Development of Mono-Material Multilayer Light Barrier Films.

Mono-material multilayer polypropylene films were developed as light barrier structures through the incorporation of mineral-filled composite layers. Trilayer films with different layer arrangements were fabricated by thermocompression from polypropylene-based films containing 0, 1 and 5 wt.% of talc and kaolinite. A monolayer polypropylene film of equivalent total thickness was used as a control. Structural, thermal, mechanical, optical, and gas barrier properties were evaluated for all films fabricated. A well-defined trilayer structure was confirmed by SEM. FTIR analysis demonstrated negligible thermo-oxidation, with no thermal-degradation during processing. Improved thermal stability and a slight modification in crystallinity were evidenced by TGA and DSC, respectively. XRD revealed the predominance of the α-form crystalline phase and a preferential polymer crystal orientation associated with the particle presence. Regarding mechanical behavior, enhanced stiffness and tensile strength without loss of sealability or puncture resistance were observed. Trilayer films exhibited significantly reduced UV and visible light transmittance, while maintaining adequate translucency, making them suitable for photosensitive packaging applications. Gas permeabilities remained nearly unchanged, confirming that the barrier performances were preserved. Overall, these mono-material multilayer composites films offer a promising and recyclable alternative to conventional multi-material light barrier packaging, combining improved UV protection, mechanical robustness, and environmental compatibility.