Rotational moulding, called also rotomoulding, is a process of making plastic hollow parts.
In rotomoulding a steel or aluminium tool (mould), which consist of two or more parts, is put into an oven. The tool is filled with plastic granules or powder that melts and changes into liquid that sticks to the internal walls of the mould. It constantly and slowly rotates around two perpendicular axes. Those rotations are continued in the next phase of a process, i.e. a cooling phase, so deformation and sagging of a product is avoided.
Rotational moulding finds a wide range of applications in many branches of industry, e.g. agricultural, machinery, leisure, food and chemical industries.
Rotationally moulded products are recyclable, because polyethylene the most common material used in this process, can be reground and reused.
The advantages of rotomoulding process:
- relatively low production cost,
- rotomoulding tools are cheaper than tools used in other plastic-processing technologies,
- rotomoulded products are stress-free,
- possibility of making multi-layered products,
- possibility of making a few products in one production cycle,
- possibility of making very big products,
- possibility of making products in many different colours.
Applications:
- tanks: diesel and heating oil storage tanks, AdBlue storage tanks, chemical tanks
- underground tanks: waste-water treatment plants, septic tanks, pumping stations,
- underground inspection, manhole and cable chambers
- recycling containers,
- grit bins,
- food storage containers,
- garden furniture, plant pots, etc.
- toys,
- furniture,
- road barriers,
- kayaks,
- and many others.
The strength of rotationally moulded products depends on material properties that may vary. Sometimes, there may be a need to determine them individually and do not base on material datasheets. In such cases CENTINO cooperates with Poznań University of Technology that makes necessary tests. In 2011 and 2012 CENTINO made series of strength test of recycled polyethylene. The results presented in Master Thesis (download file - only Polish) were used for improving the parameters of grinding process and settings of a grinder.