Resins have a long history of use in rubber compounding, to facilitate compounding and to achieve suitable strength. The necessary properties are more or less the same as for the tyre industry. Resins serve many functions in rubber compounds. In uncured rubbers they function as process aids, softeners, tackifiers, pigment dispersing aids and homogenizing agents. In cured rubbers their function is as a plasticizers, extenders, and reinforcing agents. These materials are included in the rubber formulation to reduce the time and energy required to break downthe polymer, e.g., peptizers or other materials that reduce the viscosity of the rubber mix. At the same time they can help improve the dispersion of dry materials, produce smoother stocks, improve the dispersion rate of fillers, and, in some instances, increase the homogeneity of rubber blends.
In tires & rubber compounds resins:
Improve green tack;
Lowers Mooney viscosity of the compound;
Have limited influence on vulcanization time and physical properties after vulcanization;
Lowers hardness and modulus of compound after vulcanization;