Influence of chain length in nonyl-phenol ethoxylate surfactants on the film formation behaviour of methylmethacrylate-2-ethylhexyl acrylate copolymer latexes: part 1. Differential scanning calorimetry and atomic force microscopy

A comparison of the film forming characteristics of methylmethacrylate-2-ethylhexyl acrylate latex copolymers stabilised with nonylphenol ethoxylate molecules of varying chain lengths is presented. The ability of the stabiliser to segregate and diffuse from the interfacial layer into the surrounding media influences both the rate of coalescence process and structure of the film formed. Dynamic mechanical analysis, minimum film formation temperature measurements, particle size analysis, differential scanning calorimetry (DSC) and atomic force microscopy reveal the complexity of the mechanism involved in the coalescence process. A model that describes the various stages of coalescence and compaction of the latex particles indicates the effects of chain length on the film forming properties. For the stabiliser with a chain length of 20, coalescence is observed at room temperature; whereas for the stabiliser with chain lengths of 30 and 40, coalescence only occurs if the films are raised above 315 K. For the longer chain stabilisers, the effect of stabiliser-stabiliser interaction inhibits the coalescence process and DSC data indicate the occurrence of crystalline phase structure in the thin film. (C) 2001 Elsevier Science Ltd. All rights reserved.