Structure and Dynamic Mechanical Properties of Melt Intercalated Polyamide 6—Montmorillonite Nanocomposites

Abstract

Summary: Polymer‐layered silicate nanocomposites (PLSN), based on polyamide 6 (PA6) and montmorillonite (MMT) modified with an octadecylammonium salt, were produced via melt compounding in a co‐rotating twin‐screw extruder. Wide angle X‐ray diffraction (WAXD) and TEM revealed a PLSN containing 3.3% by weight (wt.‐%) of MMT to exhibit a mixed exfoliated/intercalated morphology, consisting mainly of individual silicate lamellae together with some intercalated stacks, resulting in a mean value of 1.8 lamellae per particle. In contrast, a PLSN containing a higher level of 7.2 wt.‐% MMT exhibited a more ordered intercalated structure, consisting mainly of a distribution of lamellae stacks with a mean value of 3.8 lamellae per particle. The dispersion of MMT in the PLSN generated very large polymer–filler interfacial areas, resulting in significant increase in the volume of constrained PA6 chain segments. Consequently, significant changes in the ratio of α/γ crystallites and in the thermal behaviour of the matrix PA6 were observed during WAXD, DSC and dynamic‐mechanical thermal analysis (DMTA) studies of the PLSN. In particular, damping data from DMTA showed relaxations between Tg and Tm resulting from amorphous polymer chain segments constrained at the polymer–filler interface, indicating the formation of a continuous phase of constrained polymer. In contrast, a PA6 microcomposite formed using unmodified MMT generated much lower polymer–filler interfacial area, with most of the MMT residing within large, poorly wetted aggregates. Consequently, changes to the thermal behaviour of the matrix PA6 were much less significant than those induced in the PLSN.Shear storage modulus (G′) versus temperature data for the matrix PA6, the 5T and 10T PLSN and the 5P microcomposite.magnified imageShear storage modulus (G′) versus temperature data for the matrix PA6, the 5T and 10T PLSN and the 5P microcomposite.

Efficient one-step melt-compounding of copolyetheramide/pristine clay nanocomposites using water-injection as intercalating/exfoliating aid

“…It is also worth noting that the results obtained with PEBA/NaMMT are even better than the ones reported in the literature for PA6 filled with OMMT. Indeed, at 5 wt% clay loading, the normalized E% is 1.33 [2] or 1.34 [64] while it has been found to be 1.44 in the present study. Figure 10b shows the glass transition temperature (T g ) of the PEBA matrix versus mineral content, which corresponds to PA12 blocks.…”

Tensile properties of melt intercalated polyamide 6 – Montmorillonite nanocomposites

“…The XRD data for these PLSN reported previously [11] did indicate that a more ordered, intercalated structure had developed in the PLSN as the MMT content was raised from 3.3 to 7.2 wt%. In addition, measurements of particle dimensions from TEM images [11] showed that the 5T PLSN exhibited a mean value of 1.8 silicate lamellae per particle, resulting from a particle distribution comprising a predominance of exfoliated lamellae together with a minority of intercalated lamella stacks containing between 2 and 6 lamellae. In contrast, the 10T PLSN exhibited a mean value of 3.8 silicate lamellae per particle [11], resulting from a particle distribution comprising a predominance of intercalated lamella stacks containing between 2 and 10 lamellae.…”

“…Thus, above a critical loading of MMT, proposed to be ≤ 5 wt% for MMT lamellae with aspect ratios of ≥ 100 [7], these constraints are predicted to result in the formation of an ordered nematic phase [16]. The XRD data for these PLSN reported previously [11] did indicate that a more ordered, intercalated structure had developed in the PLSN as the MMT content was raised from 3.3 to 7.2 wt%. In addition, measurements of particle dimensions from TEM images [11] showed that the 5T PLSN exhibited a mean value of 1.8 silicate lamellae per particle, resulting from a particle distribution comprising a predominance of exfoliated lamellae together with a minority of intercalated lamella stacks containing between 2 and 6 lamellae.…”

“…The outputs from the response equations determined for tensile properties are shown in Figures 1-2, in comparison to both the experimental data used to generate the curves, the 5P microcomposite and the 7T PLSN produced as a confirmation experiment. In the figures actual MMT content, as measured by ashing [11], is used rather than OMMT addition level. Figure 1 shows the development in tensile modulus for addition levels of MMT between 0 and 7.5 wt%.…”

“…In this case, FED was used specifically to provide an experimentally efficient method of determining experimental error and of fitting the experimental data, thus allowing the prediction of mechanical properties at intermediate levels of OMMT addition. For comparison, a PGW-based MMT microcomposite was produced at the mid-level of the design (nominally 5 wt% addition -experimentally 4.7 wt% [11]). The composites were identified using a simple coding system consisting of the nominal clay wt.-% followed by T or P, denoting 1.30TC or PGW respectively, as shown in Table 1.…”