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. color can be white or black mostly in granulated shape , packing mostly is PP bags . for tire and pipe usage the color demand is most of the time black from customers side .
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:
-
Plastic bottles:
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. -
Toys:
UV resistant which helps keep the toys resistant to the ray’s damaging and discoloring effects. -
Chemical containers:
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 systems:
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
PROPERTIES
Physical properties | |||
---|---|---|---|
Property | Test Method | Value | Unit |
Resin Properties | |||
Melt Flow Rate |
ASTM D 1238 @ 190 C, 2.16 kg |
0.04 |
g/10 min |
Density |
ASTM D 1505 |
0.954 |
g/cm3 |
Melting Point |
ASTM D 2117 |
131 |
C |
Vicat Softening Point |
ASTM D 1525 |
124 |
C |
Brittleness Temperature |
ASTM D 746 |
< -60 |
C |
ESCR |
ASTM D 1693 @ 50 C |
>1000 |
hrs, F50 |
(Condition: Compression Molded, 25% Igepal)
Property |
Test Method |
Value |
Unit |
Film Properties |
|||
Tensile Strength at Yield |
ASTM D 882 |
MD: -*, TD: 250* |
kg/cm2 |
Tensile Strength at Break |
ASTM D 882 |
MD: 620*, TD: 310* |
kg/cm2 |
Tensile Modulus, 2% Secant |
ASTM D 882 |
MD: 8200*, TD: 8000* |
kg/cm2 |
Elongation at Break |
ASTM D 882 |
MD : 240*, TD : 450* |
% |
Elmendorf Tear Strength |
ASTM D 1922 |
MD : 3*, TD : 80* |
g |
Dart Impact Strength |
ASTM D 1709 |
139* |
g |
(*) 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