Identification of the factors controlling the relaxation behavior of EPDM elastomers

The main objective of this study is to increase performance against high temperatures using new generation EPDM elastomers for dynamic applications and to clarify the effect of additives to EPDM elastomers. For this purpose, it was compared with natural rubber (NR60) using the new generation EPDMs with high molecular weight and narrow molecular weight distribution, called traditional EPDM (EPDM-0) and new generation EPDM (EPDM-A). EPDM-A, EPDM-A5 (5 phr), EPDM-A10 (10 phr), EPDM-A20 (20 phr), EPDM-A30 (30 phr) elastomers were prepared to compare the oil effect of new generation EPDMs. To investigate the effect of the sulfur content, EPDM-AHS with high sulfur content and EPDM-ALS low-sulfur content were prepared and compared. In the scope of the thesis, elongation at break and breaking strength were determined by the universal test device. When the results of 100% elongation were examined, it was observed that the mechanical properties of EPDM-A elastomer (1,88 MPa) were better than NR60 (prepared from natural rubber) and EPDM-0. In the second stage of the thesis, the stress properties were investigated with TSSR instrument. When TSSR results were evaluated, changes in isothermal relaxation properties occurred due to molecular weight distribution. In the new generation of EPDMs, it was observed that the force required to stretch 50% and the isothermal relaxation rate decreased as the oil content increased. When the results of the non-isothermal temperature scanning stress relaxation experiment were evaluated, a second curve was formed in the tension zone with the increase of temperature and annealing tests were performed by associating this curve with the crystallization of the material. As a result of the annealing, the service temperature increased as the number of annealing increased. In the final phase of the thesis, damping properties of natural rubber and EPDM elastomers were investigated by using universal test device. When the compression tests were examined, the energy value absorbed at EPDM-0 was determined as 23 mJ / cm3 and the energy absorbed at 10% pressure was found to be 19 mJ / cm3 in EPDM-A. These results are associated with the narrow molecular weight distribution of EPDM-A and the high cross-link density. When all these studies are evaluated, it is seen that the new generation EPDM-A will be effective in dynamic applications by increasing the mechanical properties.