This work is devoted to investigation of free-surface flow associated with drop fall. The main goal of the work is the computational and the theoretical study of the flow generated by drop falling and drop impact onto different surfaces, with relevance for spray impingement. The considered flow configurations include drop impact onto a shallow liquid layer, binary drop collision, drop impact onto a dry wall, nonisothermal drop impact onto a heated wall with the accompanying simultaneous heat transfer within the wall, and drop impact onto a porous substrate. The potential of the new interface capturing methodology developed by OpenCFD Ltd and based on the volume-of-fluid (VOF) model within the framework of Computational Fluid Dynamics (CFD) is evaluated by contrasting the results of numerical simulations to the in-house experimental results and the existing experimental and numerical result databases. The flows studied are treated as being laminar and computed in the framework of the finite-volume numerical method. In general, the numerical model and the computational procedure demonstrate good predictive capabilities by reproducing correctly the studied flows mentioned above, both qualitatively and quantitatively. All important effects observed in the experiments are reproduced and particularly some distinctive features of the flow are properly captured. The numerical simulations of the different flow configurations pertinent to spray impact provide a detailed insight into the dynamics of the flow and enable analytical modeling using simplified theoretical approaches. In particular the computational results provide all the flow details which are inaccessible by present experimental techniques, they are used to prove the theoretical assumptions and yield the required database for defining new flow patterns and their analytical modeling.

This article presents an experimental study on the surface properties of epoxy resin nanocomposites (EPNCs) manufactured with a thermosetting epoxy resin (EP)–bisphenolAdiglycidyl ether (BADGE)–2-[[4-[2-[4-(Oxiran-2-ylmethoxy)phenyl]propan-2-yl]phenoxy]methyl]oxirane) and filled with alumina nanoparticles (NPs). The NPs consist of pretreated (with a silane agent) alpha alumina with irregular shapes and a 100nmmaximumsize. Three weight fractions of NPs were studied: 1, 3, and 5 wt. (%). Two di erent epoxy (EP) resins were manufactured, one cured and postcured with bis (4-aminophenyl) methane (DDM); and another one cured with 3-dodec-2-enyloxolane-2,5-dione (DDSA) + 8-methyl-3a,4,7,7a-tetrahydro-4,7-methano-2-benzofuran-1,3-dione (MNA). The wettability and the surface roughness of the obtained EPNCs were studied through the measurement of contact angles and topographic images obtained with atomic force microscopy (AFM), respectively. Significant influence of both the loading of NPs and used curing agents was observed. EPNCs cured with DDM were shown to be hydrophobic for 0, 1, and 3 wt. (%) and hydrophilic for 5 wt. (%). Maximum surface roughness was observed for 5 wt. (%). EPNCs cured with DDSA+MNA were shown to be hydrophilic for 0 and 1 wt. (%) and hydrophobic for 3 and 5 wt. (%). The surface roughness decreased as the weight fraction of NPs increased until 3 wt. (%), and then increased for 5 wt. (%).

A presente dissertação enquadra-se num projeto de melhoria contínua do departamento de Investigação e Desenvolvimento da Ansell Portugal. Sendo o grupo Ansell líder mundial em soluções de proteção, torna-se imperativa a procura pela melhoria das propriedades dos seus produtos, tornando-os mais confortáveis e com melhor performance e segurança na sua utilização. O objetivo da presente dissertação é desenvolver um revestimento hidrofóbico (repelente a água) e oleofóbico (repelente a óleos) para luvas têxteis, usando a tecnologia sol-gel, garantindo assim têxteis com propriedades self-cleaning (auto-limpeza) e easy-to-clean (lavagem mais eficaz uma vez que as nódoas são mais fáceis de remover). A estratégia de desenvolvimento usada neste projeto requer o uso de um processo simples, de fácil aplicação no processo produtivo da empresa, sem grandes custos acrescidos, de rápida implementação, daí não se ter desenvolvido um novo polímero, mas sim ter-se usado um precursor sol-gel comercial, o Dynasylan® F 8815 (fluroalquilo siloxano), que modifica as superfícies tornando-as repelentes a água e óleos, pela diminuição da sua energia de superfície. Realizaram-se ensaios experimentais com aplicação do Dynasylan® na luva têxtil (liner) onde se verificou a eficácia deste precursor nas propriedades de repelência. A hidro- e oleofobicidade foram avaliadas pela medição do ângulo de contacto com água (para verificar a hidrofobicidade) e com diiodometano e n-hexadecano (para verificar a oleofobicidade). Otimizaram-se assim as condições de aplicação, tendo-se concluído que se deveria usar uma solução aquosa com 5% (v/v) de Dynasylan®, processar o revestimento por dip-coating, com um tempo de imersão de10 min, uma posterior temperatura de cura de 140ºC, durante 30 min. Testou-se também um pré-tratamento de plasma, mas este não produziu melhoria significativa que justificasse o investimento num equipamento de produção de plasma. Uma vez que o grande volume de vendas da Ansell Portugal é com luvas têxteis com revestimentos poliméricos, testou-se também o efeito do Dynasylan® sobre esses revestimentos. Usou-se como referência uma luva revestida com dois “dips” de polímero (imersão em dois compostos poliméricos), que tinha valores iniciais de ângulo de contacto com água, diiodometano e n-hexadecano inferiores a 90º, sendo por isso hidro- e oleofílica. Após o tratamento com Dynasylan®, os protótipos dessas luvas obtiveram ângulos de contacto com água de 159º na parte têxtil (costas da mão) e de 140º na zona com revestimento polimérico (palma da mão). Para o diiodometano, os ângulos de contacto foram de 129º nas costas e 122º na palma. Estudou-se também o processo produtivo das luvas para introdução de um novo estágio na linha de produção para incluir um tanque com solução aquosa de Dynasylan®. Os melhores resultados foram alcançados quando o Dynasylan® foi introduzido após a etapa de leaching e antes da vulcanização das luvas. Assim, esta etapa de vulcanização será também aproveitada para a cura de Dynasylan®. Realizaram-se ainda testes de durabilidade do revestimento por este ser um filme à superfície, nomeadamente o estudo de resistência à lavagem e o teste de abrasão (EN388:2005). Os protótipos mantiveram o seu revestimento repelente a água e óleos após as 5 lavagens exigidas. Relativamente à abrasão nos testes realizados com água a repelência mantem-se até ao nível 2 (nível de rutura da luva original), mas nos testes com óleo a repelência perde-se ao fim de 100 ciclos (nível 1), apesar da luva permanecer íntegra até ao nível 4. O trabalho realizado nesta dissertação permitiu obter um revestimento hidro- e oleofóbico, pela tecnologia sol-gel, em luvas têxteis, tal como era esperado, mas, também, em luvas revestidas por polímero (acrilonitrilo butadieno ou poliuretano). Este revestimento pode ser facilmente reproduzido nas atuais linhas de produção da Ansell Portugal e ser usado em diversas referências de produtos.

Polycarbonate, an amorphous engineering polymer, has excellent mechanical strength and although it s good chemical resistance, its interaction with some types of alkali and some organic solvents is weak. The main objective of this work was to study the effect of the inclusion of nanometric particle size of natural sodium clay (named Nanolite) and sodium clay treated with quaternary ammonium salt (named Cloisite 15A) in resin processing in order to investigate the variations in chemical properties, transparency and molecular structure. The characterization of nanocomposite was performed using methods of Scanning Electron Microscopy (SEM), Molar Mass Characterization by Mark-Houwink-Sakurada equation, Differential Scanning Calorimetry (DSC), Melt Flow Rate (MFR), Differential Thermal Analysis (DTA), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Chemical Resistance obtained by the contact angle technique / Fowkes method. Optical, thermal, physical and chemical testing indicated that the molecular structure of PC after the inclusion of clays remained unchanged showing no irreversible degradation. The analysis of chemical resistance through the contact angle method showed significant improvement in the surface free energy of the nanocomposites when using the organoclay (Cloisite 15A) and partial improvement when used natural sodium clay (Nanolite). The decrease in surface free energy, indicates a likely improvement in the chemical resistance of the nanocomposites.

ABSTRACT: The addition of commercial formulations and adjuvants to a tank mix may result in differences in the wettability on the plant surface, foliar uptake and herbicide efficacy. Thus, the objectives of this study were to evaluate the influence of glyphosate formulations and tank-mixture adjuvants on the contact angle (CA), uptake, metabolism and sourgrass control and the damage to the cuticular microstructure of this species caused by herbicide solutions. For this purpose, assays were carried out in a completely randomized design, and treatments distributed in a 2x5+1 factorial scheme with five replications. Two glyphosate formulations isopropylamine salt (SL) and ammonium salt (WG) combined or not with the adjuvant methylated soybean oil (MSO), mineral oil (MO), ethoxylated alkyl ester (EAE) or polyoxyethylenealkylphenol ether (PAE); and one control (water) were evaluated. CA measurements of the droplets deposited on a sourgrass leaf surface and on the standard surface (parafilm) were obtained using a tensiometer. Herbicide uptake and shikimate accumulation were simultaneously determined by chromatography and spectrometry. The control effect was assessed by observing plant survival dry weight reductions. The glyphosate SL and WG formulations had similar effects on the variables analyzed. However, mixing the adjuvants EAE, MO or MSO with either formulation of herbicide led to greater wettability and more severe damage to the cuticular microstructure, favoring glyphosate uptake and shikimate accumulation. Despite evidence regarding the treatments containing oils/surfactants, the control effect on sourgrass was similar. The combination of glyphosate formulations with such adjuvants is potentially more effective and guarantees satisfactory sourgrass control.

In this work the sessile drop technique was used in order to evaluate the melting temperature of synthetic and industrial slags, and their contact angle as a function of time and temperature on substrates of an Al2O3-SiO2-SiC-C castable containing 10 wt.% of carbon or its matrix. The best experimental conditions for the evaluation of the wetting behavior of refractory castables were attained when 25 x 25 x 10 mm³ matrix substrates and cylindrical slag pellets of 3 mm diameter and 5 mm high were used. This substrate - slag set resulted in contact angle values with good reliability. Small differences between the contact angle behavior on ground and polished matrix surfaces for synthetic slags were also detected. Additionally, industrial slags containing various oxide components, showed high values of contact angles and lower liquid spreading when compared with synthetic slags. This difference can be associated to the interaction liquid-solid at the material interface. Besides that, the wetting experiments were presented as a good alternative for measuring the melting temperatures of slags, as their values are difficult to determine due to the high oxide variety in the industrial slag compositions and the interaction between the slag and the substrate.

This paper presents a study of adsorption of xanthate with alkyl chain of two (C2XK), four (C4XK) and eight (C8XK) atoms of carbon, on pyrite from Santa Catarina, Brazil. The results showed that pyrite surface changes from hydrophilic to hydrophobic when xanthate is adsorbed increasing the contact angle to 35º for C2XK, and to 90º for C4XK and C8XK. The rate of flotation of pyrite particles after adsorption increases with the increase of the number of carbon atoms in the alkyl chain in agreement with the results of contact angle measurements.

In this article, the potential at which galena depression occurs is related to the formation of hydrophilic compounds on its surface. Reactions are proposed based on analyses by cyclic voltammetry, thermodynamic data, and X-ray photoelectron spectroscopy (XPS). Electrochemical variables, such as the redox potential, present good perspectives for selectivity in the flotation of galena and sphalerite, because in a given range of potentials, the galena surface becomes hydrophilic, as shown by measurements of the contact angle and floatability tests.

The purpose of this study was to evaluate the wettability and surface roughness of 11 Amazonian hardwoods. Surface roughness was evaluated by a profilometer, while wettability was measured by a goniometer. Distillated water and phenol-formaldehyde were employed to study wood wettability. A 10-μL drop was placed on the wood surface and the contact angle was measured every 2 seconds for 120 seconds. The Virola michelii and Trattinnickia burserifolia wood specimens analyzed presented different roughness values according to the surface evaluated, radial or tangential. Regarding wettability, Virola michelii wood showed the lowest water contact angle on the tangential surface, while the radial surface presented better wettability for phenol-formaldehyde. The wettability of the species studied was not clearly affected by surface roughness, which depends on wood density.