Enhanced Solvent Drying of Liquid Film Coatings by Fluorine-Base Polymeric Surfactant Addition

2020

The use of plasticizer has been extensively studied for enhancing the flexibility, processability, solubility, and vapor permeability of polymeric materials. However, its use in enhancing drying of polymeric coatings has been scarcely studied. In the present work, the optimization of plasticizer loading for drying characteristics and residual solvent minimization in polystyrene‐p‐xylene polymeric coatings has been investigated. Coatings were prepared by solution casting technique at various triphenyl phosphate (TPP) loadings from 0 to 7.50 wt% for two cases of initial solution volumes of 75 and 125 μl. For these two cases, respectively, the minimum residual solvent values of 0.02% and 1.61% were obtained, both at 2.50 wt% TPP loading. However, the two cases exhibited residual solvent values of 2.32% and 4.45% at 0 wt% TPP. Further, the SEM results also showed that at 2.50 wt% TPP loading, the coatings developed a dense, smooth and defect‐free morphology attributed to their minimized residual solvent content. The coatings, however, had a porous and phase‐separated morphology originally at 0 wt% TPP. The variation of residual solvent, coating thickness and drying rate with plasticizer loading followed the same behavior for different initial solution volumes. All these parameters attained their peak values consistently at 2.50 wt% TPP. The study is first of its kind to indicate massive reduction in residual solvent attributed to the addition of a nonvolatile plasticizer. TPP also imparts flame retardance to inherently inflammable polystyrene thereby facilitating its implementation in electronic devices. The obtained coatings have possible applications in electronics, electro‐optics, and food packaging.

Section: Resultsmentioning

confidence: 92%

“…The optimum additive loading for minimum drying time was found to be 1.5 wt% of SDS. Yamamura et al 28 studied the effect of fluorine based surfactant on the evaporation rate of solvent in cellulose acetate butyrate‐methyl ethyl ketone film. They obtained 10% increment in the solvent evaporation rate of these liquid films.…”

Section: Introductionmentioning

confidence: 99%

Residual solvent minimization in polystyrene‐p‐xylene coatings using a nonvolatile additive

Rawat

2020

“…These works obtained lower reduction in residual solvent 13 and did not study optimum loading for the minimum residual solvent. 14 The current work achieves the minimum residual solvent value of 0.59% of the initial solvent at 0.50 wt% loading of PEG in PVA-water coating for initial wet thickness of 1004 μm, at 25 C, 39% relative humidity, and no air-flow. A wider range of surfactant loading 0-7.50 wt% exhibiting the minima is studied and a significant reduction in residual solvent is obtained.…”

Section: Comparison With Available Studiesmentioning

confidence: 69%

“…Most of the reported works considered a narrow 14,55 or no range 56 of surfactant loading. These works obtained lower reduction in residual solvent 13 and did not study optimum loading for the minimum residual solvent 14 . The current work achieves the minimum residual solvent value of 0.59% of the initial solvent at 0.50 wt% loading of PEG in PVA‐water coating for initial wet thickness of 1004 μm, at 25°C, 39% relative humidity, and no air‐flow.…”

Section: Resultsmentioning

confidence: 99%

“…1,3,13 Rawat and Ahuja 1 lately reported that the addition of plasticizer triphenyl phosphate into polystyrene-p-xylene coatings significantly increases the drying rate and massively reduces the residual solvent. Yamamura et al 14 found increment in the evaporation of solvent methyl ethyl ketone from cellulose acetate butyrate coating using a fluorine based surfactant Megaface at 316 K. The literature on several additives for modifying drying behavior of polymeric coatings is summarized in Table 1.…”

mentioning

confidence: 99%

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Design of low cost waterborne polyvinyl alcohol coatings using plasticizer polyethylene glycol to minimize the residual solvent and coating defects

Rawat

2022

Waterborne coatings provide nontoxicity and flame-retardance but exhibit inefficient drying. The literature on drying enhancers is limited for the want of residual solvent minimization study. Here, we use polyethylene glycol-6000 (PEG), a low cost biodegradable plasticizer, to minimize the residual solvent in polyvinyl alcohol (PVA)-water coatings. Coatings were prepared at different PEG loadings (0, 0.50, 1.00, 2.50, 5.00, and 7.50 wt%) and initial conditions.The maximum drop in the residual solvent was 87% at 0.50 wt% PEG loading in the coating of initially 5% PVA and 1000 μm thickness. The effect of doubling the initial wet thickness from 500 to 1000 μm was first examined. The minimum residual solvent significantly reduced from 1.30% to 0.59%, and occurred at the same PEG loading of 0.50 wt%. However, the drying time increased and drying rate slowed down remarkably. SEM results also revealed that at the optimum PEG loading a smooth and dense coating was obtained. Thermogravimetric analysis/derivative thermogravimetric studies showed improved thermal stability and differential scanning calorimetry showed little decrease in T g at optimized PEG loading. When the initial polymer concentration was doubled from 5% to 10%, the optimum PEG loading lowered from 0.50 to 0 wt%. Simultaneously, a marked increase in the minimum residual solvent from 1.30% to 3.27% occurred, caused by the hydrophilicity of PVA and enhanced solution viscosity. On comparison with a fluorosurfactant (FS) modifier, PEG yields significantly better maximum reduction in residual solvent at substantially lower optimum loading by employing higher wet film thickness. Furthermore, PEG is significantly lower in cost and environmentally friendly than FS.

Comparison of the performances of different drying enhancers for waterborne polyvinyl alcohol films

2023

Waterborne polyvinyl alcohol (PVA) films show lower environmental impact but render high residual solvent on account of hydrophilicity of PVA and low volatility of water. Plasticizers have shown high potential to act as drying enhancers in some recent studies. Plasticizers triphenyl phosphate (TPP) and polyethylene glycol (PEG400) with their favorable chemical structures and relatively low molar masses are promising options. Their performances in drying waterborne PVA films are compared with the plasticizers used in earlier works, at different initial wet film thicknesses, polymer contents, enhancer contents, and enhancer molar masses. Films were solvent casted by drying PVA‐water solutions in a substrate. TPP causes maximum lowering of the residual solvent and does this at high drying rate corresponding to low initial wet film thickness and PVA content. The least value of residual solvent is 0.20% at optimum TPP loading. The next best residual solvent results of 0.21% and 0.59% are, respectively, exhibited by PEG400 and PEG6000, but at low drying rate for high wet film thickness, for both the enhancers; however, at high drying rate for low wet film thickness anomalous skinning increased the residual solvent. At 0.51%, Capstone FS‐63 also gives good results and at high drying rate. Their relative performances are correlated to the viscosity of cast solutions, glass transition temperature of films (DSC), and chemical structures of the polymer and enhancers. TPP thus proved to be most effective. SEM showed dense films and disappearance of defects with optimum loading of TPP, and TGA/DTG showed thermally stable coatings. In spite of the higher cost of TPP it can have useful specialized applications that exploit its excellent flame retardance features.