tackifying

Tackifying is the process of increasing the tack, or stickiness, of a coating, adhesive, or other polymer film by adding tackifier substances. In adhesive technology, tackifying agents are incorporated into base polymers to improve initial adhesion, surface wetting, and handling performance, particularly under light pressure before full curing or crystallization.

Common tackifiers include rosin and rosin derivatives, hydrocarbon resins, terpene resins, and polyterpene resins. These substances can be natural or synthetic and are chosen based on compatibility with the base polymer, desired aging properties, color, odor, and cost. Typical loadings range from a few to several tens of parts per hundred parts of polymer (phr).

Applications of tackifying agents span across many adhesive and coating systems. They are widely used in pressure-sensitive adhesives for tapes and labels, hot-melt adhesives, sealants, paints and coatings, and other polymer films where enhanced initial tack is beneficial. In some bituminous or pavement systems, tacky additives help improve bond between layers, though tack coats in paving are a distinct process from standard tackifier chemistry.

Effects and considerations: adding a tackifier usually lowers the glass transition temperature and adjusts viscosity, increasing tack and wetting. However, excessive or poorly matched tackifier can reduce cohesive strength, alter aging resistance, or introduce color and odor issues. Selection involves balancing tack, cohesion, long-term stability, and processing requirements.

See also: adhesive technology, pressure-sensitive adhesives, tack, resin, polymer additives.