The Study Of Poly(Lactic Acid)Films Modified With Graphene Oxide Nanoplatelets

In this paper,the covalent polymer functionalization of graphene oxide and its effect on poly?lactic acid?films were investigated.The graphene oxide grafted with poly?L-lactic acid??PLLA-g-GO?was synthesized via in-situ polymerization.The poly?lactic acid?composites reinforced with PLLA-g-GO were prepared by solution blending and followed by uniaxial drawing.The mechanics,thermal and barrier properties were mainly studied.Poly?L-lactic acid?was successfully grafted onto the surfaces of graphene oxide by in-situ polycondensation with commercial available L-lactic acid monomers.Fourier-transform IR?FT-IR?and XPS spectra revealed that the poly?L-lactic acid?was covalently attached to the graphene oxide.Raman spectroscopy and XPS showed the partial reduction of PLLA-g-GO.The surface performance of PLLA-g-GO was changed and can be dispersed in chloroform.The poly?lactic acid?/PLLA-g-GO composite films were prepared by solution blending with chloroform as solvent.The dispersion of PLLA-g-GO in polymer was evaluated with scanning electron microscope?SEM?and X-ray diffraction?XRD?,and found PLLA-g-GO was uniformly dispersed in poly?lactic acid?matrix.Thermogravimetric analyses?TGA?showed the addition of PLLA-g-GO improved the thermal stability of composites.The tensile strength was also increased.A large decline in oxygen permeability coefficient of composite film was obtained,where oxygen permeability coefficient was decreased by about 77.4%at a low PLLA-g-GO loading of 0.5wt%.The uniaxial drawing of poly?lactic acid?/PLLA-g-GO composite films were taken.The alignment of PLLA-g-GO in the composites was observed in SEM images.In the uniaxially drawn composite films,PLLA-g-GO platelets tended to align parallel to the film surface.The oxygen barrier performance of the drawn composite film was obviously enhanced.The drawn composite film presented a low value of oxygen permeability coefficient(1.7×10^-15cm³·cm·cm^-2·s^-1·Pa^-1),and showed a prominent decrease of 93.3%compared to the undrawn composite film.