Feasibility Study on the Application of TPU Polyurethane Elastomers in Tires
Release time:
12 Oct,2017
TPU (Thermoplastic polyurethanes) is a thermoplastic polyurethane elastomer rubber. It is primarily categorized into polyester-based and polyether-based types. TPU boasts a wide hardness range (60 HA to 85 HD), excellent wear resistance, oil resistance, transparency, and superior elasticity. As a result, it is widely used in fields such as daily consumer goods, sporting goods, toys, and decorative materials. Halogen-free flame-retardant TPU can also replace soft PVC to meet the growing environmental requirements across various industries.
Typically, bicycle tires are made of rubber and involve a complex manufacturing process that generally includes several steps: plasticizing—compounding—processing embryo components (such as inner tubes, treads, and carcass fabrics)—embryo molding—embryo vulcanization—and other related procedures before the final bicycle tire product is produced. In contrast, future bicycle tires will be made from a special thermoplastic elastomer called TPU, and their molding process will employ injection molding. All that’s required is to design and prepare the mold, then directly inject the thermoplastic elastomer in a single step to produce the bicycle tire product according to the desired specifications.
The shared bicycle boom began in 2016, and streets and alleys were soon filled with bicycles from brands like Mobike and ofo. Although the number of bicycles deployed hasn't increased further, once their service life comes to an end, recycling the used materials will become a significant challenge. The environmental damage caused by this practice goes without saying—and it sharply contrasts with current environmental protection policies. However, TPU materials can help solve this problem: TPU materials are recyclable, easily biodegradable, and place minimal burden on the environment.
Can automobile tires also be made from TPU materials? Significant progress in this area was made in 1970, when Firestone Tire & Rubber Company (Alliger et al., 1971) publicly reported on the development of experimentally cast tires for automotive applications. In recent years, China’s automobile production and sales have continued to show an upward trend, presenting a huge market opportunity for TPU tires. However, TPU still faces its own technical challenges.
The main difficulties are as follows:
(1) Certain thermal and physical properties of TPU stem from the thermoreversibility inherent in the urethane chain itself; therefore, at sufficiently high temperatures, the main chain of TPU will undergo chain scission.
(2) The reinforcement mechanism is also thermosensitive in principle, as it is related to the presence of microdomains, which must remain above their glass transition temperature or melting point during use.
(3) Even when driving slowly on the road, and even at relatively moderate temperatures, tires—under the combined effects of inflation pressure and heat—will exhibit “crack growth.”
(4) Under conditions such as emergency braking or localized overheating, the tire tread may suffer catastrophic failure.
(5) Compared to traditional materials, TPU tires are relatively more expensive to manufacture.
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