Investigation of Swelling and Dissolution Process ofNatural Rubber in Aromatic Oil

Aromatic oil has been used to promote the properties of crumb rubber modified asphalt which is an ideal method to deal with the resource utilization of waste rubber tires and by-product of refinery. Furfural extract oil(FEO) was separated into the light fraction and the heavy fraction. Swelling and dissolution process of natural rubber sheet in these three oil samples was investigated to shed light on the interaction mechanism. Crumb rubber also interacted on FEO and asphalt respectively. Energy dispersive spectrometer(EDS), thermo-gravimetric analysis(TGA) and scanning electron microscope(SEM) were used to characterize the chemical and structural properties of processed rubber. The chemical composition of processed oils and asphalt was investigated by using the hydrocarbon group analysis(SARA) and gel permeation chromatography. The results revealed that the swelling rate and mass loss of rubber in oils were much higher than those in asphalt and rose with an increasing processing temperature. The heavy fraction of FEO had more diffusion and dissolving capability than the light fraction, whilst compatibility was observed between the heavy fraction and the light fraction. Selective absorption was not observed in the study and detachment of dissolved rubber was disseminated from the outside to the inside. The cross-linking degree of the residue rubber was unchanged with the processing time, and sulfur predominantly remained in the undissolved rubber. Dissolution of crumbed rubber in oils was attributed to devulcanization, while that in the asphalt was mainly attributed to depolymerization.