Study On Thiols Targeted Desulfurizer And Its Regeneration Mechanism

At present,the demand for rubber increases,a lot of waste rubber has been produced at the same time.These waste rubber can cause serious impact on the environment if it can't be handled properly.Nowadays,the mainly waste rubber recycling ways exist many question,such as low recovery efficiency and low quality,and may cause secondary pollution.So,it's necessary to explore an effective way for waste rubber to selectively break crosslinking bond without destroying the rubber chain,so that the molecular weight of the recycled rubber is as high as possible.In this way,high quality recycled rubber and real regeneration can be achieved.In this paper,targeted desulfurizer 3,6-dioxa-1,8octanedithiol(DODT)and dithiothreitol(DTT)were used to regenerate vulcanized natural rubber and waste tire tread powder under mild conditions.In the experiment,xylene was used as the solvent.The recycled natural rubber of the two desulfurization agents both met the standard of Horikx model in which the crosslinking bond was mainly broken.When the concentration of desulfurizer was 0.03 mol/L and the desulfurization was conducted at 120?for 10-12 h,the desulfurization effect was the best,the recycled natural rubber with 100%degree of de-crosslinking and 100%sol content could be obtained,and the molecular weight could reach 100,000.The reclaimed rubber was applied again,and the processing and mechanical properties of the rubber with 20%reclaimed rubber were similar to those of the pristine natural rubber,but the processing properties and mechanical properties of the reclaimed rubber were lower than those of the pristine natural rubber.The regeneration mechanism of DODT was explored,and the result shows that it is similar to the regeneration mechanism of DTT.The regeneration process is reversible reaction.As the reaction progresses,desulfurizer into crosslinked network,and the sulfydryl reacts with the sulfur chemical bonds in the rubber crosslinking network.Finally,the crosslinking bonds are selectively cleaved.The sulfur bond forms single sulfhydryl,the desulfurizer itself forms a ring structure.The process of self-forming a ring structure promotes the reversible reaction of regeneration in the forward direction,thus achieving efficient regeneration.Two kinds of desulfurizer were applied to scrap tire tread rubber powder of regeneration.the study found that as the reaction progresses,a lot of black small particles separating out,speculating that they are the carbon black in powder.At the end of the reaction,30%of the adhesive still exists,the degree of de-crosslinking can reach 60%?70%,the content of the sol is 20%?30%,and the molecular weight of the recycled rubber can reach about 90,000.Thus,both two desulfurization agents can desulfurize the waste rubber.