Preparation And Properties Of Cross-linked Rubber Based On Dynamic Reversible Bonds

Rubber materials in long-term use will fail due to partial damage,which will shorten the life cycle of the material.The thiol-ene click reaction is an efficient and simple reaction method.In this way,the thiols can react with the diene rubber,and then the functionalized diene rubber such as self-healing diene rubber with reversible covalent bonds can be prepared.When cracks occur in the self-healing diene rubber,the dynamic reversible bonds in the rubber chain can be broken and reorganized with light,heat and other stimuli.Therefore,the rubber can repair itself,thereby increasing the service life.In this thesis,sulfhydryl compounds containing dynamic N-N bonds were synthesized,based on the thiol-ene click reaction.Through simple mechanical blending and hot pressing,a styrene-butadiene rubber containing dynamic N-N bonds was prepared.By imitative thiol-ene click reaction,a styrene-butadiene rubber containing dynamic disulfide bonds and hydrogen bonds was prepared in the same molding method,based on lipoic acid.Lipoic acid(LA)cross-linked styrene butadiene rubber has more excellent mechanical properties and self-healing ability.Then applying lipoic acid to butadiene rubber can produce the same effect.Finally,adding metal ions to the lipoic acid cross-linked rubber can improve its mechanical properties and repair efficiency.The main research contents of this paper are as follows.(1)TBD-SH cross-linked styrene butadiene rubber and LA cross-linked rubber.First,TBD-SH is synthesized as a rubber crosslinking agent.Secondly,the self-healing styrene-butadiene rubber containing N-N reversible covalent bond(TST)was prepared by double-roll milling and hot pressing,based on the click reaction.Then simulated thiol-ene click reaction(i.e.“imitative click”reaction)to prepare LA cross-linked styrene butadiene rubber(SLA).When LA is stimulated by heat,the disulfide bond in the five-membered ring is broken to form a sulfur radical,which can undergo an addition reaction with the double bond in the molecular chain.Studies have found that there are dynamic reversible disulfide bonds and hydrogen bonds in the prepared SLA,so SLA also has a self-repair function.Comparing the two materials,the synthesis yield of the former TBD-SH is only about 35%,so the synthesis cost is higher,and the mechanical properties and repair efficiency of TST are lower.(2)LA cross-linked styrene butadiene rubber(SLA)and LA cross-linked butadiene rubber(BLA).Under heat stimulation,LA can undergo a cross-linking reaction with diene rubber through a“imitative click”reaction.Adjusting the LA content can change the mechanical properties and self-repair capabilities of SLA and BLA.In SLA,the tensile strength of SLA can reach 2.45 MPa and the elongation at break is 844%.In BLA,the tensile strength of BLA reaches 2.21 MPa and the elongation at break is 519%.Due to the existence of dynamic reversible disulfide bonds and hydrogen bonds,SLA has a repair efficiency of 71%,and BLA has a repair efficiency of 73%.(3)Cross-linked styrene butadiene rubber(SLA-(Zn²⁺))with dynamic reversible Zn²⁺-oxygen coordination bond and cross-linked butadiene rubber(BLA-(Zn²⁺))with dynamic reversible Zn²⁺-oxygen coordination bond.On the basis of SLA and BLA,Zn²⁺is added to styrene-butadiene rubber and butadiene rubber respectively to make it coordinate with oxygen.Then,a self-healing rubber containing Zn²⁺-O coordination bond was prepared.Due to the strong interaction of the Zn²⁺-O coordination bond,compared with SLA and BLA,SLA-(Zn²⁺)and BLA-(Zn²⁺)have better mechanical properties and self-repairing ability.The tensile strength of SLA-(Zn²⁺)can reach 3.85MPa,and the tensile strength of BLA-(Zn²⁺)can reach 3.76 MPa.The tensile strength of SLA-(Zn²⁺)is 3.85 MPa,and the tensile strength of BLA-(Zn²⁺)is 3.76 MPa.Through the combined action of disulfide bond,hydrogen bond and Zn²⁺-O coordination bond,the self-healing efficiency of SLA-(Zn²⁺)can be increased to about76%,and the self-healing efficiency of BLA-(Zn²⁺)can be increased to about 82%.