Liquid detergents are more convenient than powdered detergents as they dissolve readily in water, generate less dust and dosing is easy. However, the stability of liquid detergents is an issue of concern. Therefore, the objective of this research is to study the formulation requirement to produce heavy-duty liquid detergents based on palm-based methyl esters sulphonate (MES) with desirable properties and performance. MES is produced from renewable and sustainable feedstock suitable to replace the conventional fossil-based surfactant, linear alkyl benzene sulphonates (LAS). Five palm-based liquid detergents (PBLDs) were formulated using C16/18 MES as the primary surfactant. The physical properties, washing performance, stability and biodegradability of PBLDs were evaluated. Performance of the PBLDs was evaluated against two commercial liquid detergents which use LAS and alcohol glucoside as surfactant (benchmark product) and it was found that the PBLDs exhibited excellent performance. PBLDs can be formulated with or without phosphates and still demonstrate good detergency. The stability study of PBLDs indicated that no appreciable hydrolysis occurred. PBLDs exhibited better biodegradability profiles compared to commercial detergent containing LAS. PBLDs passed the 60% biodegradability level within 3 to 8 d, while commercial detergent took 24 d. It was shown that palm-based C16/18 MES could be potentially formulated into liquid detergents and gave better performance than LAS based liquid detergent. Attributes of C16/18 MES should not be overlooked, which include an abundant and naturally derived palm stearin as raw material and environmental safety profiles that are superior to most synthetic surfactants.
Keywords: anionic surfactant; biodegradability; detergency; methyl ester sulphonates; palm-based liquid detergents; stable.