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Advisor(s)
Abstract(s)
O presente trabalho foi desenvolvido no âmbito da unidade curricular Dissertação/Estágio, inserida no Mestrado em Engenharia Química, ramo de Qualidade, do Instituto Superior de Engenharia do Porto. O estágio realizou-se no período de março a julho de 2021 na empresa AQUITEX – Acabamentos Químicos Têxteis S.A. e teve como principal objetivo a implementação de um método espetrofotométrico para controlo de qualidade de revestimentos cerâmicos e desenvolvimento de novos vidrados.
Com o desenvolvimento do setor nacional de cerâmica utilitária e decorativa, surge a necessidade de se implementarem métodos para o desenvolvimento e ajustes dos perfis colorimétricos. Para além disto, tendo em conta a importância da reprodutibilidade de determinado revestimento cerâmico, há necessidade de empregar uma técnica automatizada de controlo de qualidade das superfícies vidradas, relativamente aos padrões aprovados. A AQUITEX compromete-se com a inovação permanente, tendo em conta as exigências cada vez mais preponderantes por parte dos clientes e, neste seguimento, a análise colorimétrica por espetrofotometria é fulcral para uma resposta imediata aos desafios diários.
O processo do desenvolvimento do trabalho foi dividido em três fases: a preparação das pastas de grés, faiança e terracota, para a obtenção de peças planas para vidragem, a realização dos ensaios práticos de vidragem das peças, tanto para a criação da base de dados, como do controlo de qualidade das amostras e a fase de implementação do método espetrofotométrico.
O método desenvolvido teve por base o sistema de medição de cor CIELab, recorrendo ao espetrofotómetro X-rite Color i5, da Neurtek Instruments. Para a leitura das amostras foi utilizado o iluminante D65 (luz do dia média) com observador padrão de 10º, pré-definido pelo sistema. Foram criados três databases, para as pastas de grés, faiança e terracota, com dois tipos de bases, transparente brilhante e opaco brilhante para cada um. Para a base transparente brilhante, fez-se variar as concentrações dos corantes mais utilizados, para os valores de 0,1 %, 0,2 %, 0,4 %, 0,6 %, 0,8%, 1 %, 2 %, 3 %, 4 % e 5 %, num total de 23 corantes para grés, 12 corantes para faiança e 12 corantes para terracota. Para as bases opacas brilhantes de faiança e terracota foram utilizadas as concentrações de 0,2 %, 0,4 %, 0,6 %, 0,8 %, 1,5 % e 3 % nos corantes mais escuros e de 0,5 %, 1 %, 2%, 3%, 4% e 5 % nos corantes mais claros, num total de 12 corantes para faiança e 12 corantes para terracota.
Para o controlo de qualidade das amostras de produção foi definido o parâmetro de DE*, sendo o respetivo valor limite de aprovação igual a 2 unidades e os parâmetros L*, a*, b*, DL*, Da*, Db*, Opacidade e Gloss. Foi realizada a avaliação da conformidade de 17 amostras de vidrados em grés, 4 amostras de vidrados em faiança e 3 amostras de vidrados em terracota. As formulações, com as devidas correções/ajustes, em alguns casos, através da leitura de PANTONE e da leitura da cor de peças cerâmicas, demonstraram a eficiência da implementação do método espetrofotométrico.
This work was developed within the scope of the curricular unit Dissertation/Internship, part of the Master's Degree in Chemical Engineering, Quality area, of Instituto Superior de Engenharia do Porto. The internship was carried out between march and july 2021, in the company AQUITEX - Acabamentos Químicos Têxteis S.A. and had as main objective the implementation of a spectrophotometric method for quality control of ceramic coatings and development of new glazes. With the development of the national utilitarian and ornamental ceramic sector, there is a need to implement methods for the development and adjustment of colorimetric profiles. Furthermore, considering the importance of the reproducibility of a given ceramic glaze, there is a need to use an automated technique for the quality control of the glazed surfaces, in relation to the approved standards. AQUITEX is committed to permanent innovation, considering the increasing preponderant demands from the customers and, in this context, the colorimetric analysis by spectrophotometry is essential for an immediate answer to the daily challenges. The work development process was divided into three phases: the preparation of the stoneware, earthenware and terracotta bodies, to obtain flat pieces for glazing; the practical glazing tests of the pieces, both for the creation of the database and for the samples’ quality control; and the implementation phase of the spectrophotometric method. The method developed was based on the CIELab color measurement system, using the X-rite Color i5 spectrophotometer, from Neurtek Instruments. To read the samples, the illuminant D65 (average daylight) was used, with a 10º standard observer, pre-defined by the system. Three databases were created, for stoneware, earthenware and terracotta pastes, with two types of bases, brilliant transparent and brilliant opaque for each one. For the transparent glossy base, the concentrations of the most used stains were varied to the values of 0.1 %, 0.2 %, 0.4 %, 0.6 %, 0.8 %, 1 %, 2 %, 3 %, 4 % and 5 %, for a total of 23 stains for stoneware, 12 stains for earthenware and 12 stains for terracotta. For the brilliant opaque bases of earthenware and terracotta, concentrations of 0.2 %, 0.4 %, 0.6 %, 0.8 %, 1.5 % and 3 % were used in the darker stains and of 0.5%, 1 %, 2 %, 3 %, 4 % and 5 % in the lighter stains, for a total of 12 stains for earthenware and 12 stains for terracotta. For the quality control of the production samples the parameter DE* was defined, with its approval limit value equal to 2 units and the parameters L*, a*, b*, DL*, Da*, Db*, Opacity and Gloss. The conformity assessment of 17 stoneware glazing samples, 4 earthenware glazing samples and 3 terracotta glazing samples was performed. The formulations, with the necessary corrections/adjustments, in some cases, through the PANTONE reading and the color reading of ceramic pieces, demonstrated the efficiency of the implementation of the spectrophotometric method.
This work was developed within the scope of the curricular unit Dissertation/Internship, part of the Master's Degree in Chemical Engineering, Quality area, of Instituto Superior de Engenharia do Porto. The internship was carried out between march and july 2021, in the company AQUITEX - Acabamentos Químicos Têxteis S.A. and had as main objective the implementation of a spectrophotometric method for quality control of ceramic coatings and development of new glazes. With the development of the national utilitarian and ornamental ceramic sector, there is a need to implement methods for the development and adjustment of colorimetric profiles. Furthermore, considering the importance of the reproducibility of a given ceramic glaze, there is a need to use an automated technique for the quality control of the glazed surfaces, in relation to the approved standards. AQUITEX is committed to permanent innovation, considering the increasing preponderant demands from the customers and, in this context, the colorimetric analysis by spectrophotometry is essential for an immediate answer to the daily challenges. The work development process was divided into three phases: the preparation of the stoneware, earthenware and terracotta bodies, to obtain flat pieces for glazing; the practical glazing tests of the pieces, both for the creation of the database and for the samples’ quality control; and the implementation phase of the spectrophotometric method. The method developed was based on the CIELab color measurement system, using the X-rite Color i5 spectrophotometer, from Neurtek Instruments. To read the samples, the illuminant D65 (average daylight) was used, with a 10º standard observer, pre-defined by the system. Three databases were created, for stoneware, earthenware and terracotta pastes, with two types of bases, brilliant transparent and brilliant opaque for each one. For the transparent glossy base, the concentrations of the most used stains were varied to the values of 0.1 %, 0.2 %, 0.4 %, 0.6 %, 0.8 %, 1 %, 2 %, 3 %, 4 % and 5 %, for a total of 23 stains for stoneware, 12 stains for earthenware and 12 stains for terracotta. For the brilliant opaque bases of earthenware and terracotta, concentrations of 0.2 %, 0.4 %, 0.6 %, 0.8 %, 1.5 % and 3 % were used in the darker stains and of 0.5%, 1 %, 2 %, 3 %, 4 % and 5 % in the lighter stains, for a total of 12 stains for earthenware and 12 stains for terracotta. For the quality control of the production samples the parameter DE* was defined, with its approval limit value equal to 2 units and the parameters L*, a*, b*, DL*, Da*, Db*, Opacity and Gloss. The conformity assessment of 17 stoneware glazing samples, 4 earthenware glazing samples and 3 terracotta glazing samples was performed. The formulations, with the necessary corrections/adjustments, in some cases, through the PANTONE reading and the color reading of ceramic pieces, demonstrated the efficiency of the implementation of the spectrophotometric method.
Description
Keywords
Cerâmicos Revestimentos Vidrados Espetrofotometria CIELab Controlo de Qualidade Grés Faiança Terracota Ceramics Coatings Glazes Spectrophotometry Quality Control Stoneware Earthenware