Mechanical and rheological properties of polystyrene-block-polybutadiene-block-polystyrene copolymer reinforced with carbon nanotubes: effect of processing conditions

Abstract Styrene-b-butadiene-b-styrene (SBS)-based nanocomposites filled with unmodified and –COOH functionalized carbon nanotubes (CNTs) have been formulated at different processing conditions in order to provide an understanding of the influence of the processing temperature and mixing speed on the nanofillers dispersion and on the overall properties of the nanocomposites. The evaluation of the nanocomposites’ mechanical and rheological behavior reveals that the effect of the processing speed on the final properties is almost negligible. Differently, the processing temperature influences strongly the mechanical and rheological properties of SBS-based nanocomposites. Indeed, for the nanocomposites formulated at high temperatures a significant enhancement of the overall properties with respect to the neat matrix has been achieved. Moreover, morphological analyses show that the state of dispersion of both unmodified and functionalized CNTs progressively improves as the processing temperature increases. Particularly, at low processing temperatures a segregated morphology in which the nanofillers are selectively confined in the domains of the SBS matrix has been obtained, while the nanocomposites formulated at 180°C show a homogeneous and uniform CNTs dispersion throughout the matrix and a strong level of interfacial adhesion between the copolymer chains and the dispersed nanofillers.

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Study of Rheological Properties of Carbon Nanotube-Reinforced Ultrafine Cement Grouting Materials

Magazine of Concrete Research ◽

10.1680/jmacr.21.00005 ◽

2021 ◽

pp. 1-44

Author(s):

Yunxiao Liu ◽

Jiahang Zhang ◽

Yinyin Chi

Keyword(s):

Carbon Nanotubes ◽

Rheological Properties ◽

Polyvinyl Pyrrolidone ◽

Cement Grouting ◽

Grouting Material ◽

Multi Walled Carbon Nanotubes ◽

Different Diameters ◽

Grouting Materials ◽

Walled Carbon Nanotubes ◽

Ultrafine Cement

In this study, three different diameters of multi-walled carbon nanotubes (MWCNTs) dispersed by polyvinyl pyrrolidone (PVP) were used to reinforce superfine cement grouting materials. The effect of MWCNTs and polyvinyl pyrrolidone (PVP) on the rheological properties of grouting material were accordingly studied. It was found that the yield stress (τ0) and plastic viscosity (η) were slightly decreased when PVP content was low and increased when the PVP content increased. The effect of MWCNT diameter on τ0 was not found to be clear but was more significant on η. The smaller MWCNT diameter was, the more quickly η increase. It was also found that the thixotropic ring area was increased as the MWCNTs content increased. The addition of PVP and MWCNTs caused an increase in the number of entanglement points in different scales, which was the main reason for the viscosity and thixotropy increase. Therefore, the rheological properties of superfine cement grouting material should be adjusted when MWCNTs were added as a reinforcing component. Due to the wrapping of PVP on cement particles which isolates the contacting part between the water and the cement particles, it slows down the cement's hydration rate thus slows down the fluidity loss of the slurry.

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