Scanning Electron Microscopy Investigation for Monitoring the Emulsion Deteriorative Process and Its Applications in Site-Directed Reaction with Paper Fabric

Abstract

The O/W isocyanate emulsion can be used as a sizing agent to improve the waterproof performance of paper. However, the -NCO content in the emulsion diminishes with the prolongation of standing time. What is happening to this seemingly stable emulsion, especially concerning its microstructure evolution? We propose to monitor the emulsions deteriorative process by combining freeze-drying technique and SEM. Thus, the emulsion containing -NCO active group was obtained by the synthetic polymer emulsification of HDI trimers. The results of SEM demonstrate that the emulsion deteriorative process actually represents the collapsing and fusion of stable honeycomb structure with the prolongation of standing time and increasing temperature. This is possibly due to the fact that the inner aggregative HDI trimers are reacting with outside water to form urethane macromolecules, and this results in the collapsing and fusion of the honeycomb structure, as observed in SEM images. Moreover, the measurement results of -NCO content and FT-IR spectroscopy present the -NCO content as reducing with increasing standing time and temperature. This conclusion further proves our hypotheses. Additionally, the emulsions are used to treat the paper by site-directed reaction. The results show that the with the increase of the standing time and temperature, the contact angles and surface free energy show a decrease and an increase, respectively, whereas surface free energy appeared at a minimum of 29.19 mJ·m−2 when the standing time and temperature was 1 h and 25 °C.

Evaluation of Touch and Durability of Cotton Knit Fabrics Treated with Reactive Urethane-Silicone Softener

“…Titration was performed with a 0.5 N hydrochloric acid solution. The endpoint was the point where the blue or blue-violet color of the solution disappeared, and the yellow color lasted for more than 15 s. Finally, the -NCO content was determined using the following equation [23][24][25]:…”

Critical Review of Techniques for Food Emulsion Characterization

“…The understanding of emulsion behaviors can be further enhanced by microscopic analysis, which provides fundamental information about the morphology of the droplets, their concentration, and distribution [9][10][11]. Various techniques, such as optical microscopy, atomic force microscopy, transmission, or scanning electron microscopy, enable researchers to assess the structural properties of emulsions [12].…”