Flock adhesives are classified, based on chemistry, into the following categories: thermoplastics, duroplastics, elastoplastics and elastomers, dispersion adhesives, solution adhesives, solvent-free adhesives, plastisol adhesives, and hot melt adhesives. Secondary or van der Waals forces are critical in bonding the adhesive, flock, and substrate because the surfaces are polar. Surface tension and additives also affect bonding and wetting. The use of dispersion adhesives based on acrylic acid ester illustrates the range of chemical reactions of adhesives. Crosslinking by covalent bonds, including heat-induced and cold cross-linking, are also considered.