What Is a Tackifier?

Tackifier is added to the modified asphalt, and the bonding surface is wetted by surface diffusion or internal diffusion, so that the bonding strength between the modified asphalt and the adhered material is improved. There are two types of tackifiers: inorganic salt electrolytes and organic tackifiers.

Tackifier concept

Despite the tackiness of natural rubber, the adhesive strength of adhesives produced by rubber alone is still insufficient for many applications. Most commercial synthetic elastomers lack adhesion, either to themselves or to other surfaces. Therefore, in order to increase their viscosity, a resin tackifier is added. A large number of latex and solvent systems, especially when used as contact adhesives, use specific types of tackifying resins.

Tackifier effect

The relative molecular mass of common tackifiers is 200-1500, and generally has a large and rigid structure. They are thermoplastic and are usually amorphous glass bodies at room temperature. They have a wide range of softening points, ranging from liquids at room temperature to brittle hard solids with melting points up to 90 ° C. They are generally quite soluble in aliphatic hydrocarbons, aromatic hydrocarbons, and many typical organic solvents. For the US patent literature from 1976 to 2001, see the corresponding questionnaires later in this chapter. From the viewpoints of viscosity, tensile strength, color retention, and resistance to oxidation and brittleness, the selected tackifier resin will affect the quality of the adhesive. Unmodified gum and wood rosin can be converted into esters, which have a certain viscosity at first, but they have poor aging resistance after the coating is completed. Rosin esters stabilized by hydrogenation or polymerization are resistant to oxygen attack and have the best overall performance when used in adhesives. Examples are Staybe1ite Ester l0 or Fora 185 (hydrogenated rosin glyceride), Penta1yn H or Fora1 l05 (hydrogenated rosin pentaerythritol ester).

Tackifier classification

Lower softening point resin

The lower softening point resin has a greater tackifying limit effect, but this effect can only be obtained at high concentrations. The tensile strength will decrease with the increase of the tackifier concentration, and the reduction rate will be different for different tackifiers.

SBR system

The styrene-butadiene rubber system itself has poor viscosity. Tackiness occurs only when a sufficient amount of Penta1yn H tackifier is added, and a second phase appears in the adhesive film. The viscosity reaches the maximum when the tackifier concentration is 60% to 65%. However, the relationship between the softening point and the viscosity of the aforementioned tackifiers is not necessarily established for several different crystalline-resistant soft neoprene. Like natural rubber, high-viscosity synthetic rubber film loses tackiness and two-phase characteristics when continuously heated at 93 ° C.

Inorganic electrolyte

The thickening of inorganic salts is achieved through a synergistic effect with organic tackifiers or surfactants. In general, the presence of inorganic salts increases the number of associations of micelles, which leads to the transformation of spherical micelles into rod-like micelles and increases viscosity ^[1] .