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Industry: chemical · TD-NMR

Pigments, paints and dispersions

Relaxation of the liquid at particle surfaces gives a fast, quantitative picture of wetting and dispersion quality in pigments, fillers and nanoparticle suspensions.

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What it tells you

How much particle surface the liquid can reach

In a good dispersion, particles are separate and surrounded by liquid. In a poor one, they stay in clumps and hide part of their surface. A layer of liquid at a particle surface relaxes faster than liquid that moves freely, so the relaxation of the liquid reflects how much particle surface is in contact with it.

Clumps of particles with little liquid at their surfaces, and separate particles each with a layer of liquid held at the surface
Particles in a liquid, poorly and well wetted. Schematic illustration.
Typical samples

Where it is used

  • Pigment dispersions, paints, inks and coatings
  • Fillers in polymers and in liquid formulations
  • Suspensions of nanoparticles
  • Dispersions that have to stay stable in storage

Typical tasks are comparing dispersants and wetting agents, finding how long a dispersion step has to run, checking batches, and following whether a dispersion changes with time.

How it works

Following the liquid during dispersion

The relaxation rate of the liquid is measured on samples taken during dispersion, or on batches. A rising rate that reaches a plateau shows that the surface has been exposed, and a higher plateau means a larger exposed surface.

Relaxation rate of the liquid against dispersion time, reaching a high plateau for a good dispersion and a lower one for a poor dispersion
Dispersion quality seen by the relaxation of the liquid. Schematic illustration, not measured data.
Why time-domain NMR

What it adds

  • Works on opaque, concentrated and coloured dispersions as they are, without dilution
  • Gives a number that is related to the surface that is available
  • A short measurement, suitable for comparing many recipes
  • The same sample can be measured again after storage
Good to know

Points that matter in practice

  • The result depends on the surface chemistry of the particles and on the liquid, so compare dispersions that use the same materials
  • Particles with magnetic or paramagnetic components, such as iron oxides, shorten the relaxation strongly, which can be used but also has to be taken into account
  • Results are relative until they are calibrated, for example against a measured surface area
  • Compare with particle size measurements, which see something different, before drawing conclusions
How MSY Consulting helps

From your dispersion to a routine method

Send or bring representative samples. MSY Consulting runs feasibility measurements, plans the comparison and the calibration with you, and trains your team until the method is part of your routine.

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Contact

Let's talk about your application

Send an email describing your instrument and your application, and you will get a reply.

contact@msyconsulting.eu

MSY CONSULTING SAS · Wissembourg, France · LinkedIn