Ultrasonic properties and morphology of devulcanized rubber blends

Abstract

The ultrasonic properties of two devulcanized rubber (DR) blends with a styrene-butadiene-styrene (SBS) copolymer compound (ACE) are investigated using a transmission method. The DR materials are obtained from commercial rubber crumbs (RC) by a proprietary devulcanization technique. Measurements on the acoustic attenuation and travel velocity are conducted on the samples with different sample thicknesses in the pulsed mode. Attenuation coefficients of the materials are obtained by changing the frequency of the ultrasound in the tuned tone-burst mode. The two DR/ACE blends show marked differences in the attenuation and attenuation coefficient, although the ultrasonic velocities are similar. These differences arise from the variation of the remaining degree of crosslinking in the DR materials. The acoustic velocities in the three materials are similar. The morphologies of the DR/ACE blend samples, observed using scanning electron microscopy (SEM) with different staining agents, explain their similarities and differences. There are two crops of rubber particles: larger ones belong to the original rubber crumbs that survived devulcanization; the smaller ones are fragments of partially DR. These crosslinked particles contribute to the overall degree of crosslinking in the blends. The devulcanized fractions of the DR materials are dispersed in the ACE matrix. Scattering at the interface accounts for the differences in the acoustic attenuation of the samples.

Balancing mechanical properties and processability for devulcanized ground tire rubber using industrially sized single‐screw extruder

“…Enormous efforts have been made to develop a number of techniques to devulcanize waste rubbers especially ground tire rubber (GTR). These techniques mainly include thermomechnical, mechanochemical, microwave, ultrasonic, microbial, and solid state shear pulverization methods. Among these devulcanization methods, thermomechnical continuous devulcanization via shearing has a largely industrialized potential .…”

Devulcanization of Elastomers and Applications

“…The literature presents several works that discuss the different methods used to devulcanize rubbers, as mechanical and chemical mechanical method [10][11][12], microwaves method [9,[13][14][15][16][17][18][19], ultrasound method [20][21][22], chemical method [23,24], microbial method [25,26], and still other methods as bioreactor and spraying for solid-state shear [27,28]. Subsequently, when the goal is to use the recycled elastomer in the production of a blend, the role of devulcanization is to increase the interaction between the raw and recycled material, reducing the degradation of the properties of the finished product, and making it possible to increase the amount of recycled elastomer in the compound raw phase/recycled phase [29].…”