Study on foaming properties of N-acyl amino acid surfactants: Sodium N-acyl glycinate and sodium N-acyl phenylalaninate

Abstract

A detailed study on the foaming properties of sodium N-acyl glycinate(N-CnG, n = 12, 14,16,18)and sodium N-acyl phenylalaninate(N-CnP, n = 12, 14,16,18)with different carbon chain lengths were performed. The effects of hydrophilic group, hydrophobic group, surfactant concentration and temperature were evaluated on the foamability, foam morphology and foam stability by foam scanning method. The results showed that the foamability and foam stability of N-C12G were better than that of N-C12P. In addition to N-C14P, with the increase of alkyl carbon chain, the foamability of sodium N-acyl amino acid decreased, but the foaming stability gradually increased. With the increase of concentration, the foamability of the two kinds of surfactants increased first and then decreased. The increase of temperature was beneficial to the foamability of N-CnP, but the foam stability decreased. At higher temperatures, the longer alkyl chain was, the stronger the foamability and foam stability of N-CnP were. With the increasing of alkyl carbon, the maximum liquid carrying capacity and liquid drainage rate of N-CnG decreased. At the same concentration and alkyl carbon number, N-CnP had higher maximum liquid carrying capacity than N-CnG. The number of bubbles initially increased and then decreased, and the morphology of bubbles gradually changed from sphere to polyhedron.