Study On The Application Of Scorch Retarders In Rubber Formulas

In this paper,four kinds of scorch retarders,inclouding phthalic anhydride(B),N-cyclohexylthiophthalimide(CTP),N-phenyl-N-(trichloromethylsulfenyl)-benzene sulfonamide(E)and thio-dimethyl imide derivatives(GE1907),were used to study the performance of scorch retarders in three different types of formulas.The effects of species and dosage of scorch retarders on the vulcanization characteristics,scorch performance,physical and mechanical properties and filler network were investigated.In addition,the effect of scorch retarders on the vulcanization kinetics was analyzed through the rotorless vulcanizer.The results showed that these four scorch retarders could effectively prolong the scorch time and improve the processing safety of the compound.In the formula with thiazoles and dithiocarbamate as the accelerater,vulkalent E and GE1907 had significant effect on the anti-scorch performance,with the scorch time t5 being 30 minutes when the dosage was 0.25 phr.The scorch time of vulkalent CTP was liner related with its dosage,with t5 being 30 minutes when the dosage was 0.75 phr.The t5 of vulkalent B reached a maximum of 22.5 minutes when the dosage was 0.3 phr and with the increase in the amount,t5 no longer increased.In the formula in which the thiuram type accelerator was used in combination with the sulfonamide accelerator,the vulkalent CTP had the best anti-scorch performance.Vulkalent E and GE1907 and could improve the crosslink density of rubbers and improve the physical and mechanical properties while they had a significant influence on the process-vulcanization time.Vulkalent CTP could lower the crosslink density of rubbers and decrease physical and mechanical properties slightly,while it had no effect on the process-vulcanization time and the scorch time could be controlled by the dasage of due to the linear relationship to its scorch time.Vulkalent B could also improve the physical and mechanical properties,but compared to the vulkalent E and GE1907 its effect is not significant.In this paper,the classical model proposed by Coran was used to study the vulcanization kinetics of different anti–scorch systems by means of torque changes.The results showed that,the torque difference(MH-Ml)of CTP was decreased indicating the decrease of crosslink density,and the MH-Ml of E and GE1907 was increased incicating the increase of crosslink density.In the early curing stage,the activation energy of vulkalent CTP system,GE1907 system and E system was larger,which had a slower curing rate and better schorch performance and could effectively improve the storage and processing stability of the compound.In addition,raising the temperature could be used to shorten a greater extent curing time.