EPDM-rubber in blends with NR/BR-elastomers for ozone-resistant tyre sidewall applications : New approaches for improved mechanical properties

摘要

Blending of saturated ethylene-propylene-diene rubber (EPDM) with highly unsaturated rubbers, such as natural rubber (NR) and (butadiene rubber) BR, is a rapidly developing area especially for tyre sidewall applications, where the saturated elastomer can be considered as a polymeric antioxidant for the diene rubbers. However, vulcanisates of such elastomer blends are generally poor in mechanical properties. These undesirable phenomena are generally the result of the thermodynamic incompatibility of these two types of rubber, cure incompatibility and heterogeneous filler distribution in each of the rubber phases. The objective of the project covered in this thesis is to overcome these incompatibility and reinforcement problems of the NR/BR/EPDM blends by various approaches and therefore improve the final mechanical properties of such blends. Besides the mechanical properties, the mechanisms involved are studied in the present work as well. In this research generally two approaches have been explored to solve the incompatibility and uneven-reinforcement problems of the NR/BR/EPDM blends and to improve the mechanical properties: adding a compatibilising agent and modification of the EPDM. Applying MAH-EPM as compatibilising agent leads to some improvements of the mechanical properties. However, ionic crosslinking resulting from MAH-EPM with ZnO, is not thermally stable, which limits the application at high temperatures. Different modification agents have been tried and it was found that APPS works by far most effectively. Significant improvements have been obtained with APPS-modified EPDM in blends with NR/BR. There is still some room for improvement, especially for the visco-elastic properties. But due to the excellent tensile, tear and fatigue properties, it can be a serious candidate for tyre sidewall applications. Considering the modification reaction of EPDM with APPS, the reaction mechanism is not clear yet and is worth to be further explored.