For 35 years, CNEP has been investigating the ageing and the durability of formulated polymer-based materials. The applied research studies performed at CNEP are based on the fundamental knowledge of the photo-ageing mechanisms and allow predicting the service life of polymer materials for long term periods. Our approach is based on the fact that most losses of functional properties of polymers under natural weathering conditions are due to chemical changes. To be representative and reliable, a laboratory artificial photoageing experiment should therefore produce the same chemical changes as the ones occurring in natural conditions. Acceleration can then be achieved by increasing both temperature and irradiance, with a suitable balance. In this context, representative (ultra)accelerated photoageing experiments can be defined as experiments where the rates of the chemical reactions occurring in natural conditions are increased. In this webinar, our approach as well as examples of durability predictions will be presented.