Preparation And Characterization Of Aqueous Polyurethane Coatings Containing Functional Materials

Polyurethane material is a kind of multi-purpose synthetic material with many product forms,which has the advantages of great modification potential and easy functionalization.At present,it is widely used in foam plastics,coatings,fibers,adhesives,waterproof materials and other products.Emulsion is a typical research field of polymer materials science.After a long period of research,it is mature and easy to be functionalized.The emulsion is thermodynamically unstable,and the coating can be prepared by using this instability.Based on this instability,our research group proposed a brand-new coating preparation method,namely demulsification-induced fast solidification（DIFS）.1.Study on preparation of flame retardant coating:In order to prepare flame retardant coating on a large scale,RE-906 PUA tackifying emulsion was selected to prepare the coating,and microencapsulated red phosphorus（RP）and aluminum hydroxide（ATH）were added into the emulsion as additive flame retardants,and the addition amount of flame retardant was gradually increased.Finally,the maximum addition amount of RP and ATH was determined to be 20 wt%and 40 wt%.The flame retardant coating was prepared by DIFS method,and the thickness-time curve of the coating was studied.The impact resistance and adhesion of the coating were tested under different flame retardant types and content.The results showed that the impact resistance could reach 100 cm.It was found that the adhesion of the coating was related to the drying degree of the coating,and the adhesion increased with the drying time.At the maximum content,the limiting positive index（LOI）of the coating was tested,and the LOI of RP was 26.4%and the ATH.Comprehensive comparison shows that the adhesion of ATH is low at the initial stage,and the LOI value of RP is low.Finally,we chose to use both RP and ATH flame retardants to modify 906 emulsion to make up for each other’s shortcomings.Finally,we determined the best mixing ratio of ATH 20 wt%+RP 10 wt%,and drew the thickness-time relationship diagram.The impact resistance was 100cm,the adhesion reached Grade 3,and the LOI value reached 30.4%.Finally,we prepared large-area flame retardant coatings of 20*20 cm²and 2*2.2m².2.Study on preparation of superhydrophobic coating:Water-borne polyurethane emulsion was prepared with isophorone diisocyanate（IPDI）and polybutylene adipate diol（PBA）as main synthetic raw materials,and carbon nanotubes（CNTs）were treated with nitric acid to prepare carboxyl groups on CNTs,thus realizing hydrophilization of CNTs.The treated CNTs-COOH was ultrasonically dispersed in water,and the aqueous solution containing CNTs-COOH was added to the synthesis system in the water emulsification stage of water-borne polyurethane synthesis.Then,a polyurethane coating containing CNTs was prepared on the surface of metal materials by using DIFS method combined with electrochemical method.Polyurethane materials were used as matrix materials,and CNTs existed as materials to provide roughness at microscopic level.Finally,the surface of polyurethane coating containing CNTs was modified with the mixed solution of perfluorooctyltriethoxysilane（POTS）and anhydrous ethanol,and finally the superhydrophobic coating was prepared.On this basis,the super-hydrophobic coating was patterned by laser etching to realize the directional flow of water droplets.3.Research and preparation of information encryption coating:water-borne polyurethane was synthesized with IPDI and PBA as raw materials,temperature-sensitive probe molecule EU（DBM）₃ Bipy was synthesized with Eu Cl₃,DBM and bipy as raw materials,and 1,8-diaminonaphthalene and 1-aminoanthraquinone were used as fluorescent materials.All the three materials were ultrasonically dispersed in water in advance and added to the reaction in the emulsification stage.Temperature-sensitive coatings and two kinds of fluorescent coatings can be prepared respectively.Based on the advantages of DIFS method to prepare coatings on metal surface,laser etching combined with DIFS method was used to combine two kinds of fluorescent coatings,super-hydrophobic coatings and temperature-sensitive coatings,and several groups of eight-bit binary codes were designed to prepare information encryption coatings.Finally,polyurethane coatings with information encryption function were prepared in the form of binary lattice.