Macro and microthermal analysis of plant wax/surfactant interactions: plasticizing effects of two alcohol ethoxylated surfactants on an isolated cuticular wax and leaf model

Synperonic A7 and A20 are surfactants commonly used in the agrochemical industry to improve the physicochemical properties of formulations. This paper describes the use of differential scanning calorimetry (DSC) and localised thermal analysis (LTA) to investigate the bulk and surface effects of these surfactants on extracted leaf wax and an intact leaf system. Both DSC and LTA analysis reveal a plasticizing effect in the presence of the A7 surfactant. Further to this, LTA analysis allows us to spatially map micron scale variations in this effect throughout the residue of individual deposits. In contrast to this no plasticizing effect is revealed following the application of the A20 surfactant in either the DSC of LTA analysis. These results are discussed in context with the current theory of surfactant/wax interaction