Structure–thermal–morphological correlation in starch–PVA reinforced cactus mucilage bio-based composite films

Abstract

This study presents a systematic investigation of the structural, thermal, and morphological characteristics of starch–PVA reinforced cactus bio-based composite films using FTIR, DSC, XRD, TGA, DMA, and SEM analyses. FTIR results suggested enhanced intermolecular hydrogen-bonding interactions among starch, PVA, and cactus-derived polysaccharides, with possible minor ester-link formation in the presence of citric acid. DSC analysis showed a glass transition temperature (Tg) in the range of 38–40 °C and a minor endothermic transition near 83 °C associated with bound moisture relaxation. The thermal transitions observed using the PerkinElmer DSC 9 were reproducible across replicate measurements, indicating good thermal consistency of the developed composite system. XRD analysis indicated a predominantly amorphous morphology with limited semi-crystalline domains and a crystallinity index of approximately 23.32%. TGA results suggested improved thermal stability relative to plasticized starch systems, while DMA results indicated moderate storage-modulus retention and viscoelastic stability over the investigated temperature range. SEM observations of tortuous crack propagation pathways and localized deformation mechanisms. The combined results indicate that the developed composite exhibits balanced thermal and structural performance and potential for sustainable flexible bio-based material applications. However, additional mechanical, durability, water-resistance, and comparative performance studies are necessary to evaluate its suitability as a leather substitute.