Influence of magnesium carbonate loading on the compound properties of polychloroprene, natural rubber, and their blends

The effect of magnesium carbonate (MgCO₃) loading on the compound properties of polychloroprene (CR), natural rubber (NR), and their blends was investigated. The studied properties included Mooney viscosity, cure characteristics, and degree of filler-filler interaction. In addition to MgCO₃ loading, the effect of the blend ratio on such properties was simultaneously determined. The results reveal that, regardless of the rubber type and blend ratio, increasing MgCO₃ loading resulted in not only an increase in the compound viscosity, but also in the enhancements of the cure rate and state of cure. However, the effect of MgCO₃ loading on the overcured behavior was strongly dependent on the rubber type and blend ratio. For CR, the presence of MgCO₃ accelerated postcuring, whereas the opposite results were found for NR, in which the reversion rate was promoted. For CR/NR blends, a plateau behavior was obtained at a 50/50 blend ratio, where the degrees of postcuring and reversion were counterbalanced. The results also reveal that when MgCO₃ was loaded at low concentrations (≤20 phr), the degree of filler-filler interaction was very low and had no significant effect on the compound properties.