Preparation And Properties Of Self-healing Elastomer From Poly(pseudo)rotaxane Modified Waterborne Polyurethane

Waterborne polyurethane（WPU）has attracted the attention of all walks of life in recent years with the advantages of green and environmental protection.The application of polyurethane materials has gradually shifted from traditional adhesives,coatings and other fields to biological,electronic and other high-tech fields,which undoubtedly puts forward higher requirements for the performance of WPU materials.However,at present,waterborne polyurethane materials mainly have the following shortcomings:on the one hand,due to the existence of hydrophilic groups in its structure,its hydrophobic properties are poor compared with solvent polyurethane,and its mechanical properties need to be improved;On the other hand,in order to meet the needs of various products,WPU needs to be endowed with functionality.Therefore,the preparation of high strength and high toughness self-healing waterborne polyurethane elastomer can reverse the disadvantages of waterborne polyurethane and expand its application prospect.In the first part of this paper,the modification of WPU was studied by pseudopolyrotaxane（PPR）.The effects of copolymerization and blending on the mechanical properties,surface properties and thermal stability of waterborne polyurethane were studied in this paper.Compared with the elastomer prepared by blending,the toughness of waterborne polyurethane prepared by copolymerization can reach 142 MJ/m³ and the contact angle can reach 105°,indicating that the modification of WPU in this way can improve its mechanical and hydrophobic properties.The effects of different PPR content on the properties of copolymerized waterborne polyurethane were studied.When the mass fraction of PPR is 5 wt%or more,obvious agglomeration can be seen from the cross-sectional morphology of elastomer,which has an adverse impact on the properties of elastomer.In addition,the host guest interaction and hydrogen bond interaction in PPR give waterborne polyurethane good self-healing properties.In the second part of this paper,aqueous polyurethane self-healing elastomer was prepared by the synergistic effect of tannin（TA）and PPR.By introducing hydrogen bond and coordination bond,the self-healing ability of waterborne polyurethane is improved while maintaining good mechanical properties and hydrophobic ability.The effects of tannin on the mechanical properties,surface properties and self-healing properties of waterborne polyurethane were studied.The infrared results showed that the abundant hydroxyl groups in tannins could enhance the hydrogen bond interaction in polyurethane system.After tannin was introduced into waterborne polyurethane and coordinated with Fe³⁺,the tensile strength increased from 38 MPa to 46 MPa,while the change of contact angle was small.The self-healing test showed that after the tannin modified waterborne polyurethane healed at 100℃for 36 hours,compared with the original polyurethane,its self-healing efficiency increased from 56%to 90%.The coordination of Fe³⁺with tannin further promoted the improvement of healing ability,and its self-healing efficiency could be increased to more than 95 wt%.In this paper,pseudopolyrotaxane modified waterborne polyurethane is systematically explored,which has theoretical and practical significance for the application of waterborne polyurethane in a wider field.