Accelerated Testing

The best & most reliable way to assess the lifetime performance of a product, component part or material is to put it in the service environment & re-assess it after the desired service life. In today’s competitive business’s world this method of testing would take far too long. To meet our customer’s requirements we have created effective methods of accelerating lifetime tests in simulated environments.

Accelerated testing of plastic & rubber material is a complex process & does have greater uncertainties surrounding it than simple physical/mechanical characterisation. In general the greater the acceleration process, the more likely it is that the test will become unrepresentative of actual ageing. Acceleration testing only works effectively if the material under test retains its physical state & does not undergo any new physical or chemical processes as a result of the accelerant. Polymer behaviour is not straightforward, & there are limitations to the accuracy of results even at low acceleration levels.

Smithers Rapra understands the issues surrounding accelerated ageing through conducting test programmes over many years. The consultant team is aware of when you can accelerate & by how much.

Accelerated Testing Services

Heat

The most common method of accelerating ageing is to increase the environmental temperature. The empirical rule that every 10°C doubles the reaction/ageing rate is a good starting point, but is very approximate. Whilst heating, significant softening & warpage may also occur; this structural change could have an influencing effect on the functional or dynamic property. The material might also pass through a transition that introduces processes that would not occur in normal service.

Light

Light resistance is an important consideration for aesthetic properties as well as physical ones, but again accelerating the effects is far from straightforward. Light, unlike heat, is not a constant factor globally – the duration & intensity of light a material will see is dependent on its global location. Light exposure via accelerated weathering can be used to simulate this, but there are limitations that only experience can help to assess.

Fatigue

When implementing fatigue testing, major consideration needs to be given to test speed & rate. Rubber & plastics unlike metals are not fully elastic – they have a viscous behaviour element & this behaviour is sensitive to time (creep/relaxation) The long tangled polymer chains also generate heat as they move past one another. Increasing the test speed therefore only works if the polymer reacts in a representative manner & does not undergo any significant internal shear heating during the test.