The melt viscosity of petroleum resins is often determined by the relative molecular mass, relative molecular mass distribution, and structural characteristics of the resin.
When processing at high shear speeds, the viscosity of monodisperse or narrow molecular weight distribution polymers is higher than that of wide distribution of the same polymer; under the same injection and extrusion processing conditions. The broad relative molecular mass distribution is more fluid than the narrowly distributed sample.
The hot melt adhesive with low melt viscosity can be spread well on the substrate, which increases the contact area between the hot melt adhesive and the substrate, improves the degree of hot melt adhesive infiltration of the adherend, is conducive to heat The strength of the interface between the melt and the adherend is improved; but the melt viscosity is too low.
On the one hand, it may cause the filler in the hot-melt adhesive system to settle, resulting in uneven distribution of the material composition; on the other hand, it may cause the hot-melt adhesive to be unfavorable for bonding due to the reduction in cohesive strength. The melt viscosity of petroleum resin is preferably 150 ~ 250mPas.