Traditionally Hydrophilic fillers and thickners were used to control the rheological properties of polyurethane (RTV-1) sealants. Since these are moisture-cured systems, the filler is normally pre-dried before the use. This is both are inconvenient and expensive.Even when the filler is pre-dried, the viscosity of the polyurethane system increases on aging. This is probably related to premature cross linking of the polyurethane polymer groups with the hydrophilic filler's surface. Where as, our range of modified fillers and thickners can impart reasonable sag resistance with moderate viscosity increase without the need of pre drying.
As 1K sealants and the Isocyanate component of 2K PUR sealants are very much sensitive to moisture, Synthetic fillers are suitable for their thixotropy, because its moisture absorption is extremely low.