Materials for rotational moulding

Materials for Rotational moulding:
1. PVC plastisols: Originally thick, viscous liquid PVC plastisols were used with the process and the process was known as slush moulding. These vinyl dispersions mainly made toys, beach balls, artificial flowers and similar objects. In this process the liquid was placed in a closed mould which was then rotated and heated until the plastisol was fused.
2. Today almost any thermoplastic can be used for rotoforming due to the advent of powdered PE and a wide variety of products can be manufactured by this process. Now parts are also manufactured from cellulosics, nylon, polycarbonates, acetal, styrenes etc. However LDPE and HDPE is the most widely used material. Nowadays crosslinked PE with improved strength, environmental resistances and toughness is employed.
3. The use of thermosets in rotoforming is still in early stage. A resin grade which will not become brittle or a technique which can add fibrous reinforcements uniformly should be developed in order to popularize the rotoforming process as the heating stage may be entirely eliminated or the parts may be removed from the mould and be post cured thus making the moulds free for the next cycle during the curing stage of the present cycle.
4. In composite moulding, two resins are used to form one part. One resin melts and forms the outer skin of the part. The second resin then melts, fuses to the 1st and forms the inner skin. A variation of this process is the production of foamed parts in which two or three resins are used. The first resin will melt and form the outer skin. Then the foaming resin will melt and foamed. The third resin then melts and fuses to the foam to form the inner skin. This process is used in the production of small boats, and similar parts.