The science behind rotomolding

Humanity is always trying to find ways to improve itself and become better. We have seen this in the many inventions that we have been able to achieve over the years. Each technology that we manage to introduce is meant to make our lives better and easier. The manufacturing process of various products using various materials has been improving over the years for a very long time now. For instance, the manufacturing of plastic products saw the introduction of a special manufacturing process called rotomolding. This process finds use in the manufacture of a wide range of plastic products, especially storage tanks.

Tanks that are used to store various materials such as chemicals and water need to be designed to be strong enough to handle the pressure and that is where rotomolding comes in. this process is used to manufacture tanks of different wall thicknesses. How thick the walls of a tank are usually depends on factors such as what chemical is being stored, application of the tank, and the temperature at which the tank will be used.

The chemical process of rotomolding
During the process of rotomolding, the mold to be used to make the plastic product is mounted in the oven before it is heated using burners that burn natural gas. The mold is rotated at the rate of between 4 and 12 rotations per minute. The plastic is melted and it builds a series of thin layers around the mold. The plastic takes the shape of the mold and more thin layers are added. After the process has completed, the mold together with the plastic are removed from the oven and allowed to cool. The mold is then unbolted to reveal the completed tank.

This whole process takes an amount of time that depends on the size of the tank and the thickness of its walls.
Typically, it takes between 20 minutes and 6 hours.

Technology improves the science of rotational molding
Due to improvements in technology over the years, the molds that are used today are usually equipped with telemetry systems that help with the monitoring of temperatures during the molding cycle. These systems help to tell the people in charge of the manufacturing process the exact temperature at which the plastic is melting. Thus, it is possible to know the exact moment at which antioxidant system should be introduced and the temperature at which the molding cycle cross-links. It is also possible to know when to stop rotating and heating the tank during the production process.

Better technology prevents unzipping
When high-density linear polyethylene chemical storage tanks start cracking, the process cannot be stopped. A small crack can lead to catastrophic failure eventually and there is no stopping it. The tank simply ‘unzips’ itself in a process called notch sensitivity. Notch sensitivity cannot be avoided. The only way to eliminate them is to use cross-linked polyethylene because this material prevents unzipping by using molecular ‘bridges’.

XLPE tanks have been subjected to a lot of drop tests and they have always passed the test with flying colors. That is why most manufacturers today are shifting to XLPE and abandoning linear polyethylene. That means that the next time you go shopping for a chemical storage tank, you should settle for one that is made from XLPE.

Click on this link https://www.grangerplastics.com/rotational-moulding/ to get more information about rotomolding.