Crystallisation of sodium dodecyl sulfate and the corresponding effect of 1-dodecanol addition

Sodium dodecyl sulfate (SDS) exhibits crystallisation upon exposure to low temperatures, which can pose a problem in terms of product stability. In this study, non-isothermal crystallisation of SDS is investigated via differential scanning calorimetry (DSC) at concentrations that are typical of those present in many industrial liquid detergents. At different low temperatures, the crystal structures are analysed with X-ray diffraction (XRD) and it is concluded that ice formation during the surfactant crystallisation process occurs below 0 °C. The capability of the alcohol precursor, 1-dodecanol, as a seeding material for SDS crystallisation is also investigated through the use of DSC and optical microscopy. These results show that 1-dodecanol can successfully act as a seed for SDS crystallisation. Upon cooling an SDS aqueous system, the crystallisation peak in the DSC thermogram shifts to a higher temperature in the presence of 1-dodecanol. Therefore, any remnant alcohol precursor in surfactant-based formulations could have a negative impact on the product stability upon exposure to cold climates.