Paints, Inks and Surface Coatings Industries

Particle size and rheological properties govern many key properties that are important to the coatings industry. For example, flocculation, hue/tint strength, hiding/transparency, dispersability, stability, gloss/flatting and film appearance, viscosity and weather resistance are some examples.

Other properties related to dry paint applications (powder coatings) include flowability and materials handling issues. Particle size and rheological determination are thus key features of the characterization of pigments, fillers and additives that are present in wet and dry applications.

Malvern's range of particle size analyzers and rheometers can be used to characterize all types of system:

• Solvent and aqueous based systems
• Dry powders (pigments, fillers, dry paints)
• Suspensions (finished coatings)
• Emulsions (liquid in liquid) systems

Nanomaterials and Dispersion Stability

The long-term stability of aqueous and organic systems can be examined with Malvern's Zetasizer instruments as the zeta potential provides an indication of suspension stability or otherwise. Also, Malvern rheometers and viscometers can be used to measure the bulk flow properties of materials to assess stability.

Nano sized materials (typically 100% < 100 nm) can be measured on Malvern's Dynamic Light Scattering (DLS) instruments, the Zetasizer Nano S and Zetasizer Nano ZS, while the larger conventional pigments and fillers/extenders can be easily measured on the standard diffraction instruments (Mastersizer 2000) with appropriate wet or dry sample dispersion units. The Bohlin Gemini, CVO and C-VOR rheometers can be used to determine the bulk flow properties under a range of process and end use conditions.

The measurements can be used to examine the dispersion and stability issues with pigments (all small dry materials are agglomerated). This will give vital clues as to how a material will behave in a customer's plant as well the obvious QC pass/fail criteria.

Typical materials in this area include titanium dioxide, calcium carbonate, carbon black, metal flakes and micaceous pigments as well as the inorganic and organic colored pigments.

Titanium dioxide is always coated with materials such as silica, alumina, zirconia in order to prevent the photo-catalytic decomposition of organic materials it is in contact with. The zeta potential-pH plot of such systems as well as the particle size is routinely measured. Titanium dioxide can be made either virtually opaque (optimum particle size around 250 - 350 nm) or virtually transparent (30 - 50 nm) dependent simply on particle size.

Powder coatings are a challenge in terms of coatings technology and particle size is crucial in the economics of application. The goal of thin films giving excellent protection to the substrate underneath is clearly directly influenced by the ability to make materials of a defined distribution but with the desired flow and application properties as measured with a Malvern rheometer.

Developing new or improved products quickly and maintaining or improving batch-to-batch quality and consistency are two cornerstones of your business. Competitive pressures never stop and your customers expect your products to perform exactly the same every time they buy it.

Whether you are involved in new product development or quality assurance and control, Malvern Instruments provides a wide range of particle characterization and rheological solutions and support that can help you maintain -even widen your competitive edge.