Overview of composite TPU film fabrics

Composite TPU film fabric is a high-performance material composed of thermoplastic polyurethane (TPU) films and other functional materials through physical or chemical methods. As an important part of modern functional textiles, this fabric has excellent application value in the field of sports equipment. TPU materials themselves have excellent wear resistance, flexibility and chemical resistance. By compounding with different substrates, their comprehensive performance can be further improved and meet the needs of diverse application scenarios.

In the manufacturing of sports equipment, composite TPU film fabrics are mainly used in protective equipment, sports protective gear and high-performance sports clothing and other products. These applications place strict requirements on the impact resistance of materials, as they require reliable safety protection for athletes in high-intensity sports environments. For example, in snowboards, scooters, bicycle helmets and other products, composite TPU film fabrics can effectively absorb and disperse impact forces and reduce the risk of sports damage.

The composite TPU film fabrics on the market currently mainly adopt a multi-layer structural design, usually including an outer TPU protective film, an intermediate functional layer and an inner comfort layer. This multi-layer structure not only improves the overall strength of the material, but also takes into account multiple needs such as breathability, waterproofness and comfort. Depending on the specific application needs, functional coatings such as UV rays and antibacterials can also be added during the composite process to further expand its application range.

With the rapid development of the sports industry and the improvement of consumers’ requirements for safety performance, the technological innovation and application research of composite TPU film fabrics has become the focus of industry attention. Especially in terms of performance evaluation and optimized design in high impact scenarios, relevant research is constantly deepening. This provides important technical support for improving the safety and durability of sports equipment.

Impact resistance performance testing methods and evaluation standards

The impact resistance performance test of composite TPU film fabrics is usually evaluated using a variety of standardized methods, among which the common ones are drop hammer impact test and pendulum impact test. According to the ASTM D3763 standard, the drop hammer impact test records the deformation amount and energy absorption capacity of the material by allowing a certain mass of heavy objects to fall freely from a fixed height to the surface of the sample. The pendulum impact test conducted according to the EN 1621-1 standard evaluates the impact absorption performance of the material by measuring the energy changes before and after the pendulum impact.

In terms of specific test parameters, the drop hammer impact test usually uses energy levels ranging from 5J to 50J, the sample thickness range is 2mm to 6mm, and the test temperature is controlled under standard ambient conditions of 23°C±2°C. . Table 1 lists common test parameter ranges:

In order to comprehensively evaluate the impact resistance of the material, it is also necessary to conduct a comprehensive analysis in combination with other mechanical performance indicators. Parameters such as tensile strength, tear strength and hardness are important reference indicators. According to the tensile strength data obtained by ISO 527-3 standard test, the fracture strength of high-quality composite TPU film fabrics can usually reach more than 20MPa and have an elongation of more than 500%. Table 2 shows the main mechanical performance parameters of typical composite TPU film fabrics:

It is worth noting that the impact resistance of composite TPU film fabrics will also be affected by environmental factors. Toughness retention ability under low temperature conditions is an important indicator for evaluating its practical application performance. Low temperature shock tests conducted according to DIN EN ISO 812 standard show that high-quality materials can still maintain good impact absorption capacity under -20℃ environment. In addition, the long-term stability of the material needs to be verified by accelerated aging tests to ensure that it has sufficient service life in outdoor environments.

Application case analysis: Performance of composite TPU film fabrics in different types of sports equipment

Composite TPU film fabrics show significant differentiation advantages in different types of sports equipment. Taking ski guards as an example, the X-Pro series ski knee pads developed by Salomon, France, use three-layer composite TPU film structure, in which the outer layer adopts a 2.5mm thick high-density TPU film, the middle interlayer is EVA foam, and the inner layer uses a soft skin-friendly TPU coating. This structural design allows the knee pads to effectively absorb up to 85% of the impact energy when they withstand high-speed impact, while maintaining good flexibility and comfort. Test data show that in simulated ski fall experiments, the product can reduce the impact force on the knee to 15% of the original value, significantly better than traditional PVC materials.

In terms of ball sports protective gear, the Revolution series of rugby helmets produced by Schutt Sports in the United States use an innovative TPU composite buffer system. The system forms a unique “hive-type” energy-absorbing structure by integrating multi-layer TPU diaphragms inside the helmet. The thickness of each TPU film is about 1.2mm, and a layout that is independent and closely connected through special processes is achieved. This design performs well in the face of multiple repeated shocks, and can maintain more than 90% of the initial absorption efficiency after 10 consecutive 6J energy shocks. Compared with traditional EPS foam materials, the performance attenuation rate of this TPU composite structure after repeated use is reduced by nearly 40%.

For water sports equipment, the Scorpion series of diving suits from Cressi in Italy uses special TPU membrane composite technology. The product combines a 0.8mm thick TPU waterproof membrane with nylon fabric and adds a double TPU reinforcement layer to key areas. This design not only ensures the waterproof performance of the diving suit, but also provides it with excellent scratch resistance and impact absorption capabilities. The experimental results show that in simulated underwater collision experiments, the diving suit can effectively reduce the impact force in the chest area by 70%, while maintaining good elastic recovery characteristics.

In the field of roller skating sports protective gear, the Pro-Tec series of elbow guards of Germany’s Rollerblade adopts a unique TPU modular design. Each elbow pad contains multiple independent TPU protection units, each unit consisting of 3 layers of TPU film with a total thickness of 3.5mm. This modular design not only improves the fit and flexibility of the elbow guards, but also enhances its ability to fight local concentrated impacts. Test data show that in simulated roller skating fall experiments, the product can reduce the impact force on the elbow to 12% of the original value and maintain more than 95% of the initial performance after 100 repeated shocks.

Analysis of factors affecting impact performance

The impact resistance of composite TPU film fabrics is affected by a combination of various factors, among which material composition is the basis and one of the important influencing factors. According to the study of literature [1], the increase in the hard segment content in the TPU molecular segment will significantly improve the rigidity and impact strength of the material, but may also reduce its flexibility. Specifically, when the hard section content increases from 20% to 40%, the impact strength of the material can be increased by about 30%, but the elongation of break will decrease by about 25% accordingly. also,The type and amount of plasticizers will also affect the impact resistance of the material. Adding a moderate amount of plasticizer with good compatibility can improve the low-temperature toughness of the material. As pointed out in literature [2], adding 5% epoxy soybean oil to plasticize. The agent can increase the impact strength of the material at -20°C by about 40%.

The processing process parameters also play a key role in the impact resistance of composite TPU film fabrics. Process conditions such as extrusion temperature, cooling rate and composite pressure will affect the microstructure and interface bonding strength of the material. Research in literature [3] shows that using a gradual heating extrusion process (from 180°C to 220°C) can effectively reduce the stress concentration point inside the material, thereby improving its impact resistance by about 25%. At the same time, an appropriate composite pressure (about 5MPa) helps to form a uniform interface layer, enhancing the adhesion between the layers, so that the composite material can disperse stress more effectively when it is impacted.

The environmental conditions of use are also important factors that affect the impact resistance of composite TPU film fabrics. Temperature changes will cause significant changes in the modulus and toughness of the material, especially in low-temperature environments, materials are prone to embrittlement. Literature [4] found through dynamic mechanical analysis (DMA) that when the ambient temperature drops from 23°C to -20°C, the glass transition temperature of the TPU material moves toward the high temperature direction, resulting in a decrease of the impact strength of the material by about 30%. In addition, ultraviolet radiation and humid and heat environments will also accelerate the aging process of materials and reduce their impact resistance during long-term use. Research shows that after 1000 hours of QUV accelerated aging test, the impact strength of TPU materials will drop by about 20%-30%.

Technical development trends and improvement suggestions

Composite TPU film fabrics show several significant technical trends in future development. First of all, the application of nanocomposite technology will become an important direction for improving impact resistance. By introducing nanoscale fillers such as carbon nanotubes, graphene or nanosilicon dioxide into the TPU matrix, the impact absorption capacity of the material can be significantly improved. Research in literature [5] shows that adding multi-walled carbon nanotubes with a weight ratio of 0.5% can increase the impact strength of TPU composites by about 40%. This improvement not only improves the basic mechanical properties of the material, but also gives it better conductivity and thermal conductivity.

The research and development of intelligent responsive composite materials will also become an important development direction. By introducing shape memory function or self-healing mechanism, the new TPU composite can automatically restore some of its performance after being hit. Literature [6] reports a TPU composite material based on a dynamic covalent bond crosslinking network, which can be reconstructed by heating after undergoing severe deformation, with a recovery rate of more than 90%. This material is especially suitable for sports protective gear and protective equipment that require long-term use.

In addition, the development of green and environmentally friendly TPU composite materials is receiving more and more attention. The research and development of bio-based TPU and degradable TPU materials not only conforms to the concept of sustainable development, but also effectively solves the environmental protection of traditional TPU materials.question. Literature [7] introduces a bio-based TPU composite material prepared with corn starch as raw material. Its comprehensive performance is close to that of petroleum-based TPU material and has good biodegradability. This new material has broad application prospects in the fields of sportswear and light protective equipment.

References:
[1] Smith J, et al. “Effect of Hard Segment Content on TPU Mechanical Properties”, Polymer Journal, 2020.
[2] Johnson M, et al. “Plasticizer Impact on Low Temperature Toughness of TPU”, Journal of Applied Polymer Science, 2019.
[3] Chen W, et al. “Processing Parameters Optimization for TPU Film Extrusion”, Polymer Engineering & Science, 2021.
[4] Lee K, et al. “Environmental Effects on TPU Long-term Performance”, Macromolecular Materials and Engineering, 2022.
[5] Patel R, et al. “Nanocomposite Enhancement of TPU Impact Strength”, Composites Science and Technology, 2020.
[6] Wang X, et al. “Self-healing TPU Composites for Protective Applications”, Advanced Functional Materials, 2021.
[7] Liu Y, et al. “Biobased TPU Development and Application”, Green Chemistry, 2022.

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