The revolution in the manufacturing and production of plastics came about due to rotomoulding. It uses high temperature and low pressure, using bi-axial rotation and heat to melt and solidify plastics in any desired shape and size. This process has proved to be more economical than all other processes but is time consuming.
Phases of Production
The molding process comprises of four distinct phases. They are-
• Filling up the mold by a calculated amount of the plastic polymer, mostly in powdered state
• Heating the filled mold in the oven (or heating chamber) while it simultaneously rotates, till all the polymer has melted and dispersed to the wall. The empty mold must be rotated on at least two mutually perpendicular axes, at different velocities to prevent the plastic powder from settling down. The time period for which the mold is in the oven is also critical and needs to be monitored as overheating will degrade the quality and under heating will not melt it sufficiently. If the plastic powder doesn’t melt completely, it will adhere to the walls and cause bubbles in the final product
• Cooling the molten polymer, which is usually done by a fan. This is the time taking phase. It must be sufficiently cooled so that it can be held by the operator and detached from the mold. On cooling, it will shrink, thus facilitating in the removal of the mold. The rate of cooling down must be measured as too quick a rate will result in uneven cooling and produce a disfigured part
• Removing the plastic and giving it the final finishing
Recent Developments
Previously, the monitoring of the heating and cooling chambers was done manually based on hit and trial method, thus producing inefficient products. But with recent developments in the plastics rotational moulding process, the air in side these chambers can be monitored and controlled effectively.
Mold Releasing Agents
After the cooling comes the removal of the product from its mold. If the product has cooled down correctly, it will shrink and thus come off from the walls. But good Mold Release Agents (MRA) are used to perfectly separate the mold from the plastic. Some of the MRA’s are-
• Sacrificial coatings- silicone coatings have to be repeatedly applied so that it doesn’t entirely stick to the outer layer of the plastic or to the walls of the tool
• Semi-permanent coatings- such a coating lasts a few releases if applied properly. It needs re-painting after a few releases. It is mostly made up of a polysiloxane.
• Permanent coatings- they do not require an operator to be applied but damage easily if misused. It is usually a PTFE coating.
With these improvements, the plastic polymer industry has seen a boom in the recent years. Click here to know more about #http://www.grangerplastics.com/.
Phases of Production
The molding process comprises of four distinct phases. They are-
• Filling up the mold by a calculated amount of the plastic polymer, mostly in powdered state
• Heating the filled mold in the oven (or heating chamber) while it simultaneously rotates, till all the polymer has melted and dispersed to the wall. The empty mold must be rotated on at least two mutually perpendicular axes, at different velocities to prevent the plastic powder from settling down. The time period for which the mold is in the oven is also critical and needs to be monitored as overheating will degrade the quality and under heating will not melt it sufficiently. If the plastic powder doesn’t melt completely, it will adhere to the walls and cause bubbles in the final product
• Cooling the molten polymer, which is usually done by a fan. This is the time taking phase. It must be sufficiently cooled so that it can be held by the operator and detached from the mold. On cooling, it will shrink, thus facilitating in the removal of the mold. The rate of cooling down must be measured as too quick a rate will result in uneven cooling and produce a disfigured part
• Removing the plastic and giving it the final finishing
Recent Developments
Previously, the monitoring of the heating and cooling chambers was done manually based on hit and trial method, thus producing inefficient products. But with recent developments in the plastics rotational moulding process, the air in side these chambers can be monitored and controlled effectively.
Mold Releasing Agents
After the cooling comes the removal of the product from its mold. If the product has cooled down correctly, it will shrink and thus come off from the walls. But good Mold Release Agents (MRA) are used to perfectly separate the mold from the plastic. Some of the MRA’s are-
• Sacrificial coatings- silicone coatings have to be repeatedly applied so that it doesn’t entirely stick to the outer layer of the plastic or to the walls of the tool
• Semi-permanent coatings- such a coating lasts a few releases if applied properly. It needs re-painting after a few releases. It is mostly made up of a polysiloxane.
• Permanent coatings- they do not require an operator to be applied but damage easily if misused. It is usually a PTFE coating.
With these improvements, the plastic polymer industry has seen a boom in the recent years. Click here to know more about #http://www.grangerplastics.com/.
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