Functional Additives

Dualite microspheres are hollow polymeric microspheres containing  a hydrocarbon core such as isobutane and isopentane. 

We supply 2 types of microspheres:

• unexpanded microspheres
  where the shells are several microns thick and the hydrocarbon cores are primarily liquid and under pressure. They are available in a wide range of particle sizes and operating (expansion) temperatures.  Sizes range from a low of 6 – 9 microns to a high of 45 – 50 microns.  Expansion temperatures, which are varied by the manufacturers by adjusting the copolymer compositions, range from 70 – 80 C for the polyvinylidene chloride microspheres to over 200 C for acrylonitrile beads.
• expanded coated microspheres
  are created by heating the unexpanded microspheres in the presence of a fine particulate mineral, usually calcium carbonate.  The microsphere’s polymer shells soften in the heat and expands significantly from the pressure of the hydrocarbon cores.  The expanded version is a much larger microsphere with a thinner polymer shell coated with mineral particles. After expansion, particle sizes range from 25 microns to over 200 microns.  The hydrocarbon cores are completely gaseous and less dense than the unexpanded microsphere, with densities in the range of 0.030 – 0.130 g/ml.  They are sometimes referred to as microballoons.

Related article: Get the Right Mix of Microspheres & Solvents in Your Formula

The Use of Microspheres

The primary benefits of using microspheres are weight reduction and cost reduction.  The cost reduction is based on the microsphere mixtures replacing materials that are more expensive on a per volume basis.  There are also some potential performance improvements such as thermal insulation, sound damping, and reduced drying time.

Customers incorporate microspheres into their products in several ways:

1. Expanded microspheres can be added to liquid mixtures directly and dispersed with low shear mixing. No elevated temperatures are needed or desired. The microsphere mixtures can then be applied by any number of low shear application methods.
2. Unexpanded microspheres can be added to liquid mixtures and dispersed with low to medium shear mixing. Elevated temperatures are not needed at this point.  However, the microspheres will need to be expanded at some point in a controlled fashion to take advantage of their properties.  Care must be taken to expose the microspheres to the correct temperature range for an optimum period of time while the matrix material is pliable enough to allow the microspheres to expand.
3. Unexpanded microspheres that will be added to thermoplastic materials are best handled via a master batch which is a concentrated pre-dispersion. The master batch polymer must have a working temperature below the start of the microsphere. The master batch can be incorporated into a bulk polymer with simple mixing.  The microspheres must be expanded at some point in a controlled fashion as described in #2 above.

Choosing the right microsphere for your specific application involves considering several factors.  Following these guidelines will help you better understand the use of microspheres in your process and products.  This will increase your chances of success and save you time and money by making the right decision up front.

If you have any questions regarding your microsphere project, please contact Chase Corporation for an expert opinion