Isothermal crystallization kinetics and melting behavior of poly(l-lactic acid)/WS2 inorganic nanotube nanocomposites

Abstract

Environmentally friendly and biocompatible tungsten disulphide inorganic nanotubes (INT-WS 2 ) were introduced into a poly(L-lactic acid) biopolymer matrix to generate novel nanocomposite materials through an advantageous melt-processing route. The effects of INT-WS 2 on isothermal crystallization and melting behaviour of PLLA have been investigated. INT-WS 2 has excellent acceleration effectiveness on the melt-crystallization of PLLA better than the promising nano-sized fillers reported in the literature (e.g. carbon nanotubes, graphene oxide, cellulose nanocrystals). In particular, the addition of INT-WS 2 remarkably influences the energetics and kinetics of nucleation and growth of PLLA, reducing the fold surface free energy by up to 18 %. In the same way, the final crystallinity and subsequent melting behaviour of PLLA were controlled by both the incorporation INT-WS 2 and variation of the crystallization temperature. These observations will enable the development of novel melt-processable PLLA/INT-WS 2 nanocomposites with improved crystallization behaviour for many eco-friendly and biomedical applications.

Effect of WS2 Inorganic Nanotubes on Isothermal Crystallization Behavior and Kinetics of Poly(3-Hydroxybutyrate-co-3-hydroxyvalerate)

“…Equation (2) can be rewritten as:logfalse[−lnfalse(1−Xfalse(tfalse)false)false]=logk+nlogt and the values of log [−ln(1 − X ( t ))] plotted versus log t , allowing the Avrami exponent n and the crystallization rate constant k to be calculated from the slope and intercept of the linear fit, respectively. It is rare that the Avarmi equation can be used to describe the entire crystallization process, but is widely accepted as valid at the early stage of crystallization, as previously reported in our studies for nylon-6/IF-WS 2 [21] and PLLA/INT-WS 2 [25]. Linear regressions of these straight lines at low levels of crystalline transformation (5–40%) yielded the Avrami exponents ( n ) shown in Table 1.…”

Effect of tungsten disulfide nanotubes on crystallization of polylactide under uniaxial deformation and annealing

“…The intensity ratio I peak /I valley is constant for the amorphous UNST films, but after stretching (ST0) it increases with the concentration of nanotubes first slowly up to 0.2 wt% and then with a sudden jump at 0.3 wt%, remaining almost constant the final concentration of 0.6 wt%. While the stretching itself does not induce noticeable crystallization in PLA (ST0, WS 2 = 0 wt%) (but probably just a chain alignment), the nanotubes promote crystallization by acting as nucleation agents [23]. The value of I peak /I valley for the conditions ST3 and ST10 is very similar to and larger than the corresponding ST0 value.…”

“…Despite these advantages, to the best of our knowledge, only a few studies are reported in literature on PLA-WS 2 nanocomposites, mainly focused on thermal properties of samples obtained by melt-mixing [21][22][23][24][25]. These studies show that WS 2 NTs remarkably influence the kinetics of nucleation and growth of the PLA during the cold crystallization.…”

Improving the Thermal and Mechanical Properties of Poly(l-lactide) by Forming Nanocomposites with an in Situ Ring-Opening Intermediate of Poly(l-lactide) and Polyhedral Oligomeric Silsesquioxane

“…However, improving the crystallinity is often not effective if only the temperature gradient and cooling rate are controlled, and the temperature cannot be controlled easily in real manufacturing. The final and maybe the most promising approach is to add some organic and/or inorganic particles as nucleating agents to the PLLA matrix, such as sodium stearate [30], nano-clays [31], graphite particles [32], triclosan nanoparticles [33], tungsten disulphide inorganic nanotubes (INT-WS 2 ) [34], or magnesium oxide nanoparticles [35]. Compounding with these particles by physical blending is a conventional method of fabricating PLLA composites and was proved to be convenient to improve the crystallization behavior of PLLA.…”