Fogging on agricultural greenhouse covering films reduces solar transmission, resulting in insufficient photosynthetically active radiation and hindering crop growth. In this study, a long-acting antifogging composite film was developed by incorporating diatomite (DE) and sorbitan tristearate (STS) into low-density polyethylene (LDPE). The introduction of STS enabled the surface of LDPE to undergo a transition from hydrophobic to hydrophilic. The film has the ability of preventing fogging and increasing solar irradiation inside the greenhouse by 15%. On the 30th day of the hot fog test, the failure area of the film was only 20%, and the introduction of DE reduced the diffusion coefficient of STS from 0.2 to 0.06 cm 2 min −1 . Rheological properties and crystallinity testing revealed the interaction mechanism between STS and LDPE molecules. Greenhouse cultivation experiments showed that the chlorophyll content of Chinese cabbage ( Brassica rapa ssp. chinensis ) and spinach ( Spinacia oleracea ) grown under the antifogging film increased by 24% and 30%, respectively. This antifogging film can be produced on a large scale using the casting method and offers significant potential for improving the quality of greenhouse crops.
Robust antifogging films have significant potential for a wide range of applications on the surfaces of transparent materials. Nevertheless, currently either their preparation methods are complex or their mechanical properties such as hardness, wear, scrub and water resistance are yet to be improved before they can be applied in practical applications. In this work, we have developed a facile room temperature approach to fabricating free-standing films of excellent antifogging properties and mechanical robustness. Glutaraldehyde (GA) was used to cross-link polyvinyl alcohol (PVA) and ultraviolet (UV) light was applied to initiate polymerization of poly (ethylene glycol) diacrylate (PEGDA), leading to robust interpenetrating networks (IPN). The films also had excellent mechanical properties with pencil hardness up to 8H, Taber wear-resistance up to 10,000 cycles, and sponge scrub resistance up to 300 cycles. The tensile strength and tearing strength of films reached as high as 100 MPa and 700 kN/m, respectively, much higher than those of free-standing films reported so far. This approach may hold great potential for broad application on various substrates, particularly those with low glass transition temperatures (e.g., transparent plastic films). It may expand the possibilities for future applications of free-standing antifogging films for screens, optical lenses and so on.
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