PET – We know our plastics


This month’s feature plastic is Polyethylene terephthalate, otherwise known as PET.

The largest use of PET comes from synthetic fibres, with bottle resin production a close second. In textile terms, PET is often dubbed “polyester” and PET for packaging resins.

But PET is also suitable for injection moulding, and is often used by the electronics industry.

We use PET when we’re injection moulding and overmoulding for customers from the electronics sector for: electrical casings, electrical housings, electrical switches and capacitors.

In every single one of our projects, material selection has a huge bearing on the success of the end product – it’s reliability, performance and cost.

A crucial part of what we do is to ask the right questions.  That way, we can apply our injection moulding knowledge to determine the most suitable material, as part of the New Product Development Process (NPD).

On more than one occasion PET has proved the best candidate.

  • An over-moulded rocker switch
  • Part of a chassis-mounted switch

Image of a rocker switch: Front is overmoulded onto in-mould decoration (IMD) polycarbonate

As we know only too well, every polymer and thermoplastic has its strengths and weaknesses:


  • 100% recyclable – made to be remade
  • Good electrical properties
  • Hard, stiff and strong (fillers are available i.e. glass)
  • Dimensionally stable and absorbs little water
  • Good gas barrier properties
  • Good chemical resistance (except to alkalis)
  • Can be transparent and colourless


  • Poor resistance to heat above 85°
  • Poor chemical resistance to alkalis
  • Cost – varies from £2.0/kg for co-polyster moulding resin

Give us a call when you’re in the NPD phase, it’s the best time – in terms of saving delays and costs – to seek advice about the most suitable materials.  Reviewing what your product needs to do, the environment it will end up in, its frequency of usage and whether it will need to withstand chemical applications.

We’re here to give you greater visibility of the material selection options available to you, for your next product.  Is it for the electronics sector manufacturing or another industry sector?  Call us on 01425 613131 or email