Selective Decomposition of Waste Rubber from the Shoe Industry by the Combination of Thermal Process and Mechanical Grinding

• Published in: Polymers Vol. 14; no. 5; p. 1057
• Main Authors: Xiao, Qiao, Cao, Changlin, Xiao, Liren, Bai, Longshan, Cheng, Huibin, Lei, Dandan, Sun, Xiaoli, Zeng, Lingxing, Huang, Baoquan, Qian, Qingrong, Chen, Qinghua
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 07.03.2022; MDPI
• Subjects: Carbon; Decomposition; filling rates; Footwear industry; Fourier transforms; Grinding; grinding temperature; Infrared analysis; Interfacial bonding; Lasers; Liquid chromatography; Molecular weight; Morphology; Oxidation; Particle size; Particle size distribution; Rosin; Rubber; Sol-gel processes; Spectrum analysis; thermo-mechanical grinding; Vulcanization; waste rubber; Zinc oxides; United States > US; China; grinding temperature; filling rates; waste rubber; thermo-mechanical grinding
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym14051057

A major challenge in waste rubber (WR) industry is achieving a high sol fraction and high molecular weight of recycled rubber at the same time. Herein, the WR from the shoe industry was thermo-mechanically ground via the torque rheometer. The effect of grinding temperature and filling rate were systematically investigated. The particle size distribution, structure evolution, and morphology of the recycled rubber were explored by laser particle size analyzer, Fourier transform infrared spectroscopy (FTIR), sol fraction analysis, gel permeation chromatography (GPC), differential scanning calorimeter (DSC), and scanning electron microscope (SEM). The results indicate that the thermo-mechanical method could reduce the particle size of WR. Moreover, the particle size distribution of WR after being ground can be described by Rosin's equation. The oxidation reaction occurs during thermal-mechanical grinding. With the increase of the grinding temperature and filling rate, the sol fraction of the recycled WR increases. It is also found that a high sol fraction (43.7%) and high molecular weight (35,284 g/mol) of reclaimed rubber could be achieved at 80 °C with a filling rate of 85%. Moreover, the obtained recycled rubber compound with SBR show a similar vulcanization characteristics to pure SBR. Our selective decomposition of waste rubber strategy opens up a new way for upgrading WR in shoe industry.