Self-healing polyurethane (PU) material, double-layer self-healing PU film, and preparation method and use thereof

A method for preparing a double-layer self-healing PU film, wherein the double-layer self-healing PU film comprises a soft-layer PU film arranged on a surface of a matrix;

• and
• a hard-layer PU film arranged on a surface of the soft-layer PU film,
• wherein the soft-layer PU film is prepared from a PU material I of a self-healing PU material;
• and the hard-layer PU film is prepared from a PU material II of the self-healing PU material;
• the PU material I is prepared from raw materials comprising a polyol substrate I, a diisocyanate I, a tin-based catalyst I, a T-type chain extender, and a chain extender I at a molar ratio of (10-20):
• (20-40):(1-3):(2-8):(8-12);
• the PU material II is prepared from raw materials comprising a polyol substrate II, a diisocyanate II, a tin-based catalyst II, the T-type chain extender, a metal salt, and a chain extender II at a molar ratio of (10-20):(20-40):(1-3):(5-10):(2.5-10):(5-10);
• a metal ion in the metal salt being one or more selected from the group consisting of Zn2+, Cu2+, and Fe3+;
• the polyol substrate I and the polyol substrate II each are independently selected from the group consisting of a polyester polyol and a polyether polyol;
• and
• the T-type chain extender has a structure represented by formula A:
• and
• the method comprises the following steps:
• subjecting a feed solution comprising the polyol substrate I, the diisocyanate I, and the tin-based catalyst I to prepolymerization I to obtain a prepolymerization product system I;
• mixing the prepolymerization product system I with a solution of the T-type chain extender to obtain a first mixture, and subjecting the first mixture to chain extension I-I to obtain a chain extension product system I-I;
• and mixing the chain extension product system I-I with the chain extender I to obtain a second mixture, and subjecting the second mixture to chain extension I-II to obtain the PU material I;
• subjecting a feed solution comprising the polyol substrate II, the diisocyanate II, and the tin-based catalyst II to prepolymerization II to obtain a prepolymerization product system II;
• mixing the prepolymerization product system II with a solution of the T-type chain extender to obtain a third mixture, and subjecting the third mixture to chain extension II-I to obtain a chain extension product system II-I;
• mixing the chain extension product system II-I with a solution of the metal salt to obtain a fourth mixture, and subjecting the fourth mixture to coordination to obtain a coordination product system;
• and mixing the coordination product system with the chain extender II to obtain a fifth mixture, and subjecting the fifth mixture to chain extension II-II to obtain the PU material II;
• and
• coating the PU material I onto the surface of the matrix to obtain a PU material I film, and subjecting the PU material I film to drying I to obtain the soft-layer PU film;
• and coating the PU material II onto the surface of the soft-layer PU film to obtain a PU material II film, and subjecting the PU material II film to drying II to obtain the hard-layer PU film, thereby forming the double-layer self-healing PU film on the surface of the matrix.