Molecular interactions between rubber and asphalt

The analysis of the interactions between rubber and asphalt was carried out. The swelling rate and equilibrium of rubber penetration with the selected asphalt components were found to be dependent on these components and the rubber content in asphalt. At fixed conditions of stirring asphalt with rubber, the equilibrium swell value decreases with the increase in rubber content. From the gel permeation chromatography (GPC) analysis, it follows that the lighter asphalt components penetrate more readily into the internal matrix of the polymer. The gas chromatography-mass spectrometry (GC-MS) study allowed us to assess which components penetrated from asphalt into the rubber and which moved from rubber to asphalt. It has been found that of the nonpolar components, the n-alkanes and n-alkylbenzenes, possess the highest propensity to penetrate into rubber particles. Preferential absorption of the compounds with linear aliphatic chains into the rubber suggests that these components have a good compatibility with the linear polymeric skeleton of the rubber. During immersion of the rubber in hot asphalt, the fatty acids, which are the components of the curing system of the polymer, move from rubber to asphalt, and they are most probably concentrated in the naphthene-aromatic fraction of the asphalt. The electron paramagnetic resonance (EPR) study confirmed the effect of the immersion time of rubber in asphalt and of the shear on the swelling rate.