Yunyun Shi

A simple strategy to achieve very low percolation threshold via the selective distribution of carbon nanotubes at the interface of polymer blends

Selective distribution of carbon nanotubes (CNTs) at the interface of immiscible polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) is achieved via a combination of adding maleic anhydride grafted ABS (ABS-g-MA) and using an appropriate processing procedure. The composite shows a much lower percolation threshold of 0.05 wt%. The value obtained here is the smallest percolation threshold reported so far, comparing with those in the literature.

Super toughening of the poly(L-lactide)/thermoplastic polyurethane blends by carbon nanotubes

Carbon nanotubes (CNTs) were introduced into the poly(L-lactide)/thermoplastic polyurethane (PLLA/TPU) blend to prepare the ternary nanocomposites. The results showed that CNTs selectively localized in the TPU phase, leading to a morphological change from the sea-island morphology to the quasi-cocontinuous morphology. The high content of the CNTs induced the formation of the percolated network structure. Consequently, super toughened PLLA/TPU/CNTs nanocomposites were prepared successfully. More apparent cavitation of the TPU phase and the intensified local plastic deformation of the PLLA matrix under the impact load were observed on the impact-fractured surface of the ternary nanocomposites. This was believed to be the main toughening mechanisms for the ternary nanocomposites. After being annealed, besides the morphological change of the nanocomposites, PLLA matrix also exhibited a large number of crystalline structures. Furthermore, the impact toughness of the ternary nanocomposites was enhanced further.

MICROSTRUCTURE EVOLUTION OF ISOTACTIC POLYPROPYLENE DURING ANNEALING: EFFECT OF POLY(ETHYLENE OXIDE)

The microstructure evolution of isotactic polypropylene (iPP) during annealing is reported. A few amount of poly(ethylene oxide) (PEO) which exhibits much lower melt temperature compared with iPP was introduced into iPP in this work. The crystalline structure of iPP was detected using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), and the relaxation of iPP was characterized using dynamic mechanical analysis (DMA). The variation of PEO morphology was investigated by scanning electron microscopy (SEM). The results show that the crystallization, including the primary crystallization and second crystallization during annealing, as well as the relaxation of iPP matrix is promoted with the presence of PEO.