Response Surface Optimisation of Polydimethylsiloxane (PDMS) on Borosilicate Glass and Stainless Steel (SS316) to Increase Hydrophobicity

Abstract

Particle deposition on the surface of a drying chamber is the main drawback in the spray drying process, reducing product recovery and affecting the quality of the product. In view of this, the potential application of chemical surface modification to produce a hydrophobic surface that reduces the powder adhesion (biofouling) on the wall of the drying chamber is investigated in this study. A hydrophobic polydimethylsiloxane (PDMS) solution was used in the vertical dipping method at room temperature to determine the optimum coating parameters on borosilicate glass and stainless steel substrates, which were used to mimic the wall surface of the drying chamber, to achieve highly hydrophobic surfaces. A single-factor experiment was used to define the range of the PDMS concentration and treatment duration using the Response Surface Methodology (RSM). The Central Composite Rotatable Design (CCRD) was used to study the effects of the concentration of the PDMS solution (X1, %) and the treatment duration (X2, h) on the contact angle of the substrates (°), which reflected the hydrophobicity of the surface. A three-dimensional response surface was constructed to examine the influence of the PDMS concentration and treatment duration on contact angle readings, which serve as an indicator of the surface’s hydrophobic characteristics. Based on the optimisation study, the PDMS coating for the borosilicate glass achieved an optimum contact angle of 99.33° through the combination of a PDMS concentration of X1 = 1% (w/v) and treatment time of X2 = 4.94 h, while the PDMS coating for the stainless steel substrate achieved an optimum contact angle of 98.31° with a PDMS concentration of X1 = 1% (w/v) and treatment time of X2 = 1 h. Additionally, the infrared spectra identified several new peaks that appeared on the PDMS-treated surfaces, which represented the presence of Si-O-Si, Si-CH3, CH2, and CH3 functional groups for the substrates coated with PDMS. Furthermore, the surface morphology analysis using the Field Emission Scanning Electron Microscopy (FESEM) showed the presence of significant roughness and a uniform nanostructure on the surface of the PDMS-treated substrates, which indicates the reduction in wettability and the potential effect of unwanted biofouling on the spray drying chamber. The application of PDMS and PTFE on the optimally coated substrates successfully reduced the amount of full cream milk particles that adhered to the surface. The low surface energy of the treated surface (19–27 mJ/m2) and the slightly higher surface tension of the full cream milk (54–59 mJ/m2) resulted in a high contact angle (102–103°) and reduced the adhesion work on the treated substrates (41–46 mJ/m2) as compared to the native substrates.

Large scale synthesis of mesoporous and nonporous silica submicron particles via polymer‐derived ceramic method

“…In order to verify the formation of inorganic silica ceramic and complete pyrolysis of PDMS upon heat treatment, FTIR analysis was performed. According to Figure 1A, no peaks corresponding to the C–H bond (2950 cm −1 ) and Si–CH 3 (1250 cm −1 ) were detected, 25 showing the organic polymer's total decomposition. It can be deduced that other samples pyrolyzed at higher temperatures are entirely inorganic.…”

Fast‐Crosslinking Enabled Self‐Roughed Polydimethylsiloxane Transparent Superhydrophobic Coating and Its Application in Anti‐Liquid‐Interference Electrothermal Device

“…On the contrary, the presence of additional peaks, notably CH 3 (2969 cm −1 ), Si─CH 3 (1258 cm −1 ), and Si─O (841 cm −1 ) indicate the coverage of PDMS. [ 46 ] The formed PDMS coating endows the substrate with highly water repellent, and consistent special‐like water droplets sitting on the surface as the droplets gradually evaporate over time without impaling into the superhydrophobic coating (Figure 5b). In addition to water, PDMS‐treated glass exhibits remarkable superhydrophobicity to common drinks, such as milk (151.8°), coffee (154.5°), coke (153°), red wine (152.7°), juice (153.3), and tea (152.4°) (Figure 5c).…”

Enhancing polytetrafluoroethylene (PTFE) coated film for food processing: Unveiling surface transformations through oxygenated plasma treatment and parameter optimization using response surface methodology

“…Excessive power or prolonged treatment durations can result in surface damage, causing etching, cracking, or weakening of the material. Moreover, there is a risk of uneven treatment, with some areas being over-treated while others receive insufficient modification [6]. Moreover, the high-energy oxygen ions in the plasma engage with the surface of PTFE, leading to the fragmentation of carbon-fluorine bonds and the subsequent removal of material.…”

“…The volumetric gas flow rate was adjusted to 30 cm 3 /minute and controlled through a mass flow controller (MKS). Prior to deposition, the samples underwent air plasma treatment (30W, 150 mTorr) for 2 minutes to eliminate contaminants on the membrane and activate its surface [6]. The separation distance between the two electrodes was kept at 3 cm, and the plasma was generated within the space between them.…”

“…This can lead to reduced product yield and potential degradation in quality [1]. By integrating numerous innovative methods, manufacturers can significantly mitigate issues associated with adhesive particles in spray drying, leading to improved product quality, increased efficiency, and reduced production costs [6].…”