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(a) Transmission electron microscope (TEM) image of hydrophobic fume silica nanoparticle agglomerates. (b) Scanning electron microscope (SEM) image of hydrophobic silica nanoparticle coating sprayed on a glass surface from chloroform solution. Note the formation of hierarchical surface features. The inset is the photograph of a water droplet in a non-wetting state on this surface.
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Due to increasing environmental concerns related to bio-persistence of petroleum based polymers, research efforts have intensified towards developing biodegradable materials with equivalent performance properties. Among these properties liquid repellence is one of the most challenging to obtain due to the fact that most biopolymers such as polysacc...
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... weeks in the vials. At the end of two weeks a slight separation (a thin white precipitate) of the nanoparticles were observed. Before proceeding with the polymer nanocomposite prepara- tion, stable solutions of HMFS in chloroform were spray coated on aluminum foil surfaces in order to investigate the state of their morphology upon spray casting. Fig. 1a shows the trans- mission electron microscope (TEM) image of the silica nano- particles deposited from the solution. The particles are in an agglomerated chain like state. Spray coated particle surface morphology is shown in Fig. 1b. The morphology resembles that of lotus leaf in which spherical and porous micron sized bumps form ...
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... spray coated on aluminum foil surfaces in order to investigate the state of their morphology upon spray casting. Fig. 1a shows the trans- mission electron microscope (TEM) image of the silica nano- particles deposited from the solution. The particles are in an agglomerated chain like state. Spray coated particle surface morphology is shown in Fig. 1b. The morphology resembles that of lotus leaf in which spherical and porous micron sized bumps form hierarchical surface texture. This allows water droplets to remain on a non-wetting state as shown in the inset of Fig. ...
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... from the solution. The particles are in an agglomerated chain like state. Spray coated particle surface morphology is shown in Fig. 1b. The morphology resembles that of lotus leaf in which spherical and porous micron sized bumps form hierarchical surface texture. This allows water droplets to remain on a non-wetting state as shown in the inset of Fig. ...
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... surface polarity by the interacting solid surface-liquid or solid-solid couples has the consequence of reducing the interfacial free energy between the liquid/solid or solid/solid contacts. 32 silica consists of spherical nanoparticles (NPs) which are fused together forming secondary particles and then agglomerate into tertiary particles (see Fig. 1a). The resulting powder has an extremely low bulk density and high surface area. 33 It serves as thickening agent and viscosity stabilizer in cosmetics, toothpastes, food additives, antiperspirant sprays, medicines, paints, coatings, printing inks, adhesives, etc. Lately, hydrophobically modied fumed silica (HMFS) combined with ...
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... In order to characterize the hydrophobic wetting properties of the nano- particles, nanoparticle dispersions in chloroform (1% by weight) were sprayed on silicon wafers and le to dry overnight. The nal dry nano-particulate lm was white in color and found to be extremely water repellent with a WCA approximately 176 and RA 1 . As was shown in Fig. 1b the resulting surface nanoparticle lm morphology is made up of circular sponge- like micro-features that are aggregates of the silica NPs. Higher magnication images (see Fig. S1 of the ESI †) unveil the presence of secondary sub-micrometer features that are responsible for the super water-repellency of the coated surfaces. It appears ...
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... to dry overnight. The nal dry nano-particulate lm was white in color and found to be extremely water repellent with a WCA approximately 176 and RA 1 . As was shown in Fig. 1b the resulting surface nanoparticle lm morphology is made up of circular sponge- like micro-features that are aggregates of the silica NPs. Higher magnication images (see Fig. S1 of the ESI †) unveil the presence of secondary sub-micrometer features that are responsible for the super water-repellency of the coated surfaces. It appears that all these micron and sub-micron sized features are coated with hexamethyldisilazane (HMDS) which was used to transform hydrophilic silica nanoparticle surfaces into ...
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... is important to note that the surface morphology of the superhydrophobic nanocomposite coatings is dictated by the nanoparticles. In other words, if one compares Fig. 1b with 6c, it becomes evident that the biopolymer mainly acts as a binder or adhesive rather than a component that modies the surface texture of the coating. In the case of lycopodium spores embedded in Mater Bi®, a somewhat different wetting behav- iour was observed. Lycopodium spore loadings up to 40% in Mater Bi® yielded higher water contact ...
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... particles in chloroform solution producing coat- ings with better lycopodium particle distribution. Fig. 7 shows high and low magnication SEM images of sprayed composite surfaces composed of 40 wt% Mater Bi® and 60 wt% lycopo- dium. Although the lycopodium dispersion in the coatings is much better than the particulate coatings shown in Fig. S1 of the ESI, † the micro-particles are still not closely packed as seen in Fig. 7a. The presence of amorphous Mater Bi® deposits is evident both on the lycopodium spores ( Fig. 7c and d) but also on the substrate (Fig. 7b and c). It is believed that due to the lack of particle close packing (preventing the formation of a continuous ...
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... the effect of thermal curing temperature and duration on the superhydrophobicity of the Mater-Bi®/HMFS nano- composites was studied. As a model system we used the 50% HMFS loaded nanocomposite. As seen in the Fig. 10, droplet roll of angles decreased up to 200 C when curing time was limited to 30 minutes. However, when curing time was increased to 60 minutes and 120 minutes, slight increases in RAs were observed especially at 200 C and 220 C. At 250 C and above, roll off angles increased considerably rendering the coatings "sticky". This is ...
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... hardness of M70 similar to polycarbonate attached to a linear abraser. Different small weights were placed on the abrading disk in order to increase the downward force. The corresponding force per area during abrasion tests were 1155, 1343, 1717, 1936 and 2123 Pa, respectively. The tests were stopped at the end of 18 abrasion cycles. As seen in Fig. 11 the rst two abrasion tests did not considerably affect the superhydrophobicity and water droplet roll of angles. Abrasion tests conducted with 1717, and 1936 Pa force, considerably reduced static water contact angles while remaining above 150 . Droplet roll off angles exceeded 10 aer the 10 th abrasion cycle converting the surfaces ...
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... were tested to evaluate the performance of this coating on other materials. The coatings displayed similar non-wetting properties irrespective of substrates on which they are applied such as aluminium, silicon wafers, polyester sheets, copy paper and textiles. In the case of textiles 130 C was not used as it could damage the textile texture. Fig. 12, for instance, shows a photograph of water and mineral oil droplets placed on a cotton fabric functionalized with the same coating having a 2 wt% uoroacrylic coating as a second layer. As it can be seen from the photo, both oil and water droplets maintain a non-wetting state on such porous substrates as ...
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Citations
... Researchers achieved a water contact angle of approximately 150°. However, the coatings were sticky, preventing water droplets from moving freely across the surface, commonly referred to as the "rose petal effect" [93]. Recently, a superhydrophobic coating using lycopodium spores with a combination of two natural waxes (Carnauba wax and Beeswax) has been fabricated. ...
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... The high affinity of water molecules toward the TPCS could penetrate the micro-air gap and contradict the theory of lotus leaves. Therefore, scientists introduced the rose petal effect to explain the high adhesion of water molecules on the surface and the acquired WCA values (42). The rose petal effect showed that the microgap between the water droplet and the film's surface (theory of lotus leaf effect) was not observed due to high adhesion between the water and the TPCS films (43). ...
This study focuses on investigating the effect of hybrid nanofillers on the hydration characteristics and soil biodegradability of the thermoplastic corn starch (TPCS) hybrid nanofiller biocomposite (TPCS-HB) films. The data were benchmarked with that of the pure TPCS and TPCS single nanofiller biocomposite (TPCS-SB) as control films. The water absorption properties of TPCS, TPCS-SB, and TPCS-HB films were analyzed and fitted with the standard Guggenheim–Anderson–de Boer equation to study the water activity of the films. Besides, the water permeability test, water vapor permeability, and soil biodegradability of the films were also studied and correlated with the films’ surface morphology. The results indicated that the TPCS-HB films possess excellent hydration resistance and comparable biodegradable rate with the TPCS-SB films. The optimal water resistance properties were achieved when the optimal ratio of nanobentonite/nanocellulose (4:1) was incorporated into the TPCS matrix. The outcomes of this study provide an innovative idea and new insights that, by using natural and hybrid nanofillers, the hydrophobicity of the TPCS films could be enhanced. TPCS-HB films show great potential to be developed into a fully green biodegradable TPCS biocomposite film, especially for single-use plastic applications.
... Therefore researchers are exploring ways to make use of more sustainable and environment-friendly methods and materials to produce superhydrophobic surfaces. The list includes the use of fluorine-free compounds, waterborne coatings, cellulose-based materials, natural waxbased materials, reactive polymeric materials and silicon-based biocompatible materials (Bari et al., 2016;Milionis et al., 2015;Athanasios et al., 2014;Rather et al., 2017a;Ju et al., 2017;Rather et al., 2017b;Anitha et al., 2018;Anitha et al., 2017;. Additionally, the addition of nanofillers in the polymer matrix also affects the biodegradability of the polymeric material in nanocomposite (Bari et al., 2016). ...
... Milionis et al. dispersed hydrophobic nano-silica nanoparticles into the biopolymer matrix (Mater-Bi) to fabricate bio-degradable non-stick superhydrophobic nanocomposite (Athanasios et al., 2014). The WCA of the coatings exceeded above 160 • and SA lowered (~1 o ) with increasing content of nano-silica. ...
... In recent years, several studies on the development of biodegradable superhydrophobic coatings have been conducted; however, many of these coatings are not suitable for use in food packaging. Milionis et al. (2014) studied the effects of biodegradable superhydrophobic nanocomposite coatings formed by the combination of a starch-based thermoplastic with hydrophobic nano-silica and spores of lycopodium. However, chloroform was used as the solvent, which is considered harmful to human health. ...
The natural phenomenon of superhydrophobicity that occurs in plants and animals has been a current topic for research and development with the goal of widening its applications. However, a more complete understanding of such surfaces is necessary to assess the effects of morphology, chemical structure, and surface roughness. In the food sector, such investigations tend to be at an early stage, although superhydrophobic surfaces (SHS) are known to hold promise for food packaging, processing, safety, and preservation. A review of the phenomenon of superhydrophobicity, the parameters to be evaluated for producing superhydrophobic surfaces, and the main impact factors is presented. A current research thrust in food packaging entails the application of superhydrophobic surfaces to reduce food waste. The main problems, technological challenges, future trends and directions for this application are also discussed in this work.
... Plastics are used in a variety of industries and household appliances nowadays. Petrochemical-based plastics are widely used for daily living, primarily for a variety of applications in the packaging industry [2]. Over 120 million tons of plastic are used every year all over the world. ...
Environmental concerns associated with synthetic plastics are detrimental and have made it very crucial to develop biodegradable polymers for commercial and industrial uses. This work investigates the biodegradability of starch (biopolymer) based bioplastics through the soil burial test (SBT) technique. The biopolymeric films were synthesized from 190 and 250 µm biopolymer particulates of manihot esculenta and triticum aestivum. Blends from each particle size were produced in varied proportions with other additives. The biopolymeric films were characterized by physical, physiochemical, thermal, and microstructural tests. The biodegradability of starch-based polymers was determined by a soil burial test for 30 days where topsoil was used as a source of microbial activity. The conventional polyethylene film was also applied to the test. The bioplastic films were observed to have cracks on the surface and became hard and brittle at the end of the testing period. The total weight loss of 46.55–63.77 % was achieved by the bioplastic films. The LDPE film showed no trace of macro-structural changes or any weight reduction throughout the soil burial test. This research concludes that bioplastic films outperformed ordinary plastic films, as they were proven to be biodegradable; and can be employed efficiently in packaging applications.
... This was because the addition of MCC to TPS films could increase the hydrogen bond between MCC and starch molecules to form composite films with a low surface strength, such that the water hardly penetrated into the interior of the films. 51,52 On the other hand, MCC could also fill the pores formed between starch and starch molecules, reducing capillary water absorption between starch molecules. Compared to only paper, paper-plastic composites showed higher water resistance. ...
BACKGROUND
Different thermoplastic starch (TPS) films were prepared with or without the addition of microcrystalline cellulose (MCC) obtained via the melt‐extrusion method, and then the hot‐press method was used to produce environmentally friendly TPS‐based film/paper composites to replace petroleum‐based materials.
RESULTS
The paper–plastic composites exhibited good interfacial adhesion from the scannign elctron microscopy images. It was seen that 5 wt.% MCC was added to reinforce the mechanical properties of TPS films, such that it also improved the barrier properties of MCC@TPS/paper composites and extended the path of water vapor through TPS films, which decreased the water vapor transmission rate of MCC@TPS/paper composites. TPS/paper composites and MCC@TPS/paper composites have better physical properties (i.e. smoothness, flexibility and folding resistance) than only paper. In particular, it was found that the water contact angle of MCC@TPS/paper composites and TPS/paper composites were higher than single‐layer paper. Furthermore, MCC reinforced paper–plastic composites demonstrated good barrier properties which can meet the requirement of the need for lower water sensitive materials in the food packaging industry.
CONCLUSION
Thermoplastic corn starch‐based film/paper composites have good application properties as a potential source of bioplastic materials. © 2021 Society of Chemical Industry.
... For example, silica dioxide (SiO 2 ) particles can introduce water resistance to thermoplastic starch (with lycopodium spores) and isosorbide epoxy resin through post salinization. 108,109 Zinc oxide (ZnO), 110,111 titanium dioxide (TiO 2 ), 112,113 and clay 114 have been demonstrated to improve the hydrophobicity of conventionally hydrophilic polymers including chitosan, epoxy, starch, and alginate. In addition, nanoparticles can even render the surface less vapor permeable, largely due to the tortuous paths introduced by the nanoparticles. ...
Concerns of petroleum dependence and environmental pollution prompt an urgent need for new sustainable approaches in developing polymeric products. Biobased polymers provide a potential solution, and biobased nanocomposites further enhance the performance and functionality of biobased polymers. Here we summarize the unique challenges and review recent progress in this field with an emphasis on self-assembly of inorganic nanoparticles. The conventional wisdom is to fully disperse nanoparticles in the polymer matrix to optimize the performance. However, self-assembly of the nanoparticles into clusters, networks, and layered structures provides an opportunity to address performance challenges and create new functionality in biobased polymers. We introduce basic assembly principles through both blending andin situsynthesis, and identify key technologies that benefit from the nanoparticle assembly in the polymer matrix. The fundamental forces and biobased polymer conformations are discussed in detail to correlate the nanoscale interactions and morphology with the macroscale properties. Different types of nanoparticles, their assembly structures and corresponding applications are surveyed. Through this review we hope to inspire the community to consider utilizing self-assembly to elevate functionality and performance of biobased materials. Development in this area sets the foundation for a new era of designing sustainable polymers in many applications including packaging, construction chemicals, adhesives, foams, coatings, personal care products, and advanced manufacturing.
... [50][51][52][53] However, most of these methods require complicated fabrication and surface treatment, which oen involve chemical reactions in organic solvent. [54][55][56][57][58][59] It is much more challenging to create a durable hydrophobic surface using simple and straightforward waterborne coating formulations. Taking advantage of the unique nanoparticle assemblies discovered in this study, we have created a waterborne formulation that can provide both superhydrophobicity and strong adhesion even aer water immersion. ...
Understanding biobased nanocomposites is critical in fabricating high performing sustainable materials. In this study, fundamental nanoparticle assembly structures at the nanoscale are examined and correlated with the macroscale properties of...
... A convenient, low-cost, and scalable technique is the deposition of colloidal nanoparticle suspension that contains nanoparticles and hydrophobic molecules, like long-chain hydrocarbons [17,18], fluorinated hydrocarbons [19], and silicones [20,21]. Despite the efforts and resources spent over a decade, application of superhydrophobic surfaces in practice is minimal, limited mainly by its weak durability and stability, the cost associated with expensive materials and processes [22,23], and to some extent, environmental and health concerns due to fluorocarbons [24,25]. Notably, the lack of inorganic particles at nanoscale dimensions (<100 nm) and monodisperse forms at an industrial scale with an affordable price is a major issue in the commercialization of superhydrophobic coatings. ...
Commercial application of superhydrophobic coatings is hindered by insufficient durability and use of materials with high costs and limited availability. In this study, we report a robust water impact resistant all-organic superhydrophobic coating that is prepared from low-cost colloidal dispersion composed of carnauba wax and candle soot. The colloidal dispersion is stable and can be spray-coated onto virtually any surfaces. The coated surfaces exhibit superhydrophobicity with a water contact angle of 172° and sliding angle of 3°, and retain superhydrophobicity even after 400 cycles of continuous water spray with an impact pressure of 7.4 kPa. The synergetic combination of candle soot and carnauba wax, together with the deposition method, solvent used to disperse materials, and spray-coating distance are critically important for the superhydrophobicity and mechanical durability. The robustness of the coatings emerges from the two-tier hierarchical structure of the dried particles which is formed by evaporation induced self-assembly of wax molecules and candle soot nanoparticles. Applications in self-cleaning and oil/water separation are demonstrated, where a coated membrane can be continuously operated, solely driven by gravity, and can separate common organic liquids such as hexane and toluene from water with a separation efficiency of more than 90 % at a high flux of 1061 L / (m² h).
... Originating from the large amount of hydroxyl groups in starch, there exists strong intermolecular and intramolecular hydrogen bonding which leads to thermal degradation of starch before its melting point. Therefore, several strategies have been presented in the last decades to obtain thermoplastic starch (TPS) and its derivatives for broadening their industrial applications: namely (i) the utilization of small-molecular plasticizers including water, urea, citric acid and polyols like glycerol, glycol, ethylene glycol, 1,3-propanediol, etc., where water is the cheapest and the most processing aid for starch (Mekonnen, Mussone, Khalil, & Bressler, 2013;Taghizadeh & Favis, 2013); (ii) blending with thermoplastic polymers like poly (butylene adipate-co-terephthalate) (PBAT), poly (lactic acid) (PLA), poly (vinyl alcohol) (PVA) and polyethylene (PE), where interactions between those polymeric chains and starch molecules are weak and thus plasticizers and compatibilizers are always necessary (Chotiprayon, Chaisawad, & Yoksan, 2020;Martin & Averous, 2001); (iii) chemical modification, especially grafting copolymerization with acrylamide, acrylic acid, methyl methacrylate, methacrylic acid and so forth (Lehmann, Volkert, Hassan-Nejad, Greco, & Fink, 2010;; and (iv) development of nanocomposites involved in nanofillers like nanoclay and nano-silica, a supplementary method to mainly enhance the mechanical properties or hydrophobicity of TPS materials (Milionis, Ruffilli, & Bayer, 2014). ...
It is still a big challenge to obtain hydrophobic thermoplastic starch with outstanding mechanical performance due to the inevitable usage of typical hydrophilic plasticizers like glycerol during processing. Herein, we report a novel hydrophobic thermoplastic starch using a supramolecularly induced thermoplasticization technique. To achieve this aim, a functional sucrose-based ionic liquid crystal (ILC) including numerous chloride atoms has been firstly synthesized, and the obtained ILC molecules are then used as supramolecular inducers to thermoplasticize corn starch granules. Thermoplasticity and hydrophobicity of the prepared supramolecularly induced thermoplastic starch (STPS) with different ILC contents have been extensively investigated. Mechanism of the supramolecularly induced thermoplasticization has been investigated using molecular simulation as well. The prepared STPS with the maximum tensile strength of 8.4 MPa and water contact angle of about 117° show large potential applications in green and sustainable packaging materials.
