Mixing time influence on fatigue crack growth in a carbon black-filled natural rubber vulcanizate

Various processing parameters affect the dispersion of carbon black (CB) in a rubber matrix, of which mixing time plays a major role. The physical properties of a green compound namely bound rubber and Mooney viscosity along with mechanical and fatigue crack growth (FCG) are affected by the dispersion of filler particles. To determine the effect of mastication on dispersion, the mixing time was varied from 120 s to 600 s where it was gauged that an optimum range of mixing times display better dispersion. The difference in dispersion between the green and the cured compounds was also stark due to the flocculation mechanism. Longer mixing times do not show much decrease in agglomerate size on curing, that is, approximately 2%, whereas shorter time has led to a decrease of 20%. The FCG properties were studied using a tear and fatigue analyser, where the FCG rate displays a similar trend with the dispersion of CB.