Effect of Clay on Thermal, Mechanical and Gas Barrier Properties of Biodegradable Poly(lactic acid)/Poly(butylene succinate) (PLA/PBS) Nanocomposites

A series of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS)/layered silicate nancomposites were prepared by simple melt extrusion of PLA/PBS/Cloisite 30BX (organically modified MMT) clay. Extruded and compression moulded samples containing 1, 3, 5, 7 and 10 wt.% of clay having 80 and 20 wt.% of PLA and PBS respectively, were prepared to investigate morphological, thermal, mechanical and gas barrier properties of these biodegradable nanocomposites. Wide angle X-ray diffraction (WAXD) was used to assess the periodic distance of the clay layers. WAXD indicated an exfoliated structure for nanocomposites containing 1 and 3 wt.% of C30BX, while, dominantly intercalated structures were noticed for nanocomposites having 5, 7 and 10 wt.% of C30BX. Transmission Electron Microscopy (TEM) images confirmed mixed morphology of intercalated and exfoliated structure even for nanocomposites having 1 and 3 wt.% of C30BX, while some clusters or agglomerated tactoids were detected for higher clay containing (>3 wt.%) nanocomposites. Thermo gravimetric analysis (TGA) revealed the thermal stabilities of polymer blend and their nancomposites. Nanocomposite with 3 wt.% C30BX clay showed enhanced thermal stability compared to other nanocomposites. The effect on the crystallinity, investigated by Modulated Differential Scanning Calorimetry (MDSC) showed slight improvement for nanocomposites having 1, 3, 7 and 10 wt.% of C30BX studied. However, nanocomposites having 5 wt.% of clay content showed higher crystallinity compared to the rest of the nanocomposites. Mechanical properties (tensile strength, % elongation at break and Young's modulus) were measured by Instron Universal Testing Machine. Tensile strength and Young's modulus initially increased for nanocomposites of up to 3 wt.% of clay but then decreased with the introduction of more clay. Oxygen permeabilities of the nanocomposites were also measured. Barrier properties were improved by approximately 26% with the increase of clay content in these nanocomposites.