Mussel-bionic composite coatings based on biomass polyurethane and its adhesive mechanisms of humid interface with cementitious materials

The humid adhesive of the concrete protecting coatings has been a common problem and faces challenges in underground, ocean, bridge and tunnel engineering, and its adhesive mechanisms of humid interface with cementitious materials have little scientific backing. In this study, the bionic composite coatings based on biomass polyurethane were fabricated by utilizing catechol chemistry of mussels and coordination crosslinking strategy for enhancing the humid adhesive properties. The environmentally benign biomass polyurethane (PU) derived from epoxidized soybean oil were synthesized by the prepolymerization method through hydroxylation and stepwise polymerization. The chemical grafting of dopamine (DA) combined with coordination crosslinking of Mn2+ strategy was employed for the composite modification of the Biomass PU. The effect of molar ratios of DA and Mn2+ on the tensile and thermal properties, water resistance, crystallinity, UV aging, molecular structure, morphology of the Biomass PU and its adhesive strength with cementitious materials were investigated. The pull-off testing results show that the optimum dry and humid adhesive strength between the coating and cementitious materials are 9.08 MPa and 9.47 MPa respectively when the molar ratio of DA/Mn2+ is 2:1, which increases by 29.34 % and 90.93 % compared with pristine biomass PU. The synergistic effect of catechol moieties and Mn2+ in enhancing the cross-linking and promoting the hydration film drainage combined with interfacial interaction has been demonstrated. These insights can be feasible for designing high performance polymer coatings with excellent humid adhesive properties and also can boost the development of biomimetic science in concrete protecting and repairing.