| 摘要 |
Motor vehicle parts based on an ethylene, alpha-olefin, diene monomer elastomeric polymers exhibit excellent low temperature compression set. Previously, such compression set performance in the amorphous region was believed to be non-responsive to ethylene content once the amorphous region was reached. However, within certain ranges, ethylene content has been shown to have an effect on low temperature compression set even in the amorphous region. These motor vehicle parts are particularly useful where extremes of ambient temperatures maybe incurred. In a preferred embodiment, the invention is a vehicle part, such a brake part or belt including an ethylene, alpha -olefin, diene elastomeric polymer. The elastomeric polymer has a low ethylene content, and the vehicle part made from a compound based on the elastomeric polymer will have improved low temperature compression set. The vehicle part comprises the elastomeric polymer where the polymer has ethylene present in the range of from 50-60 mole percent, ethyldiene norbornene present in the range of from 0.2-5 mole percent and an alpha -olefin, selected from propylene, hexene-1 and octene-1, where the alpha -olefin makes up the remainder of the elastomeric polymer. The ethylene composition distribution of the elastomeric polymer is such that the ethylene in 90 % of the polymer fractions varies by no more than +/- 4 % by weight. The Mw/Mn will be in the range of 2-4, the inherent viscosity in the range of 1.2-3.2 and the Mooney Viscosity (1+4) @ 125 DEG C in the range of from 10-80. The vehicle part will have an instantaneous compression set at -40 DEG C, less than 80 %. |
