Thermoplastic polyurethane (TPU) not only possesses the rubber-like properties of crosslinked polyurethanes—such as high strength and excellent wear resistance—but also exhibits the thermoplastic behavior characteristic of linear polymer materials, thereby expanding its applications into the plastics sector. In particular over the past few decades, TPU has become one of the fastest-growing polymer materials.

TPU film is an important application form of TPU material, and in recent years, with the development and advancement of high technology, it has been increasingly widely adopted. However, due to factors such as its difficult processing and product instability, no manufacturer in mainland China has yet achieved satisfactory mass production of TPU film.

1. Current Status of TPU Film Production and Application

1.1 Analysis of the Production Status of TPU Films

The production of TPU materials is primarily concentrated in the United States, Western Europe, and Japan, with Taiwan in China also accounting for a significant share. Internationally renowned companies include Bayer, Dow, Mobay, and DuPont. In Taiwan, China, several influential TPU manufacturers have emerged, such as Sanhong Chemical, Gaoding Chemical, Risheng Chemical, and DingZing Chemical. TPU films represent an important application of TPU and also constitute one of its most promising markets. Major producers of TPU films include Germany’s Bayer, Taiwan’s DingZing Chemical, and South Korea’s Jin Xing Chemical; among these, DingZing Chemical has particularly distinguished itself in the industry.

However, on the one hand, TPU film products exhibit highly unstable characteristics during the manufacturing process, requiring advanced technologies and equipment for both development and testing. On the other hand, due to competition from other materials and economic factors, TPU film production must evolve toward greater efficiency—enabling the repeated production of high-quality TPU films at lower costs. At the same time, there is a growing demand for a wider variety of TPU films, with thicknesses ranging from thinner to thicker, as well as the integration of more sophisticated high-tech solutions to enhance their physical properties and thereby achieve higher added value. These two aspects have become bottlenecks that are hindering the development of domestic TPU manufacturers in China.

1.2 Current Status of TPU Film Applications

Due to its high strength, excellent wear resistance, superior elasticity, and weather resistance, TPU films are widely used in fields such as the automotive industry, footwear materials, garment laminating, ready-to-wear clothing, chemicals, electronics, and healthcare. As many countries place increasing emphasis on environmental protection—especially since the European Union banned the use of PVC in footwear materials and other products—people have been striving to find alternative materials that are equally suitable.

Due to its environmentally friendly, non-toxic nature, as well as its ease of recycling and biodegradability, TPU film has become an excellent alternative to PVC materials in footwear applications. Moreover, wherever PVC can be used, TPU can readily serve as a substitute. As a crucial credential for entering the European and American markets, inspection reports from internationally renowned testing organizations such as SGS, ASTM, JIS, and FDA are also highly important.

For example, the renowned film brand DingZing Film has long since obtained these certifications. Its films boast stable quality, are non-toxic and non-polluting, free from the eight hazardous heavy metals, and can be incinerated and biodegraded—factors that have earned this brand widespread recognition worldwide.

TPU films are divided into two major categories: polyester and polyether. Among these, polyester-based products exhibit superior heat resistance and chemical resistance, making them widely used as replacements for PVC products. Polyether-based products, on the other hand, offer excellent low-temperature resistance, hydrolysis resistance, and anti-mold and antibacterial properties, and are extensively employed in products that come into contact with water.

The application areas of TPU films can be broadly categorized into the following aspects:

(1) Waterproof and moisture-permeable TPU films for textiles—thanks to the introduction of high-tech hydrophilic groups, these TPU films not only exhibit excellent waterproof performance but also boast superior moisture permeability. This groundbreaking material, combined with advanced textile laminating technologies, significantly enhances the added value of textiles. Representative examples include DingZing’s Dintex brand and Germany’s Gore-Tex brand. As innovative and practical fabrics, they have become immensely popular among consumers.

(2) TPU film series that resist yellowing and are designed to protect against ultraviolet radiation.

(3) TPU film for hot-melt adhesive applications.

(4) TPU films used in footwear materials—thanks to their excellent printability and ease of processing—have made TPU the preferred film material for specialized footwear such as sneakers, casual shoes, and sandals. For instance, internationally renowned sportswear brands like Nike, Reebok, Converse, and Adidas, as well as well-known domestic brands such as Anta, Li-Ning, Xtep, and Hongxing Erke, are all loyal users of TPU films. Additionally, TPU films are also an ideal choice for creating three-dimensional trademarks.

       (5)吹气制品上的TPU薄膜 值得指出的是，由于合成TPU时原料的比例和反应时的温度不易控制，加上TPU 本身的不稳定导致其厚度不好控制，所以生产商通常不以薄膜的面积作为销售的尺度。实际销售中往往是以公斤作为销售的尺度，只有这样做才能真实反应材料量的价值。而需要使用薄膜的企业往往只考虑用多长、多宽的材料。所以，TPU薄膜的长度(码)及重量(公斤)经常需要被转换 TPU薄膜的市场价大约是RMB70元/kg，它的价格随着石油和其合成原料的增减而作相应的变动。

2. Research on TPU Films

2.1 Research on Raw Materials for TPU Films

Process procedure: The three raw materials are heated separately in their respective storage tanks at temperatures of 90℃, 70℃, and 40℃. They are then fed into a mixing head via metering pumps. A high-speed rotating rotor thoroughly mixes the materials uniformly. The mixture is then injected onto a conveyor belt, where it passes through a curing oven, causing the TPU liquid to solidify into sheets. Next, the sheets are crushed or cut into pellets and fed into an extruder, where they are re-extruded at 132℃ to produce secondary granules.

2.2 Processability Study

The development of TPU films is closely linked to the processing methods for TPU materials and also places new demands on the performance of raw materials. Since domestically produced TPU pellets often fail to meet processing requirements, even when domestic manufacturers are capable of producing them, they mostly rely on importing TPU pellets from abroad.

The main processing methods for TPU films include blow molding, cast film extrusion, T-die extrusion, and calendering. Typically, the final products do not require vulcanization or crosslinking reactions, which helps shorten the production cycle. Moreover, waste materials can be recycled and reused. TPU films can be extensively formulated with additives and fillers to enhance specific physical properties, improve processability, or reduce costs.

Precautions for Processing:

① Ensure that the material remains in the dryer for 4 hours, as TPU raw materials are prone to moisture absorption.

② The viscosity of the material is highly sensitive to temperature and its fluctuations; therefore, it’s important to carefully control the reaction temperature as well as the local temperature at the die.

③ In terms of thickness, the thickness distribution of mass-produced films is quite poor. Therefore, it is essential to accurately measure the thickness of TPU films during the production process, tailored to the processing method being used, in order to achieve better control over film thickness.

④ The structural design of the mold must ensure smooth material flow and must not allow any material to accumulate or滞留.

⑤ Due to the properties of TPU materials, the drive power required for processing equipment is 1.5 to 2.0 times greater than that needed for processing some common plastics.

Blown film extrusion is a relatively new process with relatively low production volumes. Before processing, the material should be dried. The drying temperature range for TPU is 82–121°C.

Strictly speaking, TPU films should not contain plasticizers, as plasticizers themselves are toxic chemicals. However, due to technological and equipment limitations, many companies are compelled to use them in order to reduce the viscosity of the material, lower its hardness, and decrease its molecular weight, thereby making it easier to process. The downside of this practice is that it can cause TPU films to become brittle, develop unpleasant odors, and exhibit oil migration—a phenomenon that significantly compromises both the physical properties and environmental friendliness of the films.

Currently, the thinnest TPU film available in the world is 10 μm thick. Japan’s Mirac-tran TPU can achieve thicknesses in the tens of micrometers, while DingZing’s TPU film can be as thin as 12 μm—exceeding the performance of TPU film manufacturers from South Korea, Japan, and the United States. TPU film products are ideally suited for processing methods such as heat pressing, high-frequency welding, sewing, or bonding with adhesives. They are also well-suited for ink printing, vacuum forming, or high-frequency compression to create three-dimensional effects.

2.3 Performance Study of TPU Films

The performance of TPU films is primarily studied in terms of tear resistance, abrasion resistance, flexural resistance, water resistance, resistance to yellowing, low-temperature performance, heat and oxidation resistance, antimicrobial and antifungal properties, oil resistance, gas permeability, and biomedical properties. Experimental results demonstrate that, compared with conventional plastic film materials, TPU films exhibit superior performance in all these aspects.

2.4 Testing of TPU Films

Currently, the thickness tolerance of TPU films mass-produced internationally remains quite large. Under these circumstances, to capture a larger share of the market, it is essential to equip advanced production lines with sophisticated measurement and control technologies. There are two primary objectives in inspecting TPU films: first, to detect holes and defective products; second, to use inspection results to precisely control the thickness of the TPU film. The thickness distribution of the film is measured by a thickness gauge that moves up, down, left, and right around the film bubble.

Some other sensing elements and capacitive sensing elements are also entering the thin-film measurement market. Currently, in the global TPU film inspection process, most manufacturers find 7 to 10 small pinholes per roll of TPU film. Only a very small number of manufacturers can achieve just 1 to 2 pinholes per roll—sometimes even zero pinholes.

Due to the difficulty in controlling the raw material ratios and reaction temperatures involved in TPU film production, many customers have expressed dissatisfaction and complaints about inaccuracies in TPU film products. On-site experience has shown that even on the same day and using the same machine, products of the same specification can sometimes exhibit significant variations. Therefore, for TPU manufacturers aiming to grow stronger and larger, it is crucial to increase investment in both production technology and measurement equipment. Only by doing so can they ensure that their products meet quality standards and satisfy customer needs. However, advanced TPU film testing equipment tends to be extremely expensive; thus, for many small- and medium-sized TPU film producers, controlling film thickness and minimizing defect rates remains a major challenge.

When inspecting TPU films during the customer’s purchase process, it’s important to note that you shouldn’t cut a small piece of the film for observation. Instead, use a large roll as your sample—only then can you accurately detect subtle details and differences. Currently, TPU films that are completely smooth, without any water ripples or particles, are ideal for printing logos on clothing and footwear. To protect the TPU film and maintain its excellent surface finish, PE, PET, or release paper is often used as a protective layer. As a result, what you typically see in practice is a two-layer TPU film; simply remove the protective layer before using it.

4. Prospects for TPU Films

TPU film is a green material, and thanks to its excellent performance and environmental friendliness, it is increasingly being adopted in a wide range of applications, giving it outstanding market potential.

Printability ensures that TPU films will continue to experience rapid growth in footwear applications. The automotive industry also represents a huge market for TPU films and TPU-based applications. Blowing technology has already begun to achieve rapid growth in southern Chinese cities. Waterproof and breathable membranes represent a vast market; however, since these membranes must be bonded to fabrics, if the technology is not up to par, they could damage the fabric itself. Thus, there are extremely high quality requirements for TPU films. We believe that as technology continues to advance, this industry will see even deeper development. In terms of biomedical performance, TPU films are non-toxic, do not cause allergic reactions, and exhibit no local irritation. As a result, they can be widely used in medical and hygiene-related products. In the construction industry, film laminates used as roofing underlayment materials are forecasted to become a major sector. Furthermore, using TPU films as a replacement for shorter-lived polyethylene films in greenhouse applications also holds great promise.

Additionally, according to feedback from Nike’s R&D personnel, screen printing on TPU films significantly increases both labor time and processing steps. Therefore, in order to save manpower, financial resources, and material costs, shoe manufacturers hope that TPU film suppliers can provide TPU films in any color they desire. These are precisely the areas where companies should focus their efforts.

In short, as market competition intensifies, only TPU films that are both high-quality and reasonably priced can dominate the international TPU film market. Therefore, international TPU film manufacturers should invest heavily in technological innovation, develop new product varieties, and continuously push the boundaries of creativity, thereby expanding and enhancing the market for this eco-friendly material—TPU film.