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Materials Suitable for Rotational Molding

Rotational molding utilizes various plastic materials such as Polyethylene (Linear Low Density Polyethylene LLDPE, Medium Density Polyethylene MDPE, High Density Polyethylene HDPE), Polypropylene PP, Nylon, PVC, Vinyl, Polycarbonate...

Two requirements for material properties: The material must be capable of flowing through the mold cavity as the mold rotates. The materials must also be thermally stable.  During molding process, open flame is burning at the mold surface, so the temperature inside the mold can get quite high.   

 

Polyethylene (used in 80% of the times)
Polyethylene is categorized by its density as indicated in the abbreviations LLDPE, HDPE, MDPE, LDPE, XLPE, etc.

-HDPE (High Density Polyethylene)
Stiffest, excellent chemical resistance, easy processing ability. Processed in Rotational Molding in powder form. Applications include Wall Barriers, Chemical Tanks, Logistic Pallets, Airline Containers, Cargo Containers ..  HDPE generally has a density range in the.941~0.960 g/cm³.

-LDPE (Low Density Polyethylene) LDPE is commonly recycled. LDPE has a lower tensile strength and lower density than HDPE. LDPE generally has a density range in the .910-.940 g/cm³.

-LLDPE (Linear Low Density Polyethylene) exhibits Medium stiffness, extremely durable and tough, easy to process, has excellent chemical and environmental stress crack resistance properties. Processed in Rotational Molding in powder form. Commonly processed with UV stabilization additives, Anti-Microbial additives, FDA approved grades and more. LLDPE applications include Chemical Tanks, Industrial Tanks, Shipping Containers, Toys, Tornado Shelters, Secondary Containment, Furniture!

-XLPE (Cross-Linked Polyethylene) contains a cross-linking agent which reacts with the material during the molding cycle, forming a cross-linked molecule similar to a thermoset. This reaction drastically improves the toughness of this material. Applications range from Seating, Fuel Cells, Chemical Tanks, Piping, Waste Management products… Due to the cross linking process, the cross linked materials are not recycleable.

 

EVA Co-polymer
This polymer approaches elastomeric materials in softness and flexibility. It exhibits good barrier properties, stress crack resistance, low temperature durability, hot melt adhesive and water proof properties.

 

Polyvinylchloride
PVC compounds are moderate in costs and are easily processed with the proper equipment. Applications include planters, dolls, toys, Dog Toys  and more.

 

Nylon ( Nylon 6 and Nylon 12) More expensive than other plastics
Nylon 6 exhibits excellent tensile strength, stiffness and impact strength. Very high heat resistance so properties are maintained at elevated temperatures. It excels in chemical resistance.

 

Polycarbonate
Highest impact resistance of all rigid plastics. Polycarbonate has very high heat resistance.

 

Polypropylene
PP is stiffer than PE, and also has a higher heat distortion temperature, excellent chemical and environmental stress crack resistance and very resistant to abrasions. However, Polypropylene is extremely brittle and has very low impact properties currently.  It is expensive in comparison to PE.

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