Melt mixing activated Zn-BDC MOF for sustainable packaging: enhancing barrier properties in PLA/PCL nanocomposites

Sustainable packaging remains a key challenge in the transition away from petroleum-based materials. This study explores the development of biodegradable films based on a poly(lactic acid) (PLA)/polycaprolactone (PCL) blend, with 30 wt% PCL as the dispersed phase. To enhance moisture barrier performance, a zinc-based metal–organic framework with 1, 4-benzenedicarboxylic acid (Zn-BDC MOF) was synthesized and incorporated into the blend at 1 wt%, 3 wt%, 5 wt%, and 7 wt% loadings via melt mixing using a co-rotating twin-screw micro-compounder, ensuring homogeneous dispersion. The melt mixing process facilitated the activation of Zn-BDC MOF by enhancing its surface exposure and promoting coordination interactions with the polymer chains, as evidenced by FTIR shifts in carbonyl and methylene bands, indicating modified intermolecular interactions. These changes were linked to increased PLA crystallinity and disrupted PCL crystallinity, highlighting Zn-MOF’s dual structural role. Thermal and morphological analyses (2D WAXS, DSC, TGA, SEM), along with dynamic mechanical testing (DMA) and surface assessments (contact angle, AFM), demonstrated enhanced interfacial compatibility between PLA and PCL. Notably, 3 wt% Zn-MOF displayed optimal performance, with a higher storage modulus and improved dispersion, without significant agglomeration. Surface analysis revealed a progressive decrease in contact angle and increased roughness, indicating improved hydrophilicity and heterogeneity. Despite the increased surface polarity, water absorption and vapor permeability were reduced at moderate Zn-MOF loadings, attributed to increased tortuosity and densified morphology, which limited water diffusion pathways. Overall, the incorporation of Zn-MOF into PLA/PCL blends significantly enhances compatibility, and moisture resistance, thereby establishing this nanocomposite system as a promising candidate for sustainable packaging.

Graphical Abstract