Effect of mesogenic organic salts on vulcanization and physical properties of rubber compounds

The effect of mesogenic organic salts as reinforcing fillers for non-ionic elastomers such as natural rubber and styrene–butadiene rubber has been investigated. The influence of cation size (thallium and sodium) and organic chain length (thallium(I) pentanoate and thallium(I) dodecanoate) on vulcanization parameters, physical and mechanical characteristics and rheological behaviour has also been analysed. In general, the maximum torque of the vulcanizates increases in the presence of the salts and is clearly manifested in a noticeable increase in tensile modulus and strength of the composites. The thallium(I) salts are more effective reinforcements than the sodium salt, and the length of the organic chain has hardly any influence on the mechanical properties. The composites based on the thallium(I) dodecanoate salt show a very peculiar rheological behaviour with a ‘plateau’ in the elastic modulus and loss modulus versus temperature plots which is related to solid phase I, existing between 83.5 and 127 °C, characterized as a plastic condis phase. This issue is especially interesting for the fabrication of devices such as sensors to control, for instance, the security (resistance of a material) as a function of temperature. © 2013 Society of Chemical Industry