Background and application of knitted fabric composite TPU fabric for agricultural greenhouse covering
As an important part of modern facility agriculture, agricultural greenhouses provide crops with a suitable growth environment and significantly improve crop yield and quality. However, traditional agricultural greenhouse covering materials (such as polyethylene films, glass, etc.) have many limitations in thermal insulation performance and light transmittance. For example, although polyethylene films are low in cost, they have poor weather resistance and thermal insulation effects; although glass has good light transmittance, they are large in weight and fragile, making it difficult to construct. These problems prompted scientific researchers to continuously explore new covering materials to meet the needs of modern agriculture for efficiency, environmental protection and durability.
In recent years, knitted fabric composite TPU (thermoplastic polyurethane elastomer) fabric has gradually become a popular choice in the field of agricultural greenhouse coverage due to its unique performance advantages. This material not only has excellent thermal insulation performance by combining the knitted fabric base material with the TPU coating, but also effectively improves light transmittance, while taking into account the characteristics of lightweight, weather resistance and durability. Research shows that knitted fabric composite TPU fabric can significantly reduce heat loss in greenhouses in winter, while reducing the impact of UV radiation on crops in summer, thereby optimizing the crop growth environment.
This article aims to deeply explore the insulation and light transmission technology of knitted fabric composite TPU fabric in agricultural greenhouses, analyze its working principle and practical application effect, and comprehensively display the material by citing famous foreign literature and experimental data. Technological advantages and development prospects. The article will also list product parameters in detail in the form of a table so that readers can understand their performance characteristics more intuitively.
Structure and characteristics of knitted fabric composite TPU fabric
Knitted fabric composite TPU fabric is a multi-layer composite material, and its core structure consists of three layers: the outer layer is TPU coating, the middle layer is a high-strength knitted fabric substrate, and the inner layer can be attached according to specific needs. Layer of functional film or coating. This structural design not only imparts excellent mechanical properties to the material, but also makes it excellent in thermal insulation and light transmission properties.
Material composition and physical properties
The main components of knitted fabric composite TPU fabric include:
- TPU coating: Made of thermoplastic polyurethane elastomer, it has high transparency, wear resistance and UV resistance.
- Knitted cloth base material: It is usually woven from polyester or nylon fiber to provide high strength and flexibility.
- Functional inner layer (optional): such as infrared reflective film or waterproof coating to further enhance the functionality of the material.
The following are the key physical properties of the material:
| Features | Parameter value |
|---|---|
| Thickness | 0.2 – 0.5 mm |
| Density | 1.2 g/cm³ |
| Tension Strength | ≥30 MPa |
| Elongation of Break | ≥400% |
| Sparseness | 85%-95% |
Functional Features
The functional characteristics of knitted fabric composite TPU fabric are mainly reflected in the following aspects:
- High light transmittance: The high transparency of the TPU coating ensures effective light transmission, allowing crops to fully absorb sunlight for photosynthesis.
- Heat insulation performance: The knitted cloth substrate and TPU coating work together to form an effective thermal insulation layer and reduce heat loss.
- Weather Resistance: TPU materials have extremely high resistance to ultraviolet rays and climatic conditions, extending the service life of the materials.
- Waterproof and breathable: The special coating treatment makes the material both waterproof and maintains a certain degree of breathable, which is conducive to regulating the humidity in the shed.
The combination of these characteristics makes knitted fabric composite TPU fabric an ideal covering material for agricultural greenhouses, especially suitable for crop cultivation that requires a long-term stable environment.
Principles of thermal insulation and light transmission technology of knitted fabric composite TPU fabric
The excellent performance of the knitted fabric composite TPU fabric is mainly attributed to its unique thermal insulation and light transmission technology. The following explains its working principle from the micro level and the macro level respectively.
The working principle of the micro level
At the microscopic level, knitted fabric composite TPU fabrics achieve efficient thermal insulation and light transmission functions through the following mechanisms:
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Optical properties of TPU molecular chains: TPU coatings are made of thermoplastic polyurethane elastomers, and their molecular chains have high transparency and low refractive index, which allows light to penetrate the material to the greatest extent possible Without scattering. According to the American Society for Materials and Testing (ASTM) standard testing methods, the light transmittance of TPU coatings can reach more than 90%, which is crucial for plant photosynthesis.
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Knitted cloth base materialThermal insulation effect: A complex fiber network structure is formed inside the knitted fabric substrate, and these tiny voids can effectively prevent heat conduction. Research shows that this structure can significantly reduce the heat transfer rate and reduce the temperature difference inside and outside the greenhouse. In addition, the porosity of the knitted fabric also allows a certain amount of air to flow, thereby avoiding the problem of excessive humidity caused by excessive sealing.
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The role of infrared reflective layer: In some high-end products, the knitted fabric composite TPU fabric is embedded with an infrared reflective layer. This reflective layer can reflect most of the infrared rays and prevent excessive heat from entering the greenhouse, especially in high temperatures in summer, which is particularly important. A study published in Journal of Agricultural Science and Technology showed that TPU fabrics with infrared reflective layers can reduce the temperature inside the greenhouse by about 5°C, significantly improving the crop growth environment.
Mathematical working principle at the macro level
From a macro perspective, knitted fabric composite TPU fabric realizes efficient thermal insulation and light transmission functions through the overall structural design:
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Synonymity of a double-layer structure: The combination of TPU coating and knitted fabric substrate forms a complete double-layer structure. The TPU coating is responsible for blocking ultraviolet rays and harmful radiation in the external environment, while ensuring efficient light transmission; the knitted cloth substrate assumes the main insulation and support role. This double-layer design not only improves the overall performance of the material, but also enhances its durability and stability.
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Airflow Control and Heat Exchange Management: The surface of the knitted fabric composite TPU fabric has been specially treated to control the airflow direction and speed without affecting the light transmission. For example, some products have tiny grooves or textures on the surface, which can guide the flow of hot and cold air, thereby optimizing heat exchange efficiency in the greenhouse. Experimental data show that this design can make the temperature distribution in the greenhouse more evenly and reduce the occurrence of local overheating or supercooling.
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Dynamic Response Capability: Knitted fabric composite TPU fabric has a certain flexibility and can adjust its performance as changes in the external environment. For example, in cold weather, the material will automatically increase its thermal insulation effect; in hot weather, the internal temperature is reduced by an infrared reflective layer. This dynamic response capability is due to the elasticity of the TPU molecular chain and the adaptability of the knitted fabric substrate, so that the material is always in a good working state.
To sum up, the thermal insulation and light transmission technology principles of knitted fabric composite TPU fabric involve multiple levels of synergy, from microscopic molecular chains to macroJudging from the structural design, each part provides important support for the overall performance of the material. This comprehensive performance makes knitted fabric composite TPU fabric an ideal choice for agricultural greenhouse coverage.
Practical application cases and comparison analysis of knitted fabric composite TPU fabric
Knitted fabric composite TPU fabric has been widely used in actual agricultural projects in many countries, especially in Europe and North America, and its superior performance has been verified many times. The following uses specific case and experimental data to analyze the differences in thermal insulation properties and light transmittance between this material and other traditional covering materials, such as polyethylene films and glass.
Case 1: Dutch greenhouse project
In a large greenhouse project in the Netherlands, researchers compared the performance of knitted fabric composite TPU fabrics with traditional polyethylene films. The results show that during winter nights, the temperature in the greenhouse using TPU fabric is about 3°C higher than that in the greenhouse using polyethylene film. In addition, the greenhouses of TPU fabric also have higher light intensity during the day, with an average light transmittance of 92%, while the polyethylene film is only 80%. This result directly improves the growth rate and yield of crops.
| Material Type | Average light transmittance (%) | The temperature difference between winter night (°C) |
|---|---|---|
| Knitted fabric composite TPU fabric | 92 | +3 |
| Polyethylene film | 80 | 0 |
Case 2: California Vineyard Project in the United States
In a vineyard in California, USA, scientists compared the effects of knitted fabric composite TPU fabric with glass covering. Although glass has a high initial light transmittance (95%), it is expensive to maintain due to its high weight and is not resistant to impact. In contrast, TPU fabric not only maintains a light transmittance of more than 90%, but also significantly reduces the impact of ultraviolet rays on vines. Experimental data show that vineyard yields using TPU fabrics increased by about 15%, while reducing the risk of damage caused by extreme weather.
| Material Type | Light transmittance (%) | UV filtration rate (%) | Maintenance Cost Index |
|---|---|---|---|
| Knitted fabric composite TPU fabric | 90 | 98 | Low |
| Glass | 95 | 70 | High |
Data Analysis and Conclusion
Through the data analysis of the above cases, it can be seen that knitted fabric composite TPU fabric is superior to traditional materials in terms of thermal insulation performance and light transmittance. Its lightweight design and high weather resistance make it particularly suitable for use in modern agricultural facilities, which not only improves crop yields but also reduces operating costs. In addition, the flexibility and durability of TPU fabrics also provide greater convenience and economicality for agricultural production.
International standards and certification for knitted fabric composite TPU fabric
In order to ensure that the quality and performance of knitted fabric composite TPU fabrics comply with international standards, a series of strict specifications and certification systems have been established around the world. These standards cover the physical properties, chemical composition, environmental protection requirements and safety of the material to ensure its reliable application in agricultural greenhouse coverage.
Overview of international standards
At present, knitted fabric composite TPU fabric mainly follows the following international standards:
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ISO Standards: The International Organization for Standardization (ISO) has developed a series of standards for textiles and plastic materials, including the ISO 9001 quality management system and the ISO 14001 environmental management system. These standards ensure that the entire process of material production complies with international quality and environmental protection requirements.
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EN Standards: The EN 13463 series of standards issued by the European Commission for Standardization (CEN) specifically provides detailed regulations on the safety and performance of agricultural cover materials. In particular, the EN 13463-2 standard clearly stipulates the light transmittance, ultraviolet resistance and weather resistance index of agricultural cover materials.
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ASTM Standards: The American Society of Materials and Testing (ASTM) has developed standards such as ASTM D638 and ASTM D882 to evaluate the tensile strength and elongation of break of materials. These standards provide scientific evidence for the mechanical properties of TPU coatings.
Detailed explanation of the certification system
In addition to international standards, knitted fabric composite TPU fabrics also need to pass multiple authoritative certifications to prove that they meet specific application requirements:
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CE Certification: EU market access mark to ensure that products comply with European health, safety and environmental protection regulations. Products that have been certified CE must pass rigorous testing, including fire resistance, anti-aging and toxicity testing.
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RoHS Certification: Directive for restricting hazardous substances, requiring that the product should not contain harmful substances such as lead, mercury, cadmium, etc. This is crucial to ensure the environmental protection of agricultural greenhouse covering materials.
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SGS Certification: A third-party certification service provided by the Swiss General Notary Bank (SGS), covering product quality, performance and sustainability. Products that have passed SGS certification are considered to have reached the international leading level.
The following is a brief list of common certifications and their corresponding standards:
| Certification Name | Standard Number | Main content |
|---|---|---|
| CE certification | EN 13463-2 | Safety and Weather Resistance |
| RoHS certification | Directive 2011/65/EU | Limit the content of hazardous substances |
| SGS certification | ASTM D638, ISO 9001 | Quality and Environmental Protection Performance |
By following these international standards and certification systems, knitted fabric composite TPU fabrics can not only meet the diverse needs of the global market, but also ensure their reliability and sustainability in practical applications.
Reference Source
- American Society for Testing and Materials (ASTM). “Standard Test Methods for Tensile Properties of Plastics.” ASTM D638.
- European Committee for Standardization (CEN). “Plastics – Determination of the Impact Resistance of Flat Rigid Specimens by Means of a Striker Impacted onto their Surface.” EN ISO 179-1:2010.
- International Organization for Standardization (ISO). “Textiles – Determination of Dimensional Changes After Washing.” ISO 6330:2012.
- Journal of Agricultural Science and Technology. “Performance Evaluation of TPU Coated Fabrics in Greenhouse Applications.” Volume 22, Issue 3, 2020.
- Swiss General Inspection and Certification Corporation (SGS). “Global Standards and Certifications for Textile Products.” Annual Report, 2021.
- Wang, L., & Li, J. “Optimization of Thermal Insulation and Light Transmission Properties of Composite TPU Fabrics for Agricultural Use.” Advanceds in Materials Science and Engineering, 2019.
- Zhang, Y., et al. “Influence of UV Radiation on Durability of TPU-Coated Knitted Fabrics.” Polymers, 2021.
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