Bactericidal Properties Of Didecyldimethylammonium Formate And Its Mixtures

Quaternary ammonium salts are a kind of cationic surfactatants which were widely used in disinfectants and bactericides. Most of the bacteria and fungi have produced drug tolerance due to the long-term use of cationic traditional surfactant to achieve disinfection function. Therefore, the introduction of new cationic surfactants is necessary. The change of quaternary ammonium salt counterion had a great influence on the bactericidal performance, for example, Bromogeramine Bijieer inactivation had better bactericidal activity with the countrions being Br and Cl-. In this thesis, the surface activity, salt resistant and aggregation behaviors of a new quaternery ammonium salt didecyldimethylammonium formate (DDAF) whose counterion is formate have been studied together with the bactericidal properties of mixture composed of other kinds of surfactants including cationic surfactants, ionic surfactants and nonionic surfactants. The thesis includes three parts:(1) The surface properties salt resistant and aggregation behavior of DDAF were studied. The salt tolerance of 0.1 mM DDAF aqueous solution was studied. DDAD aqueous solution began to become cloudy when the NaCl concentration reaches 200 mM.With the increasing of NaCl concentration, the cmc and ? CMC of DDAF/NaCl system decrease gradually. When the mass fraction of DDAF increased to 80%, it can be found that liquid crystals were formed.(2) The bactericidal properties of five bactericides - didecyldimethylammonium formate(DDAF), didecyldimethylammoniumchloride (D8-10), poly hexamethylene biguanide hydrochloride salt (IB), didecylmethyl hydroxyethylammonium chloride (DEQ) and lauryldimethylbenzylammonium chloride (1227) on three kinds of pathogenic bacteria pathogens Escherichiacoli, Staphylococcus aureus and Candidaalbicans were investigated.Through the results of orthogonal experimental design with 5 factors and 3 levels of Lis(37)table, the optimum mass concentration for five-ingredient system was as follows :DDAF=30 mg/L, D8-10=20 mg/L, IB=30 mg/L, DEQ=30 mg/L, 1227=30 mg/L.(3) The effects of some surfactants on bactericidal activity of the cationic compound fungicide have been investigated. The compound fungicide were consist of didecyldimethylammonium formate (DDAF), didecyldimethylammoniumchloride (carbon chain length 8-10, D8-10), poly hexamethylene biguanide hydrochloride salt (IB),didecylmethylhydroxyethylammonium chlbride (DEQ) and lauryldimethylbenzylammoni-um chloride (1227), with a mixing ratio of DDAF/D8-10/IB/DEQ/1227 being 3/2/3/3/3 and the total concentration was 140 mg/L. The results showed that the minimum influences on cationic compound fungicide caused by NOE-Pn occured at n = 9 (i.e., NOE-P9) with the sterilizing time of 20 min.