Multicomponent Modification of Polyethylene-Based Films for Enhanced Hydrophobicity and Balanced Gas Transport and Water Vapor Barrier Properties

Hydrophobic gas-permeable polyethylene films with balanced water vapor resistance and gas transport properties are desirable for membrane applications; however, achieving an effective balance between moisture barrier performance and gas permeability remains challenging. In this work, dense non-porous polyethylene-based composite films were fabricated through melt blending and film casting by incorporating fluorinated ethylene propylene copolymer (FEP), polyethylene wax (PE wax), and hydrophobic silica nanoparticles (SiO2). The effects of multicomponent modification on surface properties, crystallization behavior, morphology, and transport performance were investigated. The optimized formulation, PEH-2, containing 3 wt% PE wax and 1 wt% hydrophobic SiO2 based on the LLDPE/POE matrix, exhibited the most balanced transport performance. The synergistic regulation of surface energy, interfacial morphology, and diffusion pathways by FEP, PE wax, and SiO2 enhanced hydrophobicity while maintaining CO2 transport capability. The dense composite structure increased resistance to water vapor diffusion, whereas regulated molecular pathways facilitated CO2 transport. PEH-2 exhibited a water contact angle of 110.75°, a CO2 transmission rate of 6498 cm3·m−2·day−1 at 0.1 MPa, and a WVTR of 1.20 g·m−2·day−1. The CO2 transmission rate/WVTR ratio (approximately 5.4 × 103) was used to evaluate the balance between gas transport and moisture barrier performance. This study provides a scalable strategy for designing polyethylene-based composite membranes with balanced moisture resistance and gas transport properties.