Study On Adhesive With Fast-speed Curing At Room Temperature And High Adhesive Force

Polyurea adhesive widely used in the field of construction and anticorrosion show high mechanical performance, excellent corrosion resistance, environmental friendliness and fast-speed curing. However, the poor adhesive force to metals and bad filling capability limit its application in functional paints such as radar absorbing coatings. Therefore, improving its adhesive force to the metals and filling capability become a key problem.This paper systematically studies the factors effecting on adhesive force of polyurea. Firstly, a modified polyurea adhesive was prepared by prepolymerization of a steric-type curing agent-aromatic amine terminated polyether and the HDI. The effect of mass ratio for A,B part and the degree of hydrogen bonding on the mechanical properties was studied. The results showed that the introduction of steric curing agent can effectively improve wettability of the coating to the substrate, lower the number of hydrogen bonds between moleculars within the coating, and raise the number of free hydrogen bonds, effective increasing the adhesive force of polyurea up to 25.98 MPa; Secondly, another steric-type curing agent-polyaspartic acid ester-polyether was prepared by Michael Synthesis. The effect of chain length of the polyether on the gelling time and adhesive performance was studied. The results indicated that increasing of the chain length of the polyether, gelling time was also extended and the coating exhibited good wetting effect. Nevertheless, its adhesive performance was poor. The reason is that the polyaspartic acid ester-polyether is a secondaryamine-type curing agent, which greatly reduces the overall polarity of the adhesive system as well as the number of active binding sites between the coating and the substrate. Through the above research, it is clear that to improve adhesion of polyurea adhesive, the gelling time should firstly be prolonged, which improves the wettability, and then increase the number of free polar functional group in the adhesive system.Based on above studies, the epoxy-polyurea adhesive was prepared by introducing the epoxy adhesive abundant in free polar hydroxyl groups to the polyurea adhesive system. The effect of epoxy resin content on mechanical properties of the adhesive was studied, and the relationship between the structure and the property of the adhesive was established via the dynamic mechanical analysis and the microstructure analysis. The results showed that, when the epoxy content was below 50%, the adhesive reached 38.79 MPa, combining both the fast curing of the polyurea and the high adhesion of the epoxy. Meanwhile, the coating had a good impact resistance and flexibility. The filling resistance of the adhesive was good and the volume filling ratio of the filler went up to about 30%. Dynamic mechanical analysis and microstructure analysis suggested that the adhesive formed the IPN structure with good compatibility.This research provides a practical basis and a possible way for introducing RAC into the polyurea adhesive. RAC adhesive was prepared with high strength, high toughness, high filling ratio, and fast surface drying, laying a practical foundation for radar absorbing coatings.