Research On Influencing Factors Of Drying Rate And Film Properties Of Waterborne Polyurethane For Furniture

The waterborne wood lacquer has many advantages such as non-toxic,safe and environmentally friendly.However,at present,there are still gaps in the core technology of waterborne lacquer film formation and curing between China and foreign countries,in which the finishing technology and drying technology have to be further improved and developed,while finishing and drying processes are key technical links in the manufacture of furniture.In this paper,the effects of paint,substrate,finishing process and drying process on the surface drying time,hard drying time and coating film hardness,adhesion and wear resistance of waterborne polyurethane paints were systematically studied to clarify the effects of the resin,substrate type,finishing process,and the drying process on the film drying and film quality.The research results of this paper are summarized as follows:1)The surface drying time and hard drying time of the paint and the hardness,adhesion and abrasion resistance of the coating film are greatly affected by the properties of the film-forming resin.Under the test conditions,M1 has the slowest drying speed at 50°C and 50% relative humidity,and there is no difference between M2 and M3;coating film hardness and adhesion of M2 are better than M3,respectively reaching 2H and 0 grade,M1 and M3 are all H and 1 grade,but the wear resistance of M2 coating film is slightly poor;the surface smoothness of M2 and M3 coating film is relatively good,and the thermal stability of M2 coating film is better.Comprehensive comparison,M2 is better than M1 and M3.2)The substrate affects the drying rate of the paint,the hardness and adhesion of the coating film,but has little effect on the abrasion resistance of the coating film.Among them,M2 has the fastest drying speed on Fraxinus mandschurica veneer plywood and Prunus serotina Ehrh.veneer plywood,followed by Quercus rubra veneer plywood,slightly slower on Quercus alba and Entandrophragma cylindricum veneer plywood;After drying,M2 on Prunus serotina Ehrh.,Entandrophragma cylindricum veneer plywood and Fraxinus mandschurica veneer plywood has the best hardness of the coating film,up to 2H,followed by Quercus alba and Quercus rubra veneer plywood,which is H;The adhesion of the coating film on Prunus serotina Ehrh.veneer plywood,Entandrophragma cylindricum veneer plywood and Quercus rubra veneer plywood is the best,grade 0,followed by Fraxinus mandschurica and Quercus alba veneer plywood,grade 1;The difference in abrasion resistance of the coating film on the upper surface of different substrates is not obvious;after the substrates was coated with the primer,the surface flatness is deteriorated,and after the finish paint is applied,the surface flatness is improved.3)The finishing process has no obvious effect on the surface drying time and hard drying time of the paint,but it affects the actual operation time and production efficiency,and has no obvious influence on the hardness,adhesion and abrasion resistance of the coating film.The hardness and adhesion of the coating film on the “one bottom one side”,“one bottom two sides” and “two bottom two sides” process are 2H and 0,respectively,but the coating film abrasion resistance is not much different;after three kinds of crafts,there is little difference in the flatness of the coating film surface.For the sake of comprehensive consideration,it is recommended to use the “one bottom and two sides” finishing process.4)As the drying temperature increases or the relative humidity decreases,the surface drying time and the hard drying time of the coating film decrease in turn,and the relative humidity has a more obvious effect on the surface drying time of the coating film.Under different temperature conditions,the primer drying time(BI),topcoat finish(SI)and secondary finish(SII)are extended in the dry time,and the drying time difference between SI and SII is decreased gradually after the drying temperature is increased.Compared with the drying temperature,the difference of water volatilization speed of BI,SI and SII in the early drying stage is more obvious under different relative humidity.The drying temperature and relative humidity have no obvious effect on the hardness and adhesion of the coating film.After drying at different temperatures and humidity,they are 2H and 0 grades respectively;the loss of 100-turn coating film loss gradually increases with the increase of drying temperature and relative humidity.