Laponite Imparts Ultraviolet Shielding Properties in Polylactic Acid/Guar Gum Bilayer Packaging

ABSTRACT PLA films are a sustainable alternative to conventional plastics. However, their high cost and limited optical and mechanical properties present challenges that need to be addressed. Bilayer films based on polylactic acid (PLA) and guar gum (GG), with and without Laponite (Lap), were developed and characterized regarding their physical, mechanical, optical, and barrier properties. PLA‐films were produced by thermocompression and subsequently coated with GG‐based solutions containing 0% or 15% (w/w) Lap. The addition of GG and Lap increased the film thickness (148.9 → 170.7 μm) as well as the moisture content (0.4% → 3.0%). Contact angle measurements revealed that the incorporation of GG increased hydrophobicity (water contact angle: 86.3° → 101.4°), while oil wettability was improved with the addition of Lap. TP (PLA‐film) showed the highest tensile strength (58.2 MPa) and modulus of elasticity (2.3 GPa), while PLA‐films coated with guar gum containing Lap (PLA‐GG‐Lap) showed reduced stiffness and toughness and slightly improved elongation at break (4.8%). Colorimetric analysis indicated minimal variation (Δ E < 2), while opacity and UV barrier properties were improved by the incorporation of Lap, with transmittance at 280 nm decreasing from 55.6% (TP) to 17.7% (TPGL). PLA‐GG‐Lap were used as packaging for grape juice, reducing the degradation of anthocyanins when exposed to UV light, highlighting its potential food application.