Potentialin situpreparation of aliphatic polyamide‐based nanocomposites: The organoclay‐polyamide salt interaction

Abstract

In situ intercalative polycondensation is applied for the preparation of polyamide (PA) n,6-clay nanocomposites, namely poly(ethylene adipamide) (PA 2,6), poly(hexamethylene adipamide) (PA 6,6), and poly (dodecamethylene adipamide) (PA 12,6). For this purpose, two different polymerization routes are considered; a lowtemperature melt polymerization technique and the conventional solution-melt one. Under the specific experimental conditions, lack of clay exfoliation is detected through XRD measurements, which is proved irreversible even when twin-screw extrusion is attempted as an additional step. The resulting PA n,6-clay structures are found dependent on the diamine moiety length; more specifically, an intrinsic interaction between the polyamide monomer and the organoclay surfactant is indicated. An ion exchange occurs between the two competitive species, that is, diamine and surfactant cations, leading to flocculated clay structures.

Applying the Traditional Solution Melt Polymerization for the in situ Intercalation of Polyamide 6.6‐Clay Nanocomposites

“…Focusing now on the nanostructures achieved, the X‐ray diffraction (XRD) spectra revealed a shift of the characteristic clay peak to the higher angle of 2 θ ≈ 6.6°, corresponding to a collapsed d ‐spacing of 13.6 Å and thus indicating the existence of a portion of flocculated nanoparticles despite the extent of nanofiller exchange (Figure 6, pre‐extrusion). This observation has been thoroughly explained in a previous paper of ours: 19 a competitive ion exchange between the diamine component of the polyamide salt and the organoclay alkylammonium surfactant takes place during in situ intercalation and leads to clay interlayer collapse due to bridging 19. However, the final process step of twin–screw extrusion and the high shear applied enhanced the dispersion of OMT2a and OMT2b platelets, resulting in partial clay exfoliation as evidenced by the absence of organoclay peaks in the relevant XRD spectra (Figure 6II and 6III).…”

“…In order to have an estimation of the molecular size of the formed PA 6.6 nanocomposites, the relative viscosity of all grades, before and after extrusion was measured (Figure 2). 17, 19–24 The obtained η rel values demonstrated an important organoclay influence on the polymerizability of the PA matrix. More specifically, the fully organically exchanged clays, i.e.…”

Nanocatalysis in Polyamide 6.6 Solid‐State Polymerization

“…[12] Indeed, the X-ray diffraction (XRD) spectrum of the herewith obtained nanocomposite showed complete disappearance of the characteristic clay peak, indicating an exfoliated clay structure (Figure 1). The crystal morphology of the prepolymers was also examined, as it may influence the possible SSP rate-controlling steps.…”

“…It is a fact that improved properties in terms of strength, heat deflection temperature, dimensional stability, gas barrier, flame retardancy, and electrical conductivity can be listed as highlighting features of PA nanocomposites. [8][9][10][11][12] A combination of the SSP process of PA 6.6 -one of the most commercially important nylons corresponding to 40% of the total PAs demand [13] -with nanotechnology benefits, would potentially result in advanced tailor-made PAs suitable for specialty applications. As a result, the investigation of nanoparticles influence on SSP appears very significant and attractive, also to the polymerization process itself; this interest is even more enhanced due to the fact that published literature on nanocomposites SSP is restricted so far to the case of poly(ethylene terephthalate) (PET).…”

Facile preparation of nylon 6 nanocomposites based on clay reinforcement and core‐shell latex toughening: Morphology, properties, and impact fracture behavior

“…37, 38 The dispersion of the organic clay may be optimized compared to standard melt compounding processes due to the intercalation with the monomer and a consequent shear energy input in the twin-screw extruder. As a result of the homogeneously dispersed clay, the mechanical properties should be significantly increased.…”