In order to ensure the durability of the product, one of the things that must be considered in the design of the damping rubber is the performance retention over time. The reason for the aging of the damping rubber over time comes from many aspects, but the main ones are aging phenomena such as hot oxygen, dynamic fatigue, and ozone. Among them, the influence of heat is one of the main factors in the change of the environment in which the rubber is used.
To improve the heat resistance of natural rubber-based materials, the following methods are often used:
(1) Optimization of cross-linking morphology: for the damping rubber optimized for cross-linking morphology, for reasons of physical properties and processing properties, in most cases, cross-linking is carried out by using sulfur. In order to improve the heat resistance of the sulfur cross-linking system, it is necessary to select a vulcanization system in which the cross-linking form of the monosulfide system can be obtained. However, since the cross-linking form of the monosulfide system deteriorates the fatigue resistance of the vibration-damping rubber, how to combine heat resistance and fatigue resistance is important in improving the heat resistance of the natural rubber-based material. Most of the formulations use a semi-effective vulcanization system.
(2) Selection of anti-aging agent: Since the damping rubber is used under dynamic conditions, its aging (oxygen aging, ozone aging, and fatigue aging) is much more serious than static, and the various aging factors not only act alone but also exert a role on the rubber in various coupling forms. For example, mechanical influence factors (load, vibration conditions, etc.) often involve oxygen, ozone, and light in the atmosphere. In addition, heat (temperature) also participates in the action, which causes the rubber to be sticky (cut cross-linking) hardening (cross-linking progress) or cracks and cracks, so the use of the anti-aging agents and their cooperation are very important.
(3) Application of blended rubber, etc. It is a common method to mix about 30% of EPDM in natural rubber for the purpose of improving ozone. However, in improving the heat resistance of the vibration-damping rubber, mainly used are SIR and EPDM-based IIR.
Nishiue Takeshi et al. produced a shock absorber by using natural rubber, a butadiene rubber containing an unsaturated bond, and a metal salt containing a -OH group organic acid having a carbon number of more than 4, and some other additives. This kind of shock absorbers has good durability and compression set properties. The compression set at 22 °C for 22 hours and 40 °C for 148 hours was 17.0 and 11.7%, respectively. O kada Osamu got the vibration-damping rubber material by blending EPDM rubber and EAM rubber.
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