Crystallization kinetics study of poly(L‐lactic acid)/carbon nanotubes nanocomposites

Abstract

Effects of carbon nanotubes (CNT) on the isothermal crystallization kinetics of poly(L‐lactic acid) (PLLA) were quantitatively investigated using the Avrami equation and the secondary nucleation theory of Lauritzen and Hoffman. CNT via grafting modification with PLLA could well disperse in the PLLA matrix and give significantly enhanced crystallization rate and crystallinity of PLLA as analyzed by differential scanning calorimetry and polarized optical microscopy. Analysis of isothermal crystallization kinetics using the Avrami equation demonstrated that CNT significantly enhanced the bulk crystallization of PLLA. Analysis of spherulite growth kinetics using the secondary nucleation theory of Lauritzen and Hoffman found that CNT could expand the temperature range of the crystallization regime III of PLLA. Values of the nucleation constant (Kg) in crystallization regimes III and II of PLLA both increased with increasing CNT contents. The Kg III/Kg II ratios were found to be close to the theoretical value 2 but were not clearly found to depend on the CNT contents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 983–989, 2010

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

“…5b), suggesting a three-dimensional crystallization growth and simultaneous homogeneous nucleation mechanism. Likewise, there are other reports of the Avrami exponent around 2 [19] and between 3.2 and 4.3 [14]. The higher n values are attributed to three dimensional spherulitic growth with a sporadic or a combination of sporadic and simultaneous nucleation type, while the lower values are associated to two dimensional growth with instantaneous and some sporadic nucleation [5].…”

“…Thus it is reasonable to speculate that INT-WS 2 can serve as a powerful nucleating agent for fast moulding of PLLA articles in practical processing. Figure 6b CNC [14]; octavinyl-POSS [17], GO [22], CNT-g-PLLA [19]). …”

“…Effective nucleating agents reported for PLLA are zinc phenylphosphonate (PPZn) [9] and p-tert-butylcalix [8] arene [10], talc [11], uracil [12] and N,N 0 -bis(benzoyl) suberic acid dihydrazide [13], whilst cellulose nanocrystals (CNC) [14], titanium dioxide (TiO 2 ) nanowires [15], polyhedral oligomeric silsesquioxanes (POSS) [16,17], nanclay (MMT) [18], carbon nanotubes (CNTs) [19], nanocalcium carbonate (CaCO 3 ) [20], nano-zinc citrate (ZnCC) [21], graphene oxide (GO) [22] and fullerenes (C60) [23], are known as nanocomposite-forming additives. However, the fabrication of high quality nanocomposites normally requires chemical treatment to reduce the surface energy in order to ensure good particle dispersion and strong interaction and adhesion between the nanofiller and polymer matrix.…”

Crystallization modification of poly(lactide) by using nucleating agents and stereocomplexation

“…To enhance the compatibility, PLA grafted CNTs (i.e. PLA-g-CNT) were applied (55,56). Consequently, a crystallinity of 12-14% was obtained with 5-10 wt% of the PLA-g-CNT at a moderate cooling rate of 5°C/min (56).…”

Effects of carbon nanotubes on polymer physics

“…157 A significant increase in growth rate was found for polylactide; the authors offered no explanation for this hard-to-understand observation. 161 A detailed study on single carbon nanotube fibers showed that the growth rate of the transcrystalline morphology for isotactic polypropylene approximately matched that measured for carbon or Kevlar fibers, indicating that the surface characteristics do not affect the growth rate. 217 The attachment of a crystallizing polymer on a surface of a carbon nanotube via a covalent bond has been shown to speed crystallization rate at low overall relative crystallizations and slow the rate at higher relative crystallizations with an overall slower rate as compared to unattached polymers in one study.…”