Preparation and properties of self-healing polyurethane wood coatings with borate ester bonds
Polyurethane(PU)is a common polymer material,which is a multiblock copolymer prepared by the addition reaction of organic isocyanates and polymer polyols.Its performance is between plastic and rubber,with characteristics of high hardness,good elasticity,oil resistance,wear resistance,low temperature resistance,and aging resistance.It is widely used in the fields of construction,automotive,aviation,insulation,footwear industries,and home furnishings,and also used as raw materials for making adhesives and coatings.Polyurethane coatings have the advantages of strong adhesion,wear resistance,scratch resistance,good glossiness,and high decorative performance,playing an important role in wood and automobile industries.However,PU coatings are prone to damage and produce microcracks during long-term service.When microcracks are exposed to corrosive media such as air,water,and salt,the diffusion of mi-crocracks is accelerated,significantly reducing the protective and aesthetic properties of coatings.Self-healing coatings can extend the service life.In this study,firstly,diethanolamine(DEA)and 4-methyl phenylboronic acid(HPBA)were used to prepare borate ester bond compound with hydroxyl and amino terminated groups(NCBC).Boric acid ester bond compounds with hydroxyl terminated at both ends(MN)were subsequently prepared via the reaction between NCBC and 4,4-diphenylmethane diisocyanate(MDI).Then,self-healing polyurethane(PU)and its coatings were pre-pared with polytetrahydrofuran(PTMEG-1000),using MDI as raw materials and MN as chain extender.The elemental analysis,1H nuclear magnetic resonance and Fourier transform infrared spectroscopy structural analysis proved that NCBC and MN compounds were successfully prepared,and NCBC had good water resistance.The results showed that the introduction of MN(n(MDI)∶n(NCBC)=1∶2.0)into polyurethane provide wood coatings with high strength and good self-healing properties.The tensile strength of self-healing PU was 6.06 MPa,and the tensile strength after repai-ring was 5.47 MPa,with the self-healing efficiency was 90.2％.The pencil hardness of polyurethane coating on the sur-face of wood can reach up to 3H,the adhesion level was Lever 0,the impact resistance was greater than 50 cm,and the flexibility of film was 2 mm.The scratches on the film surface were completely healed after being repaired at 60 ℃ for 12 h,indicating that the self-healing polyurethane coating has good self-healing performance.
万方数据
维普
