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It is speculated that the hydrolysis and polycondensation reaction of MTMS in emulsion droplets led to the formation of PMSQ, which is much more hydrophobic than silica surrounding the droplet.
The reason for the lower hydrophobicity of coatings T8 and T7 may be that the lower concentration of sodium silicate leads to the formation of larger PMSQ particles.
(15.) Xiang, H, Zhang, L, Wang, Z, Yu, X, Long, Y, Zhang, X, Zhao, N, Xu, J, "Multifunctional Polymethylsilsesquioxane (PMSQ) Surfaces Prepared by Electrospinning at the SolGel Transition: Superhydrophobicity, Excellent Solvent Resistance, Thermal Stability and Enhanced Sound Absorption Property." J.
The chemicals used in this study were PMSQ (GR653L, Techneglas), TMES (Aldrich), chromium(III) oxide (Sigma-Aldrich), sulfuric acid (Aldrich), PMMA (CM205, Chimei), PC (PC110, Chimei), and PC/ABS (PA756, Chimei).
Afterwards the TMES-coated substrates were coated with PMSQ layers by dip coating at a speed of 5 mm/min, and then dried at 90[degrees]C for 30 min.
By pressing the 3 M Scotch tape on the PMSQ coating and stripping it off, the percentage of peeling area was calculated by counting the area of PMSQ coating peeled off from the substrate due to poor adhesion.
2, TMES was used in this study to react with hydroxyl groups forming Si-([[CH.sub.3]).sub.3] groups bonded to the polymer surface to enhance the surface interaction with PMSQ for improving the interfacial adhesion.
The effects of the surface pretreatments of polymer substrates before PMSQ coating on the adhesion of PMSQ on polymer were studied as shown in Table 1.
Table 1: The adhesion of PMSQ coatings on several polymers after different surface treatments Substrate surface treatments Percentage of peeling area(%) PMMA PC PC/ABS No treatment >95% >95% >95% [O.sub.2] plasma >95% >95% <5% Chromic acid Damage >95% <15% TMES coating (without oxidation pretreatment) >60% >95% >95% [O.sub.2] plasma, then TMES <1% ~70% <5% Chromic acid, then TMES Damage >50% <1% Further efforts were attempted to improve the adhesion of PMSQ film to the PC substrate by varying the chromic acid treatment time to increase the hydroxyl groups on the PC surface, followed by the dip-coating of TMES for 1 min.
Table 2: The adhesion of PMSQ coating on the PC substrate, pretreated with chromic acid solution for varying time then dip-coated with TMES for 1 min before PMSQ coating 15s 30 s 1 min 2 min 5 min Percentage >95 >95 >50 >50 >50 of peeling area The percentage of peeling area was measured by the cross cut tests Table 3 further shows the hardness of PMSQ on different polymers measured by the pencil hardness test.
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