Continuous devulcanization of waste tires by using a Co‐rotating twin screw extruder: Effects of screw configuration, temperature profile, and devulcanization agent concentration

Abstract

Recently, for reasons both economical and environmental, recycling of waste tires based on (styrene butadiene rubber)/(natural rubber) (SBR/NR) has been widely considered. Response surface methodology (RSM) has been used to predict SBR/NR devulcanization behavior in a co‐rotating twin screw extruder. In this study, variable parameters were barrel temperature, screw configuration, and content of devulcanization agent. A Box‐Behnken design for the three variables, at three levels, was chosen. The sol fraction of devulcanized rubber, Δtorque (difference between maximum and minimum curing torque), and mechanical properties of revulcanizate samples were considered as the responses. The results indicated that an increase of devulcanization agent content at a certain temperature caused the sol fraction to increase. Samples including a higher sol fraction showed a lower cross‐link density. Sol fraction for high shear rate screw configuration was lower than that for other screw configurations. Tensile strength of revulcanized rubber showed a decrease with a rise of devulcanization temperature. Moreover, a relationship connecting the residence time in the extruder with stagger angle and length of different kneading blocks were obtained. J. VINYL ADDIT. TECHNOL., 19:65–72, 2013. © 2013 Society of Plastics Engineers

A novel industrial technique for recycling ethylene-propylene-diene waste rubber

“…In mechanical processes, a shearing action is applied to the rubber which breaks down the rubber network. Shearing can be created on a two roll mill [10][11][12], in a batch mixer [4], or in a singleor twin-screw extruder [13][14][15][16][17]. Irradiation processes include microwave [18][19][20][21][22] and ultrasonic wave devulcanization [23,24].…”

A comparative study of ground tire rubber devulcanization using twin screw extruder and internal mixer

“…It was chosen as a good indicator of devulcanization efficiency [21]. It was performed by soxhlet extraction with toluene as solvent.…”

“…However, gel content is simpler and good measurement and calculation to indicate devulcanization efficiency [21]. Meanwhile, the structural change may be analyzed using FTIR [22], DSC and TGA [21].…”

“…In order to measure degree of devulcanization, techniques as gel/sol content [2,[20][21][22][23] and crosslink density [20,22] were applied. However, gel content is simpler and good measurement and calculation to indicate devulcanization efficiency [21].…”

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].…”