Manipulating Crystallization for Simultaneous Improvement of Impact Strength and Heat Resistance of Plasticized Poly(l-lactic acid) and Poly(butylene succinate) Blends

Abstract

Crystalline morphology and phase structure play a decisive role in determining the properties of polymer blends. In this research, biodegradable blends of poly(l-lactic acid) (PLLA) and poly(butylene succinate) (PBS) have been prepared by melt-extrusion and molded into specimens with rapid cooling. The crystalline morphology (e.g., crystallinity, crystal type and perfection) is manipulated by annealing the molded products from solid-state within a short time. This work emphasizes on the effects of annealing conditions on crystallization and properties of the blends, especially impact toughness and thermal stability. Phase-separation morphology with PBS dispersed particles smaller than 1 μm is created in the blends. The blend properties are successfully dictated by controlling the crystalline morphology. Increasing crystallinity alone does not ensure the enhancement of impact toughness. A great improvement of impact strength and heat resistance is achieved when the PLLA/PBS (80/20) blends are plasticized with 5% medium molecular-weight poly(ethylene glycol), and simultaneously heat-treated at a temperature close to the cold-crystallization of PLLA. The plasticized blend annealed at 92 °C for only 10 min exhibits ten-fold impact strength over the starting PLLA and slightly higher heat distortion temperature. The microscopic study demonstrates the fracture mechanism changes from crazing to shear yielding in this annealed sample.

Crystallization behavior analysis and reducing thermal shrinkage of poly(lactic acid) miscibilized with poly(butylene succinate) film for food packaging

“…When PLA was blended with 20%wt PBS, the coalescence of PBS phase in PLA matrix was clearly observed. This result indicated poor interfacial adhesion between PLA and PBS phases, as several other studies reported 11,19,24,27,30,31 . Notably, the homogeneous phase in the PLA/PBS blend was effectively improved by SA addition, especially at a high SA content of 0.5 phr.…”

“…This result indicated poor interfacial adhesion between PLA and PBS phases, as several other studies reported. 11,19,24,27,30,31 Notably, the homogeneous phase in the PLA/PBS blend was effectively improved by SA addition, especially at a high SA content of 0.5 phr. It was worth mentioning that PLA esterified with the PBS chains through in situ reactive blending, brought the miscibility in the PLA/PBS blend system.…”

One-Pot Reactive Melt Recycling of PLA Post-Consumer Waste for the Production of Block Copolymer Nanocomposites of High Strength and Ductility

“…In turn, the transparency of the reactive nanocomposite confirms good dispersion and spatial distribution of clay within the polymer matrix. Table 4 provides the tensile data of various bio-based and petroleum-based polymers, together with the similar PLA-based block copolymers prepared by different synthesis routes [37][38][39][40][41][42]. From the analysis of the mechanical data reported in Table 4, it is evident that the tensile properties of PLA-PEG block copolymers reported in the literatures are quite different.…”

“…Biodegradable poly(butylene adipate-co-terephthalate) (PBAT, Ecoflex from BASF) is characterized by high elongation at break (>300%), with strength and modulus of 18.8 and 30 MPa, respectively [40]. A relatively higher modulus (450 MPa) is reported for poly(butylene succinate) (BioPBS, FZ91PD from PTT MCC Biochem), with a tensile strength of 33.3 MPa and elongation at break of 330% [41]. Considering the benefits obtained with a nanoscale distribution of clays within the polymer matrix in terms of improved mechanical properties at low filler content, PLA-based block copolymer composites of this study exhibit comparable properties to some petroleum-based polymers grade widely used in packaging applications such as polypropylene [42].…”