Carbon Black and Calcium Lignosulfonate Reinforced Rubber Composites

Rubber compounds based on SBR and NBR were filled with constant amount of carbon black – 25 phr and calcium lignosulfonate – 30 phr. Glycerol as cheap and environmentally friendly softener was added into the rubber compounds in concentration scale from 0 to 20 phr to plasticize the rubber matrix and the biopolymer and to improve the adhesion between the components of rubber compounds. The results revealed that the addition of glycerol resulted in the decrease of rubber compounds viscosity. Based on dynamical-mechanical analysis it can be concluded that glycerol softened lignosufonate and lowered its glass transition temperature. The softened lignosufonate was better distributed and dispersed within the rubber matrices, which was clearly demonstrated by performing scanning electron microscopy. Glycerol contributed to better adhesion and compatibility between the rubber and the biopolymer, which was subsequently reflected in improvement of tensile behavior of vulcanizates. Due to compatibility in polarity among rubber matrix, biopolymer and plasticizer, higher tensile strength, and higher enhancement of tensile strength in dependence on glycerol content exhibited composites based on NBR. The main point of the work was to show that improvement of the composites properties can be reached by simple addition of suitable plasticizer into the rubber formulations with applied biopolymer without additional cost and time-consuming treatment procedures.