High-density polyethylene
Properties:
– Thermophysical properties of high density polyethylene (HDPE)
– Density: 961kg/m
– Melting point: 131.8°C
– Temperature of crystallization: 121.9°C
– Latent heat of fusion: 188.6 kJ/kg
– Thermal conductivity: 0.54 W/m.°C. at °C
– Specific properties of HDPE
– Crystallinity: 61%
– High strength-to-density ratio
– Strong intermolecular forces and tensile strength
– Resistance to many solvents
– Challenging to glue, joints made by welding
– Applications of HDPE
– Drinking water and waste water pipes
– Cell liners in sanitary landfills
– Preferred by pyrotechnics trade for mortars
– Manufacturing milk bottles, jugs, and hollow goods
– Growing market in countries like China and India
Production:
– Industrial production methods
– Ziegler-Natta polymerization and Phillips slurry process
– Catalysts used in each method
– Impact of processing on HDPE properties
– Molecular weight determines properties
– Adjusting methods for ideal results
– Processing and commercial products
– Injection molding for complex shapes
– Extrusion molding for constant-profile products
– Blow molding for hollow products like bottles
– Rotational molding for large seamless parts
– Method selection based on product requirements
See also:
– Related polyethylene types
– Cross-linked polyethylene (PEX)
– Low-density polyethylene (LDPE)
– Linear low-density polyethylene (LLDPE)
– Medium-density polyethylene (MDPE)
– Ultra-high-molecular-weight polyethylene (UHMWPE)
References:
– Sources for further reading
– Pipe materials. level.org.nz
– Market Study: Polyethylene HDPE. Ceresana Research
– Thermal properties of HDPE composites. Polymer Degradation and Stability
– Thermoforming HDPE. Dermnet.org.nz
– Materials comparison: HDPE and LDPE. Makeitfrom.com
High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes and plastic lumber. HDPE is commonly recycled, and has the number "2" as its resin identification code.
In 2007, the global HDPE market reached a volume of more than 30 million tons.