Tailoring The Morphology And Properties Of Biodegradable Poly(lactic Acid)/poly(butylene Adipate-co-terephthalate)Blends By Graphene Nanoplatelets

Poly(lactic acid)(PLA)is a biobased fully biodegradable polyester which has enormous potential as an alternative to the petro-based non-biodegradable materials,due to its excellent processability and good mechanical strength.Nevertheless,PLA has the drawbacks,such as brittle and poor thermal stability,restricting its widespread applications.Blending PLA with biodegradable flexible poly(butylene adipate-co-terephthalate)(PBAT)is expected to improve its toughness without compromising the biodegradability.However,PLA is incompatible with PBAT,leading to weak interfical adhension between PLA and PBAT and poor mechanical properties.Adding nano fillers is one of the most effective ways in tailoring the morpholog and properties of PLA/PBAT blends.In this work,graphene nanoplatelets(GNP)were added into the PLA/PBAT blends to tailor the morphology and properties of PLA/PBAT blends.The main results are as follows:(1)The effect of GNP on the morphology and properties of PLA/PBAT blends.At first,PLA/GNP masterbatch were prepared by solution method.Then,the PLA/PBAT/GNP nanocomposites are prepared by melt blending.The transmission electron microscopy(TEM)results show that PLA and PBAT are incompatible and exhibit sea-island distribution.The GNP nanoparticles are located in the minor PBAT phase and large agglomeration is detected.With increasing the content of GNP.the droplet of PBAT phase grows bigger and starts to deforim.The tensile testing results show that PBAT has a significant toughening effect on PLA.The addition of'GNP further improves the toughness of PLA/PBAT blends with a maximum improvement of 23%while retaining the tensile strength and tensile modulus.The crystallization behavior of PLA was investigated by using differential scanning calorimetry(DSC)and polarized optical microscopy(POM).The results show that the addition of PBAT and GNP promotes the crystallization of PLA in the blends.The thermogravimetric analyses(TGA)show that the introduction of GNP improve the thermal stability of PLA/PBAT matrix.Rheological property measurements reveal that the storage modulus and complex viscosity of theblends inerease with the addition of FNP.(2)The effect of PEO on the dispersity of GNP and properties of PLA/PBAT/GNP nanocomposites.To promote the dispersion of GNP,a freezing-dried poly(ethylene oxide)(PEO)/GNP masterbatch was prepared,and then the PLA/PBAT/GNP nanocomposites were obtained by blending the masterbatch with PLA and PBAT.Since the molecular weight of PEO may affect its compatibility with PLA,PEO with three different molecular weights were used in this work.TEM results show that the GNP nanoparticles are located in the minor PBAT phase and the introduction of PEO improves the dispersion of GNP.In addition,the lower the molecular weight of PEO,the better the dispersity.The tensile testing and TGA results show that PLA/PBAT/GNP nanocomposites have excellent mechanical properties and thermal stability due to better dispersion of GNP.The toughness of PLA/PBAT/GNP nanocomposites with a maximum improvement of 94.4%without sacrificing the tensile strength and tensile modulus,compared with that of GNP1 nanocomposites.Rheological property measurements reveal that the storage modulus and complex viscosity of the blends decrease with the addition of PEO and the effect is more pronounced for PEO with lower molecular weight.