Preparation And Properties Of Self-healing Elastomer Based On Multiple Reversible Effects

Self-healing polymers currently becoming the subject of increasing interest as an emerging smart materials because of their ability to repair the internal and surface damage spontaneously.The combination of self-healing technology and polymers is of great significance,especially for commercial rubber elastomer materials.If a self-repairing system can be introduced into the rubber network to transform it into a self-healing material,it can not only prolong the service life of materials and products,but also can recycle them to realize sustainable development of resources.However,it is still a great challenge so far to prepare recyclable rubbers that combine excellent self-healing properties with good mechanical strength,and is also recyclable.Herein,in this paper,we prepared self-healing epoxidized natural rubber(ENR)elastomer material and polyurethane elastomer material based on multiple reversible effects,explored the relationship between structure and properties in detail,and clarified their respective self-healing mechanism.This paper hopes to overcome the disadvantage of self-healing ability and mechanical properties of materials commonly existing in the current research by introducing multiple reversible effects into the elastomer network,and to prepare self-repairing elastomer materials with good mechanical properties.On one hand,we report the use of epoxidized natural rubber(ENR),a reactive polymer presenting dual functional groups(unsaturated double bonds and epoxy sites)available for cross-linking,to prepare a dual cross-linked self-healing ENR based on dynamic disulfide metathesis and thermoreversible hydrogen bonding.Specifically,different structures of aromatic disulfide compounds are introduced into the same system to promote the disulfide metathesis and thus improving the self-healing efficiency of the materials.As a result,the dual cross-linked ENR shows high strength(9.3±0.3 MPa)?high self-healing efficiency(up to98%)and ideal recyclability.In addition,cyclic fatigue tensile test shows that the self-healing properties of the present material are not affected by the form of damage,whether it is complete fracture or cyclic fatigue damage,and the repair can be repeated multiple times.In addition,we also explores the recycling property of this self-healing rubber through recovery experiments,after crushing and re-vulcanization,the recycled rubber can still maintain 78%of its original properties.On the other hand,in order to improve the strength of self-healing materials and achieve the goal of mild condition repair,polyurethane elastomer was used as the matrix material.We prepared a self-healing polyurethane elastomer with high strength,high toughness and high repair efficiency by introducing dynamic disulfide bonds and reversible borate esters cross-linked network into the system.FT-IR results show that there is a strong hydrogen bond in the system,which is more conducive to self-healing of the material.DMA results show that the introduction of multiple reversible effects reduce the apparent activation energy(Ea)of the material,resulting in stronger segmental mobility,which is benefit for self-healing process.DSC and XRD results show that the material has good crystallization properties,which helps to improve the mechanical strength of the material,and the crystal has thermoreversible properties and does not limit the movement of the molecular chain under healing conditions.The repair tests show that the original strength of this material can reach 23.3±0.3 MPa,the elongation at break is up to 1177±56 %,the cut and spliced sample can be restored to 99% of its original strength after being repaired at 60 ? for 24 h,and the repair can be repeated multiple times.Besides,the multiple response repair features of this material makes it possible to repair damage by thermal processing or water-assisted heating.The self-healing polyurethane is expected to be applied to the preparation of a self-healing surface protective coating.