Poly(L‐lactide) crystallization induced by multiwall carbon nanotubes at very low loading

Abstract

Poly(L‐lactide) (PLLA)/multiwall carbon nanotube (MWNT) composites were prepared by the solvent‐ultrasonic‐casting method. Only very low concentrations of MWNTs (<0.08 wt %) were added in the composites. Isothermal and nonisothermal crystalline measurements were carried out on PLLA/MWNT composites to investigate the effect of MWNTs on PLLA crystalline behavior. DSC results showed that the incorporation of MWNTs significantly shortened the crystalline induction time and increased the final crystallinity of the composite, which indicated MWNTs have a strong nucleation effect on PLLA even at very low concentrations. The nonisothermal crystallization measurements showed that the MWNTs greatly speed up crystallization during cooling. From isothermal crystallization results, both PLLA and PLLA/MWNT composites samples closely followed a relationship based on Lauritzen‐Hoffman theory, with the regime II to III transition shifting to lower temperature with increasing MWNT concentration. A double melting peak appeared in both nonisothermal and isothermal measurements. The conditions under which it appeared were found to closely depend on the regime II‐III transition temperature obtained from Lauritzen‐Hoffman theory. From the magnitude and position of melting peaks, it is proposed that the double melting peak is caused by a disorder‐order crystal phase transition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2341–2352, 2009

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

“…Besides, another possible interpretation was due to the phase transition from a 0 -form crystal to a one and the melting of the as-transformed a crystals. Obviously, there exist more or less divergences among these different melting mechanisms, and up to now, no consensus has been reached as for the exact origin of multiple melting behavior of PLLA [45][46][47][48][49]. Therefore, a further investigation of the melting behavior of PLLA is needed to deeply understand the origin of this phenomenon.…”

Development of novel melt-processable biopolymer nanocomposites based on poly(l-lactic acid) and WS2 inorganic nanotubes

“…However, another possible interpretation in the case of PLLA is due to the phase transition from α′-form crystals to α-crystals and the melting of the astransformed α crystals. 14,[44][45][46] To date no consensus has been reached as for the exact origin of the multiple melting behaviour of PLLA. Fig.…”

“…Thus, the lower HDT is an important bottleneck for the expansion and diversification of poly(lactic acid) applications. 5 A series of effective nucleating agents have been reported for PLLA including talc, 8 uracil, 9 N,N′-bis(benzoyl) suberic acid dihydrazide, 10 and phenylphosphonic acid, 11 whilst nanoclay (MMT), 12 carbon nanotubes, 13,14 nano-calcium carbonate (CaCO 3 ), 11 nano-zinc citrate (ZnCC), 15 graphene oxide (GO) 16 and fullerenes (C60) 13 have been shown to provide the added advantage of acting as reinforcements for the polymer. The degree of crystallinity is also an important index for the characterization of crystallization properties of materials.…”

Poly(lactic acid)/Poly(ethylene glycol) Polymer Nanocomposites: Effects of Graphene Nanoplatelets

“…The above change of cold crystallization behavior in the PLA/PEG/xGnP nanocomposites results from the combined effects of nucleation and diffusion controlled growth processes. On the other hand, the nucleation ability of xGnP toward PLA matrix gives rise to the decreasing of cold crystallization temperature at higher xGnP loadings [22,23].…”