Process We use Linear Low Density polyethylene (LLDPE) raw material with density 0.932 to 0.936 mm per cubic cm and MFI range from 3 to 6 per 10 minutes. Raw material that we use has good mechanical strength, high environmental strength , crack resistance, material stability over a wide range of temperate and cycle time. The resin will have a fast and broad cure cycle, provide shrinkage from part to part and exhibit good wrap resistance.
Additives: The LLDPE granules in its original form cannot be process for tank manufacturing in rotational molding. It has to be converted in to color granules. This coloring is takes place with addition of color concentrate during extrusion process. Base raw material is LD. Loading of Colorant If black the percentage of carbon (at least 50%). If Milky white then percentage of titanium. 'Carbon' in black master batch act UV stabilizer therefore it will be added to the level of 2 to 3 % of LLDPE. Other wise tank life during expose to sunlight will be less and tank may develop crack.
Advantages of Rotational Molding:
One part construction: Virtually stress free parts totally closed or opening.
Uniform wall thickness,
Metal inserts as integral parts.
Product from this process can offer excellent load bearing properties and resistance to stress cracking and corrosion.