Underbody sealers are widely used for underbody protection against corrosion for motor vehicles.
Underbody sealers consist mainly of PVC-plastisols or PMMA-plastisols. They are applied by airless-spray guns and cure at temperatures of 130 °C to 140 °C.
The hydrophilic fumed silica grades AEROSIL® 200, AEROSIL® 300 and AEROSIL® 380, which have high specific surface areas, are used widely as thickening agents and thixotropes for PVC-plastisols and PMMA-plastisols. The hydrophobic fumed silica grade AEROSIL® R 972 can be used also as thixotrope and improves additionally the hydrophobicity of the PVC and PMMA-plastisols. Furthermore, the fumed silica specialties AEROSIL® R 711 and AEROSIL® R 7200 , which have acrylic groups on the surface, improve the rheological and mechanical properties of PMMA-plastisols. Additionally, Dynasylan® MTMO, which is a mercapto silane, enhances the adhesion of the PVC-plastisols to the sheet metals.
TEGO® AddBond LTH is used in PVC-plastisols for seam sealers.