Superhydrophobic coatings with contact angles (CAs) > 150° and sliding angles (SAs) < 10° have become the focus of research and industrial development studies for water repellency applications. Furthermore, superhydrophobic coatings have shown to reduce ice adhesion by means of their low surface energy chemistry and nano/micro roughness. Superhydrophobicity can be achieved by combining the chemistry and the roughness of the surface, inspired by the lotus leaf composition and structure. Durability enhancement of superhydrophobic surfaces is a critical issue for commercial and industrial applications. Consequently, the use of superhydrophobic surfaces in practical applications is limited due to their poor mechanical abrasion resistance and hostile environmental conditions. Covalent bonding of the micro/nano particles to the binder material was identified as essential for durability enhancement. This review summarizes the state of the art of the design, preparation techniques of durable superhydrophobic coatings and the characterization techniques for durability evaluation.

Hybrid sol–gel superhydrophobic coatings based on alkyl silane-modified nanosilica were synthesized and studied. The hybrid coatings were synthesized using the classic Stöber process for producing hydrophilic silica nanoparticles (NPs) modified by the in-situ addition of long-chain alkyl silanes co-precursors in addition to the common tetraethyl orthosilicate (TEOS). It was demonstrated that the long-chain alkyl substituent silane induced a steric hindrance effect, slowing the alkylsilane self-condensation and allowing for the condensation of the TEOS to produce the silica NPs. Hence, following the formation of the silica NPs the alkylsilane reacted with the silica’s hydroxyls to yield hybrid alkyl-modified silica NPs having superhydrophobic (SH) attributes. The resulting SH coatings were characterized by contact angle goniometry, demonstrating a more than 150° water contact angle, a water sliding angle of less than 5°, and a transmittance of more than 90%. Confocal microscopy was used to analyze the micro random surface morphology of the SH surface and to indicate the parameters related to superhydrophobicity. It was found that a SH coating could be obtained when the alkyl length exceeded ten carbons, exhibiting a raspberry-like hierarchical morphology.

This study focused on the effect of Multi Wall Carbon Nanotubes (MWCNT) content and its surface treatment on thermo-mechanical properties of epoxy nanocomposites. MWCNTs were surface treated and incorporated into two epoxy systems. MWCNT's surface treatments were based on: (a) Titania coating obtained by sol-gel process and (b) a nonionic surfactant. Thermo-mechanical properties improvement was obtained following incorporation of treated MWCNT. It was noticed that small amounts of titania coated MWCNT (0.05 wt %) led to an increase in the glass transition temperature and stiffness. The best performance was achieved adding 0.3 wt % titania coated MWCNT where an increase of 10 °C in the glass transition temperature and 30% in storage modulus were obtained.

Superhydrophobicity (SH) is defined by a water contact angle (CA) higher than 150° and sliding angle (SA) of less than 5°. SH is a desirable property for a wide range of applications, from the aerospace industry to basic commodities. SH is obtained by a combination of two main principles: low surface free energy and surface roughness. While implementing the proper chemistry and the right hierarchical micro-nano structure, numerous methods can be used to fabricate SH coatings and surfaces, among them being the sol-gel technology. Sol-gel technology is a widely-used fabrication method since it requires only mild conditions. A hybrid sol-gel, composed of inorganic silica and organically modified silanes, forms into a threedimensional gel network. It is a synergetic hybrid which possesses both silica network's properties such as hardness, and organic phase's properties like flexibility and good adhesion. Considering the potential applications of SH coatings, the science and technology communities encounter the challenge to fabricate a durable, transparent superhydrophobic coating which can be manufactured on an industrial scale. Furthermore, since roughness is an essential condition for obtaining SH, transparency may be reduced. Therefore, fine-tuning is necessary in order to achieve both SH and transparency. The following review is dedicated to SH coatings fabricated using the sol-gel method. Along with a comprehensive review of the sol-gel process itself, the effects of various precursors, nanoparticles and fabrication techniques on the coating properties are discussed. Water repellency, mechanical properties and adhesion can be tailored by incorporating organo-functionalized silanes and silica nanoparticles. Adhesion is obtained by creating a covalent bond between the coating and the substrate under thermal or radiation curing. Furthermore, adding the organic component to the mixture as a precursor rather than as a post-silylation agent contributes to the required surface roughness.

Biodegradable polymers offer environmental advantages compared to fossil-based alternatives, but they currently lack the stretchability required for demanding applications such as mesh fabrics for woven flexible intermediate bulk container (FIBC) bags and stretch, shrink, and cling films. The goal of this research is to enhance the stretchability of biodegradable blends based on 80% poly(butylene adipate-co-terephthalate) (PBAT) and 20% poly(lactic acid) (PLA) through reactive extrusion. Radical initiator (dicumyl peroxide (DCP)) and chain extenders (maleic anhydride (MA), glycidyl methacrylate (GMA)) were employed to improve the melt strength and elasticity of the extruded films. The reactive blends were initially prepared using a batch mixer and subsequently compounded in a twin-screw extruder. Films were produced via cast extrusion. 0.1% wt. DCP led to a 200% increase in elongation at break and a 44% improvement in tensile strength. Differential scanning calorimetry and scanning electron microscopy revealed enhanced miscibility between components. Shear and complex viscosity increased by 38% and 85%, compared to the neat blend, respectively. Reactive extrusion led to a better dispersion and distribution of the phases. An improved interfacial adhesion between the phases, in addition to higher molecular weight, led to enhanced melt strength and improved stretchability.