Rheological Behavior of Polypropylene Nanocomposites with Tailored Polymer/Multiwall Carbon Nanotubes Interface

Maleic anhydride grafted polypropylene (MA‐g‐PP) or polypropylene (PP) was noncovalently coated onto acid functionalized multiwall carbon nanotube (f‐MWNT) through solution mixing. These coated f‐MWNTs and pristine MWNT (p‐MWNT) were melt microcompounded with neat PP to form PP/f‐MWNT and PP/p‐MWNT nanocomposites at 0.1–1 wt% MWNT concentration. Complex viscosity and tan δ (ratio of loss modulus to storage modulus) behavior of these systems were studied using dynamic frequency sweep test, while relaxation time, activation energy, and melt homogeneity were also calculated and compared. Among the three types of samples, PP/f‐MWNT masterbatch‐based nanocomposite demonstrated not only the presence of interphase but also good processability. As a consequence, increase of both the crystallization rate in the presence of shear and the melt elasticity during annealing were found only in the masterbatch‐based samples but not in the PP/p‐MWNT. The mechanism of such increased melt elasticity was attributed to the formation of the space‐spanning network, which is consistent with the Cole–Cole plot showing similar behavior to the branched polymers in the literature. This has implications in polymer processing due to suggested changes in the balance between melt strength and polymer flow. Nanocomposite rheological behavior has also been correlated with the mechanical properties. POLYM. ENG. SCI., 59:1763–1777, 2019. © 2019 Society of Plastics Engineers