A 2014 KPMG customer survey report demonstrated the increasing demand of driving comfort and sustainable development. With the longer lifespan of modern vehicles, more attention has been placed on to products’ lifetime performance. Ageing of rubber components in the engine mount was known to be one of the key elements related to the compromised driving experience in used vehicles. This thesis will investigate how the properties of the rubber component change, and why. Links among mechanical properties, microstructures and chemical composition of the aged carbon black filled vulcanised natural rubber used in a commercial engine mount are to be revealed.
By investigating used engine mounts, the changes of stiffness for rubber in the used engine mount was established, which were identified to be related to post-curing, thermal degradation, oxidative degradation, filler re-agglomeration and loss of additives. Among these ageing mechanisms, the most dominating factors were post-curing and loss of additives, which increased the stiffness of the rubber by 45% in a four-year-old car that has driven by 80 thousand kilometres.
The impact of the acting ageing mechanisms was identified through aerobic and anaerobic artificial ageing experiments. The artificial ageing experiments provided knowledge about how each ageing mechanism progresses in the material and how they interact with each other. It also demonstrated the limitations of artificial ageing on simulating certain ageing mechanisms.
This is the first time such a comprehensive investigation has been made to identify the causes of different ageing mechanisms on specimens from real vehicles and discuss how the ageing mechanisms impact on the material individually. Hopefully this work could provide useful information for the industry and other academics in the area when designing rubber relevant products or investigating ageing behaviour of similar materials.
