Ana Dotan

The Relationship between Water Wetting and Ice Adhesion

Ice accretion on aircraft leads to difficulties in aircraft flight control due to weight increase and change in weight distribution. Conventionally these difficulties are overcome using anti-icing or de-icing products, such as freezing depressants and heating devices. A more cost effective way to solve these problems would be to use ice repellent surfaces (ice-phobic). As a first step in this direction the relationship between water wettability and ice adhesion was investigated. Using the appropriate chemistry and tailoring the surface roughness a variety of polycarbonate-coated surfaces were created: these included ultra-hydrophilic and ultra-hydrophobic surfaces and surfaces with surface properties in between the extreme ultra-surfaces. Ice adhesion tests and contact angle measurements indicated that the higher the contact angle the lower is the adhesion of ice. The best results were obtained in the case of ultra-hydrophobic surface treatment that led to an 18 fold decrease in ice adhesion compared to the untreated aluminum surface.

Toughening of Epoxy Adhesives by Nanoparticles

With the emergence and commercialization of nanoparticles, new opportunities have emerged for toughening of epoxy adhesives using nanoparticles without sacrificing strength, rigidity and glass transition temperature, as is the case with conventional elastomeric tougheners. Inorganic Fullerene-like tungsten disulfide (IF-WS2) nanoparticles and functionalized nano-POSS (Polyhedral-Oligomeric-Sil-Sesquioxane) were used to study the effects of nanoparticles on the toughening and mechanical properties of low and high temperature curing epoxy systems. Experimental results indicated that IF-WS2 increased the fracture toughness by more than 10 fold in both epoxy systems at very low concentrations (0.3–0.5 wt%) while increasing its storage modulus and preserving its glass transition temperature. Epoxy functionalized POSS demonstrated an increase in toughness in addition to preserving rigidity and thermal properties at higher concentrations (3 wt%). It was postulated that chemical interaction of the sulfide and the epoxy matrix and the inherent properties of WS2 were the decisive factors with respect to the outstanding nano-effect in the case IF-WS2.

Prospective materials for biodegradable and/or biobased pressure-sensitive adhesives: a review

A pressure-sensitive adhesive (PSA) is an adhesive system that is permanently tacky and adheres to a variety of surfaces with light pressure without phase changes. These adhesives are most commonly found in adhesive tapes such as the Scotch® tape or Post-it® notes. The majority of PSAs are petroleum-based products and usually not biodegradable. The amount of waste generated from these products is quite large as these products are considered disposable. The present review focuses on biodegradable elastomers and how they can be useful in PSAs. This review also covers some novel PSA systems that are biobased or biodegradable.

15 – Biobased Thermosets

Thermosets from renewable sources have been a research focus for the last few decades. Bio-based thermoset resins are considered important candidates for sustainable development since they present the potential to reduce both CO2 footprints and the dependence on petroleum. In order to reduce the ecological impact of a polymer without compromising mechanical and thermal behavior, in some cases, partially bio-based raw materials are accepted. High bio-content resins based on low-toxicity raw materials are the goal for future bio-based thermoset polymers. Free formaldehyde bio-based phenol resins and free bisphenol A–epoxy resins are some examples of this green chemistry concept. The importance of the conversion of biomass into sustainable bio-based polymers is discussed. Chemical pathways developed to make monomers for thermoset polymers from vegetable oils, sugar, and bio-based polyphenols (lignin, tannin, cardanol) will be reviewed.

Characterization of Hybrid Epoxy Nanocomposites

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. MWCNTs 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.