Synthesis of TRITON™ X-based phosphate ester surfactants and their self-charring behavior

Abstract

This paper describes the synthesis and characterization of a series of TRITON™ X-based surfactants with a predominantly alkyl phenol ethoxylate (APE) backbone and a phosphate ester chain end. Four phosphate-terminated TRITON™ X (or APE) derivatives (OPE2–OPO(OH) 2, OPE5–OPO(OH) 2, OPE10–OPO(OH) 2, and NPE10–OPO(OH) 2) were prepared from commercially available octyl phenol ethoxylate (OPE) of different oxyethylene units ( n = 2, 5 and 10), nonyl phenol ethoxylate (NPE) of 10 oxyethylene units and phosphorous pentoxide via a simple condensation reaction. Depending on their composition and chain length of oxyethylene units used in the reaction, the surfactants show different self-charring behaviors. The phosphate-terminated TRITON™ X of the lowest number of oxyethylene units (i.e. OPE2–OPO(OH) 2) gives the largest amount of char (up to 23 wt%) at 600 °C under air condition. The carboxylic acid-terminated TRITON™ X derivatives (i.e. OPE–COOH) were also tested for comparison.