Preparation And Performance Study Of Room Temperature Fast-curing Epoxy Coating

The hydroxyl and ether bonds give the epoxy coating good adhesion to the matrices,excellent chemical resistance,and high bond strength.It is limited in practical use in the direction of paint because of the slow curing and high viscosity of epoxy resin at room temperature and other shortcomings.Moreover,with the development of carbon neutrality,the importance of environmental protection is increasingly growing.Due to its high VOC emissions,traditional solvent based coatings have gradually been phased out and replaced by water-based,solvent-free coatings.Therefore,solvent-free epoxy coating with fast curing at room temperature(RT)has become one of the important research directions.To solve the problem of long curing time and low efficiency of solvent-free epoxy coatings at RT,in this work,on the one hand,the curing agent was modified to improve reaction activity and to accelerate the curing rate at RT;on the other hand,introducing highly active functional groups into the resin can improve the activity of and accelerate the curing speed of the resin.The main work of this paper is as follows:(1)Using thiourea,ethylenediamine and 2,4,6-tris(dimethylaminomethyl)phenol(DMP-30)as raw materials,an epoxy curing agent that can quickly crosslink epoxy resin coating at room temperature was prepared.The effect of reaction conditions such as raw material ratio,reaction temperature and reaction time on the curing effect was investigated,and the structure,amine values,viscosity,curing time and thermal stability of the product were characterized.The results showed that when the raw material ratio of n(thiourea):n(EDA):n(DMP-30)was 1.2:1:1.2,the reaction time was 42 min,the reaction temperature was 120℃and the viscosity was 56800 m Pa-s,the E-51 coating could be cured rapidly within 45 min,achieving a fast curing effect at room temperature;when the temperature reached 80℃,the TED curing agent started to decompose,and when the temperature reached 300℃,the curing agent lost 50%of its weight,and its thermal stability performance was good.(2)Epoxy acrylate was modified with an allyl functional group and the preparation process of epoxy acrylate(EA)was investigated.At the same time,due to the high viscosity of EA,ethylene glycol/methacrylic acid-modified epoxy resin was used to prepare epoxy acrylate(EA*)with low viscosity.The results showed that the reaction temperature was 100℃,the accelerator content was 1 wt.%,the molar ratio of an epoxy group to methacrylic acid was 1:0.95,and the polymerisation inhibitor was p-hydroxyanisole.When ethylene glycol was used as a modifier,the reaction temperature was 95℃,the promoter content was 0.2 wt.%,the molar ratio of epoxy resin to modifier was 1:0.2,EA*was obtained and the viscosity of epoxy acrylate decreased from2870 m Pa·s to 1890 m Pa·s.Epoxy varnish was prepared with EA*and E-51 as the main resin,diluent and additive were added,and the epoxy coating curing fast at room temperature could be prepared by the reaction of varnish and curing agent TED.When the content of EA*is 10 wt.%and the content of the hardener is 40 wt.%,the gel time of the varnish is 3.8 min and the surface drying time is 57 min.Pencil hardness is 3H-4H,adhesion is 5.5 MPa,glossiness of 60°is183.7,solid content is 99.4%,5%mass loss temperature is 402℃,and water contact angle is 94°.The flexural strength of the painted body is 0.7 MPa.Impact strength is 47 k J/m~2.(3)Solvent-free epoxy road marking coatings with fast curing at room temperature were prepared using solvent-free epoxy varnish as the base material,Shuangfei powder(commercially available)as the filler and titanium dioxide as the pigment.The effects of filler content and hardener content on the curing properties,mechanical properties and water absorption properties of the coatings were investigated.The results show that when the m(filler):m(base)ratio is 1:1,the content of titanium dioxide is 3 wt.%and the content of TED curing agent is 25 wt.%,the gel time of the coating is 3.5 min and the surface drying time is 50 min.The hardness of the pencil after curing is>6H,the adhesion is 6.4 MPa,the tensile strength is 9.3 MPa,the 60°gloss is103.2 and the solids content is 99.7%.The coating’s elongation at break,flexural strength and impact strength were 4%,1.4 MPa and 54.7 k J/m~2 respectively.The coating in saturated calcium oxide and 5%Na Cl did not blister or delaminate within 24 h.