Crystallization improvement of poly(L‐lactide) induced by functionalized multiwalled carbon nanotubes

Abstract

In the present work, the crystalline structures and the melting behaviors of poly(L‐lactide) (PLLA) obtained after being annealed at different conditions have been investigated through differential scanning calorimetry and wide‐angle X‐ray diffraction, respectively. To improve the crystallization of PLLA, functionalized multiwalled carbon nanotubes (f‐MWCNTs) are introduced into PLLA. Our results show that by prolonging the annealing duration or enhancing the annealing temperature, the degree of crystallinity of PLLA gradually increases. Very important, the addition of f‐MWCNTs promotes the cold‐crystallization of PLLA dramatically even at relatively lower annealing temperature or in shorter annealing duration. Further results show that, whether in neat PLLA or in PLLA/f‐MWCNTs nanocomposite, only α form crystal forms during the annealing process. The glass transition temperature shifts to high temperatures because of the increase of crystallinity. F‐MWCNTs exhibit great heterogeneous nucleation effect for PLLA crystallization through enhancing the nucleation density, leading to homogeneous and tiny spherulites formation in a very short time. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 326–339, 2009

Rigid amorphous phase and constrained polymer chains in poly(L‐lactide) nanocomposites with carboxylated carbon nanotubes prepared via reactive melt mixing

“…Both the annealing time and presence of MWCNT increased the glass transition temperature of PLLA. Thus, they verified that amorphous polymer chains were significantly influenced by the presence of crystallized polymer chains . In this work, we tried to distinguish and quantify the influence of the crystalline phase and the presence of MWCNTs on the RAF of the polymer matrix.…”

The plasticizer‐assisted formation of a percolating multiwalled carbon nanotube network in biodegradable poly(L‐lactide)

“…The above change of cold crystallization behavior in the plasticized PLLA/MWCNT composites is resulted from the combined effects of nucleation and diffusion controlled growth processes. On the one hand, the nucleation ability of MWCNTs towards PLLA matrix can give rise to the decreasing of cold crystallization temperature, 21,25,26 which could become significant with the MWCNT Figure 4 Temperature dependent loss factor in the plasticized (a) and virgin (b) composites. loadings.…”

Effects of carbon nanotubes on glass transition and crystallization behaviors in immiscible polystyrene/polypropylene blends

“…7), one can observe that some FMWCNTs are present in the particles of PP and others still maintain in PS matrix. This observation is different from our previous observation in PP/ethylene‐ co ‐vinyl acetate/FMWCNTs [33–35], in which FMWCNTs at high content tend to migrate from dispersed ethylene‐ co ‐vinyl acetate phase to the matrix (PP phase) when the composites exhibit the sea‐island morphology. In that work, the reason is partially attributed to the relatively small particles, which cannot contain the FMWCNTs.…”