Search Results (3)

Coatings are often applied in the materials industry to impart hydrophobic properties to the produced materials. Commonly used coatings contain plastics as well as perfluorinated compounds, which pose challenges for environmental sustainability due to their persistence and end-of-life impacts. Coatings based on natural wax, such as rapeseed, soy, palm or beeswax, constitute a key bio-based and more sustainable alternative. These waxes exhibit high hydrophobicity while also being biodegradable, offering opportunities to replace fossil-derived coatings within circular-economy material systems. Wax coating constitutes a protective layer that undergoes biodegradation after a certain amount of time. This paper presents the results of studies concerning the development of a wax coating characterized by a coarse microstructure that increases water resistance, and an appropriate susceptibility to biodegradation. It was revealed that all the analysed coatings were susceptible to biodegradation, although their rates varied markedly depending on wax type and form. The biodegradation of palm wax in bulk form and as a thick layer was 17% and 80%, respectively, after 180 days. Palm wax exhibited a pronounced ability to bind inorganic and organic matter deposits, which reduced the degradation rate. When applied as a thin coating, palm wax did not form such a barrier. Palm wax significantly influences coating durability because its surface undergoes morphic changes induced by bio-surfactants secreted by microorganisms. These changes the adhesion of organic and inorganic matter particles, and the layer thus established limits the diffusion of oxygen, enzymes and microorganisms to the wax coating. The tests demonstrated that the addition of palm wax to wax mixtures allows the degradation rate to be controlled, and that its inhibitory effect is strongly dependent on the geometry of the material. Full article

The widespread phase-out of long-chain per- and poly-fluoroalkyl substances (PFASs) has created an urgent need for durable, fluorine-free water-repellent finishes that match the performance of legacy chemistries while minimising environmental impact. Here, the performance of an eco-friendly hybrid organic–inorganic treatment obtained by the in situ hydrolysis–condensation of triethoxy(octyl)silane (OS) in an amino-terminated polydimethylsiloxane (APT-PDMS) aqueous dispersion was investigated. The sol was applied to plain-weave cotton and polyester by a pad-dry-cure process and benchmarked against a commercial fluorinated finish. Morphology and chemistry were characterised by SEM–EDS, ATR-FTIR, and Raman spectroscopy; wettability was assessed by static contact angle, ISO 4920 spray ratings, and AATCC 193 water/alcohol repellence; and durability, handle, and breathability were evaluated through repeated laundering, bending stiffness, and water-vapour transmission rate measurements. The silica/PDMS coating formed a uniform, strongly adherent nanostructured layer conferring static contact angles of 130° on cotton and 145° on polyester. After five ISO 105-C10 wash cycles, the treated fabrics still displayed a spray rating of 5/5 and AATCC 193 grade 7, outperforming or equalling the fluorinated control, while causing ≤5% loss of water-vapour permeability and only a marginal increase in bending stiffness. These results demonstrate that the proposed one-step, water-borne sol–gel process affords a sustainable, industrially scalable route to high-performance, durable, water-repellent finishes for both natural and synthetic textiles, offering a viable alternative to PFAS-based chemistry for outdoor apparel and technical applications. Full article

In this study, particle loading, polyfluorinated alkyl silanes (PFAS or FAS) content, superhydrophobicity, and crack formation for nanocomposite coatings created by the spray coating process were investigated. The formulations comprised hydrophobic silica, epoxy resin, and fluorine-free or FAS constituents. The effect of FAS content and FAS-free compositions on the silica and epoxy coatings’ chemistry, topography, and wetting properties was also studied. All higher particle loadings (~30 wt.%) showed superhydrophobicity, while lower particle loading formulations did not show superhydrophobic behavior until 13% wt. FAS content. The improved water repellency of coatings with increased FAS (low particle loadings) was attributed to a combination of chemistry and topography as described by the Cassie state. X-ray photoelectron spectroscopy (XPS) spectra showed fluorine enrichment on the coating surface, which increases the intrinsic contact angle. However, increasing the wt.% of FAS in the final coating resulted in severe crack formation for higher particle loadings (~30 wt.%). The results show that fluorine-free and crack-free coatings exhibiting superhydrophobicity can be created. Full article