HDPE for Conveyor Rollers

History of HDPE
At the last hours of the nineteenth century, a German chemist named Hans von Pechman detected a precipitate while working with methane and ether. Thirty years after the discovery, an American chemist named Carl Shipp Marvel succeeded in creating high density residue by applying high pressure on ethylene. British chemists Eric Fawcett and Reginald Gibson produced a solid form of Polyethylene in 1935 and it was used for Radar cable insulation during World War II.

The actual breakthrough came in 1953 by Karl Ziegler and Erhard Holzcamp when they invented High Density Polyethylene (HDPE). The process was enhanced by using a catalyst and low pressure. For his remarkable invention, Karl Ziegler was awarded the Nobel Prize in Chemistry in 1963.

Source of HDPE
High density polyethylene is a petroleum product. About 1.75 kg of petroleum is spent to produce 1.0kg of HDPE. As a common practice, HDPE is recycled. World market volume of HDPE is around 30 million tons a year. It’s harder and stronger than other PE versions. It’s slightly heavier and less ductile than LDPE.

Chemistry
HDPE is a linear polymer having no branches. Due to the compact structure of the molecule, its density is higher and possesses higher chemical resistance than other PE products. It’s opaque and tolerates high temperatures (120 degrees C) for a short while and 110 degrees C for continuous operation.

Physical Properties
HDPE offers wonderful physical properties which widens the possibility of its versatile uses. Properties may be shown as below:

• Very good resistance against Acids, Alcohols, and Bases (no attack)
• Good resistance against Aldehydes, Esters, Aliphatic and Aromatic Hydrocarbons, Ketones and Mineral and Vegetable oils (minor attack)
• Low resistance against Halogenated Hydrocarbons and Oxidizing Agents (moderate attack)
• Temperature Tolerance: Max. 120 deg C, Min – 100 deg C
• Melting Point: 130 deg C
• Tensile Strength: 4550 psi
• Hardness: SD 65
• Specific Gravity: 0.95
• Autoclavable: No
• Ultraviolet Resistance: Poor

Uses of HDPE
The unique chemical and Physical properties of HDPE suggest versatile uses of the material. Some of its present uses are listed below:

• Bottles for various purposes including food and chemicals
• Gasoline tanks
• Pipes and pipe fittings
• Plastic bags
• Children’s toys
• Geomembrane for hydraulic application

Its light weight, hardness, temperature tolerance and acid tolerance suggest some other uses of HDPE, such as conveyor rollers. A belt conveyor or a roller conveyor requires a large number of rollers. Some of them are Drive Rollers while a large number of them are called Iidlers. The drive roller is coupled with the driving motor and it applies the power for the conveyor to run and the idlers move by the frictional force applied on them through the moving belt.

Why HDPE for Rollers
Conveyor Rollers are necessary to be hard, rugged, temperature tolerant and moisture proof. HDPE has all these properties and is thus favorable for such uses. Mostly conveyors work under the temperature limit of HDPE. It’s lighter than conventional roller material, so a HDPE roller requires less energy to rotate than others. Its hardness is suitable for the purpose. So HDPE rollers are possible to use in place of metal rollers. The advantages of HDPE over metals as a roller material are such:

• Saves energy because it’s lighter
• It’s cheaper
• It’s less vulnerable to corrosion
• It’s easy to handle

Having so many advantages over metal, HDPE is now being welcomed as an alternative for the manufacture of conveyor rollers and is being used worldwide. The process industries that use HDPE rollers are:

• Pulp and Paper
• Fertilizer
• Mining
• Sand processing
• Food and Pharmaceuticals
• and many more