Optimum processing parameters for coating polyester with silica nanoparticles using gravity sedimentation

Gao et al. have proposed a facile method of silica nanoparticle synthesis called the solvent varying technique (SVT). Silica nanoparticles (SNPs) have been synthesized using the SVT. The diameters of the SNPs produced by these recipes are sensitive to drying temperature especially when they are used to form photonic crystal films on the surface of textiles. The colour appearance of the coated fabrics can be affected by unused reactants from the colloidal suspensions. These form a thin layer on the surface of the SNPs, which can adversely affect the constructive interference of light from the photonic crystal. In this paper, the original SNP solutions have been processed using a centrifuge and solvent replacement technique in order to reduce this problem. A TEM was used to record the morphology of the surface of the original and centrifuged particles. The resultant images show that there were fewer impurities present on the surface of the centrifuged SNPs than that of the original SNPs. DLS was used to measure the diameters and dispersion of the original and the centrifuged particles. A spectrophotometer was used to measure the reflectance of the samples. The chromaticities of the coated fabrics using both the original and centrifuged SNPs dried at a range of temperatures (40 degrees C, 60 degrees C, 80 degrees C and 100 degrees C) have been compared. It was determined that the centrifuged SNPs could be dried at higher temperatures than previously reported with little effect on the colour appearance of the photonic crystals. Graphical abstract