Numerical Simulation Of Solvent Diffusion Process During Drying Of Coated Fabrics

Different from the impermeable substrate,fabric is porous fiber material.In order to study the diffusion mechanism of solvent in the curing process of coating porous materials,two-dimensional and three-dimensional solvent diffusion models of polymethylmethacrylate / acetone coated glass fiber fabrics were established based on the heat transfer equation,Fick diffusion equation and the relationship equation of coating solution volume with time.This drying model was verified by confocal Raman spectroscopy.Finally,the effects of coating thickness,solvent mass fraction,drying temperature,air velocity,fabric texture,fabric thickness and porosity on the solvent diffusion process in coated fabrics were studied by three-dimensional pore model.The conclusions were as follows:(1)The predicted values of the two-dimensional model and the three-dimensional model were consistent with the experimental values of Raman measurement.They can be used to quantitatively calculate the solvent concentration at any position and at any time in the drying process,and can predict the curing time,residual solvent concentration and coating thickness at drying equilibrium.However,the twodimensional model can’t reflect the effect of pore structure on solvent diffusion,so it is necessary to establish a three-dimensional pore model to study the effect of different pore shapes on solvent diffusion.(2)The thicker the initial coating thickness was,the slower the solvent diffusion was,and with the increase of the initial coating thickness,the longer the drying time was,the thicker the drying thickness was at equilibrium.Using the diffusion model of solvent in the drying process of coated fabric,the relationship between the initial coating thickness and drying equilibrium time and the drying coating thickness can be obtained,thus the drying equilibrium time and drying coating thickness corresponding to different initial coating thickness can be obtained.(3)The higher the solvent concentration,drying temperature and wind speed,the faster the solvent diffusion in the coated fabric system,and the shorter the drying equilibrium time.However,when the solvent mass fraction is higher than 80%,the drying temperature is higher than 80 ℃ and the wind speed is higher than 1.0278 M /s,the drying equilibrium time in the system is not significantly shortened.For PMMA acetone coated fabric system,it is suggested that the solvent mass fraction is 80%,the drying temperature is 80 ℃,and the drying air speed is 1.0278m/s.(4)When the yarn density and warp / weft density of the fabric are fixed,the diffusion rate of solvent in the coated fabric is 3 / 1 twill < 5 / 3 satin < 2 / 1 twill <plain weave,that is,plain fabric is conducive to solvent diffusion.Under the same environmental conditions and initial solvent concentration,the thinner the fabric was,the greater the porosity was,and the shorter the curing time was.The equation of fabric thickness and porosity to drying time was obtained,which provides a theoretical basis for industrial production.