Multiresponse optimization of Ar/O 2 cold plasma treatment for fully biobased PLA/luffa fiber biocomposites

The intrinsic incompatibility between hydrophilic natural fibers and hydrophobic biopolymer matrices remains a critical challenge in the development of high-performance fully biobased composites. This study presents a novel multiresponse optimization framework for Ar/O 2 cold-plasma surface modification of Luffa fibers to enhance the mechanical performance of polylactic acid (PLA)/Luffa biocomposites. A Box–Behnken experimental design combined with response surface methodology was employed to model and optimize the effects of plasma power (100–180 W), the Ar/O 2 gas ratio factor (20–100% according to the defined composition scale), and treatment time (5–15 min) on four key mechanical responses: tensile strength, flexural strength, impact energy, and puncture resistance. The optimal conditions, determined using Derringer’s desirability function, were 152 W, a gas ratio level of 72%, and 10.5 min, yielding an overall desirability of 0.894. Compared with untreated controls, the optimized biocomposites exhibited improvements of 29% in tensile strength, 75% in flexural strength, 27% in impact energy, and 49% in puncture resistance. Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analyses revealed plasma-induced chemical, morphological, and structural modifications of the fibers that were consistent with improved fiber–matrix interaction and more efficient stress transfer. This study addresses a critical gap in the development of scalable and solvent-free surface-modification strategies for lignocellulosic fibers used in high-performance biocomposites. The findings demonstrate that optimized Ar/O 2 cold-plasma treatment provides an effective and environmentally responsible strategy for developing sustainable packaging and lightweight automotive components, offering a promising alternative to conventional chemical treatments.