Preparation And Damping Mechanism Study Of EPDM/ENR Damping Materal With Broad Temperature Range

Polymers have been widely used as damping materials to control vibration and reduce noise, which attributes to the thermodynamic transformation or mechanical relaxation. During the relaxation process, part of the vibration energy can be dissipated as heat due to the friction of between polymer chains. To meet the requirements of practical damping applications, good damping materials should exhibit a high loss factor(tanδ>0.3) over a temperature range of at least 60~80°C. While in general,the glass transition temperature(Tg) of most polymers especially rubbers are much lower than the ambient temperature, and the transition temperature range is relatively narrow as well,therefore,broadening the temperature range of viscoelastic damping materials, especially improving the damping performance at high temperature region has become an important research topic. Based on our former research,in this paper,binary and multi-components damping materials with broad temperature range based on Ethylene-Propylene-Diene rubber(EPDM),a kind of saturated nonpolar rubber,and epoxidized natural rubber(ENR),a kind of unsaturated rubber with strong polarity, were prepared,and the damping mechanism of those materials was investigated in detail.Binary blends based on EPDM/ENR-50(the epoxidation degree is 50%) were prepared and the damping mechanism of those blends was investigated in detail. Loss factor(tanδ) versus temperature curves of those blends showed two separate and expanded loss peaks when compared with those of pure cured EPDM and ENR-50, the lower temperature peaks are related to the Tg of EPDM, peaks at higher temperature correspond to the Tg of ENR-50. The outshift of the Tg in the EPDM/ENR-50 blend with blend ratio of 75/25 is significant and the value of tanδ is appropriate of all the binary blends, the Tg of EPDM phase shift from-50°C to-59.6°C,while the Tg of ENR-50 phase shift from 0.2°C to 33.2°C,the tanδ value of the trough between two damping peaks is 0.127. TEM, SEM/EDS and TEM were used to characterize and analyse elements distribution, the microstructure and morphology in the EPDM/ENR-50(75/25) blend. According to the research,we explain the out-shift of the Tgs in the EPDM/ENR-50 binary blend as: during vulcanization,curatives can migrate from saturated phase(EPDM) to unsaturated phase(ENR-50) in the saturated and unsaturated elastomer blending system, which leads to large differences in cross-link extent of the difference phases as compared to those of pure cured ones. As the variation of the cross-link extent, the slightly cross-linked EPDM phase shows a lower Tg and the tightly cross-linked ENR-50 phase shows a higher Tg.Based on the EPDM/ENR-50 binary blends, multi-components blends based on EPDM/ ENR-50/ENR-45/ENR-25 were prepared and investigated. Among those blends, the one with blend ratio of 65/15/10/10 gave the best and particularly stable damping property with high tanδ value of 0.3 of effective damping temperature range from-81.2°C to 40.0°C. In order to further improve the mechanical property and damping property at higher temperature range, another ternary blends based on EPDM/ENR/CR were prepared. TEM and AFM images indicated that the additional ENR-40、ENR-25 and CR play a role of compatibilizer which leads to a better interfacial compatibility,which improve the damping property through and between two peaks. Moreover, the addition of CR made the Tg of ENR-50 in the ternary blends move to a higher temperature(43.5°C), which further improved the damping property of the blend at high temperature range, the mechanical property was significanty improved at the same tiome. The effects of carbon black concentration, plasticizer contents on the damping properties, mechanical properties of those two blends were studied in detail as well. The multi-component blend exhibited great comprehensive properties when filled with 8 phr(parts per hundreds of rubber)white mineral oil and 20 phr carbon black. When filled with 6 phr dioctyl phthalate(DOP) and 40 phr carbon black, the ternary blend has a damping temperature range with tanδ≥0.3 covers a wide range of 120°C(from-48.3 to 72.6°C), and the tensile strength and elongation at break is 23.2 MPa and 423% respectively,achived a good balance between damping property and mechanical property.