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Polyethylene is used more than any other thermoplastic polymer. There
is a wide variety of grades and formulations available that have an
equally wide range of properties. In general, the outstanding
characteristics of polyethylene are:
Toughness, Ease of processing, Chemical resistance, Abrasion
resistance, Electrical properties, Impact resistance, Low coefficient of
friction, Near-zero moisture absorption.
The three most commonly used grades of polyethylene are: Low Density,
High Density and Ultra high molecular weight.
Low Density Polyethylene (LDPE)
LDPE, was the first of the polyethylene’s to be developed. It is a
corrosion resistant, low density extruded material that provides low
moisture permeability. LDPE has a fairly low working temperature, soft
surface and low tensile strength. It is an excellent material where
corrosion resistance is an important factor, but stiffness, high
temperature and structural strength are not important considerations.
Features:
Lightweight, Formable, Impact Resistant, Excellent Electrical Properties,
Machinable, Weldable.
Fabrication:
LDPE can be fabricated using the following techniques. Hot gas welded,
Fusion and butt welded, Ultra-sonic sealed, Die cut, Vacuum formed
Thermo-formed, Machined with wood or metal working tools.
Applications:
Chemical resistant tanks and containers, Food storage containers,
Laboratory equipment, Disposable Thermo-formed products, Corrosion
resistant work surfaces, Vacuum formed end caps and tops, Moisture
barriers.
High Density Polyethylene (HPDE)
HPDE is more rigid and harder than lower density materials. It also has
a higher tensile strength, four times that of low density polyethylene,
and it is three times better in compressive strength. HDPE meets FDA
requirements for direct food contact applications. It also is accepted by
USDA, NSF and the Canadian Department of Agriculture.
Features:
Abrasion Resistant, the extremely high molecular weight of HDPE combined
with its very low coefficient of friction provides and excellent abrasion
resistant product preventing gouging, scuffing and scraping.
Exceptional Impact Strength:
HDPE is one of the highest impact resistant thermoplastics available and
maintains excellent machine ability and self- lubricating characteristics.
Properties are maintained even at extremely low temperatures.
Chemical Resistant:
HDPE has very good chemical resistance of corrosives as well as stress
cracking resistance (with the exception of strong oxidising acids at
elevated temperatures). Certain hydrocarbons cause only a light surface
swelling at moderate temperature.
Water Resistant:
Moisture and water (including saltwater) have no affect on HDPE. It can be
used in fresh and salt water immersion applications.
Fabrication:
HDPE can be fabricated using the following techniques: Hot gas welded,
Fusion and butt welded, Ultra-sonic sealed, Die cut, Machined with wood or
metal working tools, Vacuum formed, Thermo-formed
Applications:
Food cutting boards, Corrosion resistant wall coverings, Pipe flanges,
Lavatory partitions, Chemical Plants, Radiation shielding, Self supporting
containers, Industrial tanks and sinks, Boat trailer skids.
Index to types of
Polyethylene's listed below
HDPE 300 Black, Natural
HMWPE 500 Natural
UHMWPE 7000 Natural
Ultra UHMWPE Green
UHMWPE, Static Reduced 7000SR Black
Typical properties of various
Polyethylene's
| Plastic
Type: Polyethylene |
UHMWPE |
UHMWPE Ultra |
UHMWPE Static
Reduced |
HMWPE |
HDPE |
| Code |
7000 |
Ultra |
7000SR |
500 |
300 |
Specific Gravity
g/cm3 |
0.93
|
0.93
|
0.95
|
0.952
|
0.945
|
Min/Max Service
Temp in Air °C |
-260
+90
|
-260
+90
|
-200
+90
|
-100
+80
|
-50
+80
|
Tensile Strength Yield
MPa |
>20
|
>20
|
>20
|
28
|
23
|
Tensile Strength Break
MPa |
>40
|
>30
|
>30
|
36
|
32
|
Impact Resistance
DIN 5305 Notched Impact Strength MJ/mm2 |
>100 |
No
Break |
- |
>20 |
- |
Hardness
Shore D |
61
|
63
|
63
|
64
|
63
|
Coefficient of Thermal
Expansion
mm/(mmxK)X10- 6 |
200
|
200
|
200
|
200
|
200
|
Dielectric Strength
KV/mm |
45
|
45
|
-
|
150
|
75
|
Surface Resistivity
Ohms |
>1X1014
|
-
|
>1X108
|
>1X1015
|
>1X1015
|
Relative Abrasion
Loss by Sand Slurry compared to UHMWPE 7000=90 |
90
|
80
|
90
|
290
|
335
|
These values are representative of those obtained under standard ASTM
conditions and should not be used to design parts which function under
different conditions.
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Download High Density Polyethylene MSDS

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