Photochromic Microcapsules for Textile Materials by Spray Drying—Part 1: Production and Characterization of Photochromic Microcapsules

Abstract

This study, which is the first in a three-part series, deals with the encapsulation of photochromic dyes by spray drying. An aqueous ethyl cellulose dispersion and a spirooxazine-based photochromic dye were used as a shell and core material, respectively. The effects of main encapsulation parameters, such as solvent type, inlet temperature, feed rate, solid content, and aspirator rate were investigated. The encapsulation results were evaluated by scanning electron microscopy (SEM) images, particle size measurements, thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The microcapsules obtained from a water-ethanol mixture exhibited photochromic properties. For microcapsule production, the optimum feed rate, total solid content, and aspirator rate were determined. Capsule formation improved with increased inlet air temperature. Spray drying to produce photochromic microcapsules could be a practical method for production of photochromic smart textiles.

Photochromic Microcapsules for Textile Materials by Spray Drying: Part 2—Exergy Analysis of Spray Drying Process

“…On the contrary, it should be noted that the resultant microcapsule diameter is closely related to the drying air temperature and for photochromic dye microencapsulation a decrease in the spray drying air temperature led to an increase in the mean diameter of microcapsules. 22…”

“… a 1.0/0.4 ratio of water–ethanol was used for solution preparation to completely dissolve the photochromic dye, and ethanol was fully evaporated before spray drying. 22 …”

“…However, in the case of photochromic microcapsules, it was observed that microcapsule formation could only be obtained at a fixed solution flow rate. 22 Therefore, the flow rate of the microencapsulation solution was constant since there was a restriction of capsule formation. Since the drying air outlet temperature also varied proportionally to the air inlet temperature, the increase in the drying air temperature in the dryer subsystem did not affect the exergy destruction rate significantly.…”

Photochromic Microcapsules for Textile Materials by Spray Drying—Part 3: Application of Photochromic Microcapsules on Cotton Fabrics

“…The photochromic microcapsules containing HALS were also used in this study to improve fatigue resistance of the samples. The capsules were produced according to the method specified in the previous study, 20 and three different HALS concentrations (5%, 10%, and 20%) were added to the feeding solution. The parameters applied during the spray drying process were as follows: shell-to-core ratio = 2:1, water-to-ethanol ratio = 1:0.4, inlet temperature = 150°C, aspirator ratio = 95%, and feeding rate = 3 mL/h.…”

“…In this article, the application of the photochromic dyes encapsulated by spray drying onto cotton fabrics was investigated. The encapsulation parameters were examined in the previous part of this study, 20 and as a continuation of that study, the performance investigation of spray-dried photochromic microcapsules on the cotton fabrics, such as color build up, UV protection property, washing durability and fatigue resistance, was done. Although color build up of photochromic textiles has been studied extensively, it will be a first for textiles including spray-dried photochromic microcapsules.…”