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Discussion on Tire Retreading and Reuse Technology
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AESEE 2020
IOP Conf. Series: Earth and Environmental Science 512 (2020) 012146
IOP Publishing
doi:10.1088/1755-1315/512/1/012146
1
Discussion on Tire Retreading and Reuse Technology
Wang Qiang*, Jiang Li, Wang Yunlong, Qi Xiaojie and Wang Guotian
School of Automobile and Traffic Engineering, Heilongjiang Institute of Technology,
Harbin, Heilongjiang, 150050, China
*Corresponding author’s e-mail: 630702666@qq.com
Abstract. China has basic state policies of developing circular economy and promoting the
reuse of waste materials. They are also regarded as important guarantees for the sustainable
development of mankind. The recycling of used tire resources has gradually become a
consensus among people as a sunrise industry. Countries all over the world attach great
importance to the retreading and reuse of used tires, especially in developed countries who
have taken used tires as an important industry to save rubber resources. Tire retreading is a way
of recycling resources, which can save rubber raw materials, solve the environmental pollution
of waste tires, and make full use of the value of tires. There is no 'three-waste' emission during
prevulcanization retreading of used tires. It is a green environmental protection industry, which
not only can save a lot of rubber, steel wire, petroleum energy and other resources, but also can
realize the reduction, reuse and recycling of used tires. Tire retreading is an active way to
recycle used tires, it is regarded as extension and processing reuse of the tire industry. They are
of positive significance for promoting the comprehensive utilization of resource conservation,
transformation of economic growth mode and sustainable development. The characteristics,
technological process of tire retreading technology, current situation and development trend of
retreading tire are discussed comprehensively in the paper.
1.Introduction
The reuse of used tires mainly includes five modes, such as tire retreading, mechanical pulverization,
low-temperature pulverization, combustion decomposition and combustion power generation. Where
in tire retreading is the most effective way to reuse used tires. The production of automobile tires is
increasing at an average annual rate of 10% all over the world with the rapid development of
automobile industry, while the annual production of automobile tires is growing at a rate far higher
than the world average level in China, which is 2 ~ 3 times higher than the world average level. The
global annual production of automobile tires is expected to exceed 2 billion, and the annual production
of Chinese tires is expected to exceed 1 billion by the end of 2020, thereby China will become the
world center of tires. Nearly 200 million used tires are produced in China every year, and the number
will be increased at a more alarming rate. Used tires have strong heat resistance and mechanical
resistance. It is difficult to degrade used tires, thereby resulting in more and more prominent tire 'black
pollution' problem. Tire retreading be adopted for saving rubber resources, saving energy and
protecting the environment on the one hand, it also also can promote the reuse of waste resources and
greatly improve the utilization rate of 'black pollution' on the other hand. The rapidly developed tire
retreading industry has low service life due to the lack of technological innovation in China, thereby
further affecting the use of retreaded tires and indirectly increasing the environmental pollution[1,2].
AESEE 2020
IOP Conf. Series: Earth and Environmental Science 512 (2020) 012146
IOP Publishing
doi:10.1088/1755-1315/512/1/012146
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2.Characteristics of tire retreading process
Tire is composed of composite materials, such as rubber, cord and steel wire, wherein tire rubber is
processed by natural rubber through synthesis. A small amount of additives and assistance are added
to form an elastomer. Tire retreading refer that the outer layer of worn tires are polished after repaired
(as shown in figure 1), a layer of buffer rubber is pasted, and then the tread rubber is further pasted,
and the product is vulcanized finally, thereby obtaining retreaded tires which can be further used. The
main structure of retreaded tires is shown in figure 2. The structure of the carcass is the same as that of
the new tire. The main difference lies in that a layer of buffer rubber is added to the worn tread and
then the tread rubber is pasted[3,4].
1) Tread rubber
Tire outermost layer surface contacted with the road surface is provided with a layer of pattern
rubber. Its tread pattern structure and form are different under different road conditions as shown in
figure 3. It is made of rubber and additives which are mixed and suppressed. Excellent wear resistance,
impact resistance, aging resistance, and high tensile strength, elasticity and tenacity are required.
FIG. 1 Carcass after polishing 1- tread rubber 2- buffer rubber 3- bonding surface 4- carcass
FIG. 2 Main structure of retreaded tire
2) Buffer rubber
Buffer rubber is used for bonding steel wire cord carcass and tread rubber in the process of tires
cold retreading as shown in figure 4. It can buffer and transitioning the impact on the tread, thereby
forming ladder-shaped stretching stress match, guaranteeing the stress uniform distribution of
retreaded tires under high load, and reducing the stress concentration. Buffer rubber belongs to a
bounded transitional layer beneficial to uniform heat dissipation, thereby ensuring the service life of
retreaded tires.
FIG. 3 Tread rubber FIG. 4 Buffer rubber
3)Carcass
Wirecord fabric and rubber composite material are mainly used as carcass for radial tires of trucks
as shown in figure 1. Wirecord fabric for carcass is mainly used to improve the fatigue resistance and
wear resistance. High strength and small diameter steel wires and stable production process are
required. The performance of wirecord fabric, rubber performance and the combination performance
of the the wirecord fabric and rubber in the used carcass for retreaded tires are lower than that of the
new carcass due to the aging phenomenon of rubber.
AESEE 2020
IOP Conf. Series: Earth and Environmental Science 512 (2020) 012146
IOP Publishing
doi:10.1088/1755-1315/512/1/012146
3
3.Process specification of prevulcanized tire retreading
The principle of 'repairing before retreading' is generally adopted for the technological procedure of
prevulcanization retreading technology, mainly including seven processes such as initial inspection
procedure, grinding procedure, external grinding procedure, repair procedure, forming procedure,
vulcanization procedure and final inspection procedure. The main process specifications for
prevulcanization retreading can be simplified as follows: choose used carcass→ used carcass cleaning
→used carcass drying →used carcass inspection → local repair (including grinding, coating of rubber
cement, gluing, pasting of the reinforcement pad, local vulcanization and other operations for carcass
nail hole, caves and other lesions) - used carcass grinding (including tire crown round grinding as well
as grinding and dressing for local uneven area) → rubber cement (brushing) coating → pasting of
buffer rubber → pasting of pattern prevulcanized tread → installation of package sleeve (including
installation of package sleeve ring, or sulfide inner tube and removable rim) → vulcanization in
vulcanizing tank→ removal of the package sleeve (including removal of the package sleeve ring, or
vulcanized inner tube and detachable rim) → finished product quality inspection → storage as shown
in figure 5[5,6].
FIG. 5 Main process specification of prevulcanization retreading
4. Status of tire retreading reuse technology
There are two tire retreading technologies mainly currently: mold vulcanization method and
prevulcanization tread method, wherein the mold vulcanization method is regarded as the traditional
technology. The pre-vulcanized tread represents advanced level and development trend of global tire
retreading industry. Intact new tread can be produced by the two tire retreading technologies. The
following aspects should be mainly considered for either technology[7].
(1) Used carcass quality. Both hot retreading or cold retreading technology can be applied if the tire
is retreaded for the first time and it belongs to a radial tire; if the tire is retreaded or the second or third
time, excellent results can be obtained through hot retreading technology in most cases. If there are
defects in the shoulder or side of the tire, the hot retreading technology should be used.
(2) Quality of tread and other raw materials: There are prominent difference in cold or hot
retreading technology if the operation level, tread and other raw material quality are the same.
However, the tread performance of the hot retreading tire is obviously much better than that of the
cold retreading tire if the tire is used in the harsh working conditions such as quarrying plant or
construction site.
(3) Retreading equipment: The advanced degree and control precision of the retreading equipment
have a great impact on the quality of finished products after the retreading of tires.
(4) Operator's technical level: only the correctly trained operators can be competent in each process
of retreading, and the operators should have skilled retreading technology and experience.
(5) Cost of retreading equipment: the investment for the establishment of a hot treading plant is
much higher than the establishment of a cold reading plant of the same scale relatively speaking
AESEE 2020
IOP Conf. Series: Earth and Environmental Science 512 (2020) 012146
IOP Publishing
doi:10.1088/1755-1315/512/1/012146
4
mainly because hot retreading technology requires vulcanization machines, molds, etc., and higher
investment is generally required for the equipment.
(6) Cost of tread and other raw materials. The cost of raw materials such as tread used in extruder
or winding machine is relatively high.
The following national standards and industry standards are formulated for the production of
retreaded tires in China currently, including 'GB7037-2007 Truck Retreaded Tires', 'GB14646-2007
Car Retreaded Tires' and 'HG/ T3979-2007 Construction Machinery Retreaded Tires'. There are
following problems in China tire retreading[8].
(1) People have low consciousnesses to use the retreaded tires, thereby hindering the retreaded tire
market. Many tire use enterprises or individuals, especially private car owners, think that there is a
serious safety risk of retreaded tires, and there is even a misunderstanding 'retreaded tire is equivalent
to suicide', who would rather buy new tires at a high price rather and are not willing to use retreaded
tires.
(2) Lack of relevant policies, regulations, guarantee and incentive mechanisms for tire retreading:
the state attaches great importance to the development of the tire industry, the industry policy and
financial support for retreaded tires are insufficient. Some tire retreaded enterprises are facing
difficulties in development due to the lack of policy support and capital support for equipment renewal.
(3) Chaos in used tire sales market and insufficient management standards: there is no effective
recycling-reuse system in the sales market of used tires in China, and non-standard management of the
sales market leads to the ineffective recycling of used tire resources for tire retreading, and there is no
close cooperation between the retreading enterprises and the tire recycling enterprises.
(4) Backward tire retreading process and technology: tire retreading enterprises are basically still in
the era of small workshop in china, the equipment replacement cycle is long, equipment technology is
backward, and most retreading process is still based on traditional or experienced process, thereby
resulting in the unstable quality of retreaded tires, and there are certain safety risks.
The life cycle of tire products will go through the scientific process of 'use - retreading - reuse -
scrapping - residual value utilization' with the continuous development of technology so that 'black
pollution' is converted into 'black energy'. The tire retreading industry has weak technical force in
China fundamentally speaking, and the basic theory of retreaded tires is lacking compared with new
tires. Therefore, it is of positive significance for the future development of the tire retreading industry
to strengthen the research on the technical basic standards and related basic theories of tire retreading.
5. Development trend of tire retreading reuse technology
The average retreading rate of used tires is 60% throughout the international market, which is as high
as 90% in European and American countries and only 15% in China . France, Japan, Italy and the
United States have advanced tire retreading equipment and technology all over the world. China is in
the medium and lower level. Professional tire retreading enterprises are mostly based on 'cold
retreading method'. Some affiliated retread tire factories under new tire manufacturing enterprises are
mostly based on the traditional 'hot retreading method'. For example, the ratio of retreading trunk tires
through 'hot retreading' and 'cold treading' each year is about 4:1. 90% in the tire retreading factory of
Britain Goodyear. 90% of tire treading plants under Michelin in France use the precise 'hot retreading
method' developed by the company, and they occupy most tire retreading market in Europe.
Bridgestone Japan also uses its own developed precise 'hot retreading method' mostly. 'Cold retreading
method' is only used for retreading grade I tires. The ratio of 'hot retreaded' and 'cold retreaded' tires
used by Continental Germany is close to 1:1. Car tires and the aviation tire s are nearly not retreaded
in China. The trunk tires are mostly retreaded through 'cold retreading method'. Engineering tires are
based on tire categories, specifications and use requirements. 'Hot retreading method' is mostly
adopted during retreating of large or huge engineering tire retreading. The process technology level is
more and more mature. 'Cold retreading method' is adopted for retreading in some tire retreading
plants aiming at medium and small-sized engineering tire retreading. Most retreating plants are based
on 'hot retreading method'[9].
AESEE 2020
IOP Conf. Series: Earth and Environmental Science 512 (2020) 012146
IOP Publishing
doi:10.1088/1755-1315/512/1/012146
5
The technology of engineering tire prevulcanization retreading is developed rapidly in foreign
countries, which is developed slowly in China because the engineering tires retreaded through
prevulcanization has unstable quality mainly and different performances among engineering retreaded
tires. The retreading of engineering tire prevulcanization tread method will gradually replace the
retreading of mold vulcanization method with the development of technology. The tread aging degree
of prevulcanization tread low temperature retreading method is lowered by more than 50% compared
with traditional 150 ℃ high temperature method, thereby the service life of retreaded tires is
comparable to the performance of the new tires, which is especially suitable for long-distance driving.
The tire wearing and burst risks of the tires are lowered during normal operation because of fast heat
radiation and wear resistance on the one hand, and the rubber layer of the tires can not be softened
easily with higher wear-resisting mileage on the other hand, which is more in line with economic
principles. Because the retreaded tires made by the prevulcanization tread low-temperature retreading
method has the advantages of 'wire resistance, punching resistance, oil saving, lateral skid prevention
and low price', high retreading rate, easy process, low cost and high energy saving effect. The
retreaded tire mileage is equivalent to that of new tires, thereby gradually replacing the former mold
vulcanization method retreading technology. It has become the mainstream in the tire retreading
technology, which is regarded as the future development direction of retreaded tires[10].
Acknowledgments
Fund Project: Project supported by basic scientific research business expenses of Heilongjiang
Provincial Undergraduate Universities (2018CX07); Heilongjiang Natural Science Foundation Project
(LH2019E115); Heilongjiang Institute of Technology PhD Research Startup Fund Project (2016BJ02)
Author: Wang Qiang (1981-), male, Harbin, associate professor, doctor of engineering, postdoctor.
Research interests: vehicle tire technology, vehicle driving safety.
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