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Devulcanization of natural rubber compounds by extrusion using thermoplastics and characterization of revulcanized compounds

  • Rafael BarbosaEmail author
  • José Donato Ambrósio
ORIGINAL PAPER
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Abstract

Rubber recycling is a subject of high interest, regarding the complexity to develop a feasible method for material recovery without main chain degradation. In this research, Natural Rubber compounds were thermomechanically devulcanized in a continuous way through a co-rotating and intermeshing twin-screw extruder. Four process parameters were evaluated: screw rotation speed, barrel temperature, sulfur concentration and auxiliary thermoplastics (PP or EVA). Devulcanized samples were characterized by their soluble fraction, crosslink density, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR), demonstrating the rising of free natural rubber chains concentration after extrusion. Horikx theory was also used for qualitative analysis. The samples were revulcanized with or without virgin rubber compound addition and characterized by tensile, hardness and dynamic-mechanical tests (DMA). Better mechanical performances were achieved using thermoplastics due to greater second phase incorporation confirmed by scanning electron microscopy (SEM). Compounds extruded with EVA showed even better properties retention, with values around 86% for tensile strength, 110% for elongation at break and 99% for hardness, indicating this material as a promising assistant in vulcanized rubber recycling.

Keywords

Devulcanization Natural rubber Recycling Twin-screw extruder Ethylene-vinyl acetate (EVA) 

Notes

Acknowledgements

The authors would like to thank PPGCEM/UFSCar and CCDM/UFSCar for the laboratory facilities and technical support.

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.

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Copyright information

© The Polymer Society, Taipei 2019

Authors and Affiliations

  1. 1.Materials Science and Engineering Post-graduation ProgramFederal University of São Carlos – PPGCEM/UFSCarSão CarlosBrazil
  2. 2.Materials Characterization and Development CenterFederal University of São Carlos -CCDM/UFSCarSão CarlosBrazil

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