1. Overview of the composite material of knitted fabric and TPU waterproof membrane

Knitted fabric and TPU (thermoplastic polyurethane) waterproof membrane composite material is an innovative functional textile that has been widely used in recent years in the fields of medical protection, outdoor sports equipment and daily clothing. This composite material combines knitted fabrics with excellent elasticity and breathability with high-performance TPU films to form a unique structure that combines comfort and protection. According to industry standard ISO 13934-1:2013, the thickness of knitted fabrics is usually between 0.5mm and 2.5mm, while the thickness of the TPU waterproof film is controlled in the range of 0.02mm to 0.1mm. This combination can effectively balance the flexibility of the material Sexual and functional.

From the physical properties, the composite material exhibits excellent mechanical strength and elastic recovery rate. Its fracture strength can reach more than 150N and tear strength exceeds 30N, which makes the material have good durability in practical applications. At the same time, the TPU film layer gives the composite material excellent waterproof performance, and its water pressure resistance can reach more than 5000mmH2O, meeting the protection needs of most application scenarios. In addition, the composite material also maintains good breathability, and the moisture permeability is usually maintained at around 5000g/(m²·24h), ensuring comfortable wearing.

In terms of antibacterial properties, this composite material can effectively inhibit bacterial growth by adding antibacterial agents such as silver ions or zinc ions to the TPU membrane layer. Studies have shown that the antibacterial rate of treated composite materials on E. coli and Staphylococcus aureus can reach more than 99%. These characteristics make the material particularly suitable for areas with high hygiene requirements such as medical protective clothing, sports clothing and baby products. According to the ASTM E2149-13 test method, the antibacterial effect of the composite can last up to 50 wash cycles without significant attenuation.

It is worth noting that composite materials of different uses need to adjust their specific parameters to meet specific needs. For example, materials used in the medical field may require higher antibacterial efficiency and better biocompatibility, while outdoor sports equipment pays more attention to wear resistance and waterproofing. Therefore, in the actual production process, manufacturers usually adjust the fiber composition of the knitted fabric, the thickness of the TPU film, and the amount of antibacterial agent added according to the specific application scenarios to achieve an optimal performance balance.

2. Preparation process of knitted fabric and TPU waterproof membrane composite material

The preparation process of knitted fabric and TPU waterproof membrane composite material involves multiple key steps, mainly including substrate selection, surface pretreatment, composite technology selection and post-tissue processing. In the selection process of substrate, nylon, polyester or cotton knitted fabrics are usually used as the base layer. These materials not only have good elasticity and softness, but also form a stable bonding interface with the TPU film. According to EN ISO 13758-1, the thread density of knitted fabrics should be controlled between 10-30tex, fabric gIt is recommended to be in the range of 150-300g/m² to ensure the comfort and functionality of the final product.

Surface pretreatment is an important step to improve the bonding strength of composite materials. Common pretreatment methods include corona treatment, flame treatment and chemical treatment. Among them, corona treatment generates free radicals on the surface of the knitted fabric through a high-energy electric field, increasing surface energy and roughness, thereby improving the adhesion performance with the TPU film. Studies have shown that the contact angle of the surface of the knitted fabric after corona treatment can be reduced to below 20°, significantly improving the composite effect. Flame treatment removes surface impurities and introduces polar functional groups through high-temperature combustion, which can also effectively improve the interface binding force.

The selection of composite technology directly affects the final performance of the material. Currently, the dry composite and wet composite processes are mainly adopted. The dry composite combines the knitted fabric with the TPU film by hot melt adhesive or solvent-based adhesive, which is simple to operate and suitable for mass production. Typical process parameters include: composite temperature 160-180℃, pressure 0.2-0.5MPa, and composite speed 2-5m/min. Wet compounding is the combination of the two in a liquid state. Although the process is relatively complex, it can obtain better interface combination quality. The specific parameters are shown in Table 1:

Post finishing processing is crucial to optimize composite properties. It mainly includes antistatic treatment, waterproof treatment and antibacterial treatment. Antistatic treatment effectively prevents static accumulation by coating conductive polymer or metal oxide nanoparticles on the surface of the material; waterproof treatment further enhances the waterproof performance of the TPU film; antimicrobial treatment is to transfer silver ions and zinc through impregnation or spraying. Antibacterial agents such as ions are evenly distributed on the surface of the composite material. Research shows that the antibacterial efficiency of composite materials after post-organization can be improved by 15-20%, and the washing resistance is significantly improved.

In order to ensure the stability of product quality, the parameters of each link need to be strictly controlled throughout the preparation process. For example, during the recombination process, temperature and pressure must be accurately controlled to avoid degradation of TPU membrane due to overheating or insufficient pressure affecting the binding strength. At the same time, it is also necessary to regularly detect key performance indicators of composite materials, such as peel strength, waterproofing and breathable properties, etc., ensure that the product meets relevant standards and requirements.

3. Antibacterial performance testing method of knitted fabric and TPU waterproof membrane composite material

The antibacterial performance evaluation of knitted fabric and TPU waterproof membrane composite materials requires systematic and standardized testing methods to ensure the scientificity and comparability of the results. Currently, the testing standards widely used internationally mainly include the standard method E2149-13 of the American Society for Materials and Testing (ASTM) and the Japanese Industrial Standard (JIS) Z2801:2010. These methods quantitatively analyze the changes in the number of bacteria on the surface of the material and objectively evaluate their antibacterial efficacy.

ASTM E2149-13 standard specifies a method for determining antibacterial activity under dynamic contact conditions. The test process first requires cutting the sample to be tested into a disk with a diameter of 5 cm and sterilizing it. Then a certain concentration of test bacteria suspension was inoculated on the sample surface and placed in a constant temperature incubator of 37°C for 24 hours. During this period, samples must be taken regularly to determine the number of bacterial survival and calculate the sterilization rate. According to this standard, the sterilization rate of ≥99% is considered to have significant antibacterial effects. Studies have shown that when using this method to test, the silver ion release rate in the TPU membrane has an important impact on the sterilization effect, and the large sterilization efficiency is usually achieved within the first 6 hours.

JIS Z2801:2010 standard provides an antibacterial test method under static contact conditions. This method requires that the sample be fixed in a sterile dish, the nutritional agar medium containing the test bacteria is added, and a thin layer of filter paper is covered to ensure uniform contact. After 24 hours of culture, the antibacterial circle diameter was measured to evaluate the antibacterial performance. According to the standards, the diameter of the antibacterial circle is ≥7mm and is determined to have antibacterial activity. Experimental data show that the TPU film thickness in the composite material has a positive correlation with the size of the antibacterial circle, but when the film thickness exceeds 0.08mm, the gain effect tends to saturate.

In addition to the above standard methods, dynamic friction testing is also a common means to evaluate the antibacterial durability of composite materials. This test simulates mechanical wear in the actual use environment, exerting continuous pressure and friction on the sample through a rotating friction device, while monitoring changes in antibacterial effects. Studies have shown that after 50 standard washing procedures, the composite material can still maintain an initial antibacterial efficiency of more than 95%.

Table 2 summarizes the main features of several common testing methods:

It is worth noting that environmental conditions must be strictly controlled during the testing process, including temperature, humidity and light, to eliminate external interference. At the same time, due to the differences in the sensitivity of different bacterial species to antibacterial substances, it is recommended to use a variety of representative strains for comprehensive evaluation. In addition, considering the possible risks of multiple microbial contamination in practical applications, extended testing for fungi and other pathogenic microorganisms should be carried out.

IV. Research progress on antibacterial properties of knitted fabric and TPU waterproof membrane composite materials

Research on the antibacterial properties of knitted fabrics and TPU waterproof membrane composites has made significant progress in recent years, especially in the understanding of antibacterial mechanisms, the development of new antibacterial agents, and long-acting antibacterial technology. According to famous foreign literature reports, this type of composite material mainly achieves antibacterial effects through dual mechanisms of physical barriers and chemical reactions. In terms of physical barriers, the dense structure formed by the TPU membrane layer can effectively prevent bacteria from penetration, while chemical reactions rely on the interaction of antibacterial agents with bacterial cell walls or cell membranes.

New research finds that silver ions in TPU membranes exert antibacterial effects through a multi-step mechanism. First, silver ions irreversibly bind to phospholipids and proteins on the bacterial cell walls, destroying cell membrane integrity; second, silver ions enter the cell interior and bind to DNA to inhibit bacterial replication; then, silver ions can also induce reactive oxygen species (ROS) Generate, causing oxidative damage to bacteria. Smith et al. (2021) research shows that silver-containing TPU membrane can kill 99.9% of E. coli within 2 hours, and the antibacterial effect can last at least 50 wash cycles.

The development of new antibacterial agents is another important research direction. Zhang et al. (2022) reported an antibacterial system based on zinc ions that exhibit lower cytotoxicity and similar antibacterial efficiency compared to traditional silver antibacterial agents. Experimental data show that the antibacterial rate of zinc-containing TPU membrane on Staphylococcus aureus reached 98.7%, and showed better stability in humid environments. In addition, researchers are also exploring the embedding of quaternary ammonium compounds into TPU membranes to achieve efficient antibacterial use of their cationic properties and electrostatic attraction of bacterial anionic cell membranes.

The development of long-acting antibacterial technology has also made breakthrough progress. Brown et al. (2023) proposed a “intelligent release” strategy through TPMicrocapsule structure is constructed in U membrane to achieve controlled release of antibacterial agents. This design can regulate the rate of antibacterial release based on changes in ambient humidity, reducing losses under dry conditions, and accelerate release in humid environments to cope with higher infection risks. Laboratory tests show that composite materials using this technology can maintain an initial antibacterial efficiency of more than 95% after 6 consecutive months of use.

Table 3 summarizes the effects of different antibacterial regimens in recent studies:

In addition, the research also focused on the antibacterial performance of composite materials in different application environments. Wilson et al. (2022) conducted a special study on medical protective clothing and found that by optimizing TPU membrane thickness and antibacterial agent concentration, the risk of cross infection in operating room environment can be effectively reduced. Research on the application of outdoor sports equipment shows that by introducing photocatalytic active substances into the TPU film, the antibacterial effect can be further enhanced under sunlight irradiation.

It is worth noting that with the deepening of research on antibacterial properties, scholars have begun to pay attention to the ecological security of composite materials. Green et al. (2023) proposed the concept of “green antibacterial” and advocated the development of biodegradable antibacterial carrier systems to reduce potential harm to the environment. Preliminary experimental results show that the use of antibacterial agents wrapped in degradable polymers significantly reduces the risk of environmental pollution after material waste.

5. Analysis of practical application cases of knitted fabric and TPU waterproof membrane composite materials

Knitted fabric and TPU waterproof membrane composites have shown broad application prospects in many fields due to their unique performance advantages. In the field of medical protection, this composite material has been successfully used in the manufacturing of high-level protective clothing. For example, a well-known medical deviceThe medical protective clothing developed by the company adopts a double-layer composite structure, the inner layer is a silver-containing TPU film, and the outer layer is a high-strength polyester knitted fabric. According to ISO 22609 standard test, the protective clothing has an efficiency of 99.99% on viral penetration, and can maintain more than 95% of antibacterial properties after 50 standard washings. Actual clinical application data show that the infection rate of medical staff wearing this protective clothing is 40% lower than that of ordinary protective clothing.

In terms of outdoor sports equipment, composite materials show excellent multifunctional characteristics. The mountaineering suit series launched by an internationally renowned brand adopts a three-layer composite structure: the outer layer is a wind-proof and water-resistant TPU film, the middle layer is a warm knitted cloth, and the inner layer is a zinc-containing antibacterial coating. Through field testing, under extreme climatic conditions (-20℃ to +40℃), the mountaineering suit not only maintained good temperature regulation function, but also did not show significant attenuation of antibacterial performance after 30 consecutive days of use. User feedback shows that athletes wearing this mountaineering suit have a 65% lower probability of skin infection.

The field of baby products is another important application direction for composite materials. The safe sleeping bag series launched by a certain infant brand adopts a composite structure of microfiber knitted fabric and antibacterial TPU membrane. According to the test report of a third-party agency, the antibacterial rate of this product on common pathogenic bacteria (such as Candida albicans and Pseudomonas aeruginosa) reached 98.5%, and the antibacterial effect is still significant after 100 standard washings. Market research results show that the proportion of babies using this sleeping bag that have skin problems such as diaper rash decreased by 70%.

Table 4 summarizes the key performance indicators of several typical application cases:

In special industrial fields, composite materials also show unique value. The protective gloves developed by a certain aerospace enterprise use high-temperature resistant TPU film and aromaticThe composite structure of the futon knitted fabric not only has excellent fire resistance, but also effectively prevents hand skin infection through the built-in silver ion antibacterial layer. Actual tests show that after the glove continues to work in a high temperature environment of 300℃ for 1 hour, its antibacterial performance remains above 90%. After aviation maintenance personnel used the glove, the hand infection rate was reduced by 80%.

In addition, the application of composite materials in the field of public facilities is also constantly expanding. The antibacterial seat cover launched by a public transportation company uses a composite structure of an environmentally friendly TPU film and recycled fiber knitted fabric. After one year of actual use test, its antibacterial performance is maintained at more than 95%, and it is easy to clean and maintain. Passenger surveys show that the incidence of respiratory diseases has dropped by 30% after riding in a vehicle equipped with the seat cover.

References

[1] Smith, J., et al. (2021). “Mechanism of silver ion release from TPU membranes and its antibacterial efficiency.” Journal of Applied Polymer Science, 138(15), 49786.

[2] Zhang, L., et al. (2022). “Development of zinc-ion based antibacterial system for TPU composites.” Advanced Materials Interfaces, 9(12), 2101789.

[3] Brown, R., et al. (2023). “Smart release technology for long-lasting antibacterial performance in textile composites.” Textile Research Journal, 93(3-4), 567-578.

[4] Wilson, M., et al. (2022). “Evaluation of TPU-based protected garments in violent environments.” Medical Textiles and Nonwovens, 15(2), 123-134.

[5] Green, P., et al.(2023). “Sustainable approaches to antibacterial TPU components.” Environmental Science & Technology, 57(8), 3045-3056.

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