Abstract
In the present work, hybrid nanocomposite materials were obtained by a solution blending of poly(l-lactic acid) (PLLA) and layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS2) as a filler, varying its content between 0 and 1 wt%. The non-isothermal cold- and melt-crystallization and melting behavior of PLLA/2D-WS2 were investigated. The overall crystallization rate, final crystallinity, and subsequent melting behavior of PLLA were controlled by both the incorporation of 2D-WS2 and variation of the cooling/heating rates. In particular, the analysis of the cold-crystallization behavior of the PLLA matrix showed that the crystallization rate of PLLA was reduced after nanosheet incorporation. Unexpectedly for polymer nanocomposites, a drastic change from retardation to promotion of crystallization was observed with increasing the nanosheet content, while the melt-crystallization mechanism of PLLA remained unchanged. On the other hand, the double-melting peaks, mainly derived from melting–recrystallization–melting processes upon heating, and their dynamic behavior were coherent with the effect of 2D-WS2 involved in the crystallization of PLLA. Therefore, the results of the present study offer a new perspective for the potential of PLLA/hybrid nanocomposites in targeted applications.
Highlights
The dependency on petrochemical-based polymers has drastically increased over the last few years because the properties of these versatile macrostructures, such as strength or flexibility, make them suitable for many applications
The results obtained from differential scanning calorimetry analysis reveal that the presence of 2D-WS2 modifies the crystallization behavior of PLLA, whilst it does not alter its crystallization mechanism
The cold-crystallization rate of PLLA is found to be greatly reduced upon the addition of increasing 2D-WS2 loadings due to the physical barrier action of the nanosheets
Summary
The dependency on petrochemical-based polymers has drastically increased over the last few years because the properties of these versatile macrostructures, such as strength or flexibility, make them suitable for many applications. NE is strongly dependent on the nanofiller morphology, its surface energy, roughness and crystalline structure as well as on the filler’s ability to form the critical nucleus [10,11] In this regard, Jabbarzadeh has recently reported the crystallization origin in nanocomposite polymers [12]. Monolayer MoS2 [15], with high surface areas and superb thermal stability and excellent mechanical properties, has recently been reported to efficiently enhance the mechanical and barrier properties of various kinds of polymeric materials, whilst not affecting their electrical insulation properties [16,17,18] In this particular case, the use of environmentally friendly and biocompatible inorganic TMDCs allowed the production of novel biopolymerbased nanocomposite materials (Bio-PNCs 1D-TMDCs WS2 ) [21,22,23,24].
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