| Wood coatings can protect the wood products and improve their surface appearance.Traditional wood coatings contain lots of organic solvent,which shows significant threaten to the atmospheric environment and health of the workers.Water-based wood coatings developed rapidly recently,but it has some disadvantages like the poor physical properties of the coating film,low painting efficiency,and slow drying speed.UV curing coatings has excellent coating properties,but the viscosity is large,which is difficult to use in painting on complex wood parts.Therefore,this paper aimed to improve the coating properties and film forming speed of waterbased coating,by analyzing the effects of water-based UV curing resin,film-forming additives,defoamer,and photoinitiator types on the coating properties of water-based UV curing wood coating were investigated,a kind of fast water-based UV curing wood coating was developed.The effects of coatings amounts and temperature on the water drying time and coating properties were studied.Besides,the surface morphology of the coating after drying was observed,and the permeability of coating in wood,chemical groups changes before and after drying,and the surface free energy were further characterized.The main conclusion were as follows:(1)A kind of fast water-based UV curing wood coating was preliminary obtained.In the coating system,adding defoamer of polyether siloxane copolymer,photoinitiator of 2959,and surfactant of organosilicon twin structure,and matting agent of ED30 showed the best coating film properties.The prepared coating has good coating properties.The adhesion level of 0-1,namely,the coating film was smooth without peeling.The pencil hardness was 2H-3H,and the abrasion value was ≤0.05g/100 r,where the film had not been wear out.The heavy metal,formaldehyde,benzene series,diethyl ether,and esters were not detected.The TVOC value was only 22 g/L,which showed excellent environmental performance.(2)With decreasing coating solid content,the effects of coating thickness on the real drying time of coating gradually increased.In case of the same coating thickness,the larger solid content,the less water drying time and the more effective evaporated water were achieved.With increasing coating thickness,the drying time increased,but gaps were found among water evaporating rates.When drying,the evaporation rate of water was too fast,the surface of the coating will be whitened,the hardness and adhesion will decrease,and the drying of the coating should control the evaporation rate of water.(3)The effect of temperature on drying time is significant.In the range of 35 ℃ —65 ℃,the surface drying time,Hard drying time and complete drying time of the coating film decrease with increasing temperature.When wet film thickness of 60μm with 35°C,the surface drying time is between 90-120 s,Hard drying time is 4min,and the complete drying time is 20min;when the temperature is raised to 65°C,the wet film surface drying time is Between 30-60 s,Hard drying drying time is 1-2min,and the complete drying time is shortened to 6min.The total dry time is much longer than the time spent on the hard work.When the temperature is raised above 55 °C,pinholes and fine bubbling appear on the surface of the coating film.(4)As the coating amount increases,the hydroxyl groups in the wood react with the coating to form hydrogen bonds or ester bonds.(5)The contact angle of water droplets on the surface of coated specimens increases with the increase of coating amount,but when uniform and continuous coatings are formed on the surface,the influence of coating amount on the contact angle is not significant;the surface coverage and smoothness of the specimens gradually increase with the increase of coating amount,and the grooves and convexities of the wood surface are filled continuously,but the back of the coating gradually appears holes and there are obvious bubbles in the coating.On the surface of the substrate,a small amount of penetration penetrates into the substrate,the maximum penetration depth is 35 micron,but the permeability of the coating does not change significantly with the increase of coating amount. |
