Reactive surfactants in heterophase polymerization. XVII. Influence of the surfactant on the mechanical properties and hydration of the films

Abstract

ABSTRACT:In the context of a European union-supported network on "Reactive Surfactants for Heterophase Polymerization," different polymerizable surfactants (surfmers) have been synthesized and engaged in the emulsion polymerization of styrene, butyl acrylate, and acrylic acid. The thermomechanical properties of films cast from these different latices are reported in this article. The evolution of the mechanical properties with temperature and the effect of water molecules on these properties are studied. We observed that the studied surfactants do not influence the properties of the dry films. However, some differences due to grafting of reactive surfactants appeared when the films were wet. The amount of water uptake is drastically decreased when only reactive surfactants are present in the film. Concerning the mechanical behavior of the wet films, a decrease of the plastic flow stress is observed for all the samples whatever the nature of the surfactant (reactive or conventional). Hence, calorimetric measurements and dynamic mechanical analysis are used to identify the possible mechanisms that induce the change in the mechanical behavior of the latex films. In the case of reactive surfactant grafted to the polymer, the very low value of water uptake is accompanied by a plasticization of the polymer. In contrast, no plasticizing effect is observed in the case of nonreactive surfactant, even if the amount of water is very large. Finally, the tensile behavior of the styrene-butyl acrylate copolymer versus temperature is analyzed in the frame of the quasi point defects (qpd) model. Both rubber elasticity and chain orientation effects are taken into account to describe the behavior laws at large extensions (i.e., ⑀ Ϸ 1.2).

Glass‐transition temperature of a polyacrylate latex film and its water whitening resistance

“…One of the reasons for the above phenomenon is related to the migration of the emulsifier to the surface of the latex film …”

“…One of the reasons for the above phenomenon is related to the migration of the emulsifier to the surface of the latex film. [31][32][33][34][35][36][37][38][39] During the drying process of a latex film, the hydrophilic species, such as emulsifier may migrate to the surface of the film as water is evaporated. Figure 3 presents the AFM phase diagrams of latex films with different hard monomer MMA contents.…”

Drying rate variations of latex dispersions due to salt induced skin formation

“…Despite this, many published studies on latex film formation concern surfactant free systems, with dispersions cleaned from surfactants and low molecular species like salt, etc. Even though the role of surfactants in the film formation process often has been neglected, there are some phenomenological studies on films made from dispersions having conventional surfactants [7,14,15] and polymerizable surfactants [16][17][18] but there are no reports on the effect of the presence of salt in dispersions on film formation. Initiators used in the emulsion polymerization process are often inorganic salts, which will reduce the electrostatic repulsion between the particles [19,20].…”

Change in Physico‐chemical Properties of PMMA and PS by Copolymerization with an Anionic Amphiphilic Comonomer: Sodium 11‐(methacryloyloxy) undecanylsulfate (MET)

“…It is believed that a plasticization effect of MET in the presence of water lowered the T g values. [20] Macromol. Symp.…”