Wettability measurement apparatus for porous material using the modified Washburn method

Abstract

In this work a cost-effective instrument for measuring the wettability of powder materials was designed and developed, which works on the modified Washburn method. The instrument measures the mass gain against time due to penetration of the liquid into the powder materials using a microbalance and LabVIEW-based data acquisition system. The wettability characteristic of different powders was determined from the contact angle using the modified Washburn equation. To demonstrate the performance of the developed instrument, the wettability of as-received corn starch and nano-coated corn starch powders was estimated with water as a test liquid. The corn starch powders coated with hydrophilic grade (Aerosil 200P) and hydrophobic grade (Aerosil R972) nanoparticles at different coating levels showed expected changes in their contact angle. Some of the results were also verified against the available standard instrument for wettability measurement and found to be consistent. The present configuration of the instrument costs about 500 US$ which is 15 to 20 times less than the available advanced models. The developed instrument is thus a cost-effective solution for wettability measurement which can be used for materials in food processing, pharmaceuticals, horticulture, textile manufacturing, civil engineering etc. The developed instrument is expected to help many small scale industries or research labs who cannot afford an expensive instrument for wettability studies.

Influence of surface modification on wettability and surface energy characteristics of pharmaceutical excipient powders

“…The apparatus and the experimental procedure used was similar to that described by Thakker et al (2013). The assembly consisted of a sample holder in the form of a cylindrical metallic tube, perforated at the bottom and hanged to a microbalance hook from the top.…”

Aplicabilidade do método modificado de Washburn para medidas de ângulo de contato de carbonato de cálcio

“…Ângulos menores que 90° indicam molhagem espontânea do sólido, acima de 90° o líquido não molha o sólido e ângulo nulo indica completa molhagem [15]. Desta forma, quanto menor o ângulo de contato, maior a molhabilidade.…”

“…No caso de pós, a gota pode ser posta sobre o pó compactado, no entanto há algumas limitações como a possibilidade do líquido dissolver ou dispersar o pó causando instabilidade no formato da gota [14], a superfície resultante pode ser rugosa mascarando os resultados ou baixos ângulos de contato levam a rápidas penetrações de líquido prejudicando a medição [16,17]. Para pós e materiais porosos é recomendado o método dinâmico de ascensão capilar adotando o método modificado de Washburn [13][14][15][16][18][19][20][21][22]. Nesse caso, acompanha-se a taxa no qual o líquido é absorvido pelo pó empacotado no interior de um cilindro sob condições controladas.…”

“…Em países emergentes como o Brasil, tensiômetros de boa qualidade e que apresentam recursos como acompanhamento online do gráfico, de fácil operação e com microbalança precisa devem ser importados por empresas de países desenvolvidos como Estados Unidos e Alemanha, encarecendo o produto. A adaptação de uma balança convencional, resultando em um aparato simplificado e semelhante ao tensiômetro, pode custar de 10 a 15 vezes menos [15]. Assim sendo, nesse estudo pretende-se medir valores de ângulo de contato de carbonato de cálcio em duas granulometrias com o propósito de avaliar a aplicabilidade do método modificado de Washburn para medidas de ângulo de contato de pós cerâmicos.…”

Surface chemical changes of atmospheric pressure plasma treated rabbit fibres important for felting process

“…This method is based on measurement the mass of water soaked into fibres in time [33]. Mass of the fibres in tube was the same for each measurement (0.33 g) and fibres were always compressed to the same volume.…”