Highly dispersed polyamide‐11/halloysite nanocomposites: Thermal, rheological, optical, dielectric, and mechanical properties

Abstract

Bio-based polyamide 11 and natural halloysite nanotubes (HNTs) were used for the preparation of PA-11/HNT nanocomposites with varying nanotubes concentrations by melt extrusion using a masterbatch dilution process. The prepared nanocomposites were analyzed for microstructural changes, transparency, thermal stability, rheological behavior, dielectric, and mechanical properties. The HNT nanotubes are well dispersed in PA-11 matrix in the studied composition range as shown by microscopy and spectrophotometry. Interestingly, good halloysite dispersion in PA-11 matrix increases the tensile strength and Young modulus of PA-11 without sacrificing the ductility. Highly dispersed nanotubes also bring favorable changes in the thermal stability, dielectric, and rheological characteristics of PA-11. Additionally, glass transition temperature, crystallization temperature, and degree of crystallinity of the nanocomposites tend to increase with increase in nanotubes loading. Thus, PA-11 can become a tailor-made material with multifunctional characteristics, thanks to the addition of HNTs.

Toughening of poly(lactic acid) without sacrificing stiffness and strength by melt-blending with polyamide 11 and selective localization of halloysite nanotubes

“…This preferential orientation is inhibited in presence of PLA showing a single peak in PLA/PA11. But, upon addition of HNTs, preferential orientation reappears, which is in accordance with the literature [27]. The intensity of shoulder peak increases with increasing filler concentration.…”

“…During cooling (Figure 5b), the neat PLA/PA11 blend shows two peaks, one big at ~98°C and another small one at around 165°C indicating the fractionated crystallization of PA11. Crystallization at the higher temperature corresponds to bulk crystallization of PA11, which takes place due to effective heterogeneity in the PA11 phase, and crystallization at the lower temperature corresponds to crystallization of PA11 droplets, which needs much larger supercooling [13,27]. The fractionated crystallization process becomes less evident when the HNTs are added with a reduced peak at 98°C indicating a lower number of fine droplets as observed in TEM image (Figure 4), while peak at 165°C increases drastically.…”

“…Higher viscosity of nanocomposites arises from the network structure of HNT-rich PA11 phase as observed from the morphological images of the nanocomposites (section 3.2). Another possible reason for increased viscosity of nanocomposites is the higher flow resistance of macromolecules due to the interaction between HNTs and the polymer [27]. Both storage modulus and complex viscosity are the highest for 6 wt% HNTs.…”

Toughening of poly(lactic acid) without sacrificing stiffness and strength by melt-blending with polyamide 11 and selective localization of halloysite nanotubes

“…Presence of amorphous PA11 chains could activate the chain mobility of PLA, thereby advancing the cold crystallization of PLA. Furthermore, the surface of the dispersed PA11 domains might also act as a nucleating center and thereby enhance the crystallization of the PLA in the blends, which is accordance with the reported literature [7]. Then, decrease in Tcc in ternary nanocomposites is due to characteristic changes of PA11 phase related to migration of HNTs to PA11 matrix bringing further decrease in Tcc of PLA phase.…”

“…The melting temperature remains unaltered with increasing filler concentration. The appearance of shoulder peak is attributed to the melting of preferentially oriented PA11 macromolecules, in the presence of nanofillers [7]. The intensity of shoulder peak increases with increasing filler concentration.…”