Plastic Material Selection

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Material Selection

When designing a product, the material in which it is to be produced is just as critical as its physical form.  At LVS Small Plastic Parts, we work in combination with our preferred material suppliers to make sure that the correct material for a particular application is chosen.  This must be a priority, as flow characteristics and shrinkage rates will have a major impact on tooling design.

When selecting a material, consideration should include –

  • What is the application and what physical attributes will be an advantage. For example, does the component need to be lightweight, be rigid or flexible, or withstand high pressure or temperature variations.
  • How long will the component need to last and what environmental factors might it be subjected to?
  • Is the part to be purely structural, or is physical appearance a consideration? As well as colour, surface textures such as a grained effect can be introduced, or post moulding finishes such as painting, plating or printing can be applied.
  • Are there any regulatory requirements associated with the products application. For example, is traceability critical, does it need to be food safe or suitable for young children to handle?

There are two main groups of polymers (plastics), Thermoplastics and Thermosets.

Thermoplastics

Thermoplastics are more widely used within the moulding sector than thermosets, being used to produce everything from washing up bowls to automotive components.  They are characterised by the way in which they are processed, i.e. they are heated until molten and then cooled in a mould so that they solidify into the required shape.

There are many grades of thermoplastic materials, each grade offering differing properties to a finished component.  They can be roughly grouped into commodity and engineering grades.

Common commodity grades are Polypropylene (PP), un-expanded Polystyrene (PS) and Polyethylene (PE, also known as polythene).  These grades are ideal for mass produced price sensitive products, (lower cost per kilo) are easily processed and can be readily recycled.

Engineering grades usually offer a particular characteristic, and as their name suggests, are often used where a component needs certain properties.  For example, nylon grades are resistant to shock and can be readily machined or reinforced with fillers such as glass filaments.  Polycarbonate is ideal for clear lens production, while Acetal is often used for its high structural rigidity.

There are also now some thermoplastic grades that can substitute harder to process thermoset materials such as rubber.  Examples are TPE and TPU, these being processed on standard injection moulding machines, but having the flexibility associated with an elastomer.

At LVS Small Plastic Parts, we process all thermoplastic material grades, and we can help you select the best option for your application.  Once the right material is identified, we can add further refinement by considering additives that can be introduced.  For example, these can be used to further enhance structural characteristics, provide an exact colour (RAL), or even introduce resistance to UV light, antistatic or antimicrobial properties.

Thermosetting Polymers

Thermosetting Polymers are processed using a chemical reaction that permanently solidifies them into the required shape.  They cannot be reprocessed but offer characteristics such as resistance to chemical attack and elevated levels of heat (saucepan handles are a common application).  Some grades also act as ideal electrical insulators, so can be used in switches and sockets.