Enhanced rheological properties of carbon nanotubes reinforced natural rubber/butadiene rubber nanocomposites

Abstract Effects of carbon nanotubes (CNTs) content and the in situ surface modification via bis(triethoxysilylpropyl) disulfide (Si75) and (3‐aminopropyl) triethoxysilane (KH550) on the rheological properties of rubber nanocomposites are explored. Results from the strain sweep demonstrate that the filler network of the nanocomposite is enhanced when the hydroxylated CNT (HCNT) is incorporated. The promotion of filler–rubber interaction in nanocomposite reinforced with modified CNT is validated by both stress relaxation and strain sweep measurements. The die swell ratio ( B ) declines with increasing HCNT content and rises with a heightened shear rate. Compared to those without HCNT, B of the nanocomposites, which contained 5 phr HCNT, decreased by 5.4%, 7.0%, and 17.3% at 50, 200, and 500 s −1 , respectively. The Si75‐modified HCNT and the carboxylated CNT (CCNT) reduce the B ‐value of the extrudates at 500 s −1 by 3.7% and 3.0%, respectively. However, the extrudates filled with KH550‐modified HCNT or CCNT showed a larger B due to pre‐crosslinking, as demonstrated by stress relaxation and swelling tests. Furthermore, it is also found that the application of KH550 has an acceleration effect on the curing reaction, increasing the curing efficiency by 8.5%. Highlights The promotion of filler–rubber interaction is validated by RPA. The dimensional stability of the composites is improved after incorporating CNT. The extrudates with Si75 exhibit a reduced B and improved surface morphology. CNT content increase raises M H , M L , and shortens the t 10 of the composite.