Thermal hazard assessment of cyclohexane-type liquid crystal monomer from the Grignard cross-coupling reaction by different calorimeters

The thermal hazard assessment of cyclohexane-type liquid crystal monomers (CLCMs) from the Grignard cross-coupling reaction is challenging because the thermal hazard assessment involves the Grignard reagent. In this study, different calorimeters in semi-batch and batch modes were used to investigate the exothermic behaviour of CLCM. The enthalpy of formation of the Grignard reagent (320.87 - 380.46 kJ mol −1 ) was higher than that of the cross-coupling reaction (70.92 - 108.68 kJ mol −1 ). The heat accumulation in semi-batch mode decreased to 12.15% when compared with 100% observed in batch mode. Furthermore, the Grignard reagent decomposed at 470.39 K, with a low activation energy ( E a ) of 110.99 - 129.67 kJ mol −1 . Finally, based on the Stoessel criticality diagram, the thermal risk of the CLCM was found to be class 4 in batch mode and class 3 in semi-batch mode. This revealed that the semi-batch mode was the most suitable dosing method for CLCMs.