Rotational molding refers to the method of producing hollow plastic products in many numbers that is in use and the fact is that it is also the fastest growing industry. The methods of processing with rotational molding such as heating, shaping, melting and cooling phases take place after the polymer is positioned in the mold and so it experiences no external pressure.
Generally, the moulds are made using cast aluminum, steel or CNC machined aluminum and this can be cheap relatively in comparison to molds used as blow molding or injection. The rotational process of plastic molding is extremely versatile, though relatively simple. The powder particles are fused together as the basic principle such that they are created as a finished product. Finally, after the mold is cooled, the finished plastic product is extracted. The rotomolding process basic cycle time varies from 20m to 1 hour, based on the complexity and size of the product.
Various plastic polymers are used and this is useful in rotational molding based on the product desired end. However, polyethylene is the commonly used plastic and this is because it can withstand the temperatures for extended periods, thereby it becomes inexpensive. Moreover, the low density polyethylene is flexible that it is resistant to fracturing.
Molders also use commonly the ethylene-butyl acrylate. The advantage on using this material is that it is crack resistant and really strong at low temperatures. Of course, it has the benefit as with thermoplastics that it can be recycled easily.
The plastics used typically in rotational molding include Polyurethane, polypropylene, nylon, elastomers, polyvinyl chloride, plastisols, ethylene vinyl acetate and polycarbonate.
Polypropylene is the widely used plastic and yet it is not the choice of molders and this is because of the fact that this material is brittle at room temperature and so very little time is required to mould a product using this material.
Many products used for daily use are products made with rotational molding, basically owing to its bespoke creations. Some of the products include:
- Traffic cones
- manhole chambers of inspection
- diesel fuel tanks and rainwater tanks
- canoes, dinghies and kayaks
- steering wheels
- garden planters, pallets and water butts
- oil recovery bank and domestic oil storage tank
Rotational molding is an effective method of molding allowing manufacturers to produce durable products featuring minimum design constraints, besides large products are manufactured easily with less wastage of material.