Influence Of Storage Condition On Filler Dispersion And Rheological Property Of Green Tire Tread

After being completely mixed,the rubber compounds are usually storage for a certain period of time at certain temperature,and only after that,the compounds can be then used for subsequent processing,such as calendering,extrusion and vulcanization.The storage conditions can affect the microstructure and rheological properties of the compound,which will further affect the performance of the final products.Instruments such as Mooney Viscometer,rotational rheometer,capillary rheometer,HAPRO torque rheometer and TEM are applied to investigate the effects of storage conditions on Mooney viscosity,shear viscosity,entrance pressure drop,Garvey die extrudate's appearance and filler dispersion of silica and silica/graphene filled SSBR/BR based tread compound.1.Effect of storage temperature.For silica filled tread compound,with the increase of storage temperature,the viscosity of rubber matrix decreases,the degree of aggregation of silica particles increases,leading to poorer silica dispersion and higher degree of “Payne effect”,subsequently leading to the increase of Mooney viscosity and elastic modulus of rubber compound.Due to the addition of silane coupling agent Si69 in the compound system,the decomposition of Si69 can cause the crosslinking of the rubber molecules when the sweep temperature is higher than 120 ?,which leads to the increase of the modulus and shear viscosity and deteriorate the processability;With the increase of storage temperature from 20 ? to 40 ?,the critical temperature for the increase of the modulus and shear viscosity is reduced from 120 ? to 110 ?.Under the same extrusion temperature and extrusion rate,the shear viscosity and the entrance pressure drop of the rubber compound also increased,and the appearance of the extrusion worsened with the increase of storage temperature.For silica and graphene filled compound,the tendency for filler dispersion with the increase of storage temperature is similar to that of silica filled compounds.With the increase of storage temperature,not only happened the aggregation of silica particle,but also the pile-up of graphene sheets and aggregation of silica particles on the surface of graphene sheets due to the higher intermolecular force between graphene sheets.The Mooney viscosity,elastic viscosity,shear viscosity,entrance pressure drop increased with the increase of storage temperature.2.Effect of storage time.For silica filled with compounds,when the compound is storage at 20 ? for 6 hours,the Mooney viscosity,shear viscosity and entrance pressure drop of the compound are the lowest,the appearance of the extrudate is the best.Then,with prolonging of storage time,the degree of aggregation of the silica increases,which deteriorates the dispersion and worsens the appearance of the extrudate.For silica and graphene filled compounds,the dispersion of the filler in rubber compound becomes worse with the increase the storage time.The Mooney viscosity,elastic modulus,shear viscosity,entrance pressure drop increases and the appearance of the extrusion is worse with the increase in the parking time.3.The optimum storage conditions for silica filled tread compound is 6h and 20 ?.For silica and graphene filled system,the optimum storage condition is as short as possible,and the optimum storage temperature is 20 ?.