Strategies for compatibilization of polymer/waste tire rubber systems

prepared via melt-blending

Krzysztof Formela a, b

a Department of Polymer Technology, Faculty of Chemistry, Gda
nsk University of Technology, Gabriela Narutowicza 11/12, 80-233 Gda
nsk, Poland

b Advanced Materials Center, Gda
nsk University of Technology, Gabriela Narutowicza 11/12, 80-233 Gda
nsk, Poland

a r t i c l e i n f o

Article history:

Received 30 May 2023

Received in revised form

24 July 2023

Accepted 4 August 2023

Keywords:

Recycling

Waste tire rubber

Compatibilization

Melt-compounding

Morphology-performance relationship

a b s t r a c t

Waste tires are a low-cost and high-calorific alternative fuel, therefore energy recovery is still very

popular method of their utilization. On the other hand, waste tires are composed from high quality

components and can be considered as valuable source of raw materials. Recent trends showed that

further development of waste tire recycling technologies and waste tire rubber based materials are

crucial to design the cradle-to-cradle loops for elastomer products. This approach fits to circular economy

concept, however high content of waste tire rubber in various polymer blends or composites usually

results in deterioration of their processing and/or the performance properties. Some of those technological

issues can be resolved by choose suitable compatibilization method.

This work summarizes recent advances in the compatibilization strategies dedicated for polymer/

waste tire rubber systems prepared via a simple melt-blending, including: i) optimization of processing

conditions; ii) GTR particle size and oxidation; iii) devulcanization/reclaiming; iv) reactive blending and

v) other methods. Furthermore, the limitations and challenges related to further development of thermoplastic

composites and thermoplastic elastomers based on GTR are also highlighted.

© 2023 Kingfa Scientific and Technological Co. Ltd. Publishing services by Elsevier B.V. on behalf of KeAi

Communications Co. Ltd. This is an open access article under the CC BY license (http://creativecommons.

org/licenses/by/4.0/).

1. Introduction

According to Statista Research Department, the combined global

production of natural and synthetic rubber has increased by ~55%

over the last twenty years, from around 17.7 million metric tons in

2000 year to 27.4 million metric tons in 2020 year [1]. The European

Tyre and Rubber Manufacturers' Association estimates that around

65% of the general rubber goods production is dedicated to the

automotive industry [2]. In 2021 year, nearly 80 million vehicles

were produced worldwide, an increase of ~3% compared to 2020

year [3]. As can be seen, the global production of natural and synthetic

rubber is strongly correlated with the development of the

automotive sector.

Gerrard and Kandlikar [4] showed that the construction of an

average passenger car contains: plastics e 9.1 wt%, rubber e 1.6 wt

%, and tires e 3.5 wt%. Fukumori and Matsushita [5] classified

rubber goods used in vehicles into five main groups: tires e 67 wt%,

weather strips e 9 wt%, vibration isolators e 8 wt%, hoses e 6 wt%,

and others e 10 wt%. As can be observed, tires represent the largest

stream of rubber in vehicles.

The level of new tires production is determined by vehicle services

(e.g. seasonal tires) and the growing demand for vehicles, the

largest producers of which are currently China, Japan, and Germany.

Valentini and Pegoretti [6] indicated that in 2020 year

around 324 million new tires were sold in Europe, including: passenger

cars and light duty vehicles e 89.5% (70 wt%), heavy duty

vehicles (trucks and buses) e 4.9% (20 wt%), motorbikes and

scooters e 3.6% (1 wt%), and agricultural and off-road vehicles e

1.9% (9 wt%). As can be noticed, the main stream of waste tires are

passenger cars, light and heavy duty vehicles, which represent

94.4% (90 wt%) of the market.

Tires are complex composites made of high-quality components

and should be considered as a valuable source of raw materials

[7,8]. However, due to the presence of three-dimensional irreversible

cross-linked network rubbers cannot be easily reprocessed

and recycled, like thermoplastics. This causes serious problems

with post-production and post-consumer waste rubber management

or further recycling, especially of end-of-life tires. This also

makes rubber incompatible with the circular economy consumption

model [9].

According to the European Commission Decision 2000/532/EC,

E-mail address: [email protected]. used tires and rubber waste are classified as non-hazardous waste.

Contents lists available at ScienceDirect

Advanced Industrial and Engineering Polymer Research

journal homepage: http://www.keaipublishing.com/aiepr

https://doi.org/10.1016/j.aiepr.2023.08.001

2542-5048/© 2023 Kingfa Scientific and Technological Co. Ltd. Publishing services by Elsevier B

Adding recycled crumb rubber from vehicle tyres and polyethylene from wasted greenhouse plastic film in bitumen improves its properties at both high and low temperatures, minimizing its disposal at landfills. incorporating waste tire rubber with polyethylene can enhance the properties of asphalt, bitumen, concrete, and various industrial applications, making them more durable and sustainable.

Combining recycled polyethylene and ground tire rubber can improve the thermal and rheological properties of modified bitumen blends, making them beneficial for roofing and waterproofing applications. Smaller rubber particle sizes combined with adhesion components can produce thermoplastic elastomers with improved mechanical properties when blending waste tire rubber and low-density polyethylene.

The optimized composites made from recycled materials like tire rubber and plastics have good mechanical properties and dimensional stability, making them suitable for indoor and outdoor applications. Thermoplastic elastomer blends with waste tire rubber show promising properties for commercialization, but need further studies on dynamic mechanical, aging, thermal, and swelling properties. Additions of different quantities of reused tire powder to linear low-density polyethylene can be used in industrial applications like universal electrical cable joints, filler for electrical applications, and cable tray systems.