Applications for the curemeter maximum cure rate in rubber compound development process control and cure kinetic studies

Abstract

The rubber industry has been using curemeters for 30 years; however, the maximum cure rate (CRMAX) at the inflection point on the cure curve was not easily measured to a high level of precision. Now a digitized cure curve can be analyzed with computer software programs to produce a maximum cure rate determination to a high degree of precision. The use of CRMAX in compound development and quality control has some advantages when compared to other traditional ASTM curemeter parameters such as tc50 or tc90. For example, its calculation is not dependent on the cure test reaching the ultimate state of cure. Statistical test sensitivity studies show the CRMAX often to be the single best curemeter parameter for detecting subtle changes in a compound. CRMAX also appears to be more discriminating than other curemeter parameters in high temperature cures. In addition, changes in the values of the CRMAX with a rise in cure temperature will be discussed for different types of rubber cure systems. Also, changes in the position of the CRMAX along the cure curve (the time to CRMAX in relation to tc50) will be discussed for different cure systems. Lastly, the paper will discuss how CRMAX can be used to more accurately calculate energy of activation from cure kinetic studies.