Vilaiporn Luksameevanish and Manus Seadan

pp. 637 - 647

Abstract

Dynamic properties of raw natural rubber were examined using a hollow cylinder shaped sample
subjected to shear deformation on a laboratory Dynamic Mechanical Analyser. According to Cox-Merz’s
study, dynamic complex viscosity obtained by this method showed a good agreement with shear flow viscosity
measured by capillary rheometer. A master curve derived from the dynamic properties were then characterized. A crossing point of storage modulus (G’) and loss modulus (G’’) curves in the master curves was used
to identify the final rubbery state, which indicated the transition of rubbery state and molten state. The
position of this point depends on quantities and types of reinforcing or non-reinforcing fillers. The final
rubbery state was shifted to higher frequency or lower temperature. It was found that the final rubbery state
of CaCO3
-filled rubber compounds was shifted to higher frequency or lower temperature by approximately
4 decades, while the translation of carbon black-filled rubber compounds was lower than unfilled rubber by
about 1 decade. This phenomenon can be used to explain rubber elasticity, i.e. a decreasing of die swell of
CaCO3
 filled compounds at any high processing temperature. On the other hand, high magnitude of die
swell for carbon black filled compound was still obtained.