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In this work, we studied the parameters affecting the localization of multiwalled carbon nanotubes (MWCNTs) and its impact on morphology development of poly(methyl methacrylate)/polystyrene/polypropylene (PMMA/PS/PP) ternary blends, which originally have a thermodynamically preferred core-shell type morphology. We compared the results with the morphological prediction based on the thermodynamic approach. The MWCNTs localization and morphological features of nanocomposite samples were studied by means of melt linear viscoelastic experiments together with electron microscopy results. It was found that at 0.5 wt% of MWCNTs the original core-shell type morphology of the ternary blend samples almost remained intact. and this observation was independent of the sequence of feeding. At 1 wt% of MWCNTs, the core-shell morphology was retained only for those nanocomposite samples prepared using the sequential feeding mode. In addition, it was demonstrated that the thermodynamic predictions could be utilized for the nanocomposites containing low MWCNTs contents. However, this was not true for the nanocomposites with higher MWCNTs contents due to the predominating role of viscoelastic properties of the PS shell. C 2015 Wiley Periodicals, Inc. Adv Polym Technol 2016; View this article online at wileyonlinelibrary.com.

The main objective of the present work is to explore the role of citric acid (CA) on microstructural changes and their impact on the melt rheological behavior, mechanical performance, and shape recovery of thermoplastic starch (TPS). The results of frequency sweep test show a pronounced nonterminal storage modulus (G’) at lower frequencies (high melt elasticity) for TPS, which is found to be greatly reduced in favor of improving the processability through the addition of CA. This could be explained in terms of reduced disentanglements of amylopectin molecules, as a crucial parameter responsible for the 3D‐type interconnected microstructure of TPS, through catalyzing effect of CA on hydrolysis. The results of the temperature sweep test (cooling mode) show a pronounced liquid‐to‐solid transition at ∼136℃ for CA‐modified TPS. This transition could be attributed to the temperature‐driven significant strengthening of the formation of single helical amylose crystalline structure and/or the hydrogen bonds between hydrolyzed amylopectin chains at temperatures below 136℃. The results are found to be consistent with the results obtained from the tensile and DMTA experiments. As expected, the shape recovery of the CA‐modified TPS sample is lower than that of unmodified TPS because of the lower elastic stored energy (stiffness) in the presence of CA, which can be largely compensated by incorporating appropriate nanoparticles.

Abstract. In this work, we studied the parameters affecting the localization of hydrophobic nanosilica particles and its impact on morphology development of polyethylene/polystyrene/poly (methyl methacrylate) (HDPE/PS/PMMA) ternary blends, which originally have a thermodynamically preferred core-shell type morphology, by means of a combination of rheology and electron microscopy. An attempt was also made to compare the experimental results with thermodynamic predictions. The ternary blend samples with the same blend ratio but varying in nanosilica loadings were prepared by melt compounding using a laboratory internal mixer. It was demonstrated that the nanosilica localization which could be controlled by the sequence of feeding, would play a significant role in determining the morphology development of the nanofilled ternary blend samples. It was shown that in contrary to thermodynamic prediction of a core shell morphology for the nanofilled samples, the highly enhanced melt elasticity of nanosilica filled polystyrene phase did not allow the PS phase to form a complete encapsulating shell.

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