Studies On Preparation And Performance Of High-performance Self-healing Polyurethane

Polyurethane materials have the characteristics of easy structure control and excellent physical properties,and have been widely used in auto parts,coatings,home appliances,aerospace and other fields.Polyurethane materials cannot avoid physical damage caused by external forces during use,which will reduce the safety of the materials and shorten the service life of the materials.Self-healing material refers to a material that can repair its own physical damage and restore its original performance under specific conditions or spontaneously.If the self-healing ability of polyurethane materials can be given,it will be of special significance to further expand the application breadth of polyurethane materials,but how to design self-healing polyurethane materials with excellent mechanical properties and excellent self-healing efficiency is an urgent problem to be solved.In this paper,from the perspective of structural design of polyurethane materials,a series of high-strength self-healing polyurethane materials were prepared by introducing the quadruple hydrogen bond structure with high binding energy and excellent dynamic properties into the polyurethane system.The introduction of the quadruple hydrogen bond structure greatly improves the mechanical properties of the polyurethane material,and also endows the material with a thermally responsive self-healing ability.On this basis,we introduced the Diels-Alder chemical cross-linking network into the system.Based on the synergistic effect of the two dynamic networks,we finally obtained a self-healing polyurethane material with both ultra-high strength and high repair efficiency.In addition,we also explored the application potential of quadruple hydrogen bonding in bonding materials.The main research contents and conclusions of this paper are as follows:1.Self-healing polyurethane materials with a quadruple hydrogen bond networkWe prepared a series of self-healing polyurethane materials with dynamic cross-linked networks by introducing quadruple hydrogen bonding units(UPy)as chain extenders into the polyurethane backbone.The study found that with the increase of the quadruple hydrogen bond density,the interaction force between the polyurethane molecular chains gradually increased,and the mechanical strength also increased.The result of a physically cross-linked network.The quadruple hydrogen bond structure can also act as an energy dissipation unit when the material is subjected to external force,and its dynamic fracture and reorganization greatly improves the toughness of the material.The mechanical strength of the SHP-75 sample reaches 27.0 MPa,the toughness can reach 111.4 MJ/m3,and the elongation at break of the sample reaches 1300%.The self-healing switch of the quadruple hydrogen bond unit can be turned on under heating conditions.The repair experiment shows that the self-healing efficiency of the SHP-75 sample can reach 100%after being repaired for 24 h.When the repair temperature was increased to 100℃,the self-healing efficiency of the SHP-75 sample could reach 100%after 3 h.2.Self-healing polyurethane materials based on dual dynamic networksBased on the previous work,we have carried out research on how to further improve the mechanical properties of materials.Inspired by the dual network structure of titin,we used a biomimetic strategy to simultaneously introduce the physical cross-linking network of quadruple hydrogen bonds and the chemical cross-linking network of Diels-Alder(DA)into the polyurethane system to prepare a high-performance dual dynamic network.Self-healing polyurethane material.By controlling the ratio of the dual dynamic network,the mechanical properties of the material can be easily tuned.In such a dual network system,the existence of DA chemical crosslinking can improve the strength of the material on the one hand;on the other hand,it can play a role in stabilizing the polyurethane network structure,thereby improving the efficiency of the breaking and reorganization of the quadruple hydrogen bond units in the network.,which further enhances the toughness of the material.Based on the synergistic reinforcement effect of the dual dynamic network,the best polyurethane sample F50U50-PU finally obtained in this work has an ultra-high tensile strength of 51.9 MPa,an excellent fracture strain of 930%,an ultra-high toughness of 166.7 MJ/m3,and a high tensile strength of 91.2%.High self-healing efficiency.And due to the thermal reversibility of the dual dynamic network,the material is also recyclable for reprocessing.After three cycles of pulverization/hot-pressing,the samples still maintained mechanical properties comparable to those of the initial samples.3.High-performance water-based self-healing polyurethane materialThe force between the bonding material and the substrate to be bonded mainly depends on intermolecular forces such as hydrogen bonds and van der Waals forces.While abundant hydrogen bonds can be formed between UPy units,the work in this chapter explores the application of quadruple hydrogen bonds in bonding.We used DMPA and UPy as mixed chain extenders to prepare a series of water-based polyurethane film materials with quadruple hydrogen bond structure by "acetone method".Compared with the control samples without quadruple hydrogen bonds,the mechanical properties of the film materials with UPy groups were greatly improved,in which the tensile strength of 2/3-WPU was a maximum of 32.8 MPa,and the fracture energy also reached 32.8 MPa.150.1 MJ/m3 max.Using ethanol as the room temperature repair agent for the material,the repair strength of the material can reach 28.4 MPa after the completely cut sample is repaired at room temperature for 12 h,and the repair efficiency is 86.6%.Using 2/3-WPU as the adhesive film to bond the boards,the shear strength between the bonded steel plates can reach 2.1 MPa,and the shear force between the bonded boards exceeds 4.0 MPa.When using the initial colloid between the steel plates for secondary bonding,the shear force can be recovered to 62.2%of the initial bonding value,so the material has the potential to be used as a self-healing adhesive film.