Fabrication and film-forming mechanism of PCTFE films with exceptional water-vapor barrier and mechanical properties via solvent-assisted method

Polychlorotrifluoroethylene (PCTFE) has the outstanding water-vapor barrier performances among thermoplastics, and is with excellent transparency, high cryogenic toughness, and ultralow dielectric constant/loss. It plays an important role in high-performance packaging, electric circuit constructions, anti-corrosion coatings, cryogenic sealing, and so forth. Nevertheless, due to its borderline thermal stability and sensitivity to shearing effect, the melt-processing of PCTFE is rather difficult. Herein, a solvent-assisted method, which contained fabrication, coating, drying, and sintering of PCTFE suspension, was proposed for the fabrication of PCTFE films. The influence of processing parameters, including particle shape, drying temperature, and sintering time on the film-forming process was investigated. The as-prepared PCTFE films exhibited exceptional mechanical properties, with a tensile strength and failure strain of ∼42 MPa and ∼108 %, respectively. The water vapor transmission rate, light transmittance, and haze reached ∼0.02 g/(m2·24 h), ∼91 %, and ∼3 %, respectively. Finally, the potential film-forming mechanism was explained by the densification of PCTFE particles via capillary force, neck formation and particles coalescence driven by surface tension and viscous flow, and co-crystallization across the initial particle interfaces. In summary, the solvent-assisted method opened a new pathway for the processing of PCTFE films and is conducive to broadening their application fields.