Studies On The Evolution Of Microstructure Of Gross Rubber In The Process Of Mixing, Parkingand Remilling

In this paper, the natural rubber (NR) was used as matrix and reinforced by silica(SiO2), which modified by Si69.The evolution of the microstructure of theNR/SiO2/Si69composite was studied by gel permeation chromatograph(GPC), rubberprocessing analyzer(RPA),scanning electron microscope(SEM) and the measurementof bound rubber content. The influence of mixing, parking and remilling process on themicrostructure of gross rubber were also studied.Firstly, the effects of the molecular weight and molecular weight distribution, thedosage of silica, the initial processing temperature, mixing speed and mixing time onthe microstructure of gross rubber were studied. The results showed that, with theincrease of initial processing temperature, rubber molecular weight increased graduallyand the molecular weight distribution widened. With the increase of rotational speedand/or the processing time, the rubber molecular weight decreased and the molecularweight distribution narrowed after first widened. With the increase of the dosage ofsilica, the bound rubber content decreased after first increase, and the Payne effectbecame stronger gradually. When the dosage of silica was30phr, the content of boundrubber was the highest, while the Payne effect became stronger. With the increase ofinitial processing temperature, the bound rubber content increased. When the dosage ofsilica was20phr, the Payne effect increased gradually. When the dosage of silica was30phr, the Payne effect became stronger after first weakened. When the dosage ofsilica was50phr, the Payne effect weakened gradually. With the improvement ofmixing speed or the extension of mixing time, the Payne effect became weaker and thebound rubber content decreased after first increased.Besides, the effects of the storage time and storage temperature on themicrostructure of gross rubber were also studied. The evolution of filler networkstructure was characterized by RPA online tracking which was conducted under lowstrain and low frequency. The results showed that, at the beginning of parking, the G’of gross were similar. With the increase of storage time, the Payne effect becamestronger after first weaken and the bound rubber content increased. With the increaseof storage temperature, the bound rubber content increased and the Payne effectweaken gradually. The recovery speed of the NR/SiO2/Si69composite filler networkstructure increased with the increase of storage temperature. What’s more, the recoveryof filler network mainly concentrated in the first15minutes.Finally, the effects of remilling time and remilling shear rate on the microstructureof gross rubber were studied. The results showed that, with the extension of remillingtime and the increase of remilling shear rate, the G’ of gross rubber decreased and thebound rubber content increased.