Particle Size Analysis for fluid and dry materials

A análise do tamanho das partículas visualiza e mede a distribuição do tamanho das partículas, onde cada partícula tem um formato e volume específicos, com determinados tamanhos e formatos ideais para um processo específico. A análise do tamanho das partículas é, portanto, um procedimento padrão em muitos laboratórios de pesquisa e controle de qualidade para garantir produtos finais da mais alta qualidade.

Os métodos mais comuns usados ​​hoje para determinar o tamanho das partículas são análise dinâmica de imagens (DIA), análise estática de imagens, espalhamento estático de luz laser (SLS, também chamado de difração de laser), espalhamento dinâmico de luz (DLS) e peneiramento.

Atendendo aos requisitos da indústria, a análise do tamanho das partículas evoluiu rapidamente da moagem, peneiramento e outras técnicas de processamento de materiais nos últimos anos para acelerar o processo de caracterização de partículas, garantindo sempre precisão total. Hoje, três métodos diferentes de medição de tamanho de partículas são comumente aplicados em laboratórios e organizações em todo o mundo.

A Microtrac fabrica e fornece instrumentos acessíveis e de alta qualidade para qualquer um dos cinco processos comumente usados – análise dinâmica e estática de imagens, difração de laser, DLS e peneiramento (por meio da nossa empresa irmã Retsch).

Particle size analysis with static laser light scattering / laser diffraction

Static laser light scattering (SLS) is more commonly known as Laser Diffraction (LD) as well as being referenced from time to time as laser diffractometry, Fraunhofer diffraction or Mie Scattering.

During the interaction of the laser light with particles, diffraction, refraction, reflection and absorption result in light scattering patterns characteristic for the particle size. It is therefore an indirect method which calculates particle size distributions  on the basis of superimposed scattered light patterns caused by a whole collective of particles of which one should know the optical characteristics of the material (refraction index) for small particles to obtain reliable results.

The use of Laser Diffraction (LD) for particle size measurement has seen rapid adoption for quality control in both research and industrial environments thanks to the easy operability and versatility of the technique. It is now the de-facto standard for many who have a requirement for particle size analysis.

As it relies on a laser beam illuminating a well-dispersed sample, the size distribution is calculated from the resulting scattered light pattern. There is an assumption that all particles are spherical so the determination of particle shape parameters is not possible.

Powerful software and extremely accurate light signal detection has handed a competitive edge to material processing businesses in sectors including chemical, foodstuffs, fertilizer and pharmaceutical who rely on Laser Diffraction. They have been able to dramatically increase throughput speeds as the relatively limited resolution has to date not proved to be a major issue for them.

Análise granulométrica

Sieving (sometimes referred to as a gradation test) is perhaps the simplest way to assess particle size distribution. Sieving is useful for particles of several microns to tens of millimetres in size whether the material is organic or non-organic.

Test sieves such as those manufactured by Retsch (a sister Verder Scientific company) provide a simple cost-effective mechanical method of distributing granules into particle size classes preparing them for further analysis as each sieve in a stack has a progressively smaller mesh size. The test sieves site on a sieve shaker whether that be vibratory for a throwing motion with angular momentum, by employing a horizontal circular motion (sometimes with tapping) or with dispersion by an air jet.

For many companies the use of sieves is an entry point to the world of particle size analysis and particle characterization. It is cost effective particularly for those who might not need to characterize materials on a regular basis or where budgets are highly constrained and time taken is not an issue.