Heat Treatment Effects on the Mechanical Properties and Morphologies of Poly (Lactic Acid)/Poly (Butylene Adipate-co-terephthalate) Blends

In this study the relationships between mechanicals properties and morphology of the poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blends with or without heat treatment were investigated. The differential scanning calorimetry (DSC) analysis showed that blends have a two-phase structure indicating that they are immiscible. On the other hand, the PLA/PBAT (30/70) blend achieved the best tensile and impact strength because of its sea-island morphology, except for high PBAT content. The PLA/PBAT (70/30) and PLA/PBAT (50/50) blends showed irregular and directive-layer morphologies, in scanning electron microscopy (SEM) analysis, producing a break cross-section with various fiber shapes. Both blends showed lower tensile strength and impact strength than the PLA/PBAT (30/70). After heat treatment, the PLA/PBAT blends showed high modulus of tensile and HDT because of a high degree of crystallization. The high degree of crystallization in the blends, which originated in the heat treatment, reduced their impact strength and elongation. However, the effect of high degree of crystallization on the PLA/PBAT (30/70) blend was small because of its sea-island morphology.