Poly(l‐lactide)/poly(d‐lactide)/multiwalled carbon nanotubes nanocomposites: Enhanced dispersion, crystallization, mechanical properties, and hydrolytic degradation

Abstract

Biodegradable stereocomplex-type poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA)/multiwalled carbon nanotubes (MWCNTs) nanocomposites are prepared via simple melt blending method at PDLA loadings from 5 to 20 wt %. Formation of the stereocomplex crystals in the nanocomposites is confirmed by the phase transition in the differential scanning calorimetric profiles. Field emission scanning electron microscopy observation indicates that MWCNTs are nicely dispersed in the PLLA/PDLA/MWCNTs ternary blends with 20 wt % PDLA loading due to the increased shear stress in the melt-compounding with presence of PDLA. The overall crystallization rates are faster in the PLLA/PDLA/MWCNTs nanocomposites than in PLLA/MWCNTs nanocomposite; however, the crystallization mechanism and crystal structure of these nanocomposites remain unchanged despite the presence of PDLA. The storage modulus above glass transition temperature has been apparently improved in the PLLA/PDLA/MWCNTs nanocomposites with respect to PLLA/ MWCNTs nanocomposite. It is interesting to find that the hydrolytic degradation rates have been enhanced obviously in the PLLA/ PDLA/MWCNTs nanocomposites than in PLLA/MWCNTs nanocomposite, which may be of great use and importance for the wider practical application of PLLA/MWCNTs nanocomposites.

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

“…The PEG with M w of 2,000 g/mol showed better effect on forming stereocomplex PLA, which is more evident when the PEG content is increased to 10 wt%. SC-PLA was obtained with the assistance of making nanocomposites via melt blending in the presence of MWCNTs which acted as a nucleating agent to promote the formation of SC-PLA (94). Very recently, it was found that the stereocomplexation of PLA from the melt could also be significantly enhanced by using nanocrystal cellulose (NCC) as nuclei sites and the enhancement was more pronounced at high(er) NCC loading (25 wt%) (95).…”

Poly(lactic acid) stereocomplex formation: Application to PLA rheological property modification

“…Up to now, investigations have mainly focused on gaining an understanding of the stereocomplexation phenomenon with the emphasis on the crystallization mechanism and on the effect of different parameters such as molecular weight, optical purity as well as the blend preparation method and crystallization conditions . In terms of applications, PLA stereocomplex has been investigated as a nucleation site for PLA homocrystallization, as a thermo‐mechanical properties modifier as well as in PLA nanocomposites . However, very few reports exist on the improvement of PLA rheological properties with the use of a stereocomplex .…”

Toward environment‐friendly composites of poly(ε‐caprolactone) reinforced with stereocomplex‐type poly(l‐lactide)/poly(d‐lactide)

“…Poly(lactic acid) (PLA) has been paid considerable attention from both fundamental and practical perspectives because it is derived completely from renewable resources, and hence production is sustainable, but also it can significantly contribute to the control of green‐house gas (CO 2 ) emission as a result of carbon capture during plant growth and the eventual complete biodegradability of the PLA matrix . PLA has two stereoregular enantiomers, poly( l ‐lactide) (PLLA), and poly( d ‐lactide) (PDLA) due to the presence of a chiral carbon in the skeletal chain.…”