Effective Curative Dispersion for Uniform Mechanical Properties- A Comparison of Mixer Rotors for Finish Mixing of Curatives

Uniform curative dispersion is important in the effective preparation of rubber articles with consistently uniform mechanical properties.  Inhomogeneities of curatives resulting from poor mixing will lead to inhomogeneous network densities and, thus, significant fluctuations of mechanical properties in the final vulcanizate. Evidence of poor dispersion can be observed by monitoring the standard deviations of the vulcanizate final mechanical properties, such as final rheometer torque or modulus, or by monitoring the standard deviations of the vulcanization characteristics, such as processing and curing properties.  This paper compares 3 different rotor types for efficiency of mixing the final curatives into a simple natural rubber compound.  Curative dispersion and performance properties will be compared as a function of rotor characteristics and mixer RPM under controlled mixing conditions.