Crystallinity of biodegradable polymers reinforced with functionalized carbon nanotubes |
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Authors: | Ali Nabipour Chakoli Jiehe Sui Maryam Amirian Wei Cai |
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Affiliation: | (1) School of Material Science and Engineering, Harbin Institute of Technology, P.O. Box 405, Harbin, 150001, Heilongjiang Province, People’s Republic of China; |
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Abstract: | Well-dispersed multiwall carbon nanotubes (MWCNTs) were prepared by grafting poly(L-lactide-co-ε-caprolactone) (PLACL) biodegradable copolymer onto the sidewall of hydroxylated MWCNTs using oligomeric L-lactide (LA) and ε-caprolactone (CL). After preparation of MWCNT/PLACL composites, the effect of functionalized MWCNTs on
crystallinity of PLACL was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning
calorimetry (DSC), dynamic mechanical analysis (DMA), and polarized light optical microscopy (POM). The surface functionalization
effectively improved the dispersion and adhesion of MWCNTs which acted as reinforcing filler in the PLACL polymer matrix and
hence improved the physical and thermomechanical properties of the nanocomposites. The glass transition temperature (T
g) and the crystallinity of nanocomposites decreased in comparison with those of neat PLACL when the concentration of functionalized
MWCNTs in nanocomposites was 0.5 wt%. With further increment in concentration of functionalized MWCNTs, the T
g of composites increased until the T
g of neat PLACL, and also the crystallinity of composites increased. The functionalized MWCNTs have no significant effect on
the melting point of nanocomposites. The MWCNTs acted as heterogeneous nucleation points and increased the lamella size and
therefore the crystallinity of PLACL. Furthermore, the larger agglomerated clusters of both kinds of MWCNTs (i.e., MWCNT-grafted-PLACL
and pristine MWCNTs) are more effective than small clusters as nucleation points for growing the spherulites. |
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