There is an optimum level of carbon black for maximum energy absorption capacity. Not all rubber compositions are the same. It turns out that there is an optimum level of carbon black for maximum energy absorption capacity. One of our clients ran a series of tests on their Advanced Yerzley Oscillograph (AYO-IV) for Natural Rubber and Chloroprene Rubber at five different levels of carbon black. Their results show a definite maximum impact energy absorption level at 75 parts per hundred of rubber (PHR).