High-density polyethylene (HDPE)
Is a thermoplastic polymer produced of monomer ethylene. It is sometimes called polythene when used for HDPE pipes. With a high strength-to-density ratio, it is used in producing plastic bottles, corrosion-resistant piping, geo membranes and plastic lumber. It is commonly recycled.
It is known for its high density ratio. The density of this product can range from 930 to 970 kg/m3. Although the density of it is only marginally higher than that of low-density polyethylene, it has little branching, giving it stronger intermolecular forces and tensile strength than LDPE. The difference in strength effects the difference in density, so it has a higher specific strength. It is also harder and more opaque and can withstand somewhat higher temperatures (120 °C/248 °F for short periods).
HDPE is resistant to many different solvents so it cannot be glued.
The physical properties of this product depends on the molding process that is used to manufacture a specific sample; to some degree a determining factor are the international standardized testing methods employed to identify these properties for a specific process. For example, in rotational molding, to identify the environmental stress crack resistance of a sample, the notched constant tensile load test (NCTL) is put to use
Owing to these desirable properties, pipes constructed out of HDPE are ideally applicable for drinking water, and waste water (storm and sewage).
USES OF HDPE:
it is great for blow-molding applications, particularly food and beverage containers because it won’t leach into the bottles’ contents. In addition, it is recyclable which makes it a great choice for these highly disposable products.
UV resistant which helps keep the toys resistant to the ray’s damaging and discoloring effects.
With its chemical resistant properties, is great for laundry, shampoo, conditioner, household cleaning products, motor oil, antifreeze and recycling bins. The strength of these bottles is increased when they’ve been colored or pigmented.
pipe grade sheet has a higher molecular weight compared to the standard used in the above examples. This strengthening with its UV-resistance makes it ideal for piping and outdoor applications. Pipe grade sheet has the ability to withstand -220 to 180 degrees Fahrenheit. It’s durable in most chemical interactions which make it useful in a lot of industrial applications.
High Density Polyethylene Molecular Structure
Melt Flow Rate
ASTM D 1238 @ 190 C, 2.16 kg
ASTM D 1505
ASTM D 2117
Vicat Softening Point
ASTM D 1525
ASTM D 746
ASTM D 1693 @ 50 C
(Condition: Compression Molded, 25% Igepal)
Tensile Strength at Yield
ASTM D 882
MD: -*, TD: 250*
Tensile Strength at Break
ASTM D 882
MD: 620*, TD: 310*
Tensile Modulus, 2% Secant
ASTM D 882
MD: 8200*, TD: 8000*
Elongation at Break
ASTM D 882
MD : 240*, TD : 450*
Elmendorf Tear Strength
ASTM D 1922
MD : 3*, TD : 80*
Dart Impact Strength
ASTM D 1709
(*) Properties obtained from film produced on a pilot line
, 12 micron, BUR 5:1, MD = Machine Direction, TD = Transverse Direction
Note: Conversion factor for changing unit from kg/cm2 to MPa is divided by 10.2