Development of functional hollow particles

What are hollow particles?

"Hollow particles have void space in their body. A lot of varieties of hollow particles are sold. Diameters varies from 20μm to several mm, and hollowness ratio is 40-60%. Hollow particles are lightweight and void space prevent heat conduction, so they are widely used as insulation coating of building and roof, and as weight reduction filler for concrete products.
As environmentally friendly and low-energy products are desired in recent years, There is a strong demand for hollow particles with much smaller size, and much higher hollowness ratio."