Compatibility and interphase properties of poly(butylene succinate-co-adipate) (PBSA)/Kraft lignin films assessed by nanomechanical analyses

Abstract

The incorporation of technical lignins into biodegradable polymers to develop sustainable materials is a common valorization strategy for these biomacromolecules. PBSA and Kraft lignin (between 0 and 10 wt%) films were prepared and the phase morphology, miscibility, compatibility and interphase properties of the compounds were evaluated by atomic force microscopy quantitative nanomechanical mapping (AFM-QNM). Complementary differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) analyses were performed. The results suggested strong intermolecular interactions and partial miscibility between the components, with an average interphase thickness of approximately 55 nm. Lignin particles were homogeneously dispersed, having an average diameter of 58–117 nm, and promoted a stiffening effect in the PBSA phase. AFM-QNM measurements provided extensive qualitative and quantitative information on the morphology, nanomechanical properties of individual phases and interphase regions of PBSA/lignin films. This technique allowed a more comprehensive understanding of the compatibility and miscibility of lignin/thermoplastic compounds compared to conventional characterizations of these systems. • Phase boundaries were not observed in SEM images of PBSA/lignin films. • The morphology and interphase properties of PBSA/lignin films were assessed by AFM. • Lignin addition increased the T g and elastic modulus of PBSA. • PBSA and PBSA/lignin films presented unimodal elastic modulus distributions. • Nanomechanical properties suggested partial miscibility between lignin and PBSA.