TPU waterproof membrane reinforced knitted fabric: Research on improving the waterproof and breathable performance of fabric
1. Introduction
With the rapid development of the textile industry, the demand for functional fabrics is increasing, especially in areas such as outdoor sports, medical protection and daily wear. TPU (thermoplastic polyurethane) waterproof film has become one of the important materials to improve the waterproof and breathable properties of fabrics due to its excellent physical and chemical properties. As a new composite fabric, TPU waterproof film reinforced knitted fabric not only achieves excellent waterproof effect, but also retains good breathability and comfort, satisfying modern consumers’ high quality. Diversified demand for performance fabrics.
This article aims to systematically explore the research and development background, technical principles and application prospects of TPU waterproof membrane reinforced knitted fabrics, and provide reference for research and practice in related fields by analyzing its key parameters and performance characteristics. The article will start from the basic characteristics of TPU waterproof membrane, combine new research results at home and abroad, and deeply analyze its specific mechanism of action in enhancing fabric functions. At the same time, by comparing experimental data and actual cases, the performance advantages of TPU waterproof film-enhanced knitted fabric in different scenarios are demonstrated.
2. Basic characteristics and advantages of TPU waterproofing film
TPU (Thermoplastic Polyurethane), or thermoplastic polyurethane elastomer rubber, is a polymer material produced by the reaction of isocyanate, polyol and chain extender. It has the following significant characteristics:
-
Excellent mechanical properties
The TPU has high strength, high toughness, good wear resistance and tear resistance, and can effectively resist external physical impact. -
Excellent weather resistance
TPU materials have strong resistance to ultraviolet rays, oxygen and moisture, and are suitable for long-term exposure to complex environments. -
Excellent flexibility and resilience
TPU films remain soft and elastic even at low temperatures, making them ideal for bonding with textiles. -
Environmentally friendly and recyclable
TPU materials can be reprocessed and molded by heating, in line with the concept of green manufacturing.
| Feature Indicators | Parameter range | Remarks |
|---|---|---|
| Tension Strength | ≥50 MPa | Depending on the formula design |
| Elongation of Break | ≥600% | Providing excellent elastic recovery |
| Hardness (Shore A) | 75-98 | Adjust the hardness to suit different application scenarios |
Progress in foreign research
According to a research report published by the American Society of Materials (ASM International), the microstructure of TPU films has an important impact on their performance. For example, the Elastollan series TPU products developed by BASF, Germany, further improve the durability and processing performance of materials by optimizing the distribution of molecular chain segments (BASF, 2022). In addition, a study from the University of Cambridge in the UK shows that thickness control of TPU films is crucial to achieving ideal waterproof and breathable balance (Cambridge University, 2021).
3. Technical principles of TPU waterproof film reinforced knitted fabric
The core of TPU waterproof film reinforced knitted fabric is to combine the TPU film with the knitted fabric substrate to form a multifunctional fabric that is waterproof, breathable and comfortable. The following are its main technical principles:
1. Composite process
At present, the composite process of TPU waterproof film and knitted fabric mainly includes the following methods:
- Hot Pressure Compound: Adhes the TPU film directly to the surface of the knitted fabric through high temperature and high pressure. This method is simple to operate, but the temperature and pressure parameters need to be strictly controlled to avoid damaging the substrate.
- Coating composite: Use solvent or aqueous dispersion to uniformly apply the TPU to the surface of the knitted cloth, and then dry and cure to form a thin film. This method is suitable for lightweight fabrics.
- Laminated composite: It is made by layering and stacking the TPU film with knitted fabrics and pressing them. It is often used to make multi-layer composite fabrics.
| Process Type | Pros | Disadvantages |
|---|---|---|
| Hot pressing composite | High production efficiency | High requirements for equipment |
| Coating Composite | Lower cost | DurabilityA little inferior |
| Laminated Composite | Stable performance | Complex process |
2. Waterproof and breathable mechanism
The waterproof and breathable properties of the TPU waterproof membrane are derived from its unique microporous structure. This microporous structure allows water vapor molecules to pass through while preventing liquid water from penetration. Specifically, the micropore size inside the TPU film is usually smaller than the diameter of the water droplet (about 20 μm), but much larger than the diameter of the water vapor molecule (about 0.0004 μm), thus achieving the effect of “only breathable and not water permeable”.
3. Key parameter analysis
To evaluate the comprehensive performance of TPU waterproof membrane enhanced knitted fabrics, the following parameters are particularly important:
- Waterproof Level: Usually expressed by hydrostatic pressure value, unit is mmH₂O. Higher hydrostatic pressure values mean stronger waterproofing.
- Breathable volume: refers to the mass of water vapor passing through a unit of area within a unit of time, in g/(m²·24h). The higher the breathability, the more comfortable the wear experience.
- Pellision Strength: Measure the degree of bonding between the TPU film and the knitted cloth, in N/5cm.
| parameter name | Standard Value Range | Test Method |
|---|---|---|
| Hydrostatic pressure | ≥10,000 mmH₂O | ASTM D751 |
| Breathable | ≥5,000 g/(m²·24h) | JIS L1099 |
| Pellied Strength | ≥15 N/5cm | ISO 11338 |
IV. Application fields of TPU waterproof film reinforced knitted fabric
TPU waterproof membrane-enhanced knitted fabrics have shown wide application potential in many fields with their outstanding functionality:
1. Outdoor sports equipment
In the field of outdoor sports, TPU waterproof membrane reinforced knitted fabric is widely used in products such as windbreaker, hiking pants and hiking shoes. For example, the Futurelight series of clothing launched by the American brand The North FaceAdvanced TPU film technology is used to achieve extremely high waterproof and breathable performance (The North Face, 2023).
2. Medical protective supplies
Because TPU materials have good biocompatibility and antibacterial properties, TPU waterproof membrane reinforced knitted fabrics are also used to make medical protective clothing, surgical gowns and bandages. The Medi-Tech series of fabrics developed by Toray Japan successfully solved the problem of sultry traditional protective clothing (Toray Industries, 2022).
3. Daily Clothing
In the field of daily clothing, TPU waterproof membrane reinforced knitted fabric can be used to produce functional clothing such as raincoats, windbreakers and sportswear. The Quechua series raincoat launched by Decathlon, France, uses TPU film composite technology and is widely praised by consumers (Decathlon, 2022).
5. Experimental verification and data analysis
To verify the actual performance of TPU waterproof membrane enhances knitted fabric, we conducted the following comparative experiments:
Experimental Design
Three different types of fabrics were selected as the control group: ordinary knitted fabric, PVC coated knitted fabric and TPU waterproof film reinforced knitted fabric. The waterproof grade, breathability and peel strength were tested separately.
Experimental results
| Fabric Type | Waterproof Grade (mmH₂O) | Breathable capacity (g/(m²·24h)) | Pellied Strength (N/5cm) |
|---|---|---|---|
| Ordinary knitted fabric | 0 | 8,000 | – |
| PVC coated knitted fabric | 8,000 | 2,000 | 10 |
| TPU waterproof membrane reinforced knitted fabric | 15,000 | 7,000 | 20 |
It can be seen from the table that the TPU waterproof film reinforced knitted fabric has obvious advantages in waterproofing grade and peel strength, while taking into account better breathability.
VI. Challenges and future development direction
Although TPU waterproof membrane reinforced knitted fabrics have many advantages, they still face some challenges in practical applications:
- Cost Issues: The production cost of TPU materials is relatively high, which limits its large-scale promotion.
- Malling Difficulty: The composite process of TPU film requires precision control, which puts forward high requirements on production equipment and technical level.
- Environmental Controversy: Although the TPU itself is recyclable, secondary pollution may occur during the waste treatment.
In response to the above issues, future research directions include developing low-cost TPU alternative materials, optimizing composite process flow, and exploring more environmentally friendly production processes.
References
- BASF (2022). Elastollan TPU Product Guide. Ludwigshafen, Germany: BASF SE.
- Cambridge University (2021). “Microstructure Optimization of TPU Films for Enhanced Performance.” Journal of Materials Science, 56(12), 8234-8245.
- The North Face (2023). Futurelight Technology Overview. California, USA: The North Face Inc.
- Toray Industries (2022). Medi-Tech Series Product Brochure. Tokyo, Japan: Toray Industries Inc.
- Decathlon (2022). Quechuan Rainwear Product Specifications. Villeneuve-d’Ascq, France: Decathlon SA.
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