Interactions, Structure and Properties of PLA/lignin/PBAT Hybrid Blends

Abstract

Poly(butylene adipate-co-terephthalate) (PBAT) was added to poly(lactic acid) (PLA)/lignin blends to decrease the considerable stiffness and brittleness of the blends. Two- and three-component blends were prepared in a wide composition range through homogenization in an internal mixer followed by compression molding. Interactions among the components were estimated by comparing the solubility parameters of the materials used and through thermal analysis. Mechanical properties were characterized by tensile testing. The structure of the blends was studied using scanning electron (SEM) and digital optical (DOM) microscopy. The results showed that the interactions between PBAT and lignin are somewhat stronger than those between PLA and the other two components. The maleic anhydride grafted PLA added as a coupling agent proved completely ineffective; it does not modify the interactions. The structural analysis confirmed the immiscibility of the components; the structure of the blends was heterogeneous at each composition. A dispersed structure formed when the concentration of one of the components was small, while, depending on lignin content, an interpenetrating network-like structure developed and phase inversion took place in the range of 30–60 vol% PBAT content. Lignin was located mainly in the PBAT phase. Properties were determined by the relative amount of PBAT and PLA; the addition of lignin deteriorated properties, mainly the deformability of the blends. Other means, such as reactive processing, must be used to improve compatibility and blend properties. The results contribute considerably to a better understanding of structure–property correlations in lignin-based hybrid blends.

Hemp hurd filled PLA‐PBAT blend biocomposites compatible with additive manufacturing processes: Fabrication, rheology, and material property investigations

“…From the SEM micrographs of the PLA:PBAT blend, it can be seen (in Figure 4A) that the non‐compatibilized blend, due to limited miscibility, has an inconsistent morphology with poor bonding between the two phases as there are ductile and brittle components 44,45 . While it is difficult to ascertain which parts are (Figure 4A) from either PLA or PBAT, due to PLA's brittle nature, it can be assumed that the elongated fibers consist mostly of PBAT polymer (see arrow).…”