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Sustainable rubber recycling from waste tyres by waterjet: A novel mechanistic and practical analysis

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Title: Sustainable rubber recycling from waste tyres by waterjet: A novel mechanistic and practical analysis
Authors: Bowles, AJ
Fowler, GD
O'Sullivan, C
Parker, K
Item Type: Journal Article
Abstract: Production and disposal of car tyres are major contributors to environmental damage. The first stage in tyre rubber recycling is granulation to smaller particle sizes. The sub-optimal physical, mechanical and chemical properties of mechanically ground tyre rubber (GTR) when incorporated into recycled blends are major obstacles to wider use of this potentially sustainable, recovered resource. Consequently, newly manufactured tyres contain less than 5% recycled material. This study compares two types of GTR product: mechanically ground crumb (MGC) and ultrahigh pressure waterjet-produced rubber crumb (WJC). A novel image analysis method showed that when the two particle types were compared, MGC was associated with both greater convexity and sphericity: the geometric mean ratio of MGC/WJC sphericity was 1.67. When part-recycled rubber blends comprising 30% crumb of particle size < 300 μm were compared to virgin polymer, the WJC blend exhibited superior mechanical properties to the MGC blend. These results can be explained by the higher surface area to volume ratio of WJC when compared to MGC which results in strong bonding in new blends using WJC. Further analysis by scanning electron microscopy (SEM) elucidated significant shape and textural variation within the WJC sample, allowing grouping into two sub-categories: “W1” which comprises particles with complex geometries, and “W2” particles which have a relatively simple topology that is similar to MGC. Maximising the W1:W2 particle ratio is likely to be crucial to the optimisation of output quality in the WJC process, and so a composite model is proposed that unifies three well-established fluid effects: brittle fracturing, impact cratering and cavitation. Impact cratering and cavitation effects should be maximised by altering process parameters with the aim of producing a higher proportion of crumb with a more irregular surface morphology to achieve better bonding properties in recycled rubber blends. It is anticipated that this improvement in processing will allow more recycled material to be incorporated into future car tyre production, thereby closing a significant loop in the circular economy.
Issue Date: 1-Sep-2020
Date of Acceptance: 11-May-2020
URI: http://hdl.handle.net/10044/1/85318
DOI: 10.1016/j.susmat.2020.e00173
ISSN: 2214-9937
Publisher: Elsevier
Start Page: 1
End Page: 15
Journal / Book Title: Sustainable Materials and Technologies
Volume: 25
Copyright Statement: © 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: Innovate UK
Funder's Grant Number: 102405
Keywords: Science & Technology
Technology
Green & Sustainable Science & Technology
Energy & Fuels
Materials Science, Multidisciplinary
Science & Technology - Other Topics
Materials Science
Waste-tyre
Waterjet
Recycling
Image-analysis
Fluid-mechanics
ULTRASONIC DEVULCANIZATION
GROUND RUBBER
CRUMB-RUBBER
CAVITATION
SHAPE
JET
PULVERIZATION
OPTIMIZATION
CHALLENGES
AGGREGATE
Science & Technology
Technology
Green & Sustainable Science & Technology
Energy & Fuels
Materials Science, Multidisciplinary
Science & Technology - Other Topics
Materials Science
Waste-tyre
Waterjet
Recycling
Image-analysis
Fluid-mechanics
ULTRASONIC DEVULCANIZATION
GROUND RUBBER
CRUMB-RUBBER
CAVITATION
SHAPE
JET
PULVERIZATION
OPTIMIZATION
CHALLENGES
AGGREGATE
Publication Status: Published
Embargo Date: 2021-05-29
Article Number: ARTN e00173
Online Publication Date: 2020-05-29
Appears in Collections:Civil and Environmental Engineering
Geotechnics



This item is licensed under a Creative Commons License Creative Commons