Recycling of rubber: Analysis of an industrial thermo-mechanical devulcanization process
Dr Edith Peuvrel-Disdier
MINES ParisTech - CEMEF
Sophia Antipolis, France
The recycling of rubber in the industry has become highly important due to environmental and financial reasons. A recycling approach is to devulcanize the rubber in order to reintroduce it as raw material. This is a challenging process since the objective is to rupture the rubber network by breaking sulfur bridges without damaging the polymer chains (devulcanization process). In the present work, a devulcanization process known as “High Shear Mixing” (HSM) was investigated. A machine was designed, built and instrumented with the purpose of studying the different phenomena occurring during the devulcanization process. During the treatment, the rubber is sheared between two cones with special geometries. During this shearing the treated rubber is self-heated, a cooling system prevents the rubber degradation due to excessive heat. The objectives of the study were to better understand the process and the physics behind, to determine a process parameter to follow the rubber evolution and to optimize the treatment.
Specific protocols were designed to better understand the exact role of the different variables (rotation speed, gap, direction of rotation, etc.) on the treated rubber. The instrumentation of the machine coupled to a systematic physico-chemical analysis of the treated rubber was fruitful to follow the different physical processes happening to the material.
Our analysis highlighted two parameters to follow the rubber treatment: the rubber temperature and the specific mechanical energy consumed during the process. This energy can be correlated to the physico-chemical state of the treated rubber and can be used as an indicator of the progression of the process. An optimal state of surface activation on the treated rubber was also described. A physical model of the rubber network evolution along the HSM treatment is proposed.
To validate the recycling efficiency, the effect of adding different fractions of treated rubber in the same raw material formulation was tested. A Taguchi method was used to design formulations and HSM factors to be tested. Reformulated mixtures were vulcanized and rubber properties were analyzed.
This work was performed in the framework of the project ECOTHER supported by BPiFrance.
R. Diaz, G. Colomines, E. Peuvrel-Disdier, R. Deterre, Thermo-mechanical recycling of rubber: Relationship between material properties and specific mechanical energy. Journal of Materials Processing Technology 252 (2018) 454–468
Dr Edith Peuvrel-Disdier got her chemical engineer diploma in 1986, her PhD on rheo-optical study of liquid crystalline polymers in 1991. She is a research scientist of National Center for Scientific Research (CNRS) working in MINES PariTech CEMEF in Sophia-Antipolis, France, since 1992. Habilitation to supervise research in 2009
Dr Edith Peuvrel-Disdier main research topics are:
- relationship between structure, flow and rheology,
- structuration of multiphase systems: immiscible polymer blends, nanocomposites