Effect Of Some Additives On Curing Behavior Of Raw Lacquer

Lacquer,also known as national lacquer,has more than 8,000 years of use in China.Due to excellent durability and corrosion resistance,it is known as the"king of coatings".However,there are also some deficiencies in raw lacquer,such as long drying time,harsh film-forming conditions,deep color and prime cost,which limits the promotion and application of raw lacquer.Domestic and foreign scholars have done a lot of work to solve problems,such as long curing time,dry conditions and so on.The problem of polymerization of raw lacquer during harvesting and storage still exists.This thesis aims at the problem of waste of raw lacquer conjunctiva and deep color.Auxiliary were used to analyze the curing behavior of raw lacquer,which include the inorganic salt,glycerol and antioxidant and so on.The main work is as follows:(1)Using inorganic salts mixed with refined lacquer,such as chloride,carbonate,sulfate,exploring the effect of curing behavior and performance of refined lacquer.The curing process of lacquer was analyzed by FT-IR,NMR,ESR and so on.The results show that the polymerization rate of lacquer is slowed down and the relative activity of laccase of modified lacquer is reduced after adding inorganic salts.Among them,at 25°C,RH=80%,when the amount of Na₂CO₃ is 0.82 wt%,the drying time of the lacquer is prolonged to 15 days,and the relative activity of laccase drops by 30%.When the ratio of0.41 wt%:0.41 wt%of Na Cl and Na₂CO₃ were added,the drying time of the lacquer was shortened from 89 h 36 min to 9 h,and the gloss was increased from 55.1 to 80.2.The comprehensive performance of the modified films was not significantly affected.(2)By adding glycerol and antioxidant to modify lacquer,the environmental temperature and humidity and formulation ratio on the curing speed of the lacquer during the curing process.The results showed that the addition of glycerol and antioxidants promote drying,increasing apparent viscosity,the micro-morphology is a porous structure.Among them,when m _{propylene glycol}:m _{refined lacquer}=6.5:10,the drying time of film was best.Under 35°C and RH=80%,LG4 had touch drying time of 1 h,a hardening drying time of 3 h 24 min,and the porous structure of the film is even more uniform,and the surface hydrophilic performance of the film is enhanced.After adding gallic acid,the color of the modified film was lightened obviously after 3 months at 40%relative humidity.The apparent viscosity and thixotropy of the modified lacquer increased with the addition of glycerol and antioxidant.(3)Salicylaldehyde Schiff base ligands and copper complexes were synthesized from salicylaldehyde,amine compounds and copper sulfate.Studies have shown that the drying time of the modified lacquer is shortened as the added amount increases.Among them,in addition to the salicyldaldehyde dientine(SED),other modified lacquer did not improve the drying performance of lacquer under normal temperature natural conditions.Under high temperature conditions,the addition of Schiff base and its copper compounds improves the thermal polymerization properties of the lacquer.When 7 wt%SED and 5wt%SPP-Cu were added,the curing speed of the modified paint was increased by 3times.After adding 1 wt%SOP,SED-Cu and SPP-Cu,the gloss of the modified film is101,102 and 104.The addition of ligand and its copper complex makes the surface of the modified film more compact and the surface hydrophobicity increased.