1000 hours) at 80°C and 1 MPa stress, superior to PP (≤ 8%), making it suitable for long-term load scenarios (such as chemical pipeline support racks).
Excellent Physical and Chemical Properties
• Chemical Resistance: Stable against most acids (e.g., sulfuric acid and hydrochloric acid), alkalis (e.g., sodium hydroxide solution, concentration ≤ 50%), and saline solutions (tolerance to pH 1-14), making it an ideal material for chemical equipment exposed to corrosive media (e.g., acid storage tank linings and reactor supports).
• Temperature Resistance: Continuous operating temperature range of -60°C to +80°C (short-term temperature resistance up to 100°C), with a brittleness temperature as low as -100°C (common plastics such as PP have a brittleness temperature of -20°C to -50°C), making it suitable for use in extremely cold environments (e.g., seals for Arctic research equipment) or high-temperature sterilization applications (e.g., brief high-temperature treatment of food processing equipment).
• Electrical Insulation: Volume resistivity ≥ 10¹⁵ Ω·cm (ISO 3915 standard), dielectric constant 2.3 (at 1kHz), making it suitable for electrical insulation components (e.g., switch panels and cable sheathing).
Precision Processing and Dimensional Stability
• Processing Precision: Extrusion process diameter tolerance is ± 0.1 mm (common plastic rod ± 0.2 mm). Custom diameters range from 3 to 200 mm (to meet different industrial needs). Lengths can be cut to meet specific requirements (e.g., 1m, 2m, or custom lengths).
• Dimensional Stability: Water absorption is only 0.15% to 0.25% (common PP is 0.1% to 0.3%, but HDPE's dimensional changes after water absorption are more manageable). The linear thermal expansion coefficient is 8 × 10⁻⁵/°C (common PP is 1.2 × 10⁻⁴/°C), and is minimally affected by temperature fluctuations (tolerance control ± 0.02 mm). This makes it suitable for applications requiring high dimensional accuracy (e.g., precision instrument guide rails).
Special Functionalities
• Self-lubrication: A low coefficient of friction (0.2-0.3) enables smooth sliding even without lubrication (e.g., conveyor guide rails, bearing bushings), reducing wear (service life 3-5 times longer than metal guide rails);
• Wear Resistance: Wear loss ≤ 0.1 cm³/(1.61 km) (ASTM D1044 standard), superior to ordinary PP (wear loss ≥ 0.5 cm³/(1.61 km)), making it suitable for high-friction applications (e.g., mining machinery components, logistics conveyor line rollers).