ABSTRACT
In this work, the effects of droplet size and reaction time on the adsorption-reaction processes between gelatin and α-[3-(2,3-epoxypropoxy) propyl]-ω-butyl-polydimethylsiloxane (PDMS-E) emulsion droplets were studied. Gelatin molecules were only physically adsorbed on the surface of the PDMS-E droplet in the 0-75 min range, which was unrelated to the droplet size (100-1000 nm). For the small-size droplets (<410 nm), the physical adsorption proceeded over 75 min followed by agglomeration. For middle-size droplets (410-680 nm), the physical adsorption finished at 125 min; subsequently, the nucleophilic reaction between the primary amino group and the epoxy group began to happen, and globular-like or core-shell colloidal particles were formed. For large-size droplets (>680 nm), the nucleophilic reaction occurred at 75 min and produced core-shell or multi-layered colloidal particles. In a word, the physical absorption or nucleophilic reaction between gelatin and PDMS-E emulsion droplets could be controlled by controlling the droplet size and reaction time. Furthermore, the soft tissue paper coated with large-size droplets exhibited excellent resistance to water permeability and flame-resistant performance, which were carried out by water resistance and flammability tests.
ABSTRACT
In this work, interfacial reaction kinetics between α-[3-(2,3-epoxypropoxy)propyl]-ω-butyl-polydimethylsiloxane emulsion droplets with different sizes and gelatin was studied. The results of amino conversion rate determination show that the reaction proceeded in two steps. Fluorescence spectra analysis indicates that step 1 (0-2 h) should be the adsorption of gelatin on droplet surface. In step 2 (2-13 h), amino conversion rate increased rapidly. The reaction rate in step 2 ( k2) was obtained by using the 2nd-order approach to model the grafting reaction kinetics. The quantitative relationships among amino conversion rate, droplet size, the concentration of surfactant, reaction temperature, and time were described by linear regression models in given ranges of conditions in step 2. Thermodynamic analysis indicates that the interfacial reaction is an endothermic reaction. After 13 h, the reaction was almost stopped.
