Overview of the composite technology of knitted fabric and TPU waterproof membrane

The composite technology of knitted fabric and TPU (thermoplastic polyurethane) waterproof film is an innovative process that has made breakthrough progress in the field of outdoor equipment in recent years. This composite material combines the excellent flexibility and comfort of the knitted fabric, as well as the excellent waterproof and breathable properties of the TPU waterproof membrane, opening up new possibilities for the design and manufacture of outdoor products. As the base layer, knitted fabric provides good elasticity, warmth and comfort with its unique three-dimensional structure, while the TPU waterproof membrane achieves reliable waterproofing function while maintaining air circulation through its molecular-level barrier characteristics.

The core advantage of this technology is to achieve a perfect balance of functionality and comfort. By applying the TPU film to the surface of the knitted fabric in a specific process, it can not only effectively prevent moisture penetration, but also maintain the moderate moisture exchange required by the human body. The thickness of this composite material is usually controlled between 0.15-0.3mm and the weight range is 80-120g/㎡, which not only ensures the lightweight of the material, but also ensures sufficient durability. Depending on different application requirements, the thickness of the TPU film and the density of the knitted fabric can be adjusted to obtain ideal performance parameters.

In the field of outdoor equipment, the application of this composite material is rapidly expanding. This technology can be seen from professional mountaineering suits to daily raincoats, from high-performance tents to waterproof backpacks. Its key indicators include: waterproofing level can reach more than 20,000mm, moisture permeability reaches 5,000g/m²/24h, tear resistance strength exceeds 60N/cm, and these parameters have reached the international leading level. In addition, the material also has good wear resistance and UV resistance, making it particularly suitable for use needs in various harsh environments.

Principles and process flow of knitted fabric and TPU waterproof membrane composite technology

The compounding process of knitted fabric and TPU waterproof film involves multiple precision steps, and key links include substrate pretreatment, coating process selection and composite temperature control. First, during the substrate preparation stage, a strict surface treatment of the knitted fabric is required. This includes removing oil and impurities from the fabric surface, while increasing surface energy through plasma or corona treatment and improving adhesion of subsequent coatings. Studies have shown that appropriate surface treatment can increase the peel strength of TPU film by more than 30% (Smith et al., 2019).

The next is the choice of the coating process. Currently, two main methods are used: solution coating method and melt extrusion method. Solution coating method The TPU is dissolved in a specific solvent, applied uniformly to the surface of the knitted cloth, and then formed a continuous film by heating the volatile solvent. The advantage of this method is that the film thickness can be precisely controlled, but there are solvent recovery and environmental protection problems. In contrast, the melt extrusion law directly heats the TPU to the molten state and then extrudes into a film. Although the equipment investment is large, it is more environmentally friendly and has higher production efficiency (Johnson& Lee, 2020).

The important parameter in the compounding process is temperature control. The melting point of the TPU is usually between 180-220℃. In order to ensure good bonding effect, the composite temperature must be set in the range of 190-210℃. Excessive temperature may lead to the degradation of the TPU and affect its mechanical properties; insufficient temperature will cause unstable bonding. Experimental data show that when the composite temperature is 205℃, the peel strength between the TPU film and the knitted cloth can reach an optimal value of 75N/cm (Chen et al., 2021). In addition, pressure and speed are also important parameters, and the composite operation is usually performed using a pressure of 0.3-0.5MPa and a speed of 10-20m/min.

It is worth noting that the influence of humidity needs to be considered during the compounding process. Appropriate ambient humidity (40-60%RH) helps to improve the leveling and adhesion of the TPU film. However, excessive humidity may cause the TPU to absorb and expand, affecting the performance of the final product. Therefore, in actual production, it is usually necessary to strictly control the temperature and humidity of the production workshop to ensure the consistency of product quality.

Application examples and performance analysis in outdoor clothing

The composite technology of knitted fabric and TPU waterproof membrane is particularly widely used in the field of outdoor clothing, especially in high-performance clothing such as professional mountaineering suits and trail running suits. Take the GTX series of mountaineering suits of an internationally renowned brand as an example. It adopts a double-layer fabric structure, the inner layer is high-elastic knitted fabric, and the outer layer is composited with a 15μm thick TPU waterproof film, and the overall weight is only 110g/㎡. The key performance parameters of this clothing are as follows:

Experiments have proved that this composite material performs well in extreme weather conditions. In an environment of minus 20℃, after 24 hours of low temperature testing, its waterproof performance did not decrease significantly (Anderson et al., 2022). In high temperature and humid environments, dynamic tests that simulate human body movement and sweating show that its moisture permeability can be maintained above 8,000g/m²/24h.

The trail running suit is another typical application case. This type of clothing usually uses lighter composite materials, with the TPU film thickness controlled at about 10μm and the overall weight reduced to 85g/㎡. It is characterized by higher elastic recovery rate and better ventilation performance. Research data shows that the tensile fracture strength of this type of material can reach 50N/cm, and the elastic recovery rate reaches 95%, meeting the needs of high-intensity exercise (Wilson & Thompson, 2021).

In practical applications, this composite material also exhibits excellent UV resistance. Through UV-A and UV-B radiation tests, the UPF value can reach 50+, effectively protecting athletes from ultraviolet damage. In addition, the windproof performance of the material is also very outstanding. Under the wind speed of 20m/s, the wind-cold coefficient only increases by 5%, which is significantly better than traditional waterproof fabrics.

Application and performance characteristics in waterproof tents

The application of knitted fabric and TPU waterproof membrane composite technology in the field of waterproof tents has unique advantages, especially in high-end camping tents and mountaineering tents. Taking a typical four-season mountaineering tent as an example, the internal and external tents are made of this composite material. The external tent uses 200D high-density nylon knitted cloth composite 25μm thick TPU film, while the internal tent uses a lighter 75D nylon fabric composite 15μm TPU. membrane. This design not only ensures excellent waterproof performance, but also takes into account both breathability and weight control.

The use of this composite material in tents has shown several superior properties. First, the TPU membrane provides a reliable waterproof barrier that keeps the interior dry even under continuous rainfall conditions. Experimental data show that there was no leakage inside the tent for 48 hours of continuous testing under simulated heavy rain environment (rainfall of 100mm/h) (Brown & Davis, 2023). Secondly, the three-dimensional structure of the knitted fabric substrate helps to improve the feel and folding performance of the material, making the tent easier to build and store.

It is worth noting that this composite material also has good anti-aging properties. Through accelerated aging test (80°C, 95% RH, UV irradiation), it was found that its waterproof performance remained above 90% of the initial value after 1000 hours. In addition, the tear resistance strength of the material reaches 100N/cm, which is much higher than that of traditional PVC coating materials, significantly improving the durability of the tent.

In practical applications, this composite material also exhibits excellent low temperature properties. In an extremely cold environment of minus 30℃, the TPU membrane will not brittle or crack, ensuring the normal use of the tent under extreme conditions. At the same time, its good moisture permeability (>5000g/m²/24h) effectively prevents the occurrence of condensation inside the tent and improves the camping experience.

Application and innovative design in waterproof backpack

The application of knitted fabric and TPU waterproof membrane composite technology in the field of waterproof backpacks has demonstrated unique innovative value, especially in high-end outdoor backpacks and tactical backpacks. Taking a professional mountaineering backpack as an example, the main material is made of 420D nylon knitted fabric composite 30μm thick TPU film, and the bottom reinforced area uses a thicker 600D Oxford fabric composite 40μm TPU film. The overall design fully takes into account the functional needs of different parts.

The application of this composite material in backpacks shows several innovative features. First of all, the seamless welding technology of TPU film completely solves the problem of traditional seams leakage, making the backpack truly all-round waterproof performance. Experimental data show that after 2000 bending tests, the waterproof performance at the weld remains above 95% of the initial value (Taylor et al., 2022). Secondly, the elastic properties of the knitted fabric substrate significantly improve the comfort of the loading system, especially in the case of long-term loading, which can effectively disperse pressure and reduce fatigue.

In terms of functional design, this composite material also supports a variety of innovative applications. For example, by adjusting the formulation and thickness of the TPU film, it is possible to achieve different degrees of moisture permeability while maintaining waterproof performance, meeting the needs of use under different climatic conditions. In addition, the printability and dyeability of the materials also provide designers with greater creative space, allowing backpack products to present more diverse visual effects.

It is worth noting that this composite material also has excellent chemical corrosion resistance. After soaking test of acid and alkali solution (pH 3-11), its physical properties have not changed significantly and are suitable for use needs in special environments. At the same time, the material’s ultraviolet resistance (UPF50+) ensures that the backpack maintains a good appearance and performance during long-term outdoor use.

Analysis of economic benefits and market prospects

The wide application of knitted fabric and TPU waterproof membrane composite technology in the field of outdoor equipment has brought significant economic benefits. According to data from international market research institutions, the global high-performance waterproof composite material market size reaches US$8.5 billion in 2022, and is expected to be carried out by 2028.It grew to US$14 billion, with an average annual growth rate of around 8.5% (Global Market Insights, 2023). This growth trend is mainly due to several key factors: firstly, the continued growth of consumers’ demand for high-quality outdoor equipment, especially the millennial and Generation Z’s preference for both functional and fashionable products; secondly, technological advancements are the best way to achieve the best quality of outdoor equipment; The production cost is reduced, making the cost-effectiveness of this composite material continuously improve.

From the perspective of production cost, although the price of TPU raw materials is relatively high, the unit cost has dropped significantly by optimizing production processes and large-scale production. Currently, the processing cost of TPU composite materials is about 2-3 yuan per square meter, which is about 30% higher than traditional PVC coating materials, but considering its longer service life and better performance, the overall economy is more To highlight. A study on the life cycle cost of outdoor clothing shows that the average service life of products using TPU composites can be extended by 30%-50%, thereby reducing the total cost of ownership of consumers (Economist Intelligence Unit, 2022).

In terms of market potential, the Asia-Pacific region has become a dynamic growth market and is expected to account for more than 45% of the global market share in the next five years. The main driving forces for this growth include: the increase in outdoor sports penetration in emerging markets, the increase in leisure demand brought about by urbanization, and the increase in consumer awareness of environmental protection. It is worth noting that with the promotion of the concept of “circular economy”, TPU composites are being favored by more and more brands due to their recyclability and low carbon footprint. Industry forecasts show that by 2030, the market share of outdoor equipment using sustainable materials will exceed 60%.

In addition, technological innovation is also constantly expanding the application boundaries of this technology. The research and development of new TPU formulas, the application of intelligent manufacturing technology, and the popularization of digital design tools will further promote the development of this field. These advances will not only help reduce production costs, but will also give birth to more innovative product forms to meet changing market demand.

Reference Source

1. Smith, J., & Wang, L. (2019). Surface treatment effects on adhesion strength of TPU films. Journal of Applied Polymer Science, 136(12), 47321.
2. Johnson, R., & Lee, H. (2020). Comparative study of coating methods for TPU film production. Polymer Engineering & Science, 60(5), 889-897.
3. Chen, X., et al. (2021). Optimization of composite parameters for TPU/knitted fabric materials. Textile Research Journal, 91(1-2), 123-135.
4. Anderson, P., et al. (2022). Performance evaluation of waterproof breathable fabrics under extreme conditions. International Journal of Clothing Science and Technology, 34(2), 234-245.
5. Wilson, M., & Thompson, A. (2021). Mechanical properties of lightweight TPU composites for sportswear applications. Materials & Design, 205, 109678.
6. Brown, G., & Davis, T. (2023). Durability testing of TPU-coated tent materials. Journal of Textile and Apparel Technology Management, 16(2), 1-15.
7. Taylor, S., et al. (2022). Welding technology advances in TPU composite materials. Industrial Textiles & Plastics, 45(3), 123-132.
8. Global Market Insights. (2023). High-performance waterproof materials market report.
9. Economist Intelligence Unit. (2022). Lifecycle cost analysis of outdoor apparent materials.
   10. Related entries from Baidu Encyclopedia: TPU material, waterproof and breathable membrane, knitted fabric composite technology

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