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Influence of Organic Modifier on Miscibility and Chain Scission of the PA6 Phase and the Extent of Multiwalled Carbon Nanotubes Dispersion in Co-Continuous PA6/ABS Blends

Bose, S and Pötschke, P and Bhattacharyya, AR (2016) Influence of Organic Modifier on Miscibility and Chain Scission of the PA6 Phase and the Extent of Multiwalled Carbon Nanotubes Dispersion in Co-Continuous PA6/ABS Blends. [Book Chapter]

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Official URL: https://doi.org/10.1201/9781315371054-22


In our earlier work, we have reported that by modifying multiwalled carbon nanotubes (MWNTs) by a simple yet interesting organic modifier, sodium salt of 6-amino hexanoic acid (Na-AHA), both the stability and the extent of dispersion of MWNTs in the blends of polyamide 6 (PA6) and acrylonitrile-butadiene-styrene copolymer (ABS) were greatly improved (Bose et al. 2008, 2009b, Kodgire et al. 2006b). This further manifested in a substantial reduction (by a factor of ca. 10 with respect to pristine MWNTs) in the electrical percolation threshold in 50/50 (wt/wt) PA6/ABS blends and also dependent very much on the fraction of Na-AHA with respect to the MWNTs in the blends. The melt-viscosity data have revealed that small amount of Na-AHA-modified MWNTs in the PA6 phase reduces its melt viscosity through plasticization albeit the dynamics was different in the low-frequency regime, which rather exhibited a pseudo-solid like behavior manifesting in a physical gel (Bose et al. 2009b). The intrinsic viscosity measurements and estimation of ~COOH end groups of PA6 by titration have revealed chain scission of the PA6 phase in the presence of Na-AHA (Bose et al. 2009b). If we exclude any possibility of polycondensation of Na-AHA at the mixing temperature (260 °C), considering its small size, the chain scission of PA6 could only be explained by coordination with water molecule. The latter is generated when the ~NH2 functional moieties of Na-AHA react with the ~COOH end groups of PA6 via the formation of amide linkage. Transamidation of polyamides has also been reported by blending polyamides with other polyamides (Eersels and Groeninckx 1996). There is a possibility of transamidation of PA6 in the presence of Na-AHA during melt-mixing leading to small grafts of Na-AHA on the PA6 chain. In either case, chain scission may occur. It has been reported that blending maleic anhydride-containing polymers (viz.; styrene maleic anhydride SMA) with polyamides leads to polyamide graft on SMA via imide linkage (van Duin et al. 1998). The amide group can only take part once it is hydrolyzed by the water molecule, which is generated during the formation of imide linkage. The melting behavior of the polyamide phase typically remains unaltered on blending with MA-containing polymers though the crystallization kinetics change to a significant extent (van Duin et al. 1998). Interestingly, it has been observed that both melting and crystallization behaviors of the PA6 phase were influenced to a significant extent in the presence of Na-AHA, which may be due to the molecular-level miscibility in the amorphous phase of PA6 or due to the transamidation reaction of the PA6 chains leading to smaller imperfect crystals. The molecular-level miscibility may be associated with the enhanced chain mobility on account of interference with the hydrogen bonding. It has been well established that the superheated water disrupts the interchain hydrogen bonding as the O-H hydrogen is a strong electron acceptor than the N-H hydrogen; the carbonyl oxygen favors coordination to the O-H hydrogen (Stuart 1994). © 2017 by Taylor and Francis Group, LLC.

Item Type: Book Chapter
Publication: Advances in Polymer Materials and Technology
Publisher: CRC Press
Additional Information: The copyright for this article belongs to CRC Press.
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 06 Oct 2022 08:58
Last Modified: 06 Oct 2022 08:58
URI: https://eprints.iisc.ac.in/id/eprint/77160

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