Unique isothermal crystallization phenomenon in the ternary blends of biopolymers polylactide and poly[(butylene succinate)-co-adipate] and nano-clay

Melt and cold isothermal crystallization studies were carried out on polylactide (PLA)/poly[butylene succinate)-co-adipate] (PBSA) neat blend and blend-clay composites. The neat blend and blend-clay composites were prepared by melt-blending in a batch mixer. The weight ratio of PLA to PBSA was fixed at 70:30, while the content of the organoclay was varied from 0 to 9 wt%. The spherulitic growth rates and morphologies of PLA and PBSA in the samples were examined through polarized optical microscopy, while the rate of crystallization and the extent of crystallinity were studied through differential scanning calorimetry. The kinetics of melt and cold crystallization of PLA were adequately described by the Avrami model. There was a strong dependence of the rate of crystallization and extent of crystallinity of PLA on the extent of clay loading and flow induced morphology. For composites with 2 and 6 wt% clay loading, uniquely slower crystallization occurred. A qualitative relationship between phase morphology and crystallization, as affected by clay loading, is therefore described.