The influence of soluble salts content on the performance of an epoxy coating system via accelerated corrosion tests

It is generally accepted that surpassing a threshold value of water-soluble salts at the substrate/coating interface can impart premature failure in painted structures. The Coatings industry has an identified need in defining a maximum allowable soluble salts content, however, a variety of threshold values are found in published data. Based on that, this work aims at evaluate the effect on epoxy coating performance of three different ranges of soluble salts content taking into account the maximum allowable values specified by NORSOK M501 and IMO PSPC MSC.215, two important standards of naval and offshore sectors. Blast-cleaned carbon steel specimens contaminated with sodium chloride solutions diluted in methanol ranging 20, 50 and 100 mg/m² NaCl were painted with two epoxy-amine paint coats. Samples were evaluated by cathodic disbondment, water immersion at 40 ºC, pull-off adhesion strength and cyclic corrosion tests. Larger blisters and loss of adhesion were observed as the soluble salts content at the interface increased. Although, it was not possible to find a critical level of soluble salts even considering data about similar coating systems. A safe soluble salt content must be chosen based on tests that closer reproduce service and environmental conditions to which a painted structure will be exposed. Keywords: Carbon steel, Corrosion, Soluble Salts Content, Epoxy, Paint.

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Obtenção de revestimento poliuretano de base aquosa com polianilina para proteção anticorrosiva do aço carbono

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2019.A literatura tem demonstrado a viabilidade de utilização da Polianilina (PAni) na proteção anticorrosiva metálica, porém, limitações no processamento dificultam seu uso. Uma das abordagens para contornar suas limitações consiste na incorporação da PAni em matrizes poliméricas, tradicionalmente empregadas na indústria de revestimentos, tal como as dispersões aquosas poliuretânicas (PUDs). As PUDs despertam grande interesse devido ao apelo ambiental e propriedades como boa formação de filme, resistência à abrasão e ao intemperismo. Assim, este trabalho consistiu primeiramente em investigar o efeito do ácido dodecil benzeno sulfônico (DBSA) e do poli(ácido 4-estireno sulfônico) (PSS) na polimerização da anilina a fim de obtê-la como sal de esmeraldina, na forma de pó facilmente redispersável e estável em meio aquoso, visando a incorporação em PUD aniônica comercial. Tais requisitos foram alcançados utilizando-se o PSS e uma razão molar de Ani:APS de 4:1. A PAni.PSS obtida apresentou condutividade elétrica de 10-3 S.cm-1, morfologia granular e tamanho médio volumétrico de partícula de 62 nm. A sua incorporação em PUD aniônica resultou em um limiar de percolação elétrico de 6 %m. Com base na curva de comportamento elétrico das misturas de PUD com PAni.PSS, revestimentos contendo entre 1 a 8 %m de PAni.PSS, abaixo da concentração volumétrica crítica de pigmento (CPVC) calculada, foram preparados. Os revestimentos foram aplicados sobre aço carbono lixado para avaliação do desempenho anticorrosivo. Revestimentos com boa aderência úmida, maior hidrofobicidade e, melhor desempenho anticorrosivo, comprovado pelo aumento no potencial de circuito aberto e no módulo de impedância eletroquímica, foram obtidos para misturas com até 3 %m de PAni. A incorporação de concentrações próximas da região do limiar de percolação elétrico e, possivelmente próximas do CPVC prático estimado com base nos resultados de impedância, resultou na formação de bolhas, perda de aderência e baixo desempenho anticorrosivo. Resultados associados ao aumento da porosidade e da incidência de defeitos nestes revestimentos.Abstract : The literature has shown Polyaniline?s (PAni) feasibility in metal corrosion prevention. However, limitations regarding PAni processability restrain its use. Blending PAni with binders typically used in the coatings industry, such as aqueous polyurethane dispersions (PUDs), is one approach to overcome its limitations. PUDs are environmentally friendly and present good film formation, abrasion and weather resistance. As a primary step, the effect of dodecyl benzene sulphonic acid (DBSA) and poly (4-styrene sulfonic acid) (PSS) was evaluated on the polymerization of aniline in order to obtain PAni powder in the conducting state, easily dispersible and stable in aqueous medium to be incorporable into a commercial anionic PUD. The requirements were achieved with PSS use and Ani:APS molar ratio of 4:1. The obtained PAni.PSS showed an electrical conductivity of 10-3 S.cm-1, granular morphology and mean volumetric particle size of 62 nm. Blending PAni.PSS with a commercial anionic PUD resulted in an electric percolation threshold of 6 %w. Based on the electrical behavior curve of the mixtures, coatings were prepared with up to 8 %w of PAni.PSS, whose concentrations were below the calculated critical pigment volume concentration (CPVC). The coatings were applied on sanded carbon steel for corrosion performance assessment. Coatings with good wet adhesion, higher hydrophobicity and better anticorrosive performance, supported by an increased open circuit potential and electrochemical impedance module, were obtained for coatings with up to 3%w of PAni. The incorporation of concentrations close to the electric percolation threshold region and possibly near the real CPVC based on the impedance results, caused failures in coatings like blistering, adhesion loss and low corrosion protection due to higher porosity and defects in these coatings

Modifica??es na preval?ncia de asma e atopia em escolares de uma regi?o de Porto Alegre - RS

Made available in DSpace on 2015-04-14T13:35:55Z (GMT). No. of bitstreams: 1 457566.pdf: 828433 bytes, checksum: dfa634f0f7cbe00efd4bdfccad709ee0 (MD5) Previous issue date: 2014-02-21Introduction: A significant increase in the prevalence of asthma and atopy was observed in epidemiological studies conducted in 1980, 1989 and 1998, with school of Porto Alegre. The continuity of this phenomenon in recent decades needed to be evaluated. Objective: Verify the changes in prevalence of symptoms of active and cumulative asthma and atopy in schoolchildren from a region of Porto Alegre. Methodology: In a cross-sectional study in which schoolchildren from 5th to 8th grade (10-18 years), four schools located in the same geographic area were interviewed. The first questionnaire covered symptoms suggestive of asthma (at some point in life or in the last twelve months) and the second was the ACT (test asthma control). In addition, skin tests were performed in 241 schoolchildren. Results: 964 students were interviewed a total of 1195 registered. The age of participants ranged from 10 to 18 years with a mean of 13.3 years. The cumulative prevalence of asthma symptoms was found to be 41,7%, symptoms of active asthma 19,9% and atopy 52,7%. Compared to previous studies, a stabilization in the cumulative prevalence of asthma and atopy occurred while decreased the prevalence of symptoms of active asthma from 22% to 14.9%. (P <0.001) Conclusions: In the last decade the prevalence of symptoms of asthma and atopy cumulative stabilized, with a reduction in the prevalence of symptoms of active asthma in the last year. This finding may help guide the search for environmental factors that are responsible for the manifestation of asthma in genetically susceptible individuals.Introdu??o: Um importante aumento na preval?ncia de asma e de atopia foi observado nos estudos epidemiol?gicos realizados em 1980, 1989 e 1998, com escolares de Porto Alegre. A continuidade deste fen?meno nas ?ltimas d?cadas precisava ser avaliada. Objetivo: Verificar as modifica??es na preval?ncia de sintomas de asma ativa e cumulativa e de atopia em escolares de uma regi?o de Porto Alegre. Metodologia: Trata-se de um estudo transversal, em que escolares de 5? a 8? s?ries (10 a 18 anos), de quatro escolas situadas em uma mesma ?rea geogr?fica foram entrevistados. O primeiro question?rio utilizado abrangia sintomas sugestivos de asma (em algum momento da vida ou nos ?ltimos doze meses) e o segundo foi o ACT (teste de controle da asma). Al?m disso, foram realizados testes cut?neos em 241 alunos. Resultados: Foram entrevistados 964 escolares de um total de 1195 matriculados. A faixa et?ria dos participantes variou de 10 ? 18 anos com m?dia de 13,3 anos. A preval?ncia de sintomas de asma cumulativa encontrada foi de 41,7%, de sintomas de asma ativa 14,9% e de atopia 52,7%. Em rela??o aos estudos anteriores, ocorreu uma estabiliza??o na preval?ncia de asma cumulativa e de atopia, enquanto diminuiu a preval?ncia de sintomas de asma ativa de 22% para 14,9%. (P<0,001) Conclus?es: Na ?ltima d?cada a preval?ncia de sintomas de asma cumulativa e de atopia estabilizou, havendo uma redu??o na preval?ncia de sintomas de asma ativa no ?ltimo ano. Essa constata??o pode ajudar a orientar a busca de fatores ambientais que sejam respons?veis pela manifesta??o da asma em indiv?duos geneticamente suscet?veis