SoftSand® rubber particles are derived from an elastomeric compound that was tailored to meet the requirements of the coatings industry. This paper examines the underlying chemistry of SoftSand rubber, and reviews the selection process and criteria that led to its formulation. In addition to strength, elastomeric qualities and numerous stability requirements, a key requirement of this formulation is the ability of the particles to adhere to common paint and coatings resins such as urethanes, acrylics and epoxies. The surface chemistry required to facilitate this is discussed. The first commercial application of this new material is also reviewed, and a starting-point formulation for acrylic floor paint is now available on the company's website.
Typically, a rubber compound contains 15 to 25 ingredients, with the rubber polymer being typically less than 50% by weight. Normally blends of different rubbers will be used as the elastomeric part of the mixture. The rest of the ingredients are principally chemicals added to improve strength, adjust hardness, modify elastic properties (modulus, resilience, elongation, dynamic properties), improve aging characteristics, develop proper color, and help the processing characteristics during manufacture. For specialized applications there are chemicals added for such properties as fire resistance, conductivity and adhesion to various substrates. The latter characteristic is one among many of the principal characteristics that makes SoftSand uniquely suitable for its intended application.