Structured polymeric microparticles via aerosol cationic photopolymerization

Production of polymeric microparticles has gone through an exponential development in the last decades. In particular, the creation of particles with non-full structures is interesting in many applications from medicine to environmental treatments. Still, there are some issues related to the use of those techniques, such as emulsion polymerization, that need a burdensome purification in the downstream processes. In our studies we tried to develop a continuous polymerization process that gives us the possibility to obtain dry structured microparticles using neither surfactants nor a liquid medium. This technique was based on an aerosol photo-induced polymerization. A solution containing the reacting monomer dissolved in a mixture of solvents is sprayed and exposed to UV-light. During the reactor passage, both reaction and phase separation occurred inside the single droplet. By adjusting the amounts and ratios of the solvents it was possible to obtain different structures. Porous particles with various tunable pore shapes and dimensions were obtained. Capsules were obtained with the addition of a co-solvent able to participate with the reaction, delaying the gelation of the structure and, thus, allowing the creation of a polymeric shell in the outer layers of the reacting droplet. As to the applications, we encapsulated an active ingredient within our particles, both porous and core-shell. The active ingredient was curcumin, an anti-inflammatory and anti-oxidant compound. We found that the addition of the active ingredient did not affect the microparticles synthesis; furthermore, the release kinetics investigation showed a slower release in case of porous particles, compared to capsules. However, porous particles were able to release the total amount of curcumin, while capsules released a lower fraction of the active ingredient

Mechanical behavior of macadamia nutshells

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Synergetic effects inside a simplified friction material: study of the role of ingredients

Brake pad formulations usually contain more than 20 components. Even if each filler effect on the final product properties are acknowledged, interaction developed between filler and matrix, as well as interaction between fillers remain unknown. For a brake pad, friction coefficient and wear can be considered as the resulting performances of all the braking process and the testing conditions. To better understand them, it is necessary to take in account thermal, morphological and physical-mechanical properties of all the friction material ingredients and their eventual mutual interaction. This point is usually left aside in literature, which represents an obvious gap towards the full mechanism comprehension. This work is devoted to the understanding of the interactions among all the ingredients, focusing on the relationship between the main thermal/mechanical properties and the tribological behavior of the composite. First of all, a simplified formulation is set up, including a limited number of components. The experimental work starts with the creation of binary systems containing only the binder and a filler, then the system gets more complex with addition of other fillers until reaching the total formulation. A systematic characterization of the material properties is performed, and analyzed using principal components analysis (PCA) method, which is a powerful dimension-reduction tool permitting to obtain from a large set of variables a graphic representation, called biplot, of the entire set of objects and variables to identify objects (samples) similarities and variables (measured properties) correlations. It is obviously only a model proposal, giving indications in order to improve the system and tailor the desired material properties modifying ingredients nature or content. The method developed here and its further data treatment using PCA can be extended to a wider investigation formulating more samples, or a deeper investigation considering more properties

Cationic UV-Curing of Epoxidized Biobased Resins

Epoxy resins are among the most important building blocks for fabrication of thermosets for many different applications thanks to their superior thermo-mechanical properties and chemical resistance. The recent concerns on the environmental problems and the progressive depletion of petroleum feedstocks have drawn the research interest in finding biobased alternatives. Many curing techniques can be used to obtain the final crosslinked thermoset networks. The UV-curing technology can be considered the most environmentally friendly because of the absence of volatile organic compound (VOC) emissions and mild curing conditions. This review provides an overview of the state of the art of bio-based cationic UV-curable epoxy resins. Particular focus has been given to the sources of the bio-based epoxy monomers and the applications of the obtained products

Natural Polyphenols and the Corrosion Protection of Steel: Recent Advances and Future Perspectives for Green and Promising Strategies

Corrosion is recognized as an unavoidable phenomenon and steel, particularly carbon steel, is strongly susceptible to corrosion. Corrosion damages cause serious material, energy, and economic losses as well as negative impacts on the environment. As a result, research interest has been focused on the development of effective corrosion prevention strategies. However, some of the most commonly used corrosion inhibitors, such as chromates and pyridines, are harmful to human and environmental health. Polyphenols are natural, non-toxic, and biodegradable compounds from plant sources or agricultural by-products. Polyphenols’ chelating capacity has been acknowledged since the 1990s, and tannins, in particular, have been widely exploited as green rust converters in phosphoric acid-based formulations to recover rusty steel. Polyphenolic compounds have recently been investigated as a method of corrosion prevention. This review overviews not only the polyphenolic rust converters, but also the application of green anticorrosive coatings containing polyphenols. Moreover, polyphenols were discussed as an active component in corrosion-inhibiting primers to also promote strong adhesion between the steel surface and the topcoat layer. Finally, an overview of the use of polyphenolic additives in coatings as sustainable systems to improve corrosion resistance is provided

Controlled release of ethylene via polymeric films for food packaging

In modern fruit supply chain a common method to trigger ripening is to keep fruits inside special chambers and initiate the ripening process through administration of ethylene. Ethylene is usually administered through cylinders with inadequate control of its final concentration in the chamber. The aim of this study is the development of a new technology to accurately regulate ethylene concentration in the atmosphere where fruits are preserved: a polymeric film, containing an inclusion complex of α-cyclodextrin with ethylene, was developed. The complex was prepared by molecular encapsulation which allows the entrapment of ethylene into the cavity of α-cyclodextrin. After encapsulation, ethylene can be gradually released from the inclusion complex and its release rate can be regulated by temperature and humidity. The inclusion complex was dispersed into a thin polymeric film produced by UV-curing. This method was used because is solvent-free and involves low operating temperature; both conditions are necessary to prevent rapid release of ethylene from the film. The polymeric films were characterized with respect to thermal behaviour, crystalline structure and kinetics of ethylene release, showing that can effectively control the release of ethylene within confined volume

UV-Cured Chitosan-Based Hydrogels Strengthened by Tannic Acid for the Removal of Copper Ions from Water

In this work, a new environmentally friendly material for the removal of heavy metal ions was developed to enhance the adsorption efficiency of photocurable chitosan-based hydrogels (CHg). The acknowledged affinity of tannic acid (TA) to metal ions was investigated to improve the properties of hydrogels obtained from natural and renewable sources (CHg-TA). The hydrogel preparation was performed via a simple two-step method consisting of the photocrosslinking of methacrylated chitosan and its subsequent swelling in the TA solution. The samples were characterized using ATR-FTIR, SEM, and Folin–Ciocalteu (F&C) assay. Moreover, the mechanical properties and the ζ potential of CHg and CHg-TA were tested. The copper ion was selected as a pollutant model. The adsorption capacity (Qe) of CHg and CHg-TA was assessed as a function of pH. Under acidic conditions, CHg-TA shows a higher Qe than CHg through the coordination of copper ions by TA. At an alkaline pH, the phenols convert into a quinone form, decreasing the Qe of CHg-TA, and the performance of CHg was found to be improved. A partial TA release can occur in the copper solution due to its high hydrophilicity and strong acidic pH conditions. Additionally, the reusability of hydrogels was assessed, and the high number of recycling cycles of CHg-TA was related to its high mechanical performance (compression tests). These findings suggest CHg-TA as a promising green candidate for heavy metal ion removal from acidic wastewater