Presently, the majority of drive shaft boots are manufactured from CR elastomers. However, due to steadily rising ambient temperatures under the hood, e.g., due to engine encapsulation, the thermal capability limit of this material has been reached.
Alternative elastomers such as ECO, VMQ, AEM, CPE, NEM and PUR - as well as the thermoplastic elastomer Hytrel*- were compared with CR in suitable laboratory tests as well as dynamic tests under simulated “Hot/Cold” operating conditions using injection molded boots. In some cases, good correlation was found between the results of the various tests.
On the basis of the test specifications, CR could be used at temperatures up to 110 °C whereas PUR and VMQ can be applied at temperatures up to 130 °C. From the selected test materials, only ECO, NEM and AEM can be used at temperatures up to 150 °C, however only ECO has a low temperature flexibility that is close to that of CR. Thus ECO is the best compromise for boot applications where a high thermal stability and a good low temperature flexibility are required.
The results of the study can be applied to similar applications.