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 nanocmnposites. 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 nanocompasites 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 I 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 nancomposnes. 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, To 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.