FAQS

What is a Polymer?

The word Polymer comes from the Greek "poly" meaning many, and "meros", parts or units. A polymer is a group of many units. You combine many monomers (one unit) to create a polymer. Polymer is often used as a synonym for "plastic", but many biological and inorganic molecules are also polymeric. All plastics are polymers, but not all polymers are plastics. Plastic actually refers to the way a material melts and flows. Commercial polymers are formed through chemical reactions in large vessels under heat and pressure. Other ingredients are added to control how the polymer is formed and to produce the proper molecular length and desired properties. This chemical process is called "polymerisation". A homopolymer results from polymerising only one kind of monomer. A copolymer results from using different monomers. Homopolymers have the same repeating unit while copolymers (which can be random, block, or graft) can vary have different numbers of repeating units. A terpolymer results from using three different monomers.

What plastics or other materials can be Rotomoulded?

The most commonly moulded plastic is linear polyethylene. This is available in Linear Low Density (LLDPE), Linear Medium Density (LMDPE) and High Density (HDPE) forms.


Crosslinked Polyethylene (XLPE) is used where exceptional low temperature impact strength is required in moulded parts.


Ultra Low Density Polyethylene (ULDPE) can be used for parts requiring extreme flexibility and low temperature performance.


Other materials include Polypropylene (PP), Nylon (PA) and Fluoropolymers – Poly Vinyl Difluoride (PVDF), Ethylene Chlorotrifluoroethylene ECTFE. These are more expensive materials than polyethylene.


Fluoropolymers are typically 30-60 times the price of polyethylene and are used only where extremely high chemical and mechanical performance is required.

What polymers do GreenAge Industries do compounding for?

GreenAge Industries providesRotomoulding Compounds/Powders for LLDPE,MDPE& Closs Linkable PE. We can also create a custom batch for your custom requirement. Feel free to contact us with your requirement.

What is The Mesh Size of the Powder for Rotomoulding Process?

The Powder size depends on the Product you want to manufacture. Generally a Powder of 500-800 Microns are used for Genral Purpose Products such as Water Tanks. GreenAge Industries provide Powders of different MFI & Density Range. Please Visit our Products Page for further details.

What colours can rotomoulded products be made in?

GreenAge Industries provides a standard colour range but any colour can be formulated if a specific colour match is required.Special effects are also possible including stone effect and metallic effect.With customised mould textures, and post mould finishing, wood effects and rock effects can be reproduced.


Color can be incorporated by dry blending a customized pigment formulation with ground natural material, or by hot melt compounding prior to grinding. With both methods, a wide range of colors is available. Our design team will evaluate specific requests. Important considerations are: base resin, pigment type restrictions (if any), environment, cost, opacity required, and part surface finish.

How does a rotomolded part compare to a blow molded part?

Although both processes make hollow parts, rotational molding offers design flexibility and molded part characteristics that are difficult to match in blow molding.

  • Complex shapes with deep draws can be rotomolded with consistent wall thickness with relative ease. Rotomolded parts actually have their thickest wall sections in outside corners where durability is often critical.
  • Rotomolding tooling can be made to provide undercut and cored features that even if possible would be very costly to tool and process in blow molding.
  • In-mold decorating and mold-in inserts are also easily accomplished with rotational molding. Rotational molding allows the designer more freedom to design to part function rather than to the constraints of the process or tooling.
How can I find out if a product can be contained in a rotomolded part?

Specific chemical resistance information is available upon request. It is important to provide additional information such as temperature, concentrations, density, and how the product is to be used.

What kind of tooling is required?

Thin wall, hollow molds of two or more sections are most common. These molds are typically cast or machined aluminum, or fabricated from steel or aluminum. Individual mold sections are fitted with frames and a clamping system. The mold is provided with a method to mount it to a rotomolding machine.

What kind of tolerances can rotomolding hold?

Typically, production part wall thickness can vary from nominal by +/- 20%, and linear dimensions by a basic +/- .030" plus .005" per linear inch of the dimension in question. Additionally, a tooling tolerance of +/- .030" plus .0025" per linear inch of dimension must be considered when molds are being built.

What radiuses can be used on rotomoulded products?

The use of correct radiuses on the corners of rotomoulded parts is critical.Sharp corners with tight radiuses are stress concentration points in moulded products and commonly are impact fracture propagation points.The correct radius to adopt will depend on the part to be moulded. Large parts may require greater radiuses. Preferably a minimum of 5mm should be used. This is particularly important on any concave internal corners in the product.

My parts are all metal now. Why should I consider rotomolded plastic parts?

Benefits include weight reduction, corrosion resistance, and reduced cost. Rotational molding provides the designer the freedom to address form along with function. Parts can be designed to be more ergonomic, and esthetically pleasing without affecting performance. In many cases rotomolded parts reduce the number of components in an assembly.

Can I have flat surfaces on my products?

It is very hard to produce large flat areas in rotationally moulded parts.Distortion during part shrinkage and cooling is common and difficult to prevent.Some jigging of parts and control of cooling will reduce distortion, but it is recommended that flat areas are not designed into parts.Straight sides can be achieved by using ribs, but it is always best to consult your rotomoulder on how to establish the best shape for your product.

What Are the Density Range & General Purpose MFI Range of Different Polymers?
Polymer Density Range g/cm³
EPS – Expanded PolyStyrene 0.02 – 0.06
PP –Polypropylene 0.89 - 0.91
LDPE – Linear Density PolyEthylene 0.91 – 0.93
HDPE – High Density PolyEthylene 0.94 – 0.96
PS – PolyStyrene 1.04 – 1.11
PVC – Poly Vinyl Chloride 1.20 – 1.55
PET – PolyEthylene Terephthalate 1.34 – 1.40
Application MFI g/ 10 min
Injection Moulding 5 – 30
Rotational Moulding 4 – 9
Film Extrusion 0.5 – 6
Profile Extrusion 0.1 – 1
Pipe Extrusion 0.1 – 2
Blow Extrusion 0.1 – 2
Vaccume Forming 0.2 – 0.5
Coating 2 – 10