| Most emulsion-type paint removers involving large amounts of organic solvents,which harm the environments and human health,can be volatile during their process and application.Besides,the paint strippers appear very strong acidity or alkalinity to lead the unstable performance and the phase separation after long term storage as result of poor removal effect.Therefore,it is of great significance to develop one kind of paint remover which is highly efficient,stable and environmentally friendly.The oil phase components of the paint remover which are the decisive factor that affects the paint removal efficiency were studied firstly.Based on the results of the single-factor experiment and orthogonal experimental design,dichloromethane was selected as the main solvent and anisole and benzyl alcohol as the co-solvents.The mixed oil phase could remove completely the polyurethane paint within 40 minutes and the epoxy resin paint within 1 hour.The effects of the oil-water ratio,the type and content of additives,and the shear rate during emulsification on the paint removal efficiency and stability were studied to screen out the optimal conditions for preparing paint remover.The paint remover emulsified at 600 rpm showed a relatively good performance at the oil-water mass ratio of 6: 4,when it was thickened by methyl cellulose and hydroxypropyl methylcellulose.Besides,the prepared paint remover was rich in water-soluble components and had a water content of up to 40%,making the paint remover components more environmentally friendly.Compared with emulsions stabilized by commonly used surfactants like ionic and non-ionic surfactants,the prepared emulsion stabilized by cetyltrimethylammonium bromide,polyvinylpyrrolidone and nano-silica was more stable and it would remain stable for more than one month.Moreover,the thickened paint remover would not show obvious phase separation within three months.Comparing the stability of the emulsion after one month,it was found that as the content of CTAB in the system increased from 1.2 × 10-4 wt.% to 1.2 ×10-1 wt.%,the extent of emulsion coalescence decreased by 20%.Zeta potential of the aqueous dispersions showed that an increased concentration of CTAB could cause nanoparticles towards higher hydrophilicity because of the double layer adsorption.Therefore,H30 particles were more easily desorbed from the network structure formed by themselves and then adsorbed to the oil-water interface,increasing the stability of the emulsion. |
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