Preparation Of Novel Sulfoxide And Sulfone Accelerators And Their Properties In Styrene Butadiene Rubber

Dithiocarbamate accelerators and thiuram accelerators,as the most commonly used super speed accelerators,have the characteristics of fast curing rate and short scorch time.Among them,zinc salt is the main accelerator of dithiocarbamate,which is easy to migrate into the natural environment and pollute the soil and water source in the process of rubber production,use and waste.Strong oxidants such as sodium nitrite and chlorine water are often used in the synthesis of thiuram accelerators.Most of these oxidants are toxic carcinogens,which are easy to pose a threat to human health in the production process.In addition,dithiocarbamate accelerants and thiuram accelerants are easy to oxidize to carcinogenic nitrosamines at high temperature,which limits their application.In order to improve this problem,the small molecular weight alkyl group in their structure is replaced by the large molecular weight benzyl group,so the benzylnitrosamines produced do not have carcinogenicity,so dibenzyldithiocarbamate is developed Zinc(ZBEC)and tetrabenzyl thiuram disulfide(TBz TD)are used as green environmental accelerators to replace other kinds of dithiocarbamates and thiuram.In this study,dithiocarbamate was used as raw material to react with dichlorosulfoxide and sulfonyl chloride respectively to obtain two kinds of dithiocarbamate derivatives containing sulfoxide group or sulfonyl group.The synthesis process is green and environmentally friendly.In order to test the effect of vulcanization accelerant and the properties of vulcanizate,a series of properties of SBR were tested:(1)Four rubber vulcanization accelerators,diethyldithiocarbamate sulfoxide(DCSO),dibenzyldithiocarbamate sulfoxide(BZSO)and sulfone accelerators,dithiocarbamate sulfone(DCSD)and dibenzyldithiocarbamate sulfone(BZSD),were successfully synthesized.The molecular structure was confirmed by FTIR,¹³C-NMR,XPS and elemental analysis.(2)The vulcanization efficiency of DCSO and DCSD in SBR was similar to that of TETD,but higher than that of ZDC,M and NS.The scorch time of DCSO and DCSD is lower than NS,higher than M,TETD and ZDC.When the ethyl group was replaced by benzyl group,the accelerator was passivated,the vulcanization efficiency of BZSO and BZSD decreased,and the scorch time increased.(3)It was found that the activation energy of quasi speed accelerator M and NS was the highest,followed by DCSO and DCSD,and that of super speed accelerator TETD and ZDC was the lowest.This is also the reason why DCSO and DCSD have longer scorch time.In addition,the activation energies of BZSO and BZSD are higher than those of DCSO and DCSD.(4)The tensile curves of DCSO and DCSD vulcanizates showed the rule of super speed accelerator.Compared with the quasi speed accelerator M and NS,the tensile strength and elongation at break of DCSO and DCSD vulcanizates were lower and the set elongation was higher.And from the aging coefficient of 3 days,DCSO and DCSD had better thermal oxidative aging resistance than ZDC and TETD,which indicated that DCSO and DCSD had more sulfur converted into more aging resistant single sulfur bond in the process of vulcanization and crosslinking.BZSO,BZSD,ZBEC and TBz TD showed similar mechanical properties and thermal oxidative aging resistance under the effect of benzyl passivation.